space travel is bad

The many, many reasons space travel is bad for the human body

Leaving earth upends almost every system inside of us.

After the astronaut Scott Kelly spent a year on the International Space Station, he returned to Earth shorter, more nearsighted, lighter and with new symptoms of heart disease that his identical twin brother did not share. (Mark Kelly, now a U.S. senator, also spent a brief time in space.)

Even their DNA diverged, as nearly 1,000 of Scott Kelly’s genes and chromosomes worked differently. (On the upside, he aged about 9 milliseconds less that year, thanks to how fast the space station circled the Earth.)

Most of these effects cleared up within a few months, but not all — underscoring the potential health hazards of space travel, many of which are unknown. These will ratchet up during ambitious future trips, such as NASA’s planned Artemis mission to the moon and later travel to Mars.

Even a partial list of the likely physical and emotional consequences of deep space travel is daunting.

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Space motion sickness sets in almost immediately. The nausea, dizziness, headaches and confusion can linger for days.

“Puffy Face Bird Leg Phenomenon” develops, as blood and other bodily fluids rush to the upper body in low gravity and stay there, swelling heads and shrinking legs.

Astronauts’ appearances can change as their faces swell. The astronauts may feel congested, as though they have a constant head cold.

Muscles atrophy by as much as 1 percent every week in weightlessness, especially in the legs.

Blood volume drops — and with less blood to pump, the heart weakens and loses its signature heart shape, growing more rounded.

Like any other muscle, the heart doesn’t need to work as hard in microgravity and will begin to atrophy without rigorous exercise.

Doused with radiation, many immune cells die and immunity is lowered. There’s also DNA damage, potentially upping cancer risk.

Inflammation spikes throughout the body, possibly contributing to heart disease and other conditions.

Bones thin by about 1.5 percent a month. Spinal discs harden.

In the head, parts of the eyeball can flatten, causing sharper distance vision and dimmer near vision.

Fluids flood the skull, diminishing smell and hearing.

Gene activity changes, including in the brain. In mice, 54 different genes in the brain worked differently after weeks in space.

Brain cells can be affected by radiation, diminishing memory and thinking (in mice).

Circadian rhythms falter, making insomnia common.

Finally, months or years of solitude — or close confinement with fellow astronauts — can lead to lasting psychological stress.

“Space is just not very hospitable to the human body,” said Emmanuel Urquieta, chief medical officer at the Translational Research Institute for Space Health in Houston, which partners with NASA to study the effects of deep space exploration.

Humans evolved in conditions of plentiful gravity and relatively slight background radiation, he said. Space is the reverse and it upends the operations of almost every biological system inside of us. —

Most of the potential health risks of space travel can be mitigated to some extent, scientists point out. Exercise, for instance, “is quite effective” at helping astronauts maintain muscle mass and bone density, said Lori Ploutz-Snyder, the dean of the University of Michigan School of Kinesiology. She was previously a researcher at NASA, where she led studies of exercise and space travel.

The New Space Age

On the space station, astronauts routinely work out for about an hour most days, she said, using specialized devices to run, cycle and lift weights, despite being weightless. But on lunar and Mars missions, which will involve smaller ships and possibly years-long durations, exercise equipment will need to be shrunk and astronauts’ willingness to keep up with the workouts enlarged.

[ To counter the effect of sitting too much, try the astronaut workout ]

The Earth’s magnetic field shields the relatively close-in space station as well from some of the worst deep-space radiation, but the lunar and Mars missions — higher and farther from Earth — will not enjoy that protection.

The moon and Mars journeys will demand advanced shielding, Urquieta said, together with drugs and supplements that might lessen some of the internal effects of the remaining — and inevitable — radiation. Antioxidants, such as vitamins C and E, could sop up a portion of the damaging molecules released after radiation exposure, while other protective drugs and nutrients are under investigation, he said.

Despite every available precaution and protection, deep space will remain a harsh, unwelcoming place for the human body. But it will also, and always, represent something else for the human imagination, Urquieta said — its endless sweep of sequined darkness sparking our ambitions, dreams and stories.

Which is why, even knowing better than most people the toll such a trip might take on him, he would go into space “in a heartbeat,” he said. “Absolutely. No question. It’s so inspiring. It’s space."

About this story

Additional design and development by Betty Chavarria. Editing by Kate Rabinowitz, Manuel Canales and Jeff Dooley. Copy editing by Wayne Lockwood.

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How bad is space tourism for the environment? And other space travel questions, answered.

Six questions to consider before launching yourself into space.

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For many, the rise of commercial space tourism is a vulgar display of wealth and power . Amid several global crises, including climate change and a pandemic, billionaires are spending their cash on launching themselves into space for fun. When Amazon founder Jeff Bezos told reporters after his first space tourism trip on Tuesday that Amazon customers and employees had “paid” for his flight, that only intensified that criticism.

But critics won’t deter Bezos and the other superrich. Space tourism is now a reality for the people who can afford it — and it will have repercussions for everyone on Earth.

In fact, all signs indicate that the market for these trips is already big enough that they’ll keep happening. Jeff Bezos’s spaceflight company Blue Origin already has two more trips scheduled later this year , while Virgin Galactic , the space firm founded by billionaire Richard Branson, has at least 600 people who have already paid around $250,000 each for future tickets on its spaceplane.

Now, as the commercial space tourism market (literally) gets off the ground, there are big questions facing future space travelers — and everyone else on the planet. Here are answers to the six biggest ones.

1. What will people actually be able to see and experience on a space trip?

The biggest perk of traveling to space is the view. Just past the boundary between space and Earth, passengers can catch a stunning glimpse of our planet juxtaposed against the wide unknown of space. If a passenger is riding on a Virgin Galactic flight, they will get about 53 miles above sea level. Blue Origin riders will get a little bit higher, about 62 miles above sea level and past the Kármán line, the internationally recognized boundary between Earth and space. Overall, the experience on both flights is pretty similar.

Welcome aboard #Unity22 , Virgin Galactic's first fully-crewed test flight. Watch the historic moment through the eyes of our mission specialists. pic.twitter.com/DEwbBkgJYl — Virgin Galactic (@virgingalactic) July 13, 2021

The view is meant to be awe-inducing, and the experience even has its own name: the Overview Effect . “​​When you see Earth from that high up, it changes your perspective on things and how interconnected we are and how we squander that here on Earth,” Wendy Whitman Cobb, a professor at the US Air Force’s School of Advanced Air and Space Studies, told Recode.

Another perk of these trips is that space tourists will feel a few minutes of microgravity, which is when gravity feels extremely weak . That will give them the chance to bounce around a spacecraft weightlessly before heading back to Earth.

But Blue Origin’s and Virgin Galactic’s flights are relatively brief — about 10 and 90 minutes long , respectively. Other space tourism flights from SpaceX, the space company founded by Elon Musk , will have more to offer. This fall, billionaire Jared Isaacman, who founded the company Shift4 Payments, will pilot SpaceX’s first all-civilian flight, the Inspiration4 , which will spend several days in orbit around Earth. In the coming years, the company has also planned private missions to the International Space Station, as well as a trip around the moon .

These trips are meant to be enjoyed by space nerds who longed to be astronauts. But there’s another reason rich people want to go to space: demonstrating exclusivity and conspicuous consumption. More than a few people can afford a trip to Venice or the Maldives. But how many people are privileged enough to take a trip to space?

“What a nice way of showing off these days than to post a picture on Instagram from space,” Sridhar Tayur, a Carnegie Mellon business professor, told Recode.

View this post on Instagram A post shared by Jeff Bezos (@jeffbezos)

2. Does commercial space travel have any scientific goals, or is it really just a joyride?

Right now, space tourism flights from Virgin Galactic and Blue Origin have only reached suborbital space , which means that flights enter space but do not enter orbit around Earth. Scientifically, that’s not a new frontier. Though these current flights use new technology, suborbital flight with humans aboard was accomplished by NASA back in the early 1960s , Matthew Hersch, a historian of technology at Harvard, told Recode.

Right now, it’s not clear these trips will offer scientists major new insights, but they might provide information that could be used in the future for space exploration. In fact, these trips are also being marketed as potential opportunities for scientific experiments. For instance, the most recent Virgin Galactic flight carried plants and tested how they responded to microgravity .

These private companies primarily see opportunities in their commercial vehicles that can be reused at scale, which will allow the same rockets (or in Virgin Galactic’s case, spaceplanes) to go to space again and again, which lowers the overall cost of space tourism.

Billionaires and their private space companies also see the development of these rockets as an opportunity to prepare for flights that will do even more, and go even farther, into space. Bezos, for instance, has argued that New Shepard’s suborbital flights will help prepare the company’s future missions, including its New Glenn rocket, which is meant for orbital space.

“The fact of the matter is, the architecture and the technology we have chosen is complete overkill for a suborbital tourism mission,” Bezos said at Tuesday’s post-launch briefing . “We have chosen the vertical landing architecture. Why did we do that? Because it scales.”

Beyond potential scientific advancements in the future, suborbital spaceflight might also create new ways to travel from one place on earth to another. SpaceX, for instance, has advertised that long-haul flights could be shortened to just 30 minutes by traveling through space.

3. Is it safe?

Right now, it’s not entirely clear just how risky space tourism is.

One way space tourism companies are trying to keep travelers safe is by requiring training so that the people who are taking a brief sojourn off Earth are as prepared as possible.

On the flight, people can experience intense altitude and G-forces. “This is sustained G-forces on your body, upwards of what can be 6 G in one direction — which is six times your body weight for upwards of 20 or 30 seconds,” Glenn King, the chief operating officer of the Nastar Center — the aerospace physiology training center that prepared Richard Branson for his flights — told Recode. “That’s a long time when you have six people, or your weight, pressing down on you.”

There’s also the chance that space tourists will be exposed to radiation, though that risk depends on how long you’re in space. “It’s a risk, especially more for the orbital flight than sub-orbital,” explains Whitman Cobb. “Going up in an airplane exposes you to a higher amount of radiation than you would get here on the ground.” She also warns that some tourists will likely barf on the ride.

There doesn’t seem to be an age limit on who can travel, though. The most recent Blue Origin flight included both the youngest person to ever travel to space, an 18-year-old Dutch teenager, as well as the oldest: 82-year-old pilot Wally Funk.

4. How much will tickets cost?

The leaders in commercial space tourism already claim they have a market to support the industry. While Bezos hinted on Tuesday the price would eventually come down — as eventually happened with the high prices of the nascent airline industry — for now, ticket prices are in the low hundreds of thousands, at least for Virgin Galactic . That price point would keep spaceflight out of reach for most of humanity, but there are enough interested rich people that space tourism seems to be economically feasible.

“If you bring it down to $250,000, the wait times [to buy a ticket] will be very long,” Tayur, of Carnegie Mellon, told Recode.

5. What impact will commercial space travel have on the environment?

The emissions of a flight to space can be worse than those of a typical airplane flight because just a few people hop aboard one of these flights, so the emissions per passenger are much higher. That pollution could become much worse if space tourism becomes more popular. Virgin Galactic alone eventually aims to launch 400 of these flights annually.

“The carbon footprint of launching yourself into space in one of these rockets is incredibly high, close to about 100 times higher than if you took a long-haul flight,” Eloise Marais , a physical geography professor at the University College London, told Recode. “It’s incredibly problematic if we want to be environmentally conscious and consider our carbon footprint.”

These flights’ effects on the environment will differ depending on factors like the fuel they use, the energy required to manufacture that fuel, and where they’re headed — and all these factors make it difficult to model their environmental impact. For instance, Jeff Bezos has argued that the liquid hydrogen and oxygen fuel Blue Origin uses is less damaging to the environment than the other space competitors (technically, his flight didn’t release carbon dioxide ), but experts told Recode it could still have significant environmental effects .

There are also other risks we need to keep studying , including the release of soot that could hurt the stratosphere and the ozone. A study from 2010 found that the soot released by 1,000 space tourism flights could warm Antarctica by nearly 1 degree Celsius. “There are some risks that are unknown,” Paul Peeters, a tourism sustainability professor at the Breda University of Applied Sciences, told Recode. “We should do much more work to assess those risks and make sure that they do not occur or to alleviate them somehow — before you start this space tourism business.” Overall, he thinks the environmental costs are reason enough not to take such a trip.

6. Who is regulating commercial space travel?

Right now, the Federal Aviation Administration (FAA) has generally been given the job of overseeing the commercial space industry. But regulation of space is still relatively meager.

One of the biggest areas of concern is licensing launches and making sure that space flights don’t end up hitting all the other flying vehicles humans launch into the sky, like planes and drones. Just this June, a SpaceX flight was held up after a helicopter flew into the zone of the launch.

There’s a lot that still needs to be worked out, especially as there are more of these launches. On Thursday, the Senate hosted a hearing with leaders of the commercial space industry focused on overseeing the growing amount of civil space traffic .

At the same time, the FAA is also overseeing a surging number of spaceports — essentially airports for spaceflight — and making sure there’s enough space for them to safely set up their launches.

But there are other areas where the government could step in. “I think the cybersecurity aspect will also play a very vital role, so that people don’t get hacked,” Tayur said. The FAA told Recode that the agency has participated in developing national principles for space cybersecurity, but Congress hasn’t given it a specific role in looking at the cybersecurity of space.

At some point, the government might also step in to regulate the environmental impact of these flights, too, but that’s not something the FAA currently has jurisdiction over.

In the meantime, no government agency is currently vetting these companies when it comes to the safety of the human passengers aboard. An FAA official confirmed with Recode that while the agency is awarding licenses to companies to carry humans to space , they’re not actually confirming that these trips are safe. That’s jurisdiction Congress won’t give the agency until 2023.

There doesn’t seem to be an abundance of travelers’ insurance policies for space. “Passengers basically sign that they’re waiving all their rights,” Whitman Cobb said. “You’re acknowledging that risk and doing it yourself right now.”

So fair warning, if you decide to shell out hundreds of thousands of dollars for a joyride to space: You’d likely have to accept all responsibility if you get hurt.

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When billionaires Richard Branson and Jeff Bezos soared into space this month aboard their companies' suborbital tourism vehicles, much of the world clapped in awe. 

But for some scientists, these milestones represented something other than just a technical accomplishment. Achieved after years of delays and despite significant setbacks , the flights marked the potential beginning of a long-awaited era that might see rockets fly through the so-far rather pristine upper layers of the atmosphere far more often than they do today. In the case of SpaceShipTwo, the vehicle operated by Branson's Virgin Galactic, these flights are powered by a hybrid engine that burns rubber and leaves behind a cloud of soot.

"Hybrid engines can use different types of fuels, but they always generate a lot of soot," said Filippo Maggi, associate professor of aerospace engineering at Politecnico di Milano, Italy, who researches rocket propulsion technologies and was part of a team that several years ago published an extensive analysis of hybrid rocket engine emissions. "These engines work like a candle, and their burning process creates conditions that are favorable for soot generation."

Related: Air pollution from reentering megaconstellation satellites could cause ozone hole 2.0

According to Dallas Kasaboski, principal analyst at the space consultancy Northern Sky Research, a single Virgin Galactic suborbital space tourism flight, lasting about an hour and a half, can generate as much pollution as a 10-hour trans-Atlantic flight. Some scientists consider that disconcerting, in light of Virgin Galactic’s ambitions to fly paying tourists to the edge of space several times a day.

"Even if the suborbital tourism market is launching at a fraction of the number of launches compared to the rest of the [tourism] industry, each of their flights has a much higher contribution, and that could be a problem," Kasaboski told Space.com.

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Virgin Galactic's rockets are, of course, not the only culprits. All rocket motors burning hydrocarbon fuels generate soot, Maggi said. Solid rocket engines, such as those used in the past in the boosters of NASA's space shuttle , burn metallic compounds and emit aluminum oxide particles together with hydrochloric acid, both of which have a damaging effect on the atmosphere.

The BE-3 engine that powers Blue Origin's New Shepard suborbital vehicle, on the other hand, combines liquid hydrogen and liquid oxygen to create thrust. The BE-3 is not a big polluter compared to other rocket engines, emitting mainly water along with some minor combustion products, experts say .

Too little is known

For Karen Rosenlof, senior scientist at the Chemical Sciences Laboratory at the U.S. National Oceanic and Atmospheric Administration (NOAA), the biggest problem is that rockets pollute the higher layers of the atmosphere — the stratosphere, which starts at an altitude of about 6.2 miles (10 kilometers), and the mesosphere, which goes upward from 31 miles (50 km). 

"You are emitting pollutants in places where you don't normally emit it," Rosenlof told Space.com. "We really need to understand. If we increase these things, what is the potential damage?"

So far, the impact of rocket launches on the atmosphere has been negligible, according to Martin Ross, an atmospheric scientist at the Aerospace Corporation who often works with Rosenlof. But that's simply because there have not been that many launches. 

"The amount of fuel currently burned by the space industry is less than 1% of the fuel burned by aviation," Ross told Space.com. "So there has not been a lot of research, and that makes sense. But things are changing in a way that suggests that we should learn about this in more detail."

Northern Sky Research predicts that the number of space tourism flights will skyrocket over the next decade, from maybe 10 a year in the near future to 360 a year by 2030, Kasaboski said. This estimate is still far below the growth rate that space tourism companies like Virgin Galactic and Blue Origin envision for themselves. 

"Demand for suborbital tourism is extremely high," Kasaboski said. "These companies virtually have customers waiting in a line, and therefore they want to scale up. Ultimately, they would want to fly multiple times a day, just like short-haul aircraft do."

The rate of rocket launches delivering satellites into orbit is expected to grow as well. But Kasaboski sees bigger potential for growth in space tourism. 

"It's like the difference between a cargo flight and a passenger flight," Kasaboski said. "There's a lot more passengers that are looking to fly."

The problem is, according to Ross, that the scientific community has no idea and not enough data to tell at what point rocket launches will start having a measurable effect on the planet's climate. At the same time, the stratosphere is already changing as the number of rocket launches sneakily grows.

"The impacts of these [rocket-generated] particles are not well understood even to an order of magnitude, the factor of 10," Ross said. "The uncertainty is large, and we need to narrow that down and predict how space might be impacting the atmosphere."

Space shuttle's ozone holes 

So far, the only direct measurements of the effects of rocket launches on chemical processes in the atmosphere come from the space shuttle era. In the 1990s, as the world was coming together to salvage the damaged ozone layer , NASA, NOAA and the U.S. Air Force put together a campaign that looked at the effects of the emissions from the space shuttle's solid fuel boosters on ozone in the stratosphere. 

"In the 1990s, there were significant concerns about chlorine from solid rocket motors," Ross said. "Chlorine is the bad guy to ozone in the stratosphere, and there were some models which suggested that ozone depletion from solid rocket motors would be very significant."

The scientists used NASA's WB 57 high-altitude aircraft to fly through the plumes generated by the space shuttle rockets in Florida. Reaching altitudes of up to 60,000 feet (19 km), they were able to measure the chemical reactions in the lower stratosphere just after the rockets' passage. 

"One of the fundamental questions was how much chlorine is being made in these solid rocket motors and in what form," David Fahey, the director of the Chemical Sciences Laboratory at NOAA, who led the study, told Space.com. "We measured it several times and then analyzed the results. At that time, there were not enough space shuttle launches to make a difference globally, but locally one could deplete the ozone layer due to this diffuse plume [left behind by the rocket]."

The space shuttle retired 10 years ago, but rockets generating ozone-damaging substances continue launching humans and satellites to space today. 

In fact, in 2018, in its latest Scientific Assessment of Ozone Depletion , which comes out every four years, the World Meteorological Organization included rockets as a potential future concern. The organization called for more research to be done as the number of launches is expected to increase.  

Worse than geoengineering 

Rosenlof's team studies the broader effects of human-made substances in the higher layers of the atmosphere using powerful NOAA supercomputers. The work is akin to predicting the proverbial butterfly effect, the influence of minuscule changes in the chemistry of the air tens of miles above Earth on climate and weather patterns on the ground. For her, black carbon, or soot, emitted by rockets burning hydrocarbon fuels, is of particular concern.

"The problem with soot is that it absorbs ultraviolet light, and that means that it could heat the stratosphere," Rosenlof said. "When you start heating the stratosphere, the layer above the troposphere [closest to the ground], you start changing the motion in the stratosphere. You are changing the energy transfer, and that could actually affect what is happening on the ground."

Rosenlof points out that many of the particles generated by some rockets have been of interest to scientists due to the possible effects they could have on the global climate in a different context — that of geoengineering , the deliberate tampering with the atmosphere with the aim of stopping or mitigating global warming. 

Rosenlof recently co-authored a paper that used the same powerful NOAA supercomputers to model what the scientists call a climate intervention. The team was interested in the climate effects of dispersing sulfur dioxide particles, which are known to reflect light away from Earth, in combination with soot (which is also part of rocket emissions) in the lower stratosphere. Soot absorbs energy from sunlight and pushes the sulfur dioxide aerosol particles to a higher altitude by warming up the surrounding air. At that higher altitude, the sulfur dioxide can start its climate-cooling work. The experiment modeled what would happen when 1.1 million tons of sunlight-reflecting sulfur dioxide mixed with 11,000 tons of black carbon were released in the upper troposphere by aircraft over a 10-day period. 

The study didn't find any significant negative effects on weather on Earth. Yet, those results do not dispel Rosenlof's concerns about the possible risks associated with the growing number of rocket launches. 

Altering the jet stream

"Black carbon in the geoengineering experiment that we did isn't as high as the stuff from these rockets," she said. "The problem is that the higher you go, the longer something lasts. Neither of them is ideal, because either of them would produce heating in places where we don't have heating right now."

According to Maggi, the soot particles generated by hybrid rocket engines are extremely small and light-weight. In fact, when he and his colleagues tried to measure the soot output of hybrid rocket engines in a laboratory, they couldn't reliably do it with precision because of the particles' minuscule size. 

"We were able to measure the particle output from solid rocket motors," Maggi said. "These are about a micron in size, and there [are] a lot of them. But because they are large, they fall to the ground more quickly. In hybrid rocket engines, we were not able to collect the soot from the plume because it's extremely fine, a few nanometres in size."

Maggi fears these particles could, in fact, stay in the stratosphere forever.

"They have the same size as the carbon emitted by aircrafts," Maggi said. "And we know that there is a layer of carbon in the atmosphere at the flight level of aircrafts which is staying there. It's very likely that particles coming from rocket motors will do the same."

The accumulation of these particles over years and decades is what worries the scientists. Just as the current climate crisis started relatively slowly as the amount of carbon released into the atmosphere grew, the pollution in the stratosphere may only start causing harm some years down the road.

Rosenlof added that in the long term, injecting pollutants into the stratosphere could alter the polar jet stream, change winter storm patterns or affect average rainfall. 

"You might go from 25 inches [64 centimeters] a year to 20 inches [51 cm] a year in some places, which maybe doesn't sound like that big of a deal unless you are a farmer trying to grow your wheat right there," Rosenlof said. "Then a subtle change in rainfall can impact your crop yields."

Work to be done 

For this reason, Fahey says, it is critical that scientific work starts now to evaluate the future risks. 

"There is this fundamental gap where we just don't have the numbers, and that means that the science is limited because we have this lack of information," he said. "We feel it is part of our responsibility [at NOAA] to assess the impact of human activity on the stratosphere. Rockets are a principal and unique source [of stratospheric pollution], the launch frequencies are increasing and the effects are accumulating."

Fahey envisions a wider research program that would analyze the emissions and impacts of individual types of rocket engines and fuels on the stratosphere. The data could be used in Rosenlof's models to better predict the effects in accordance with the expected growth of the number of launches. Fahey, however, says that a political decision would have to come first to provide NOAA and its partners with funding that would enable them to take the high-altitude aircraft to the sky again and gather the data. The good news is, he added, that the U.S. Congress seems to be aware of the problem and things might soon start to move. 

"We would like to see a national program run by NOAA or the Air Force that would develop a database with basic emission characteristics of modern propulsion systems based on observations," he said. "We could gather some data in ground tests but also in the same way that we did with the space shuttle — by flying through the plumes just after launch."

Follow Tereza Pultarova on Twitter @TerezaPultarova. Follow us on Twitter @Spacedotcom and on Facebook . 

Join our Space Forums to keep talking space on the latest missions, night sky and more! And if you have a news tip, correction or comment, let us know at: [email protected].

Tereza is a London-based science and technology journalist, aspiring fiction writer and amateur gymnast. Originally from Prague, the Czech Republic, she spent the first seven years of her career working as a reporter, script-writer and presenter for various TV programmes of the Czech Public Service Television. She later took a career break to pursue further education and added a Master's in Science from the International Space University, France, to her Bachelor's in Journalism and Master's in Cultural Anthropology from Prague's Charles University. She worked as a reporter at the Engineering and Technology magazine, freelanced for a range of publications including Live Science, Space.com, Professional Engineering, Via Satellite and Space News and served as a maternity cover science editor at the European Space Agency.

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Projected increase in space travel may damage ozone layer

• June 21, 2022
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Scientists from NOAA and The Aerospace Corp. modeled the climate response of the stratosphere to increased future emissions of black carbon from rockets burning kerosene fuel. Projected growth in rocket launches for space tourism, moon landings, and perhaps travel to Mars has many dreaming of a new era of space exploration. But a NOAA study suggests that a significant boost in spaceflight activity may damage the protective ozone layer on the one planet where we live.  Kerosene-burning rocket engines widely used by the global launch industry emit exhaust containing black carbon, or soot, directly into the stratosphere, where a layer of ozone protects all living things on the Earth from the harmful impacts of ultraviolet radiation, which include skin cancer and weakened immune systems in humans, as well as disruptions to agriculture and ecosystems.

According to new NOAA research published in the Journal of Geophysical Research Atmospheres, a 10-fold increase in hydrocarbon fueled launches, which is plausible within the next two decades based on recent trends in space traffic growth, would damage the ozone layer, and change atmospheric circulation patterns. “We need to learn more about the potential impact of hydrocarbon-burning engines on the stratosphere and on the climate at the surface of the Earth,” said lead author Christopher Maloney, a CIRES research scientist working in NOAA’s Chemical Sciences Laboratory. “With further research, we should be able to better understand the relative impacts of different rocket types on climate and ozone.” Launch rates have tripled  Launch rates have more than tripled in recent decades, Maloney said, and accelerated growth is anticipated in the coming decades. Rockets are the only direct source of human-produced aerosol pollution above the troposphere, the lowest region of the atmosphere, which extends to a height of about 5 to 10 miles above the Earth’s surface.  The research team used a climate model to simulate the impact of approximately 10,000 metric tons of soot pollution injected into the stratosphere over the northern hemisphere every year for 50 years. Currently,  an estimated 1,000 tons of rocket soot exhaust are emitted annually. The researchers caution that the exact amounts of soot emitted by the different hydrocarbon fueled engines used around the globe are poorly understood.  The researchers found that this level of activity would increase annual temperatures in the stratosphere by 0.5 – 2° Celsius or approximately 1-4°Farenheit, which would change global circulation patterns by slowing the subtropical jet streams as much as 3.5%, and weakening the stratospheric overturning circulation. 

Stratospheric ozone is strongly influenced by temperature and atmospheric circulation, noted co-author Robert Portmann, a research physicist with the Chemical Sciences Laboratory, so it was no surprise to the research team that the model found changes in stratospheric temperatures and winds also caused changes in the abundance of ozone. The scientists found ozone reductions occurred poleward of 30 degrees North, or roughly the latitude of Houston, in nearly all months of the year. The maximum reduction of 4% occurred at the North Pole in June. All other locations north of 30° N experienced at least some reduced ozone throughout the year. This spatial pattern of ozone loss directly coincides with the modeled distribution of black carbon and the warming associated with it, Maloney said.  “The bottom line is projected increases in rocket launches could expose people in the Northern Hemisphere to increased harmful UV radiation,” Maloney said.  The research team also simulated two larger emission scenarios of 30,000 and 100,000 tons of soot pollution per year to better understand the impacts of an extremely large increase in future space travel using hydrocarbon-fueled engines, and more clearly investigate the feedbacks that determine the atmosphere’s response. Results showed that the stratosphere is sensitive to relatively modest black carbon injections. The larger emission simulations showed a similar, yet more severe disruptions of atmospheric circulation and climate loss  than the 10,000 metric ton case.

Building a research foundation The study built on previous research by members of the author team. A 2010 study led by co-author Martin Ross, a scientist with The Aerospace Corporation, first explored the climate impact of an increase in soot-producing rocket launches. A second study performed at NOAA in 2017, on which Ross was a co-author, examined the climate response to water vapor emissions from a proposed reusable space launch system utilizing cleaner hydrogen-fueled rockets. “Our work emphasizes the importance of ozone depletion caused by soot particles emitted by liquid-fueled rockets,” Ross said. “These simulations change the long-held belief that spaceflight’s only threat to the ozone layer was from solid-fueled rockets. We’ve shown that particles are where the action is for spaceflight’s impacts.”   While the new research describes the influence that soot in rocket exhaust has on the climate and composition of the stratosphere, the scientists said it represents an initial step in understanding the spectrum of impacts on the stratosphere from increased space flight.   Combustion emissions from the different rocket types will need to be evaluated, they said.  Soot and other particles generated by satellites burning up when they fall out of orbit is also a growing, poorly understood source of emissions in the middle-to-upper atmosphere. These and other topics will need further research to produce a complete picture of space industry emissions and their impacts on Earth’s climate and ozone.   The study was supported by NOAA’s Earth’s Radiation Budget initiative. For more information, contact Monica Allen, NOAA Research Director of Public Affairs at [email protected] or 202-379-6693.

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Space Tourism Poses a Significant ‘Risk to the Climate’

Rockets launched by billionaires elon musk and richard branson emit black carbon in the stratosphere, where it is 500 times worse for the climate than it is on earth. billionaire jeff bezos’ rockets burn liquid hydrogen and oxygen and pose a lesser climate threat..

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The burgeoning space tourism industry could soon fuel significant global warming while also depleting the protective ozone layer that is crucial for sustaining life on Earth, a new study concludes.  The findings , published Saturday in Earth’s Future, raise additional concerns about the “billionaire space race” fueled by some of the world’s richest men.

A key focus of the study was emissions of black carbon, or soot, from the combustion of rocket fuel. Black carbon, which comes from burning fossil fuels or biomass, absorbs light from the sun and releases thermal energy, making it a powerful climate warming agent.  At lower altitudes black carbon quickly falls from the sky, remaining in the atmosphere for only a matter of days or weeks.

However, as rockets blast into space, they emit black carbon into the stratosphere where it remains, absorbing sunlight and radiating heat, for up to four years before falling back down to Earth. Black carbon emitted in the stratosphere is nearly 500 times worse for the climate than similar emission on or near the surface of the earth, the study found. Black carbon emissions from all space flights are currently relatively low but could quickly increase if projections for the growth of space tourism prove correct.

“A big ramp up in the number of space launches, which is hoped for by the space tourism industry, poses a risk to the climate by adding black carbon particles to the upper atmosphere and as a result, we should think very carefully about regulating this industry before it gets out of hand,” Robert Ryan, a researcher at University College London and the study’s lead author, said. “It would be a real shame for humanity to look back in 50 or 100 years when we’ve got thousands of rocket launches a year and think, ‘If only we’d done something.’”

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To calculate the impact of spaceflights, Ryan and colleagues produced an inventory of all pollutants released from the 103 rockets launched worldwide in 2019, as well as data on the re-entry of reusable rockets and space junk descending back into Earth’s atmosphere.

The researchers then plugged the emissions data into atmospheric chemistry and heat transfer models to determine their impact on ozone depletion and climate change. They also included recent projections of anticipated flights by space tourism companies Virgin Galactic, Blue Origin and SpaceX to plot potential future emissions from the industry.

After just three years of more than once-a-day rocket launches, space tourism would account for 6 percent of warming due to black carbon emissions despite contributing just 0.02 percent of global black carbon emissions, the study concluded.  

The study also found that rockets deplete the Earth’s atmospheric ozone layer, which protects the planet from harmful ultraviolet radiation from the sun. Rockets that burn solid, chlorine-based fuels harm ozone by releasing chlorine, which destroys ozone, directly into the stratosphere. Chlorine-containing chemicals, such as chlorofluorocarbons (CFCs), were banned under the Montreal Protocol, an international agreement to protect atmospheric ozone that was adopted in 1987. Solid fuel rockets were not part of the ban.

Regardless of the fuel type used, all rockets contributed to additional ozone depletion through the emissions of nitrogen oxides upon re-entry into the stratosphere.     

A second study that also looked at the climate and ozone impacts of rocket launches and was published earlier this month, came to similar conclusions. The study , published in JGR Atmospheres, projected that increased emissions from space tourism would also disrupt global atmospheric circulation, slowing the transport of air from the tropics to the poles in the upper atmosphere.

This decrease in circulation would result in a slight reduction of atmospheric ozone concentrations in the northern hemisphere, said Christopher Maloney, the study’s lead author and a research scientist with the National Oceanic and Atmospheric Administration.

“Anytime you see anything that impacts ozone, it’s worthy of further investigation,” he said.

Stephen Andersen, research director for the Washington-based Institute for Governance and Sustainable Development, said the recent studies further the climate and ozone concerns related to rocket launches that NASA scientists first raised nearly half a century ago.

“Over the last 45 years, they came to the same conclusion,” Andersen said of research done by NASA and others. “Current emissions are not a significant source, but they would be incredibly significant if the projections of space flights prove true.”

By one measure, public opinion turned against space tourism last year as some of the world’s most wealthy individuals blasted into space amid an ever-warming climate and the ongoing Covid pandemic.  

U.S. spaceflight company Virgin Galactic, which was founded by British billionaire Richard Branson and hopes to offer 400 flights per year from its “spaceport” in New Mexico, did not respond to a request for comment.

But, the company appears to be aware of the climate concerns posed by space tourism. In its most recent annual financial report filed with the U.S. Securities and Exchange Commission, Virgin Galactic stated that the company “may be adversely affected by global climate change or by legal, regulatory or market responses to such change.”

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Blue Origin, the space tourism company owned by Amazon founder Jeff Bezos, envisions “millions of people living and working in space for the benefit of Earth.” 

Company executives did not respond to a request for comment. Blue Origin’s rockets burn liquid hydrogen and oxygen and emit water vapor and nitrogen oxides, but not black carbon. Emissions from hydrogen fuel rockets in the upper atmosphere pose less of a threat than other rocket types, but emissions of nitrogen oxides in the stratosphere and the emissions that go into producing liquid hydrogen on earth are still a concern, Ryan said.  

Elon Musk, the founder of SpaceX and the world’s richest person, tweeted in December that SpaceX plans to remove carbon dioxide from the atmosphere and turn it into rocket fuel. Musk is also funding a $100 million prize for the development of carbon removal . While many seek to turn CO2 into fuel, such efforts remain unproven. Rockets that burn fuel derived from carbon dioxide would also likely result in emissions of black carbon and nitrogen oxides in the upper atmosphere.

Andersen said efforts to reduce emissions are helpful but international regulations are needed to curb climate and ozone threats posed by increased commercial space flights.

“They need to think before they act and they ought to consider all the options of minimizing the impact,” he said. “Then the final decision over whether it’s worthwhile to society to allow this enterprise should be made in some kind of a governance way.”

Phil McKenna

Reporter, boston.

Phil McKenna is a Boston-based reporter for Inside Climate News. Before joining ICN in 2016, he was a freelance writer covering energy and the environment for publications including The New York Times, Smithsonian, Audubon and WIRED. Uprising, a story he wrote about gas leaks under U.S. cities, won the AAAS Kavli Science Journalism Award and the 2014 NASW Science in Society Award. Phil has a master’s degree in science writing from the Massachusetts Institute of Technology and was an Environmental Journalism Fellow at Middlebury College.

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• Published: 05 November 2020

Red risks for a journey to the red planet: The highest priority human health risks for a mission to Mars

• Zarana S. Patel   ORCID: orcid.org/0000-0003-0996-6381 1 , 2 ,
• Tyson J. Brunstetter 3 ,
• William J. Tarver 2 ,
• Alexandra M. Whitmire 2 ,
• Sara R. Zwart 2 , 4 ,
• Scott M. Smith 2 &
• Janice L. Huff   ORCID: orcid.org/0000-0003-4236-7698 5  

npj Microgravity volume  6 , Article number:  33 ( 2020 ) Cite this article

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NASA’s plans for space exploration include a return to the Moon to stay—boots back on the lunar surface with an orbital outpost. This station will be a launch point for voyages to destinations further away in our solar system, including journeys to the red planet Mars. To ensure success of these missions, health and performance risks associated with the unique hazards of spaceflight must be adequately controlled. These hazards—space radiation, altered gravity fields, isolation and confinement, closed environments, and distance from Earth—are linked with over 30 human health risks as documented by NASA’s Human Research Program. The programmatic goal is to develop the tools and technologies to adequately mitigate, control, or accept these risks. The risks ranked as “red” have the highest priority based on both the likelihood of occurrence and the severity of their impact on human health, performance in mission, and long-term quality of life. These include: (1) space radiation health effects of cancer, cardiovascular disease, and cognitive decrements (2) Spaceflight-Associated Neuro-ocular Syndrome (3) behavioral health and performance decrements, and (4) inadequate food and nutrition. Evaluation of the hazards and risks in terms of the space exposome—the total sum of spaceflight and lifetime exposures and how they relate to genetics and determine the whole-body outcome—will provide a comprehensive picture of risk profiles for individual astronauts. In this review, we provide a primer on these “red” risks for the research community. The aim is to inform the development of studies and projects with high potential for generating both new knowledge and technologies to assist with mitigating multisystem risks to crew health during exploratory missions.

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Introduction.

Spaceflight is a dangerous and demanding endeavor with unique hazards and technical challenges. Ensuring the overall safety of the crew—their physical and mental health and well-being—are vital for mission success. These are large challenges that are further amplified as exploration campaigns extend to greater distances into our solar system and for longer durations. The major health hazards of spaceflight include higher levels of damaging radiation, altered gravity fields, long periods of isolation and confinement, a closed and potentially hostile living environment, and the stress associated with being a long distance from mother Earth. Each of these threats is associated with its own set of physiological and performance risks to the crew (Fig. 1a ) that must be adequately characterized and sufficiently mitigated. Crews do not experience these stressors independently, so it is important to also consider their combined impact on human physiology and performance. This “space exposome” is a unifying framework that reflects the interaction of all the environmental impacts on the human body (Fig. 1b ) and, when combined with individual genetics, will shape the outcomes of space travel on the human system 1 , 2 .

a The key threats to human health and performance associated with spaceflight are radiation, altered gravity fields, hostile and closed environments, distance from Earth, and isolation and confinement. From these five hazards stem the health and performance risks studied by NASA’s Human Research Program. b The space exposome considers the summation of an individual’s environmental exposures and their interaction with individual factors such as age, sex, genomics, etc. - these interactions are ultimately responsible for risks to the human system. Images used in this figure are courtesy of NASA.

The NASA Human Research Program (HRP) aims to develop and provide the knowledge base, technologies, and countermeasure strategies that will permit safe and successful human spaceflight. With agency resources and planning directed toward extended missions both within low Earth orbit (LEO) and outside LEO (including cis-lunar space, lunar surface operations, a lunar outpost, and exploration of Mars) 3 , HRP research and development efforts are focused on mitigation of over 30 categories of health risks relevant to these missions. The HRP’s current research strategy, portfolio, and evidence base are described in the HRP Integrated Research Plan (IRP) and are available online in the Human Research Roadmap, a managed tool used to convey these plans ( https://humanresearchroadmap.nasa.gov/ ). To determine research priorities, NASA uses an evidence-based risk approach to assess the likelihood and consequence (LxC), which gauges the level of each risk for a set of standard design reference missions (Fig. 2 ) 4 . Risks are assigned a rating for their potential to impact in-mission crew health and performance and for their potential to impact long-term health outcomes and quality of life. “Red” risks are those that are considered the highest priority due to their greatest likelihood of occurrence and their association with the most significant risks to crew health and performance for a given design reference mission (DRM). Risks rated “yellow” are considered medium level risks and are either accepted due to a very low probability of occurrence, require in-mission monitoring to be accepted, or require refinement of standards or mitigation strategies in order to be accepted. Risks rated “green” are considered sufficiently controlled either due to lower likelihood and consequence or because the current knowledge base provides sufficient mitigation strategies to control the risk to an acceptable level for that DRM. Milestones and planned program deliverables intended to move a risk rating to an acceptable, controlled level are detailed in a format known as the path to risk reduction (PRR) and are developed for each of the identified risks. The most recent IRP and PRR documents are useful resources for investigators during the development of relevant research approaches and proposals intended for submission to NASA HRP research announcements ( https://humanresearchroadmap.nasa.gov/Documents/IRP_Rev-Current.pdf ).

NASA uses an evidence-based approach to assess likelihood and consequence for each documented human system risk. The matrix used for classifying and prioritizing human system risks has two sets of consequences—the left side shows consequences for in-mission risks while the right side is used to evaluate long-term health consequences (Romero and Francisco) 4 .

This work reviews HRP-defined high priority “red” risks for crew health on exploration missions: (1) space radiation health effects that include cancer, cardiovascular disease, and cognitive decrements (2) Spaceflight-Associated Neuro-ocular Syndrome (3) behavioral health and performance decrements, and (4) inadequate food and nutrition. The approaches used to address these risks are described with the aim of informing potential NASA proposers on the challenges and high priority risks to crew health and performance present in the spaceflight environment. This should serve as a primer to help individual proposers develop projects with high potential for generating both new knowledge and technology to assist with mitigating risks to crew health during exploratory missions.

Space radiation health risks

Outside of the Earth’s protective magnetosphere, crews are exposed to pervasive, low dose-rate galactic cosmic rays (GCR) and to intermittent solar particle events (SPEs) 5 . Exposures from GCR are from high charge (Z) and energy (HZE) ions, high-energy protons, and secondary protons, neutrons, and fragments produced by interactions with spacecraft shielding and human tissues. The main components of an SPE are low-to-medium energy protons. In LEO, the exposures are from GCR modulated by the Earth’s magnetic field and from trapped protons in the South Atlantic Anomaly. The absorbed doses for crews on the International Space Station (ISS) on 6- to 12-month missions range from ~30 to 120 mGy. Outside of LEO, without the protection offered by the Earth’s magnetosphere, absorbed radiation doses will be significantly higher. Estimates for a 1 year stay on the lunar surface range from 100 to 120 mGy, and 300 to 450 mGy for an ~3-year Mars mission (transit and surface stay) 6 . The exact dose a crewmember will receive is highly dependent on exact parameters of a given mission, such as detailed vehicle and habitat designs, and mission location and duration 7 . Time in the solar cycle is also a large factor contributing to crew exposure, with highest GCR exposure occurring during periods of minimum solar activity. The lowest GCR exposures occur during periods of maximum solar activity when the heightened magnetic activity of the Sun diverts some cosmic rays; however, during maximum solar activity, the probability of an SPE is higher 8 , 9 . SPEs, which vary in the magnitude and frequency, will obviously also contribute to total mission doses so it is important to note that total mission exposures are only estimates. Further information on the space radiation environment that astronauts will experience is discussed in Simonsen et al. 5 and Durante and Cucinotta 10 .

An important consideration for risk assessment is that the types of radiation encountered in space are very different from the types of radiation exposure we are familiar with here on Earth. HZE ions, although a small fraction of the overall GCR spectrum compared to protons, are more biologically damaging. They differ from terrestrial forms of radiation, such as X-rays and gamma-rays, in both the amount (dose) of exposure as well as in the patterns of DNA double-strand breaks and oxidative damage that they impart as they traverse through tissue and cells (Fig. 3 ) 5 . The highly energetic HZE particles produce complex DNA lesions with clustered double-stranded and single-stranded DNA breaks that are difficult to repair. This damage leads to distinct cellular behavior and intracellular signaling patterns that may be associated with altered disease outcomes compared to those for terrestrial sources of radiation 11 , 12 , 13 . As an example, persistently high levels of oxidative damage are observed in the intestine from mice examined 1 year after exposure to 56 Fe-ion radiation compared to gamma radiation and unirradiated controls 14 , 15 . The higher levels of residual oxidative damage in HZE ion-irradiated tissue is significant because of the association of oxidative stress and damage with the etiology of many human diseases, including cancer, cardiovascular and late neurodegenerative disorders. These types of alterations are believed to contribute to the higher biological effectiveness of HZE particles 10 , 11 .

a HZE ions produce dense ionization along the particle track as they traverse a tissue and impart distinct patterns of DNA damage compared to terrestrial radiation such as X-rays. γH2AX foci (green) illuminate distinct patterns of DNA double-strand breaks in nuclei of human fibroblast cells after exposure to b gamma-rays, with diffuse damage, and c HZE ions with single tracks. Image credits: NASA ( a ) and Cucinotta and Durante 97 ( b and c ).

Within the HRP, the Space Radiation Element (SRE) has developed a research strategy involving both vertical translation and horizontal integration, as well as products focused on mitigating space radiation risks across all phases of a mission. Vertical translation involves the integration of benchtop research with preclinical studies and clinical data. Horizontal integration involves a multidisciplinary approach that includes a range of expertize from physicians to clinicians, epidemiologists to computational modelers 16 . The suite of tools includes computational models of the space radiation environment, mission design tools, models for risk projection, and tools and technologies for accurate simulation of the space radiation environment for radiobiology investigations. Ongoing research is focused on radiation quality, age, sex, and healthy worker effects, medical countermeasures to reduce or eliminate space radiation health risks, understanding the complex nature of individual sensitivity, identification and validation of biomarkers (translational, surrogate, predictive, etc.) and integration of personalized risk assessment and mitigation approaches. Owing to the lack of human data for heavy ion exposure on Earth and the complications of obtaining reliable data for space radiation health effects from flight studies, SRE conducts research at the NASA Space Radiation Laboratory (NSRL) at Brookhaven National Laboratory. The NSRL is a ground-based analog for space radiation, where a beamline and associated experimental facilities are dedicated to the radiobiology and physics of a range of ions from proton and helium ions to the typical GCR ions such as carbon, silicon, titanium, oxygen, and iron 5 , 17 , 18 .

Radiation carcinogenesis

Central evidence for association between radiation exposure and the development of cancer and other non-cancer health effects comes from epidemiological studies of humans exposed to radiation 19 , 20 , 21 , 22 . Scaling factors are used by NASA and other space agencies in the analysis of cancer (and other risks) to account for differences between terrestrial radiation exposures and cosmic radiation exposures 23 . The risk of radiation carcinogenesis is considered a “red” risk for exploration-class missions due to both the high likelihood of occurrence, as well as the high potential for detrimental impact on both quality of life and disease-free survival post flight. The major cancers of concern are epithelial in origin (particularly cancers of the lung, breast, stomach, colon, and bladder), as well as leukemias ( https://humanresearchroadmap.nasa.gov/Evidence/reports/Cancer.pdf ). Owing to the lack of human epidemiology directly relevant to the types of radiation found in space, current research utilizes a translational approach that incorporates rodent and advanced human cell-based model systems exposed to space radiation simulants along with comparison of molecular pathways across these systems to the human.

A key question that impacts risk assessment and mitigation is how HZE tumors compare to either radiogenic tumors induced by ground-based radiation or spontaneous tumors. As a unifying concept, NASA studies have sought to examine how space radiation exposure modifies the key genetic and epigenetic modifications noted as the hallmarks of cancer (Fig. 4 ) 24 , 25 , 26 , 27 . This approach provides data for development of translational scaling factors (relative biological effectiveness values, quality factors, dose-rate effectiveness factor) to relate the biological effects of space radiation to effects from similar exposures to ground-based gamma- and X-rays and extrapolation of results to large human epidemiology cohorts. It also supports acquisition of mechanistic information required for successful identification and implementation of medical countermeasure strategies to lower this risk to an acceptable posture for space exploration, and it is relevant for the future development of biologically based dose-response models and integrated systems biology approaches 25 . Cancer is a long-term health risk and although it is rated as “red”, most research in this area is currently delayed, as HRP research priorities focus on in-mission risks.

Shown are the enabling characteristics and possible mechanisms of radiation damage that lead to these changes observed in all human tumors. (Adapted from Hanahanand Weinberg) 24 .

Risk of cardiovascular disease and other degenerative tissue effects from radiation exposure and secondary spaceflight stressors

A large number of degenerative tissue (non-cancer) adverse health outcomes are associated with terrestrial radiation exposure, including cardiovascular and cerebrovascular diseases, cataracts, digestive and endocrine disorders, immune system decrements, and respiratory dysfunction ( https://humanresearchroadmap.nasa.gov/Evidence/other/Degen.pdf ). For cardiovascular disease (CVD), a majority of the evidence comes from radiotherapy cohorts receiving high-dose mediastinal exposures that are associated with an increased risk for heart attack and stroke 28 . Recent evidence shows risk at lower doses (<0.5 Gy), with an estimated latency of 10 years or more 29 , 30 , 31 . For a Mars mission, preliminary estimates suggest that circulatory disease risk may increase the risk of exposure induced death by ~40% compared to cancer alone 32 . NASA is also concerned about in-flight risks to the cardiovascular system ( https://humanresearchroadmap.nasa.gov/Evidence/other/Arrhythmia.pdf ), when considering the combined effects of radiation exposure and other spaceflight hazards (Fig. 5 ) 33 . The Space Radiation Element is focused on accumulating data specific to the space radiation environment to characterize and quantify the magnitude of the degenerative disease risks. The current efforts are on establishing dose thresholds, understanding the impact of dose-rate and radiation quality effects, uncovering mechanisms and pathways of radiation-associated cardiovascular and cerebrovascular diseases, and subsequent risk modeling for astronauts. Uncovering the mechanistic underpinnings governing disease processes supports the development of specific diagnostic and therapeutic approaches, is a necessary step in the translation of insights from animal models to humans, and is the basis of personalized medicine approaches.

In blue are the known risk factors for CVD and in black are the other spaceflight stressors that may also contribute to disease development. Image used in this figure is courtesy of NASA.

This information will provide a means to reduce the uncertainty in current permissible exposure limits (PELs), quantify the impact to disease-free survival years, and determine if additional protection or mitigation strategies are required. The research portfolio includes evaluation of current clinical standard-of-care biomarkers for their relevance as surrogate endpoints for radiation-induced disease outcomes. Studies are also addressing the possible role of chronic inflammation and increased oxidative stress in the etiology of radiation-induced CVD, as well as identification of key events in disease pathways, like endothelial dysfunction, that will guide the most effective medical countermeasures. Products include validated space radiation PELs, models to quantify the risk of CVD for the astronaut cohort, and countermeasures and evidence to inform development of appropriate recommendations to clinical guidelines for diagnosis and mitigation of this risk.

Elucidating the role that radiation plays in degenerative disease risks is problematic because multiple factors, including lifestyle and genetic influences, are believed to play a major role in the etiology of these diseases. This confounds epidemiological analyses, making it difficult to detect significant differences from background disease without a large study population 34 . This issue is especially significant in astronaut cohorts because those studies have small sample sizes 35 . There is also a general lack of experimental data that specifically addresses the role of radiation at low, space-relevant doses 36 . Selection of experimental models needs to be carefully considered and planned to ensure that the cardiovascular disease mechanisms and study endpoints are clinically relevant and translatable to humans 37 , 38 . Combined approaches using data from wildtype and genetically modified animal models with accelerated disease development will likely be necessary to elucidate mechanisms and generate the body of knowledge required for development of accurate permissible exposure limits, risk assessment models, and to develop effective mitigation approaches.

Risk of acute (in-flight) and late CNS effects from space radiation exposure

The possibility of acute (in-flight) and late risks to the central nervous system (CNS) from GCR and SPEs are concerns for human exploration of space ( https://humanresearchroadmap.nasa.gov/Evidence/reports/CNS.pdf ). Acute CNS risks may include altered neurocognitive function, impaired motor function, and neurobehavioral changes, all of which may affect human health and performance during a mission. Late CNS risks may include neurological disorders such as Alzheimer’s disease, dementia, or accelerated aging. Detrimental CNS changes from radiation exposure are observed in humans treated with high doses of gamma-rays or proton beams and are supported by a large body of experimental evidence showing neurocognitive and behavioral effects in animal models exposed to lower doses of HZE ions. Rodent studies conducted with HZE ions at low, mission-relevant doses and time frames show a variety of structural and functional alterations to neurons and neural circuits with associated performance deficits 39 , 40 , 41 , 42 , 43 , 44 . Fig. 6 shows an example of changes in dendritic spine density following HZE ion radiation. However, the significance and relationship of these results to adverse outcomes in astronauts is unclear, as similar decrements are not seen with comparable doses of terrestrial radiation. Therefore, scaling to human epidemiology data, as is done for cancer and cardiovascular disease, is not possible. It is also important to note that to date, no radiation-associated clinically significant operational or long-term deficits have been identified in astronauts receiving similar doses via long-duration ISS missions. It is clear that further development of standardized translational models, research paradigms, and appropriate scaling approaches are required to determine significance in humans 45 , 46 . In addition, elucidation of how space radiation interacts with other mission hazards to impact neurocognitive and behavioral health and performance is critical to defining appropriate PELs and countermeasure strategies. The current research approach is a combined effort of SRE, the human factors and behavioral performance element, and the human health countermeasures element in support of an integrated CBS (CNS/behavioral medicine/sensorimotor) plan ( https://humanresearchroadmap.nasa.gov/Risks/risk.aspx?i=99 ). Further information on this risk area is presented below in the Behavioral Health and Performance section and can also be found at the Human Research Roadmap.

Representative digital images of 3D reconstructed dendritic segments (green) containing spines (red) in unirradiated (0 cGy) and irradiated (5 and 30 cGy) mice brains. Multiple comparisons show that total spine numbers (left bar chart) and spine density (right bar chart) are significantly reduced after exposure to 5 or 30 cGy of 16 O particles. Data are expressed as mean ± SEM. * P  < 0.05, ** P  < 0.01 versus control; ANOVA. Adapted from Parihar et al. 39 . Permission to reproduce open-source figure per the Creative Commons Attribution 4.0 International License. https://creativecommons.org/licenses/by/4.0 .

To summarize, the health risks posed by the omnipresent exposure to space radiation are significant and include the “red” risks of cancer, cardiovascular diseases, and cognitive and behavioral decrements. While research on the late health risk of cancer is currently delayed, research on the in-flight effects of radiation on the cardiovascular system and CNS within the context of the space exposome are considered the highest priority and are the focus of investigations. Major knowledge gaps include the effects of radiation quality, dose-rate, and translation from animal models to human systems and evaluation of the requirement for medical countermeasure approaches to reduce the risk.

Spaceflight-Associated Neuro-ocular Syndrome

The Risk of Spaceflight-Associated Neuro-ocular Syndrome (SANS), originally termed the Risk of Vision Impairment Intracranial Pressure (VIIP), was first discovered about 15 years ago. VIIP was the original name used because the syndrome most noticeably affects a crewmember’s eyes and vision, and its signs can appear like those of the terrestrial condition idiopathic intracranial hypertension (IIH; which is due to increased intracranial pressure). Over time, it was realized that the VIIP name required an update. Most notably, SANS is not associated with the classic symptoms of increased intracranial pressure in IIH (e.g., severe headaches, transient vision obscurations, double vision, pulsatile tinnitus), and it has never induced vision changes that meet the definition of vision impairment, as defined by the National Eye Institute. In 2017, VIIP was renamed to SANS, a term that welcomes additional pathogenesis theories and serves as a reminder that this syndrome could affect the CNS well beyond the retina and optic nerve.

SANS presents with an array of signs, as documented in the HRP Evidence Report ( https://humanresearchroadmap.nasa.gov/evidence/reports/SANS.pdf ). Primarily, these include edema (swelling) of the optic disc and retinal nerve fiber layer (RNFL), chorioretinal folds (wrinkles in the retina), globe flattening, and refractive error shifts 47 . Flight duration is thought to play a role in the pathogenesis of SANS, as nearly all cases have been diagnosed during or immediately after long-duration spaceflight (i.e., missions of 30 days duration or longer), although signs have been discovered as early as mission day 10 48 . Because of SANS, ocular data are nominally collected during ISS missions. For most ISS crewmembers, this testing includes optical coherence tomography (OCT), retinal imaging, visual acuity, a vision symptom questionnaire, Amsler grid, and ocular ultrasound (Fig. 7 ).

Image courtesy of NASA.

From a short-term perspective (e.g., a 6-month ISS deployment), SANS presents four main risks to crewmembers and their mission: optic disc edema (ODE), chorioretinal folds, shifts in refractive error, and globe flattening 49 . Approximately 69% of the US crewmembers on the ISS experience a > 20 µm increase in peripapillary retinal thickness in at least one eye, indicating the presence of ODE. With significant levels of ODE, a crewmember can experience an enlargement of his/her blind spots and a corresponding loss in visual function. To date, blind spots are uncommon and have not had an impact on mission performance.

If chorioretinal folds are severe enough and located near the fovea (the retina associated with central vision), a crewmember may experience visual distortions or reduced visual acuity that cannot be corrected with glasses or contact lenses, as noted in the SANS Evidence Report. Despite a prevalence of 15–20% in long-duration crewmembers, chorioretinal folds have not yet impacted astronauts’ visual performance during or after a mission. An on-orbit shift in refractive error is due to a shortening of the eye’s axial length (distance between the cornea and the fovea), and it occurs in about 16% of crewmembers during long-duration spaceflight. This risk is mitigated by providing deploying crewmembers with several pairs of “Space Anticipation Glasses” (or contact lenses) of varying power. On-orbit, the crewmember can then select the appropriate lenses to restore best-corrected visual acuity. Approximately 29% of long-duration crewmembers experience a posterior eyeball flattening, which is typically centered around the insertion of the optic nerve into the globe. Globe flattening can induce chorioretinal folds and shifts in refractive error, posing the respective risks described above.

From a longer-term perspective, SANS presents two main risks to crewmembers: ODE and chorioretinal folds. It is unknown if a multi-year spaceflight (e.g., a Mars mission) will be associated with a higher prevalence, duration, and/or severity of ODE compared to what has been experienced onboard the ISS. Since the retina and optic nerve are part of the CNS, if ODE is severe enough, the crewmember risks a permanent loss of optic nerve and RNFL tissue and thus, a permanent loss of visual function. It should be stressed that no SANS-related permanent loss of visual function has yet been discovered in any astronauts.

For choroidal folds, improvement generally occurs post-flight in affected crewmembers; however, significant folds can persist for 10 or more years after long-duration missions. Using MultiColor Imaging and autofluorescence capabilities of the latest OCT device, it was discovered recently that one crewmember’s longstanding (>5 years) post-flight choroidal folds have induced disruption to its overlying retinal pigment epithelium (RPE) 50 . The RPE is a monolayer of pigmented cells located between the vascular-rich choroid and the photoreceptor outer segments. This layer forms the posterior blood-brain barrier for the retina and is essential for maintaining the health of the posterior retina via the transport of nutrients and fluids, among other key functions. If the RPE is damaged, it could potentially lead to a degeneration of the local retina and progress to vision impairment.

Recent long-duration head-down tilt studies have shown potential for recreating SANS signs in terrestrial cohorts 51 . However, SANS is considered a pathology unique to spaceflight. In microgravity, fluid within the body is free to redistribute uniformly. This means that much of the fluid that normally pools in a person’s feet and legs due to gravity can transfer upward towards the head and cause a general congestion of the cerebral venous system. The central pathogenesis theories of SANS are based on these facts, but the actual cause(s) and pathophysiology of SANS are yet unknown 49 . The most publicized theory for SANS has been that cerebral spinal fluid outflow might be impeded, causing an overall increase in intracranial pressure (ICP) 47 , 52 . Other potential mechanisms (see Fig. 8 ) include cerebral venous congestion or altered folate-dependent 1-carbon metabolism via a cascade of mechanisms that may ultimately increase ICP or affect the response of the eye to fluid shifts 53 , 54 . Potential confounding variables for SANS pathogenesis include resistive exercise, high-sodium dietary intake, and high carbon dioxide levels.

Image created with BioRender.com.

Discovering patterns and trends in the SANS population has been difficult due to the relatively low number of crewmembers who have completed long-duration spaceflight. This is especially true for female astronauts. However, there is now enough evidence to state—emphatically—that SANS is not a male-only syndrome. OCT has been utilized onboard the ISS since late 2013, and it has revolutionized NASA’s ability to objectively detect and monitor SANS and build a high-resolution database of retinal and optic nerve head images. Through this technology, it has been recently discovered that that a majority of long-duration astronauts (including females) present with some level of ODE and engorgement of the choroidal vasculature 48 , 55 . The trends and patterns of these ocular anatomical changes may hold the key to deciphering the pathophysiology of SANS 48 , 55 .

Beginning in 2009 in response to SANS, all NASA crewmembers receive pre- and post-flight 3 Tesla magnetic resonance imaging of the brain and orbits. Based on these images, there is growing evidence that brain structural changes also occur during long-duration spaceflight. Most notably, a 10.7–14.6% ventricular enlargement (i.e., approximately a 2–3 ml increase) has been detected in astronauts and cosmonauts by multiple investigators 56 , 57 , 58 , 59 . On-orbit and post-flight cognitive testing have not revealed any systemic cognitive decrements associated with these anatomical changes. Moreover, additional research is required to determine if spaceflight-associated brain structural changes are related to ocular structural changes (i.e., SANS) or if the two are initiated by a common cause. Thus, until a relationship is established, SANS will be defined by ocular signs.

Future SANS medical operations, research, and surveillance will focus on: 1) determining the pathogenesis of the syndrome, 2) developing small-footprint diagnostic devices for expeditionary spaceflight, 3) establishing effective countermeasures, 4) monitoring for any long-term health consequences, and 5) discovering what factors make certain individuals more susceptible to developing the syndrome.

In summary, SANS is a top risk and priority to NASA and HRP. The primary SANS-related risk is ODE, due to the possibility of permanent vision impairment; however, choroidal folds also present a short- and long-term risk to astronaut vision. Shifts in refractive error are relatively common in long-duration missions, but crewmembers do not experience a loss of visual acuity if adequate correction is available. SANS affects female astronauts, not just males, although it is not yet known if SANS prevalence is equal between the sexes. There are no terrestrial pathologies identical to SANS, including IIH. Long-duration spaceflight is also associated with brain anatomical changes; however, it is not yet known whether these changes are related to SANS. Finally, the pathogenesis of SANS remains elusive; however, the main theories are related to increased intracranial pressure, ocular venous congestion, and individual anatomical/genetic variability.

Behavioral health and performance

The Risk of Adverse Cognitive and Behavioral Conditions and Psychiatric Disorders (BMed) focuses on characterizing and mitigating potential decrements in performance and psychological health resulting from multiple spaceflight hazards, including isolation and distance from earth. Spaceflight radiation is also recognized as contributing factor, particularly relative to a deep space planetary mission. The potential of additive or synergistic effects on the CNS resulting from simultaneous exposures to radiation, isolation and confinement, and prolonged weightlessness, is also of emerging concern ( https://humanresearchroadmap.nasa.gov/Risks/risk.aspx?i=99 ).

The official risk statement in the BMed Evidence Report notes, “ given the extended duration of future missions and the isolated, confined and extreme environments, there is a possibility that (a) adverse cognitive or behavioral conditions will occur affecting crew health and performance; and (b) mental disorders could develop should adverse behavioral conditions be undetected and unmitigated ” ( https://humanresearchroadmap.nasa.gov/Evidence/reports/BMED.pdf ). Primary outcomes for this risk include decrements in cognitive function, operational performance, and psychological and behavioral states, with the development of psychiatric disorders representing the least likely but one of the most consequential outcomes crew could experience in extended spaceflight. BMed is considered a “red” risk for planetary missions, given the long-duration of isolation, extended confinement, and exposure to additional stressors, including increased radiation exposure. The Human Factors and Behavioral Performance Element within HRP utilizes a research strategy that incorporates flight studies on astronauts, research in astronaut-like individuals and teams in ground analogs, and works with the Space Radiation Element to use animal models supporting research on combined spaceflight stressors.

While astronauts successfully accomplish their mission objectives and report very positive experiences living and working in space, some anecdotal accounts from current and past astronauts suggest that psychological adaptation in the long-duration spaceflight environment can be challenging. However, clinically significant operational decrements have not been documented to date, as noted in the BMed Evidence Report. Discrete events that have been documented include accounts of adverse responses to workload by Shuttle payload specialists, and descriptions of ‘hostile’ and ‘irritable’ crew in the 84-day Skylab 4 mission, as well as symptoms of depression reported on Mir by 2 of the 7 NASA astronauts.

Currently, potential stressors affiliated with missions to the ISS include extended periods of high workload and/or schedule shifting, physiological adaptation including fluid shifts caused by weightlessness and possibly, exposure to other environmental factors such as elevated carbon dioxide (see the BMed Evidence Report). While still physically isolated from home, the presence of the ISS in LEO facilitates a robust ground behavioral health and performance support team who offer services such as bi-weekly private psychological conferences and regular delivery of novel goods and surprises from home in crew care packages. Coupled with the relatively ample volume in the ISS, near-constant real-time communication with Earth, new crewmembers rotating periodically throughout missions, and relatively low levels of radiation exposure, —it is expected that behavioral challenges experienced today do not represent those that future crews will face during exploration missions.

Nevertheless, the few completed behavioral studies on the ISS suggest that subjective perceptions of stress increase over time for some crewmembers, as shown by an in-flight study collecting subjective ratings of well-being and objective measures of fatigue 60 . Notably, it was found that astronaut ratings of sleep quality and sleep duration (also measured through visual analog scales) were found to be inversely related to ratings of stress. Another in-flight investigation seeking to characterize behavioral responses to spaceflight is the “Journals” study by Stuster 61 . This investigation provided a systematic approach to examining a rich set of qualitative data by evaluating astronaut journal entries for temporal patterns of across different behavioral states over the course of a mission (Fig. 9 ). Based on findings, some categories suggest temporal patterns while other categories of outcomes do not suggest a pattern relative to time, which may be due to no temporal relationship between outcomes and time, and/or various contextual factors within missions that negate the presence of such a relationship (e.g., visiting crew). An overall assessment by Stuster of negative comments relative to positive comments over time suggests evidence of a third quarter phenomenon in Adjustment alone, a category which reflects individual morale 61 .

Example bar graph showing distribution of journal entries related to general adjustment to the spaceflight enivronment during each quarter of an ISS mission 61 .

Other in-flight investigations support and expand upon contributors to increased stress on-orbit, including studies documenting reductions in sleep duration 62 , 63 and evaluation of crew responses to habitability and human factors during spaceflight 64 . While no studies have assessed potentially relevant mechanisms for behavioral or other reported symptoms, a recently completed investigation suggests neurostructural changes may be occurring in the spaceflight environment 56 . Magnetic resonance imaging scans were conducted on astronauts pre- and post-flight on both long-duration missions to the ISS or short-duration Shuttle missions. Assessments from a subgroup of participants ( n  = 12) showed a slight upward shift of the brain after all long-duration flights but not after short-duration flights ( n  = 6), and they also showed narrowing of cerebral spinal fluid spaces at the vertex after all long-duration flights ( n  = 6) and in 1 of 6 crew after short-duration flights. A retrospective analysis of free water volume in the frontal, temporal, and occipital lobes before versus after spaceflight suggests alterations in free water distribution 65 . Whether there is a functionally relevant outcome as a result of such changes remains to be determined. Hence, while certain aspects of the spaceflight environment have been shown to increase some behavioral responses (e.g., reduced sleep owing to workload), the direct role of spaceflight-specific factors (such as fluid shifts and weightlessness) on behavioral outcomes or functional performance has not yet been established.

Future long-duration missions will pose threats to behavioral health and performance, such as extreme confinement in a small volume and communication delays, that are distinct from what is currently experienced on missions to the ISS. Analog research is concurrently underway to help further characterize the likelihood and consequence of an adverse behavioral outcome, and the effectiveness of potential countermeasures. Ground analogs, such as the Human Exploration Research Analog (HERA) at NASA Johnson Space Center, provide a test bed where controlled studies of small teams for periods up to 45 days, can be implemented (Fig. 10 ). HERA can be used to provide scenarios and environments analogous to space (e.g., isolation and confinement, communication delays, space food, and daily tasks and schedules) to investigate their effects on behavioral health, human factors, exploration medical capabilities, and communication and autonomy. Research in locations such as Antarctica also offer a unique opportunity to conduct research in less controlled but higher fidelity conditions. In general, these studies show an increased risk in deleterious effects such as decreased mood and increased stress, and in some instances, psychiatric outcomes (see the BMed Evidence Report).

HERA is used to simulate environments and mission scenarios analogous to spaceflight to investigate a variety of behavioral and human factors issues. Images courtesy of NASA.

In 2014, Basner and colleagues 62 completed an assessment of crew health and performance in a 520-day mission at an isolation chamber in Moscow at the Institute for Biomedical Problems (IBMP). During this simulated mission to Mars, the crew of six completed behavioral questionnaires and additional testing weekly. One of six (20%) crew reported depressive symptoms based on the Beck Depression Inventory in 93% of mission weeks, which reached mild-to-moderate levels in >10% of mission weeks. Additional indications of changes in mood were observed via the Profile of Mood States. Additionally, two crewmembers who had the highest ratings of stress and physical exhaustion accounted for 85% of the perceived conflicts, and other crew demonstrated dysregulation in their circadian entrainment and sleep difficulties. Two of the six crewmembers reported no adverse behavioral symptoms during the missions 62 . Building on this work, the NASA HRP and the IBMP have ongoing studies in the SIRIUS project, a series of long-duration ground-analog missions for understanding the effects of isolation and confinement on human health and performance ( http://www.nasa.gov/analogs/nek/about ).

Finally, more recent research in the HERA analog at Johnson Space Center is underway to assess not only individual, psychiatric outcomes but also changes in team dynamics and team performance over time (Fig. 10 ). A recent publication reported that conceptual team performance (e.g., creativity) seems to decrease over time, while performance requiring cognitive function and coordinated action improved 66 . While results from additional team studies in HERA are currently under review, the Teams Risk Evidence Report ( https://humanresearchroadmap.nasa.gov/Evidence/reports/Team.pdf ) provides a thorough overview of the evidence surrounding team level outcomes.

In summary, evidence from spaceflight and spaceflight analogs suggests that the BMed Risk poses a high likelihood and high consequence risk for exploration. Given the possible synergistic effects of prolonged isolation and confinement, radiation exposure, and prolonged weightlessness, mitigating such enhanced risks faced by future crews are of highest priority to the NASA HRP.

Inadequate food and nutrition

Historically, nutrition has driven the success—and often the failure—of terrestrial exploration missions. For space explorers, nutrition provides indispensable sustenance, provides potential countermeasures to some of the negative effects of space travel on human physiology, and also presents a multifaceted risk to the health and safety of astronauts ( https://humanresearchroadmap.nasa.gov/Evidence/other/Nutrition-20150105.pdf ).

At a minimum, the need to prevent nutrient deficiencies is absolute. This was proven on voyages during the Age of Sail, where scurvy—caused by vitamin C deficiency— killed more sailors than all other causes of death. On a closed (or even semi-closed) food system, the risk of nutrient deficiency is increased. On ISS missions, arriving vehicles typically bring some fresh fruits and/or vegetables to the crew. While limited in volume and shelf-life, these likely provide a valuable source of nutrients and phytochemicals every month or two. One underlying concern is that availability of these foods may be mitigating nutrition issues of the nominal food system, and without this external source of nutrients on exploration-class missions, those issues will be more likely to surface.

As a cross-cutting science, nutrition interfaces with many, if not all, physiological systems, along with many of the elements associated with space exploration, including the spacecraft environment (Fig. 11 ). Thus, beyond the basics of preventing deficiency of specific nutrients, at best, nutrition can serve as a countermeasure to mitigate risks to other systems. Conversely, at worst, diet and nutrition can exacerbate risks to other physiological systems and crew health. For example, many of the diseases of concern as related to space exploration are nutritionally modifiable on Earth, including cancer, cardiovascular disease, osteoporosis, sarcopenia, and cataracts.

Many of the physiological systems and performance characteristics that are touched by nutrition are shown in white text, while the unique elements of spacecraft and space exploration are shown in red text.

The NASA Nutritional Biochemistry Laboratory approaches astronaut health with both operational and research efforts. These efforts aim to keep current crews healthy while working to understand and define optimal nutrition for future crews, to maximize performance and overall health while minimizing damaging effects of spaceflight exposure.

A Clinical Nutrition Assessment is conducted for ISS astronauts dating back to ISS Expedition 1 67 , 68 , which includes pre- and post-flight biochemical analyses conducted on blood and urine samples, along with in-flight monitoring of dietary intake and body mass. The biochemical assessments include a wide swath of nutritional indicators such as vitamins, minerals, proteins, hematology, bone markers, antioxidant markers, general chemistry, and renal stone risk. These data are reported to the flight surgeon soon after collection for use in the clinical care of the astronaut. Initial findings from the Clinical Nutritional Assessment protocol identified evidence of vitamin D deficiency, altered folate status, loss of body mass, increased kidney stone risk, and more 69 , 70 . These initial findings led to several research efforts (described below), including the Nutritional Status Assessment flight project, and research in the Antarctic on vitamin D supplementation 71 , 72 .

In addition to in-flight dietary intake monitoring, research to understand the impact and involvement of nutrition with other spaceflight risks such as bone loss and visual impairments, and interaction with exercise and spacecraft environment, are performed by the Nutrition Team using both flight and ground-analog research efforts. Tracking body mass is a very basic but nonetheless indispensable element of crew health 73 . Loss of body mass during spaceflight and in ground analogs of spaceflight is associated with exacerbated bone and muscle loss, cardiovascular degradation, increased oxidative stress, and more 70 , 73 , 74 . Historically, it was often assumed that some degree of body mass loss was to be expected, and that this was a typical part of adaptation to microgravity. Fluid loss is often assumed to be a key factor, but research has documented this to be a relatively small contributor, of approximately 1% of weight loss being fluid 74 , 75 . While on average, crewmembers on ISS missions have lost body mass over the course of flight, not all do 74 . Importantly, those that did not lose body mass managed to maintain bone mineral density (discussed below) 76 .

Bone loss has long been a concern for space travelers 77 , 78 , 79 , 80 , 81 . It has been shown that an increase in bone resorption was the likely culprit and that bone formation was largely unchanged in microgravity or ground analogs 77 , 78 , 79 . The search for a means to counteract this bone loss, and this hyper-resorptive state specifically, has been extensive. The potential for nutrition to mitigate this bone loss was identified early but studies of increasing intakes of calcium, or fluoride, or phosphate, were unsuccessful 74 , 77 , 79 , 82 , 83 , 84 .

Exercise provides a multisystem countermeasure, and heavy resistive exercise specifically provides for loading of bone to help mitigate weightlessness-induced bone loss.

In evaluating the data from astronauts using the first “interim” resistive exercise device (iRED) on ISS compared to a later, “advanced” resistive exercise device (ARED) (Fig. 12 ), it was quickly realized that exercise was not the only difference in these two groups of astronauts. ARED crews had better dietary intakes (as evidenced by maintenance of body mass) and better vitamin D status as a result of increased dose of supplementation and awareness of the importance of these supplements starting in 2006 76 . Bone mineral density was protected in these astronauts 76 , proving that diet and exercise are a powerful countermeasure combination. Follow-on evaluations showed similar results and further that the effects of microgravity exposure on bone health in men and women were similar 85 despite differences in pre-flight bone mass.

Sunita Williams exercising on the iRED ( a ), and on a later mission, Sandy Magnus exercises on the much improved ARED device ( b ). Images courtesy of NASA.

From a purely nutrition perspective, ISS and associated ground analog research has identified several specific dietary effects on bone health. Fish intake, likely secondary to omega-3 fatty acid intake, is beneficial for bone health 86 . Conversely, high intakes of dietary protein 87 , 88 , iron 89 and sodium 90 are detrimental to bone. The mechanism of the effect of protein and sodium on bone are likely similar, with both contributing to the acidogenic potential of the diet, leading to bone dissolution 91 , 92 . This effect was recently documented in a diet and bone health study on ISS, where the acidogenic potential of the diet correlated with post-flight bone losses 93 . The data from terrestrial research, along with the more limited spaceflight research, clearly identifies nutrition as important in maintenance of bone health and in the mitigation of bone loss. While initial evaluations of dietary quality and health are underway at NASA, much work remains to document the full potential of nutrition to mitigate bone loss and other disease processes in space travelers.

Another health risk with nutrition underpinnings is SANS, which was described earlier. When this issue first arose, an examination of data from the aforementioned ISS Nutrition project was conducted. This analysis revealed that affected crewmembers had significantly higher circulating concentrations of homocysteine and other one-carbon pathway metabolites when compared to non-cases and that these differences existed before flight 53 . Many potential confounding factors were ruled out, including: sex, kidney function, vitamin status, and coffee consumption, among others. After identifying differences in one-carbon biochemistry, the next logical step was to examine the genetics—single-nucleotide polymorphisms (SNPs)—involved in this pathway as possible causes of the biochemical differences, but perhaps also their association with the astronaut ocular pathologies. An initial study examined a small set of SNPs—five to be exact—and when the data were statistically modeled, it was found that B-vitamin status and genetics were significant predictors of many of the observed ophthalmic outcomes in astronauts 94 . Interestingly, the same SNPs identified in astronauts to be associated with ophthalmic changes after flight were associated with greater changes in total retina thickness after a strict head-down tilt with 0.5% CO 2 bed rest study 54 . A follow-on study is underway to evaluate a much broader look at one-carbon pathway and associated SNPs, potentially to help better characterize this relationship.

A hypothesis was developed to plausibly link these genetics and biochemical differences with these ophthalmic outcomes, as there is no existing literature regarding such a relationship. This multi-hit hypothesis posits that one-carbon pathway genetics is an indispensable factor, and that the combination with one or more other factors (e.g., fluid shifts, carbon dioxide, radiation, endocrine effects) lead to these pathologies. This has been detailed in a hypothesis paper 95 and in a recent review 96 . In brief, the hypothesis is that genetics and B-vitamin status contribute to endothelial dysfunction, as folate (and other B-vitamins) play critical roles in nitric oxide synthesis and endothelial function. A disruption in nitric oxide synthesis can also lead to an activation of matrix metalloproteinase activation, increasing the turnover and breakdown of structural elements of the sclera, altering retinal elasticity and increasing susceptibility to fluid shifts to induce ophthalmic pathologies like optic disc edema and choroidal folds 54 . This is likely exacerbated cerebrally due to limitations of transport of B-vitamins across the blood-brain barrier. In or around the orbit, endothelial dysfunction, oxidative stress, and potentially individual anatomical differences contribute to leaky blood vessels, and subsequent edema. This can impinge on cerebrospinal fluid drainage from the head, increasing those fluid pressures, which can impinge upon the optic nerve and eye itself, yielding the aforementioned ophthalmic pathologies. These are hypotheses proposed as starting points for further research. Given the irrefutable biochemical and genetic findings to date, this research should be a high priority to either prove or dismiss these as contributing factors in SANS to mitigate that “red” risk.

Another intriguing element from this research is that there is a clinical population that has many of the same characteristics of affected astronauts (or characteristics that they are purported to have), and that is women with polycystic ovary syndrome (PCOS) 95 , 96 . Women with PCOS have higher circulating homocysteine concentrations (as do their siblings and fathers), and also have cardiovascular pathology, including endothelial dysfunction. Studies are underway between NASA and physicians at the Mayo Clinic in Minnesota to evaluate this further. If validated, women with PCOS might represent an analog population for astronaut ocular issues, and research to counteract this could benefit both populations 87 . This research may lead to the identification of one-carbon pathway genetic influences on cardiovascular function in astronauts (and women with PCOS). This information will not be used in any sort of selection process, for several reasons, but as a means to identify countermeasures. Given the effects are intertwined with vitamin status, and likely represent higher individual vitamin requirements, targeted B-vitamin supplementation is the most obvious, and lowest risk, countermeasure that needs to be tested. There is tremendous potential for nutrition research to solve one of the key risks to human health on space exploration missions.

To summarize, nutrition is a cross-cutting field that has influence on virtually every system in the body. While we need to understand nutrition to avoid frank deficiencies, we need to understand how optimizing nutrition might also help mitigate other spaceflight-induced human health risks. Examples of this are myriad, ranging from effects of dietary intake on cognition, performance, and morale, inadequate intake on cardiovascular performance, excess nutrient intakes, leading to excess storage and increased oxidative stress, nutrient insufficiencies, leading to bone loss, insufficient fruit and vegetable intake on bone health, radiation protection, and cardiovascular health, to name a just few. Throughout history, nutrition has served, or failed, many a journey to explore. We need to dare to use and expand our twenty-first century knowledge of nutrition, uniting medical and scientific teams, to enable future exploration beyond LEO, while simultaneously benefitting humanity.

The NASA Human Research Program is focused on developing the tools and technologies needed to control the high priority “red” risks to an acceptable level—a great challenge as the risks do not exist in the vacuum of space as standalone entities. They are inherently interconnected and represent the intersection points where the five hazards of spaceflight overlap, and nature meets nurture. This is the space exposome: the total sum of spaceflight and lifetime exposures and how they relate to individual genetics and determine the whole-body outcome. The space exposome will be an important unifying concept as the hazards and risks of spaceflight are evaluated in a systems biology framework to fully uncover the emergent effects of the extraterrestrial experience on the human body. This framework will provide a path forward for mitigating detrimental health and performance outcomes that may stand in the way of successful, long-duration space travel, especially as NASA plans for a return to the Moon, to stay, and beyond to Mars.

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Acknowledgements

This review was supported in part by a grant to Dr. Patel from the Translational Research Institute for Space Health (TRISH) from the Baylor College of Medicine (The Red Risk School). It was also supported by funding through NASA Human Health and Performance Contract #NNJ15HK11B (Z.S.P., S.R.Z., J.L.H.) and NASA directly (T.J.B., W.J.T., A.M.W., S.M.S., J.L.H.).

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Drs. Z.S.P. and J.L.H. compiled and edited the overall manuscript and drafted the radiation risk overviews. Drs. T.J.B. and W.J.T. drafted the SANS risk overview, Dr. A.M.W. drafted the behavioral health risks overview, and Drs. S.R.Z. and S.M.S. drafted the nutrition risk overview. Data are available upon request.

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Patel, Z.S., Brunstetter, T.J., Tarver, W.J. et al. Red risks for a journey to the red planet: The highest priority human health risks for a mission to Mars. npj Microgravity 6 , 33 (2020). https://doi.org/10.1038/s41526-020-00124-6

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DOI : https://doi.org/10.1038/s41526-020-00124-6

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The danger of going to mars.

Many spacecraft have died trying to get to Mars. The current record for Mars missions is 18 successes, and 25 failures. The InSight mission hopes to improve the odds.

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[:05] Narrator: Come with me on a mission to outer space. Our destination is the planet Mars.

We have to travel over 300 million miles. That may seem like a long trip, but we’ll be speeding through space at 13,000 miles an hour.

(intro music montage)

[:049] Welcome to “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory in Pasadena California. I’m Leslie Mullen. I’m a science journalist, and I arrived at the Jet Propulsion Laboratory – also known as JPL — 2 years ago.

[1:04] The Lab is a jumble of buildings at the foot of the San Gabriel Mountains, and just down the road from Hollywood. But at JPL, they’re focused on stars of a different sort. JPL is like a little town, but a town full of scientists and engineers who study the mysteries of the universe and build robots to send to outer space. In my short time here, I’ve discovered there are a million stories to tell.

[1:28] The concept of this podcast is to take a close look at a single space mission, and examine it from different angles. To share the science, yes, but also the struggle and satisfaction in getting a mission off the ground. For this first season, the focus will be on the InSight mission to Mars.

[1:46] (rocket launch of InSight)

[2:13] A rocket carrying the InSight mission launched from Vandenberg Air Force Base in California earlier this year, on May 5th. It is now on its way to Mars, due to arrive at the end of November. After it lands, the robotic suite of instruments will peek below the planet’s surface, investigating the different layers that make up Mars.

[2:34] You may already know that Mars is the fourth planet from the Sun. Earth is the third planet from the Sun, so Mars is a little farther out than we are. On a clear night when you can see the stars, you may have noticed one that looked a little reddish. Sunlight bouncing off the Martian red rocks makes it look like just another star, but Mars is world: a harsh, desert, alien world.

[3:01] Over the years, NASA has sent many spacecraft to Mars. But it’s still a mysterious place, in many ways, one that we’ve only just begun to explore.

[3:10] But Mars does not welcome visitors with open arms. Many spacecraft have died trying to get there. So far there have been 43 robotic missions sent to Mars – many from the US, but Europe and Russia and even India and China have tried to go there. The current record for Mars missions is 18 successes, and 25 failures.

[3:34] Granted, some of those failures can’t be blamed on Mars – some missions, especially early on, came to an abrupt end due to rockets blowing up on the launch pad or not getting very far past Earth. But still, less than half of the missions ever sent to Mars have made it. The InSight mission hopes to improve the odds.

[3:57] Soon after InSight launched from Earth, on Mars, one of the biggest dust storms in history swirled into life.

[4:04] Bruce Banerdt: Dust storms tend to pop up on Mars on a pretty regular basis. In fact, there’s a dust storm season on Mars. Some seasons there’s small dust storms, and some seasons there are huge dust storms. And we actually just got hit with one of the big ones.

[4:17] Narrator: That’s Bruce Banerdt, the scientist leading the InSight mission. He and the InSight team were first alerted to the storm from the Mars Reconnaissance Orbiter, a satellite circling Mars. A rover on the ground, named Opportunity, sent photos back to Earth of the Martian sky growing dusty and dark, until the Sun disappeared in the sky.

[4:38] The storm grew until it covered most of Mars. We don’t have weather like this on Earth. Our storms are located in one place, and then drift to another area or disperse entirely. We’ve never, for instance, had a hurricane in the Atlantic Ocean grow and grow until it becomes a single storm enveloping most of the planet.

[4:59] But this is not the first time we’ve seen such a large storm on Mars. When NASA’s Mariner 9 orbiter reached Mars in 1971, it saw a global dust storm that was so immense, only the tops of the tallest volcanoes could be seen peeking above the haze. The Mars Global Surveyor satellite witnessed a similar massive storm in 2001.

[5:20] Those orbiters saw the storms from high above. The Viking 1 lander, in 1977, was the first time we got to see such a big dust storm from the ground. Because Viking was actually in the storm, it also could gauge the force of the winds, which topped 60 miles per hour.

[5:38] Some of you may be thinking of the beginning of the movie, “The Martian,” which saw Matt Damon’s character knocked down by a raging dust storm on Mars.

[5:46] Movie clip :”The Martian” storm:

Lewis: 1200 kilometers in diameter, bearing 24.41 degrees.

Johanssen: That’s tracking right towards us.

Lewis: Based on current escalation, estimated force of… 8600 Newtons?

Watney: What’s the abort force?

Beck: 7500.

Martinez: Anything more than that, and the MAV could tip.

Lewis: Begin abort procedure.

Watney: Let’s wait it out.

Lewis: Prep emergency departure. We’re scrubbed, that’s an order!

Lewis: Visibility’s almost zero. Anyone gets lost, home in to my suit’s telemetry. You ready?

Watney: Ready!

[Door opens to massive dust storm]

Watney: Commander, are you ok?

Lewis: I’m ok!

[6:27] Narrator: It makes for good drama, but the air is so thin on Mars — only 1 percent as dense as air on Earth — that even the strongest winds wouldn’t knock you down. In the movie, the roaring winds that rocked their spacecraft and forced them to abort the mission would actually feel like a gentle breeze.

( sound effect: waves on a beach)

[6:54] To understand how such strong winds wouldn’t feel strong, imagine you’re at the beach. A wave comes up and knocks you down. The wave is moving slowly compared to the air, but because the water is so much more dense than the air, it doesn’t take much to lift you off your feet. The opposite is what happens with the thin air of Mars. Although the winds there don’t pack a punch, they are able to pick up fine dust particles and loft them high into the air.

[7:20] Bruce Banerdt : Mars dust is extremely fine, and it’s very easy to lift up in the atmosphere. And without any moisture to have the dust particles clump together, it takes a long time for it to settle out. So these dust storms tend to kick up really fast and then die off really slowly and even after the wind’s all gone, you still have a lot of dust up there which is absorbing the sun and making it kind of dark down on the surface.

[7:40] Narrator: InSight has to enter the atmosphere of Mars, descend down through it, and land on the planet’s surface. This is known as EDL – entry, descent, and landing. On Mars, the atmosphere is thick enough to burn you up on entry, but thin enough to make landing with a parachute extremely tricky. This is why Mars landings often include rockets firing toward the ground – so-called retro-rockets — that help slow down the descent. The InSight mission is prepared to go through Entry-Descent-and-Landing for a range of conditions, including a dust storm.

[8:12] Bruce Banerdt : Those little dust particles, when you’re coming in at 15,000 miles per hour, they do act as a little bit of a sand blaster. And when we designed our spacecraft, we knew that we were coming in during dust season, so we actually added about a half an inch of extra material on the heat shield, the ablative material that actually burns off as you go into the atmosphere. The calculations and the experiments that we did on the material indicated that that was more than enough to accommodate the extra erosion that we would experience if there was dust in the atmosphere. So, even if there is still dust in the atmosphere when we land, our entry system should be perfectly happy with that kind of environment, and the parachute won’t even notice it.

[8:50] Narrator: It can take months for dust from such a big storm to slowly settle out of the air. If there’s a lot of dust in the air when InSight lands, the biggest problem for the lander will be power generation. InSight runs on solar power. Falling dust not only blocks the sunlight, it also could coat the solar panels, causing InSight to run out of energy.

[9:13] Opportunity rover, who got caught in the dust storm, is also solar powered. It went into hibernation soon after the dust storm appeared, in order to save power.

[9:22] The power does more than run the rover; it keeps it warm on frigid Martian nights. Temperatures in Opportunity’s neighborhood – the Martian equator — can dip down to negative one hundred and thirty degrees Fahrenheit, or negative 90 Celsius. Without a heater, the rover could freeze to death. It’s similar to running a car in the winter so the cold doesn’t sap the battery charge. The Martian cold may have been what ultimately killed Opportunity’s twin rover, Spirit, back in 2010.

[9:51] Opportunity is currently the longest-running mission on the surface of Mars. It’s been in operation for over 14 years, since 2004, and it survived a large dust storm in 2007. That storm led to two weeks of minimal operations, including several days with no contact from the rover, in order to save power.

[10:11] Opportunity has been in hibernation now since June 10th. Dust storms do heat the air up on Mars, so it’s possible Opportunity wasn’t fatally damaged by the cold. In September, enough dust had settled out of the atmosphere that sunlight could penetrate through the haze and recharge the solar panels.

[10:29] While waiting for the rover to wake up, to boost the team’s morale, engineers have started each day playing a song in Mission Control.

(music: Wake Me Up, Before you Go-Go )

[10:41] Wake Me Up Before you Go-Go, by Wham, is just one of many songs dedicated to the sleeping rover.

[10:52] Over the weeks their themed playlist has included “I Will Survive” by Gloria Gaynor, “I Won’t Back Down” by Tom Petty, “Here Comes the Sun” by the Beatles, and “Dust in the Wind” by Kansas.

(music: Dust in the Wind)

[11:07] Opportunity, meanwhile, remains silent and still. Mission engineers will keep listening for the rover to phone home over the next few months.

[11:18] What InSight will have to struggle with when it arrives on Mars is still to be determined.

[11:21] Bruce Banerdt : We have a lot more solar power generation capability than Opportunity, but I think that our design would be at best marginal against the darkest part of the dust storm. Once we get to Mars, if we have a dust storm like that again, it would be pretty nerve-wracking for us.

( Dust in the Wind lyrics: “Nothing lasts forever but the Earth and sky…” )

[11:43] Narrator: InSight science lead Bruce Banerdt has had his heart broken by Mars before. Years ago, he worked on the Mars Observer mission.

[11:51] Bruce Banerdt : My early career I sort of was kind of a recluse. I’d go in my office, and I’d lock the door, and just work on my computer and hope nobody ever bothered me. But then somebody came and said, “Well, we need someone to work on this space mission.” Or, “We need a scientist to help integrate this altimeter that is going to go to Mars on Mars Observer.”

[12:08] Narrator: An altimeter is used to create elevation maps that show the heights of mountains and the depths of canyons.

[12:14] Bruce Banerdt : This was going to be the first detailed elevation map of any planet outside the Earth, and it’s something that’s really critical, if you want to look at what forces there are on a planetary crust. And by the time we launched, I thought, “Well, finally we’re going to Mars, and all our problems are behind us.” And then we got close to Mars. We did our last trajectory correction maneuver before going into Mars orbit, and we never heard from it again.

[12:42] Back in ’93 I guess, which is when this was all happening, we didn’t have the fancy displays and the animations. So when we had to turn this spacecraft to do this orbit trajectory change maneuver, we slewed away from the Earth point on the radio, so we lost contact. It was supposed to fire its rockets for 40 seconds or something like that, and then turn her back around and then we reacquire the signal. We had an old CRT monitor hooked up to the DSN data feed with the signal strength just as a line across, sort of like one of those old oscilloscope displays. It turned away, and so the line goes flat at zero power. At 20 minutes or 40 minutes later, it’s supposed to kind of blip back up again and show our signal line. One of the young engineers on the project was keeping track of the time, had his pencil there on the screen, and says, “Right about here’s where we ought to get it.” We were watching, and it kept on going flat. I said, “Well, maybe we’re having a little bit of trouble acquiring.” And so, you’re just waiting for something to happen, and it’s not happening, and it’s not happening. At first, there’s lots of explanations why that not might not be true. And then there’s fewer explanations that are still consistent with it being that long. And then maybe there’s one or two things that might have gone wrong that are still not fatal, but it’s a slow motion train wreck, that you’re getting more and more of a sinking feeling and trying to stay optimistic, but there’s always a voice in the back of your mind going, “Uh oh, this isn’t good.”

[14:07] We waited to acquire the signal, and it didn’t show up. That flat line never did leave zero. That was a really, really horrible feeling to have worked on something for five or six years, and then suddenly it’s all gone. Later on, they found a design flaw in the propulsion system, which likely allowed the fuel to mix with the oxidizer in the wrong place, and probably blow a hole in the side of the spacecraft.

[14:32] When Mars Observer was lost, we took the same payload, or part of the same payload, and started a new mission with kind of the same designs, but a little bit different spacecraft called Mars Global Surveyor, which launched about four years later. It kind of just merged from Mars Observer into Mars Global Surveyor. I ended up actually working on that project for about 20 years, and it was a great project. I mean, the MOLA maps of Mars — if you’ve ever seen the map that’s kind of blue and orange, that’s our MOLA elevation map that I played a small part in helping to create. These were the first really high-resolution images that we had of Mars. You started revealing the actual geology of Mars at a level where you can visualize as a human being, and not as somebody flying in an airplane two miles up or something. That’s been one of the foundational datasets for Mars for understanding all kinds of things about that planet. That was an amazing project. That was so much fun.

[15:27] Narrator: As Bruce notes, although Mars Observer failed, the design was re-used for the successful Mars Global Surveyor. Spacecraft are often made this way. InSight, for instance, is essentially using the same architecture as the Phoenix lander that made discoveries near the Martian North Pole over ten years ago. The Phoenix lander, meanwhile, rose from the ashes of the Mars Polar Lander that crashed in 1999.

[15:58] Rob Grover oversees the Entry-Descent-and-Landing procedures InSight needs to go through in order to land on Mars.

[16:07] Rob Grover: We can’t really do full testing on Earth because the gravity is different, the atmosphere is different. We use simulation for making sure that we’re going to be successful when we land on Mars. We use a method called a Monte Carlo Simulation, which, it’s named for a game of chance, which is a little bit of what EDL is.

[16:26] So when we run the Monte Carlo simulation, we actually land eight thousand times and it provides us statistics on how we’ll perform. We randomize all the parameters that are used in modeling the landing, like the mass of the lander and how well the rocket engines are working. For each type of atmosphere we think we’re going to land in, we run a Monte Carlo. Each flight path angle or angle we’re going to hit the atmosphere we also run a Monte Carlo too. We have actually close to probably a thousand parameters. That allows us to practice the landing under multiple conditions. We do many many many Monte Carlos. For a single landing, we’ve probably run millions of times at this point over the five or so years we’ve been doing this.

[17:11] There’s a little bit of rolling the dice on EDL but we try to account for everything we possibly can. It’s a risky part of the mission, probably one of the riskiest six and a half minutes of the mission. As EDL engineers, our job is really to try and think of every possible thing that can go wrong, everything that Mars can throw at us and try and model that and make sure that the system will be able to handle that on landing day.

[17:32] Insight is the first mission to land during dust storm season. That makes it particularly challenging because the atmosphere affects the landing quite a bit. With the dust storm season, we could be landing in the middle of a global dust storm or the atmosphere could be just a regular clear atmosphere or anywhere in between. That makes a lot more variation that we have to account for when we’re designing and executing the landing. So it makes it more challenging for Insight than past missions in that respect.

[18:01] Narrator: As InSight approaches Mars this November, we’ll all be on the edge of our seats, watching for that signal, waiting to see if it beats the odds, and survives.

[18:11] But InSight almost died before it even left Earth.

[18:14] Bruce Banerdt : We had a lot of problems with InSight, and then we had to stand down from our launch in December of 2015, which was incredibly disappointing. It was really a dark time. It was almost Christmas, and then we had to give up suddenly on this mission.

[18:30] Narrator: More about that, next time.

(out music)

[18:34] If you like this podcast, rate us on iTunes and Soundcloud, and share us on Facebook, Instagram, and Twitter. We’re hashtag: nasaonamission. Also check out NASA’s other podcasts: Gravity Assist, Rocket Ranch, What’s Up, NASA in Silicon Valley, and Houston We Have a Podcast. They can all be found on NASA’s podcast page or on most podcast platforms. We’re “On a Mission,” a podcast of NASA’s Jet Propulsion Laboratory.

(out music — finis)

[19:09 run time]

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Bad Things About Space Exploration

The Disadvantages of Satellites

Though space can be a fun and exciting place to explore in science fiction, the real-life danger and expense merits serious consideration. Humans evolved in the relatively safe comforts of Earth, where air is abundant and radiation almost nonexistent - just the opposite of space. Getting to space is dangerous, as you need a ride on a giant rocket just to get there. And the expense of space exploration means only the richest countries can afford it, and even then only rarely.

Cost of Space Travel

One of the biggest criticisms against space exploration is the cost. According to the University of Florida, it costs around $500 million to launch a space shuttle. These expenses will only go up when considering longer-term space travel, such as manned explorations to Mars or Jupiter's moons. While new technology may certainly limit the inefficient costs involved in space exploration, many argue that it is still money that could be better spent on more pressing issues.

Risks: Known and Unknown

There is always the problem of unforeseen risk with space exploration. The space shuttle Challenger exploded during launch in 1986, killing seven astronauts, and the shuttle Colombia exploded during reentry in 2003, also killing seven. Radiation from the sun is a constant danger to astronauts, and there may be unforeseen risks when they are traveling far beyond the earth, exacerbated by the fact that there would be little hope of getting back home in time for help.

Justification for Space Travel

Tied in with the question of cost and risk of human life is the question of justification. Space exploration appeals to the human desire to learn about the universe; however, it does not have any straightforward, pragmatic application. While there may be some practical use in the distant future, such as possibly colonizing other planets, it is difficult to justify continued space exploration to people who are worried about immediate concerns, such as crime or the economy.

Disadvantages of Unmanned Probes

Unmanned space probes are often considered the best choice for space exploration, because they do not put human lives at risk and are relatively cheaper to launch since they do not need space for human comfort or necessities. However, there are also downsides to unmanned probes, including the fact that they cannot adapt to unforeseen circumstances. A good example of this is the Mars Climate Orbiter, which received incorrect coordinates for landing and burned upon entry before it could send any data about Mars. Over $120 million was wasted on this probe.

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• Arecibo Observatory Home Page: Manned Space Exploration
• MIT: Why the Mars Probe Went Off Course
• University of Florida: Space: The Next Generation

About the Author

Drew Lichtenstein started writing in 2008. His articles have appeared in the collegiate newspaper "The Red and Black." He holds a Master of Arts in comparative literature from the University of Georgia.

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October 1, 2023

14 min read

Why We’ll Never Live in Space

Medical, financial and ethical hurdles stand in the way of the dream to settle in space

By Sarah Scoles

Tavis Coburn

N ASA wants astronaut boots back on the moon a few years from now, and the space agency is investing heavily in its Artemis program to make it happen. It's part of an ambitious and risky plan to establish a more permanent human presence off-world. Companies such as United Launch Alliance and Lockheed Martin are designing infrastructure for lunar habitation. Elon Musk has claimed SpaceX will colonize Mars. But are any of these plans realistic? Just how profoundly difficult would it be to live beyond Earth—especially considering that outer space seems designed to kill us?

Humans evolved for and adapted to conditions on Earth. Move us off our planet, and we start to fail—physically and psychologically. The cancer risk from cosmic rays and the problems that human bodies experience in microgravity could be deal-breakers on their own. Moreover, there may not be a viable economic case for sustaining a presence on another world. Historically, there hasn't been much public support for spending big money on it. Endeavors toward interplanetary colonization also bring up thorny ethical issues that most space optimists haven't fully grappled with.

At the 2023 Analog Astronaut Conference, none of these problems seemed unsolvable. Scientists and space enthusiasts were gathered at Biosphere 2, a miniature Earth near Tucson, Ariz., which researchers had built partly to simulate a space outpost. Amid this crowd, the conclusion seemed foregone: living in space is humans' destiny, an inevitable goal that we must reach toward.

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The conference attendees know it's a big dream. But their general outlook was summed up by Phil Hawes, chief architect for Biosphere 2, who gave the opening talk at the meeting. He recited a toast made by the first team to camp out here decades ago: "Here's to throwing your heart out in front of you and running to catch up with it."

The question remains as to whether we can—and will—ever run fast enough.

In 1991 eight people entered Biosphere 2 and lived inside for two years. This strange facility is a 3.14-acre oasis where scientists have re-created different terrestrial environments—not unlike an overgrown botanical garden. There's an ocean, mangrove wetlands, a tropical rainforest, a savanna grassland and a fog desert, all set apart from the rest of the planet they're mimicking. One goal, alongside learning about ecology and Earth itself, was to learn about how humans might someday live in space, where they would have to create a self-contained and self-sustaining place for themselves. Biosphere 2, located on Biosphere 1 (Earth), was practice. The practice, though, didn't quite work out. The encapsulated environment didn't produce enough oxygen, water or food for the inhabitants—a set of problems that, of course, future moon or Mars dwellers could also encounter. The first mission and a second one a few years later were also disrupted by interpersonal conflicts and psychological problems among the residents.

Today the people who participate in projects like Biosphere 2—simulating some aspect of long-term space travel while remaining firmly on Earth—are called analog astronauts. And although it's a niche pursuit, it's also popular: There are analog astronaut facilities in places such as Utah, Hawaii, Texas and Antarctica. People are building or planning them in Oman, Kenya and Israel. And they all share the goal of learning how to live off Earth while on Earth.

The people who are mingling on Biosphere's patio, where the desert sunset casts a pink light on the habitat's glass exterior, are part of that analog world. Some of them have participated in simulation projects or have built their own analog astronaut facilities; others are just analog-curious. They are astronomers, geologists, former military personnel, mail carriers, medical professionals, FedEx employees, musicians, artists, analysts, lawyers and the owner of the Tetris Company. On this night many have donned Star Wars costumes. As the sun goes down, they watch the rising moon, where many here would like to see humans settle.

Human bodies really can't handle space. Spaceflight damages DNA, changes the microbiome, disrupts circadian rhythms, impairs vision, increases the risk of cancer, causes muscle and bone loss, inhibits the immune system, weakens the heart, and shifts fluids toward the head, which may be pathological for the brain over the long term—among other things.

At the University of California, San Francisco, medical researcher Sonja Schrepfer has dug into two of the conditions that afflict space explorers. Her research, using mice floating within the International Space Station, has revealed that blood vessels leading to the brain get stiffer in microgravity. It's part of why today's astronauts can't simply walk out of their capsules once they return to Earth, and it would play out the same way on Mars—where there's no one to wheel them to their new habitat on arrival. Schrepfer and her colleagues did, however, uncover a molecular pathway that might prevent those cardiovascular changes. "But now the question I try to understand is, 'Do we want that?'" she says. Maybe the vessels' stiffening is a protective mechanism, Schrepfer suggests, and limbering them up might cause other problems.

She also wants to figure out how to help astronauts' faltering immune systems, which look older and have a harder time repairing tissue damage than they should after spending time in space. "The immune system is aging quite fast in microgravity," Schrepfer says. She sends biological samples from young, healthy people on Earth up to orbit on tissue chips and tracks how they degrade.

Vision and bone problems are also among the more serious side effects. When astronauts spend a month or more in space, their eyeballs flatten, one aspect of a condition called spaceflight-associated neuro-ocular syndrome, which can cause long-lasting damage to eyesight. Bones and muscles are built for life on Earth, which involves the ever present pull of gravity. The work the body does against gravity to stay upright and move around keeps muscles from atrophying and stimulates bone growth. In space, without a force to push against, astronauts can experience bone loss that outpaces bone growth, and their muscles shrink. That's why they must do hours of exercise every day, using specialized equipment that helps to simulate some of the forces their anatomy would feel on the ground—and even this training doesn't fully alleviate the loss.

Perhaps the most significant concern about bodies in space, though, is radiation, something that is manageable for today's astronauts flying in low-Earth orbit but would be a bigger deal for people traveling farther and for longer. Some of it comes from the sun, which spews naked protons that can damage DNA, particularly during solar storms. "[That] could make you very, very sick and give you acute radiation syndrome," says Dorit Donoviel, a professor at the Baylor College of Medicine and director of the Translational Research Institute for Space Health (TRISH).

Future astronauts could use water—perhaps pumped into the walls of a shelter—to shield themselves from these protons. But scientists don't always know when the sun will be spitting out lots of particles. "So if, for example, astronauts are exploring the surface of the moon, and there is a solar particle event coming, we probably have the capability of predicting it within about 20 to 30 minutes max," Donoviel says. That means we need better prediction and detection—and we'd need astronauts to stay close to their H2O shield.

If you didn't get to safety in time, the nausea would come first. "You would vomit into your spacesuit," Donoviel says, "which now becomes a life-threatening situation" because the vomit could interfere with life-support systems, or you might breathe it in. Then comes the depletion of cells such as neutrophils and red blood cells, meaning you can't battle germs or give your tissues oxygen effectively. You'll be tired, anemic, unable to fight infection, and throwing up. Maybe you'll die. See why lots of kids want to be astronauts when they grow up?

From September 1991 to September 1993, eight people lived inside the Biosphere 2 research facility in Arizona, helping scientists learn how humans might live in outer space. Credit: Science History Images/Alamy Stock Photo

There's another type of radiation, galactic cosmic rays, that even a lot of water won't block. This radiation is made of fast-moving elements—mostly hydrogen but also every natural substance in the periodic table. The rays burst forth from celestial events such as supernovae and have a lot more energy and mass than a mere proton. "We really cannot fully shield astronauts from them," Donoviel says. And inadequately shielding explorers makes the problem worse: the rays would split when they hit a barrier, making more, smaller particles.

The radiation an astronaut en route to Mars might get from galactic cosmic rays at any one time is a small dose. But if you're on a spaceship or a planetary surface for years, the calculus changes. Imagine, Donoviel says, being in a room with a few mosquitoes. Five or 10 minutes? Fine. Days? Months? You're in for a whole lot more itching—or, in this case, cancer risk.

Because shielding astronauts isn't realistic, Donoviel's TRISH is researching how to help the body repair radiative damage and developing chemical compounds astronauts could take to help fix DNA damage in wounds as they occur. "Everybody's worried about waiting for the cancer to happen and then killing the cancer," Donoviel says. "We're really taking the preventive approach."

Even if most of the body's issues can be fixed, the brain remains a problem. A 2021 review paper in Clinical Neuropsychiatry laid out the psychological risks that astronauts face on their journey, according to existing research on spacefarers and analog astronauts: poor emotional regulation, reduced resilience, increased anxiety and depression, communication problems within the team, sleep disturbances, and decreased cognitive and motor functioning brought on by stress. To imagine why these issues arise, picture yourself in a tin can with a small crew, a deadly environment outside, a monotonous schedule, an unnatural daytime-nighttime cycle and mission controllers constantly on your case.

Physical and mental health problems—though dire—aren't even necessarily the most immediate hurdles to making a space settlement happen. The larger issue is the cost. And who's going to pay for it? Those who think a billionaire space entrepreneur is likely to fund a space colony out of a sense of adventure or altruism (or bad judgment) should think again. Commercial space companies are businesses, and businesses' goals include making money. "What is the business case?" asks Matthew Weinzierl, a professor at Harvard Business School and head of its Economics of Space research efforts.

For the past couple of years Weinzierl and his colleague Brendan Rousseau have been trying to work out what the demand is for space exploration and pursuits beyond Earth. "There's been a ton of increase in supply and cutting of costs of space activity," Weinzierl says, "but who's on the other side?" Space companies have historically been insular: specialists creating things for specialists, not marketing wares or services to the broader world. Even commercial undertakings such as SpaceX are supported mostly by government contracts. Company leaders haven't always thought through the capitalism of their ideas; they're just excited that the rockets and widgets work. "Technical feasibility does not equal a strong business case," Rousseau says.

Today private spaceflight companies target tourists for business when they're not targeting federal contracts. But those tourists aren't protected by the same safety regulations that apply to government astronauts, and an accident could stifle the space tourism industry. Stifling, too, is the fact that only so many people with money are likely to want to live on a place like Mars rather than take a short joyride above the atmosphere, so the vacation business case for permanent space outposts breaks down there as well.

The Biosphere 2 research facility in Arizona houses a greenhouse. Credit: Kike Calvo/Universal Images Group via Getty Images

People tend to liken space exploration to expansion on Earth—pushing the frontier. But on the edge of terrestrial frontiers, people were seeking, say, gold or more farmable land. In space, explorers can't be sure of the value proposition at their destination. "So we have to be a little bit careful about thinking that it will just somehow pay off," Weinzierl points out.

Weinzierl and Rousseau find the idea of a sustained human presence in space inspiring, but they're not sure when or how it will work from a financial perspective. After all, inspiration doesn't pay invoices. "We'd love to see that happening," Rousseau says—he thinks lots of people would. "As long as we're not the ones footing the bill."

Many taxpayers would probably agree. As hard as it is for space fans to believe, most people don't place much value on astronaut adventures. A 2023 Pew poll asked participants to rate the importance of nine of NASA's key missions as "top priority," "important but lower priority," or "not too important/should not be done." Just 12 and 11 percent of people thought sending humans to Mars and to the moon, respectively, should be a top priority. That placed those missions at the bottom of the list in terms of support, behind more popular efforts such as monitoring Earth's climate, watching for dangerous asteroids and doing basic scientific research on space in general.

Similarly, a 2020 poll from Morning Consult found that just 7 to 8 percent of respondents thought that sending humans to the moon or Mars should be a top priority. And although history tends to remember the previous moon exploration era as a time of universal excitement for human spaceflight, polls from the time demonstrate that that wasn't the case: "Consistently throughout the 1960s, a majority of Americans did not believe Apollo was worth the cost, with the one exception to this a poll taken at the time of the Apollo 11 lunar landing in July 1969," wrote historian Roger Launius in a paper for Space Policy . "And consistently throughout the decade 45–60 percent of Americans believed that the government was spending too much on space, indicative of a lack of commitment to the spaceflight agenda."

When space agency officials discuss why people should care about human exploration, they often say it's for the benefit of humanity. Sometimes they cite spin-offs that make their way to citizens as terrestrial technology—such as how telescope-mirror innovations improved laser eye surgery. But that argument doesn't do it for Linda Billings, a consultant who works with NASA. If you were interested in furthering a technology, she suggests, you could invest directly in the private sector instead of obliquely through a space agency, where its development will inevitably take longer, cost more and not be automatically tailored toward earthly use. "I don't see that NASA is producing any evidence that [human settlement of space] will be for the benefit of humanity," she says.

Whether tax dollars should support space travel is an ethical question, at least according to Brian Patrick Green of Santa Clara University. Green became interested in science's ethical issues when he worked in the Marshall Islands as a teacher. The U.S. used to detonate nuclear weapons there, causing lasting environmental and health damage. Now the islands face the threat of sea-level rise, which is likely to inundate much of their infrastructure, erode the coasts and shrink the usable land area. "That got me very interested in the social impacts of technology and what technology does to people and societies," he says.

In space travel, "Why?" is perhaps the most important ethical question. "What's the purpose here? What are we accomplishing?" Green asks. His own answer goes something like this: "It serves the value of knowing that we can do things—if we try really hard, we can actually accomplish our goals. It brings people together." But those somewhat philosophical benefits must be weighed against much more concrete costs, such as which other projects—Earth science research, robotic missions to other planets or, you know, outfitting this planet with affordable housing—aren't happening because money is going to the moon or Mars or Alpha Centauri.

And an even simpler ethical question is, "Should we actually send people on these sorts of things?" Green says. Aside from incurring significant risks of cancer and overall body deterioration, astronauts aiming to settle another world have a sizable chance of losing their lives. Even if they do live, there are issues with what kind of an existence they might have. "It's one thing just to survive," Green says. "But it's another thing to actually enjoy your life. Is Mars going to be the equivalent of torture?"

If people make the attempt, we will also have to acknowledge the risks to celestial bodies—the ones humans want to travel to as well as this one, which they may return to if they haven't purchased a one-way ticket. The moon, Mars or Europa could become contaminated by microscopic Earth life, which NASA has never successfully eradicated from spacecraft, although it tries as part of a "planetary protection" program. And if destination worlds have undetected life, then harmful extraterrestrial microbes could also return with astronauts or equipment—a planetary-protection risk called backward contamination. What obligation do explorers have to keep places as they found them? Setting aside the question of whether we can establish ourselves beyond Earth, we also owe it to ourselves and the universe to consider whether we should.

on this question, science-fiction scholar Gary Westfahl casts doubt on space travel's inherent value. In his vast analyses of sci-fi, he has come to view the logic and drive of the enterprise as faulty. "I inevitably encountered the same argument: space travel represents humanity's destiny," he says of the impetus for writing his essay "The Case against Space." Space explorers are often portrayed as braver and better than those who remain on their home planet: they're the ones pushing civilization forward. "Philosophically, I objected to the proposition that explorers into unknown realms represented the best and brightest of humanity, that progress could be achieved only by boldly venturing into unknown territories," Westfahl says. After all, a lot of smart and productive people (not to mention a lot of happy and stable people) don't spend their lives on the lam. "Clearly, history demonstrates no correlation between travel and virtue," he writes. "The history of our species powerfully suggests that progress will come from continued stable life on Earth, and that a vast new program of travel into space will lead to a new period of human stagnation," he concludes ominously.

Celestial bodies, including our moon, are at risk of contamination by microscopic Earth life. Credit: NASA’s Scientific Visualization Studio

In some ways, the desire for simpler living is part of what motivates space explorers. Astronauts are stuck with just a few people they have to get along with, or else they'll be miserable—a communal way of living that's more common to villages. They must make do with the nearby supplies or create their own, like people did before Walmart and Amazon. Communication with those beyond their immediate sphere is slow and difficult. They have a strict but straightforward and prescribed work schedule. Everything is a struggle; there are no conveniences. Unlike in a modern, digitally connected environment, their attention isn't split in many directions—they are focused on the present. Or at least that's how analog astronaut Ashley Kowalski felt during the SIRIUS 21 endeavor, an eight-month-long joint U.S.-Russia "lunar mission" that took place in a sealed space in Moscow.

Kowalski's talk at the Analog Astronaut Conference at Biosphere 2 was called "Only Eight Months." The goal of those eight months was to study the medical and psychological effects of isolation. She and her teammates regularly provided blood, feces and skin samples so researchers could learn about their stress levels, metabolic function and immunological changes. Researchers also had them take psychological tests, sussing out their perception of time, changes in cognitive abilities and shifts in interpersonal interactions. Inside they had to eat like astronauts would, guzzling tubes of Sicilian pizza gel and burger gel. Kowalski would squeeze them into rehydrated soup to make meals heartier. Via their greenhouse, they got about a bowl of salad between the six of them every three weeks.

Kowalski missed freedom and food and friends, of course. But the real struggle came with her return to the real world once the isolation was over: "reentry, not to the atmosphere but to the planet," she told the conference audience. She didn't remember how to go about having friends, hobbies or a job and had trouble dealing with requests coming from lots of sources instead of just mission control. In the Q&A period after the talk, Tara Sweeney, a geologist in the audience, thanked Kowalski for talking about that part of the experience. Sweeney had just returned from a long stay in Antarctica and also didn't quite know how to reintegrate into life in a more hospitable place. They had both missed "Earth," the real world. But it was hard to come back.

Still, the Analog Astronaut Conference crowd remained optimistic. "Where do we go from here?" conference founder and actual astronaut Sian Proctor asked at one point. On cue, the audience members pointed upward and said, "To the moon!"

Analog-astronaut work can't solve space travel's hardest problems—the intractable medical troubles, the in-red money questions, the touchy ethical quandaries. But while we all wait to see whether we'll ever truly migrate off this planet, and whether we should, these grounded astronauts will continue to escape Earth, for a time at least, without leaving it.

Sarah Scoles is a Colorado-based science journalist, a contributing editor at Scientific American and Popular Science, and a senior contributor at Undark . She is author of Making Contact (2017) and They Are Already Here (2020), both published by Pegasus Books. Her newest book is Countdown: The Blinding Future of Nuclear Weapons (Bold Type Books, 2024).

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Space tourism isn’t just joyriding.

Having rich guys like Jeff Bezos in orbit can make space travel routine and help all of us dream big.

By Shira Ovide

Maybe you’ve wondered as I have: Is there a point to rocketing rich guys like Jeff Bezos and the “Star Trek” actor William Shatner into space?

Wendy Whitman Cobb, an Air Force political scientist for space, says yes. Our conversation challenged my thinking about space projects, like those from Bezos and Elon Musk, that imagine a future away from Earth.

If you screamed “ MIDLIFE CRISIS ” when Bezos touched space last year or asked why Musk’s SpaceX company has attracted so much attention , today’s newsletter is for you.

Whitman Cobb, who has a Ph.D. in political science, said that tourist jaunts were a first step to transform space travel from outlandish to routine. And she believes that amateurs in orbit are a proving ground for worthy ambitions — including settling Mars, as Musk imagines , or colonizing space to support more people and industry than is possible on Earth, as Bezos aspires to .

To me, those sound like the escapist fantasies of billionaires. But Whitman Cobb’s optimism is a useful counterpoint to this newsletter’s regular warnings that technology is not a magical fix to our problems . Whitman Cobb agrees, but also said that technology had sometimes done magical things in space exploration.

To rewind the past decade, corporations such as SpaceX, Bezos’ Blue Origin, Northrop Grumman and the New Zealand-based start-up Rocket Lab have tried to become bigger players in spaceflight . Companies have always worked with governments on space travel, but now they’re more involved in carrying astronauts, enthusiasts, satellites and cargo to space.

There is debate about the appropriate role of governments versus corporations in space, but Whitman Cobb believes those companies have made rote space tasks cheaper and easier. That frees up NASA to dream big on projects such as pursuing moon colonies and exploring deep space.

SpaceX, Blue Origin and Virgin Galactic have also led space pleasure cruises. Those are joyrides for a tiny few, but Whitman Cobb said that they helped hone the safety of space travel and generated enthusiasm for searching beyond our planet.

“The more ‘normal’ people we see fly into space, more of the public will see this as possible and be excited by it,” she told me. “That public opinion is key to a lot of things that these companies as well as the U.S. government is doing in space.”

(Whitman Cobb said that these views were hers, and not that of the U.S. government, which employs her. She also said that she didn’t receive funding from commercial space companies.)

The ultimate goal, though, goes far beyond tourism. Musk and Bezos imagine moving people or polluting industries into space or creating a Mars civilization. I worry that is a pretext to ignore problems on Earth.

Whitman Cobb understood why I asked if those were reckless delusions, but she also doesn’t want us to lose sight of the potential benefits from dreaming. The history of space exploration, she said, is of kooky and not necessarily high-minded visions becoming doable and helpful.

The U.S. missions to the moon in the 1960s were driven by a desire to prove American superiority over the Soviet Union. Nevertheless, nationalist space missions helped spur the development of ever-smaller electronics that we use every day, improved health technology and even gave us memory foam . The past decade’s boom in commercial spaceflight has lowered the cost of space access and enabled novel ideas like small-scale satellites to map the Earth from above it.

Whitman Cobb said that the advanced technology that commercial space companies developed for spaceflight could likewise trickle down to other areas that help us.

A self-described space geek, she also said that the awe of space was a worthy goal. “It also scratches an itch, so to speak, of humanity’s longing to explore, to discover, and to understand the world around us,” she said.

I asked Whitman Cobb if she would want to live on Mars. “Absolutely,” she replied. “Maybe not forever.”

I’m not shedding all my doubts about rocket tourism or billionaires’ space fantasies. When corporations play a large role in space, they could hoard inventions rather than have them benefit the public. Space tourism also hurts the environment , and it’s not clear how much space travel and commerce is worthwhile. We know that technologies, even the helpful ones, have downsides.

Whitman Cobb wants us to have that skepticism alongside excitement. The history of space travel, she said, shows that selfish dreams can benefit all of us.

Before we go …

More Earthbound Musk news: He has gotten into hot water for his tweets. Recently, Musk also bought a big chunk of Twitter’s stock. No one quite knows what he’s doing , my colleagues Mike Isaac and Lauren Hirsch report. On Tuesday, Twitter said that Musk would join the company’s board of directors .

What does an altruist do with a cryptocurrency fortune? Sam Bankman-Fried, a co-founder of the cryptocurrency exchange FTX, is one of the world’s richest people and a believer in using scientific reasoning to do the most good. Bloomberg News tells us about the 30-year-old Bankman-Fried and asks: “Should someone who wants to save the world first amass as much money and power as possible, or will the pursuit corrupt him along the way?” (A subscription may be required.)

Related: Ezra Klein, my colleague in Times Opinion, interviewed Dan Olson, a video essayist who warns about the dangers of crypto ideology and culture.

How to recycle your gadgets properly: It’s not unusual for the batteries in electronics to start fires in landfills and recycling centers. The Washington Post explains how to dispose of your gadgets and batteries safely . (A subscription may be required.)

Hugs to this

Enjoy breakfast with these piglets, Pickle, Winnie and Domino .

We want to hear from you. Tell us what you think of this newsletter and what else you’d like us to explore. You can reach us at [email protected].

If you don’t already get this newsletter in your inbox, please sign up here . You can also read past On Tech columns .

Shira Ovide writes the On Tech newsletter, a guide to how technology is reshaping our lives and world. More about Shira Ovide

What’s Up in Space and Astronomy

Keep track of things going on in our solar system and all around the universe..

Never miss an eclipse, a meteor shower, a rocket launch or any other 2024 event  that’s out of this world with  our space and astronomy calendar .

A celestial image, an Impressionistic swirl of color in the center of the Milky Way, represents a first step toward understanding the role of magnetic fields  in the cycle of stellar death and rebirth.

Scientists may have discovered a major flaw in their understanding of dark energy, a mysterious cosmic force . That could be good news for the fate of the universe.

A new set of computer simulations, which take into account the effects of stars moving past our solar system, has effectively made it harder to predict Earth’s future and reconstruct its past.

Dante Lauretta, the planetary scientist who led the OSIRIS-REx mission to retrieve a handful of space dust , discusses his next final frontier.

Is Pluto a planet? And what is a planet, anyway? Test your knowledge here .

18 Biggest Advantages and Disadvantages of Space Exploration

President Donald Trump announced his desire in 2018 to create a sixth branch of the U.S. military that he colloquially called the Space Force. Although Congress has yet to act on this desire to take the armed forces beyond the atmosphere of our planet, in February 2019, Trump signed Space Policy Directive 4 to have these forces organize underneath the umbrella of the U.S. Air Force.

The directive formally allows the Air Force to organize, train, and equip a corps of military space personnel for actions that take place in space. “Today I’m thrilled to sign a new order taking the next step to create the United States Space Force,” Trump said during the signing ceremony. “It’s so important. When you look at defense, when you look at all of the other aspects of where the world will be some day. I mean, this is the beginning. This is a very important process.”

The initial version of the Space Force will be overseen by a civilian undersecretary and a four-star general serving as the Chief of Staff. Although this structure is not as ambitious as having a separate branch of the military, space exploration experts feel like this is a step in the right direction.

The pros and cons of exploring space are complex simply because we have limited knowledge of what lies beyond our solar system. There are still mysteries to discover about our own planet! These are the key points to consider when we begin to look at what life might look like in the vastness of space.

List of the Pros of Space Exploration

1. It is an opportunity which is available to anyone. If you have a telescope, then you have an opportunity to start exploring space. For more than 300 years, we have looked to the stars with this technology as a way to learn more about our planet and ourselves as a species. When the Hubble space telescope was launched in 1990, it gave us our first views without atmospheric interference on what the vastness of our universe was like.

With millions of images taken and tens of thousands of papers written based on the observations made from simple telescope technologies, we have learned more about the structure of our universe, its age, and the composition of our solar system in the last 20 years than our ancestors would have ever dreamed was possible.

2. It gives us an opportunity to foster genuine cooperation. Because we are a world of nation states, the investments that we make in space exploration tend to have a patriotic feeling to them. Some efforts in this scientific area are still nationally-based, but for most projects there is a spirit of cooperation between the countries of the world who have made this realm of science a top priority. We work together as the human race to operate the international space station, fund research projects, and look outward beyond the stars to see what is there. It is one of the few areas in our lives today where we set aside our boundaries to work together toward a common good.

3. It is an effort which requires us to become innovative. The 100-year Starship Program has the ultimate goal of creating a technology that will allow us to explore space. No idea is off-limits with this project. What we have found in our quest to achieve specific goals in this area of science is that there are numerous discoveries which become possible to improve our lives here at home. Everything from athletic shoes to water purification systems came about because of our push to look beyond our planet. By tackling the technological needs to stay safe in space, we can make life better for everyone down on our planet at the same time.

4. It is an opportunity to explore something new. Although there are still regions of our planet that we rarely study because of technology limitations, the vastness of the universe is a much more significant prize. Only the Voyager spacecraft have gone beyond the first boundaries of our solar system. The information they provide us nearly four decades after their launch continues to enlighten our knowledge of the universe. There are so many unanswered questions when we think about space, especially now that scientists can determine which stars have planets orbiting around them.

Is there life somewhere else in the universe? If so, would those beings look like us? There are numerous technological barriers we must cross before we could travel for long distances in the vacuum of space, but we are getting one step closer every day.

5. It creates numerous employment opportunities in a variety of fields. There are more than 18,000 people employed in the United States by NASA, along with countless contractors, freelancers, and specialists not counted in those figures. The private company SpaceX provides about 7,000 full-time high-skill positions that support the economy. Then there are the astronauts, engineers, and flight specialists who manage the actual mechanisms of space flight to consider.

Numerous indirect employment opportunities are possible because of our efforts at space exploration too. We need caterers, designers, nutritionists, personal trainers, astronomers, scientists, and many other positions to support these activities. Even though the budget for NASA is $21 billion for FY 2020, the economic returns can be five times greater because of these activities.

6. It allows us to understand our planet better. When we can observe the full scale of our planet from a high orbital position, then we can see changes that are not always possible from the ground. It gives us a way to track the changes to our environment, study ozone depletion, and measure the impacts of a warming planet. We can provide accurate prediction models for weather patterns, observe troop movements, and install safety equipment that guards against an attack. When we take full advantage of this benefit, it becomes possible to create a place in the universe that is healthier for many years to come.

7. It gives us a new perspective on our place in the universe. It took several centuries for the scientific world (back by religious zealots) to accept the fact that the Earth was not the center of the universe. When we saw that first picture from a distance of what our planet looks like from a distant point in our solar system, it became clear to see that a small, pale blue dot in the middle of the vastness of our universe puts our daily issues into a new perspective. Until we discover otherwise, this is the only home that we have. It is up to each of us to share resources, reduce conflict, and work toward a common good.

8. It allows us to identify potential dangers before they strike. The asteroid belt between Jupiter and Mars is only one source for these deadly rocks in our solar system. There may even be threats that travel through the universe to interact with our region of space from time-to-time. It would only take one significant impact to change life on our planet forever, which is why space exploration makes threat identification a top priority. If we can locate and move threatening asteroids or comets before they threaten an impact, we could stop the apocalypse before it ever gets a chance to begin.

9. It would give us access to new minerals, precious metals, and other useful items. Thanks to the asteroids which occasionally make it to the surface of our planet, we know that many of them contain iron and carbon. We also know that there is nickel, cobalt, silicon, magnesium, calcium, and several other elements present. Some might have water or oxygen contained beneath their surface. There may even be gold, platinum, and other precious metals there. We might even discover something that we’ve never encountered before.

Space exploration gives us an opportunity to access new mineral resources, allowing for the privatization of this venture. It would also give us an opportunity to start building in space because the raw materials are easy to haul and transport.

10. It gives us an opportunity to see what lies beyond in the final frontier. Unless circumstances change somehow, there will come a point in time when our species will outgrow our planet. We must begin to look for colonization opportunities in our solar system and beyond to help support the future of our race. As our scientific and technological discoveries begin to open up opportunities to visit distant stars, we can start to discover even more mysteries that will help us to answer the meaningful questions in life.

11. It could change our approach to medicine. Discovering new organic elements in space could help us to discover cures for some of our worst diseases. We really don’t know what is possible in our universe beyond the scope of basic physics. There could be untold treasures just waiting beyond our solar system to discover. Although there is always an element of risk to any exploration venture, there are great rewards often waiting for those who embrace their courage to start pressing forward. At the rate of development that we’ve seen in the 21st century, we could be looking at a very different human race in our children’s lifetimes based on the possibilities of discovery.

List of the Cons of Space Exploration

1. It could cause us harm or provide harm to other species in space. We know from experience what happens when one group of humans comes into contact with another group after generations of isolation. The diseases that transferred back and forth between Europe and the New World devastated some cultures. There were times that smallpox would kill over 90% of the local population by itself. If we encounter life on a different planet (or if they visit us), the threat of disease transmission is real. Their viruses, bacteria, and potentially unknown invaders could do as much damage to us as we could to do them. First contact would be an exciting experience, but it could also be a deadly one even though no one has any ill intent toward the other.

2. It creates high-level pollution events. We must consume fossil fuels when we launch rockets into space, which means we’re creating a significant level of pollution every time we expend fuel for exploration purposes. Even on a light load, it costs about $300,000 to fuel a rocket. Larger models could hold a half-million gallons of fuel that would be used during an entire mission. That means we are creating roughly 4 million pounds of carbon pollution with every action that we take to reach space. Then we must find a way to place these fuels safely into orbit to make our exploration efforts useful, creating even further potential problems for our atmosphere.

3. It gives us more ways to be paranoid about what others are doing. There are only five treaties which currently govern how we operate in space. Our original goal as the human race was to make it so that no one could claim a territory in orbit or our solar system that could give one nation a distinctive advantage. The creation of a Space Force could work to upset the balance that we’ve worked to create for the last 50 years. We’re already using satellites to spy on one another, monitor communications networks, and potentially target cities with weapons.

This paranoia will only increase as we push further into the stars. The only real solution to this disadvantage is to start thinking of ourselves as a planetary nation instead of one that is built on nation-states alone.

4. It will create a large amount of garbage that we must manage. Did you know that NASA tracks over a half-million pieces of space junk that orbits our planet right now? Unless we physically remove these items in some way, this garbage will linger until it falls into our atmosphere to burn up. Every item we leave behind creates a future risk for someone else. If we are going to start exploring space, then we must begin to look at ways to clean up our act before we get going. It’s bad enough that we’ve polluted our oceans with microplastics. Should a spaceship encounter that debris, it could be a deadly experience.

5. it may cause our planet to face unknown perils. A common theme in many science-fiction novels, shows, and movies is the idea that an alien race is hostile towards us. It is widely believed that water may be one of the scarcest commodities in the universe, but here we are with a planet that is more than 70% water. If we start venturing out beyond our solar system, it is entirely possible that we could encounter a species who decides that our resources are ripe for the taking. We assume that an advanced culture who could invent real-time space travel would be peaceful, but there are no guarantees. Exploring space could become an invitation for interstellar war.

6. It will always entail risk. Human beings were not meant to be in the vacuum of space. We must wear extensive protective gear to survive those conditions. Even one small leak or crack in a helmet or suit would be enough to create an adverse health condition. This issue applies to the planetary environments which we know of right now as well. Then there are the health issues to consider when the human body experiences a lack of gravity for an extended time.

NASA studied identical twins Scott and Mark Kelly when Scott took a long trip to space. Scientists monitored their bodies to see how being in a weightless environment could change the physical chemistry of a person. They discovered that genomic instability occurs, including gene expression changes, and spending a year in that environment caused a thickening of the carotid artery, DNA damage, and reduced cognitive abilities.

7. It is expensive to start exploring space. Even though the budget for NASA has not changed that much in recent years, we are spending about $200 billion per decade on our current space exploration efforts. Privatization of the industry has helped to reduce some costs, especially as SpaceX continues to work on a recoverable rocket. When you add in the costs from other countries and their space programs, our planet spends about $60 billion per year on this effort. In comparison, the United Nations suggests that it would only take half of that amount to end global hunger permanently. Should exploring space be our top priority if we’re struggling to take care of ourselves here at home?

When we examine these space exploration pros and cons, there is a certain nobleness to the idea of seeking what lies beyond the next horizon. Our society was built on the desire to explore the planet where we live. Now our culture has the itch to start pushing beyond the next boundary. Whether that means we colonize the moon, establish a community on Mars, or push toward Alpha Centauri, there is something waiting to be discovered. We’re closer than ever before to finding out what that might be.

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Christopher Wanjek

How Space Tries to Kill You and Make You Ugly

Outer space is the most noxious of substances: devoid of air and filled with a soup of deadly particles in the form of high-energy photons and energetic bits of atomic nuclei. The lack of gravity there affects every element of your being, as even the proteins in your body can’t figure out which way is up.

Books and magazine articles about space voyages often compare the adventure to setting off to new lands across treacherous oceans. Our ancestors paddled across the South Pacific in outrigger wooden canoes made by hand with primitive tools. They set off never expecting to return. They spent days, weeks, and months on the open waters, exposed to the elements, with precious little food and water. Many died along the way, but a few made it to their destination and started a new life. No doubt these early migrations tens of thousands of years ago were perilous, but it’s not as if each drop of water burns a hole in your DNA; the sea mist doesn’t destroy your brain cells; the choppy waves don’t cause fluid to build up in your eyes and cause permanent retinal damage. When you finally get to dry land, you can walk. You don’t need a team of doctors and engineers to carry you off the boat because your legs are too weak to support you. And, chances are, you will find food and water at your destination when you arrive.

Excerpted from Spacefarers: How Humans Will Settle the Moon, Mars, and Beyond, by Christopher Wanjek. Buy on Amazon.

In short, some things can actually live in water, and that which cannot live in water can cross it on driftwood. But space is both sterile and sterilizing. The challenges presented by every journey on Earth that has occurred in the centuries and millennia past, however arduous, pale in comparison to those of a journey in space beyond the Moon. Suggesting otherwise minimizes the sacrifices that the first generation of spacefarers will make. To be clear, space travel is technically feasible today from an engineering standpoint. We placed humans on the Moon fifty years ago, after all. We’ve sent probes clear out of the Solar System, and we have made soft landings of probes on the surfaces of Venus, Mars, Saturn’s moon Titan, the comet 67P / Churyumov–Gerasimenko, and several asteroids. But sending humans beyond the Moon is considered by many doctors to be so dangerous that it is tantamount to suicide.

The expected radiation exposure for a Mars excursion for an astronaut—a federal worker—far exceeds the levels permitted for terrestrial workplace activities by the US Occupational Safety and Health Administration (OSHA). To even consider going to Mars, NASA needs a special waiver from OSHA based on a principle called ALARA (As Low As Reasonably Achievable). The waiver, which NASA has, requires the agency to carefully assess the health risks to astronauts prior to launch.

Yet radiation exposure is only one danger. The NASA Human Research Roadmap has identified thirty-four known health risks and 233 “gaps” in our knowledge of risks. For example, four known health risks are associated with radiation: radiation poisoning from solar flare; brain damage; cardiovascular damage; and regular ol’ cancer. But among the gaps are questions about hereditary, fertility, and sterility effects from space radiation. So, it’s likely that there are more health risks than we realize. Here are the 34 known risks of space travel—risks that go beyond basic mechanical dangers, such as the rocket blowing up.

• concern about clinically relevant unpredicted effects of medication
• concern about intervertebral disc damage upon and immediately after reexposure to gravity
• risk of acute (in-flight) and late central nervous system effects from radiation exposure
• risk of acute radiation syndromes due to solar particle events
• risk of adverse cognitive or behavioral conditions and psychiatric disorders
• risk of adverse health and performance effects from celestial dust exposure
• risk of adverse health effects due to host-microorganism interactions
• risk of adverse health events due to altered immune response
• risk of adverse health outcomes and decrements in performance due to in-flight medical conditions
• risk of an incompatible vehicle / habitat design
• risk of bone fracture due to spaceflight-induced changes to bone
• risk of cardiac rhythm problems
• risk of cardiovascular disease and other degenerative tissue effects from radiation exposure and secondary spaceflight stressors
• risk of decompression sickness
• risk of early-onset osteoporosis due to spaceflight
• risk of impaired control of spacecraft / associated systems and decreased mobility due to vestibular / sensorimotor alterations associated with spaceflight
• risk of impaired performance due to reduced muscle mass, strength, and endurance
• risk of inadequate design of human and automated / robotic integration
• risk of inadequate human-computer interaction
• risk of inadequate mission, process, and task design
• risk of inadequate nutrition
• risk of ineffective or toxic medications due to long-term storage
• risk of injury and compromised performance due to extravehicular activity (EVA) operations
• risk of injury from dynamic loads
• risk of orthostatic intolerance during reexposure to gravity
• risk of performance and behavioral health decrements due to inadequate cooperation, coordination, communication, and psychosocial adaptation within a team
• risk of performance decrement and crew illness due to an inadequate food system
• risk of performance decrements and adverse health outcomes resulting from sleep loss, circadian desynchronization, and work overload
• risk of performance errors due to training deficiencies
• risk of radiation carcinogenesis
• risk of reduced crew health and performance due to hypobaric hypoxia
• risk of reduced physical performance capabilities due to reduced aerobic capacity
• risk of renal stone formation
• risk of spaceflight-associated neuro-ocular syndrome

Of these 34 risks, three are potential showstoppers: radiation, gravity (or lack thereof), and the need for surgery or a complicated medical procedure.

Let’s explore the gravity issue.

Some science fiction writers in the mid-20th century speculated that zero gravity would be life-giving: blood would flow more easily; arthritis would be a thing of the past; back pain would be cured for good; and aging itself would slow down. So, bring grandma along for the ride. We had hints from early in the space program that such a rosy scenario wasn’t true. Astronauts returned from just a few days of weightlessness feeling weak. But they recovered; and many thought, well, maybe it isn’t so bad. Then we spent more time in space. Russians on the Mir space station for months appeared to have some serious, prolonged health issues on their return. The Russians were tight-lipped about the health of their cosmonauts, though, so we never knew for sure. Many of these cosmonauts, championed as heroes, were rarely seen in public after their return. It was the ISS missions that drove home the message: long-term exposure to zero gravity is detrimental to human health on many levels. Kudos to NASA for that.

Kate Knibbs

Dell Cameron

Medea Giordano

Before I continue, I should first define some terms. Zero gravity, however visually convenient, can be a misnomer in the context of near-earth activity. The astronauts on the ISS are not living in the absence of gravity. Rather, they are in free-fall, forever falling over the horizon and missing the Earth. The ISS and other satellites are not floating in space because they have escaped the pull of Earth’s gravity; they stay up there because of their terrific horizontal speed. The ISS is moving at 17,500 miles per hour. If, somehow, it came to a complete stop, it would fall straight down to Earth, and down would come astronaut, cradle and all. The Earth’s gravitational force, in fact, keeps the moving satellites in orbit as a perfectly balanced counterforce, in a downward motion, to the lateral motion set in place during the launch. Without the Earth’s gravitational force (if the Earth suddenly, magically, disappeared), the satellites would shoot off in a straight line. Therefore, more accurate terms for describing the lack of sensation of gravity aboard the ISS are microgravity and weightlessness. Yet, even these terms are neither perfect nor synonymous. Astronauts on the ISS have weight, about 90 percent of their weight on Earth, which is only about 200 miles below their feet. They’d be much lighter on the Moon, actually, at just about 16 percent of their weight. Absolute zero gravity is not attainable, because gravity is the force of attraction between any two objects. But in deep space, far from the gravitational tug of any moon, planet, or star, gravity is attenuated to almost zero. I tend to use the terms zero gravity, micro-gravity, and weightlessness interchangeably in the context of space travel.

Our understanding of gravity’s effect on the body has only two data points: one and zero. On Earth, we live with a gravitational force of 1G. On the ISS, astronauts live in 0G. We really don’t know about anything in between. Air force pilots might accelerate their jets so quickly that they experience forces of 5G or higher, which sometimes causes them to black out. That’s five times the force of normal Earth gravity, which pushes blood out of their brains. But such forces typically last only a few seconds; the pilots aren’t living in a hyper-gravity environment. And anyway, we don’t care too much about forces greater than 1G because every place we want to go in our Solar System—L2 orbit, the Moon, Mars, and so on—has a gravitational force less than 1G.

What’s so special about 1G? This is simply the force we evolved with. Our bones are as thick as they are because of this precise level of gravitational force. Without the pervasive force of gravity all around them, sending constant signals to the cells, bones begin to demineralize and weaken. Muscles, too, expect a certain resistance when contracting. Without the grip of gravity, muscles atrophy and lose their tone. You can exercise in space. Astronauts on the ISS are required to exercise for two hours each day to minimize bone loss and minimize muscle loss. This works to some degree. But nevertheless, in zero gravity, bones lose density at a rate of 1 or 2 percent per month on average, compared to the rate of an elderly person on Earth losing 1 percent per year. To visualize how bad that bone loss is, consider the fact that the major obstacle to fully recycling urine into drinking water on the ISS was that the filters got clogged regularly with calcium deposits. That calcium is leached from the bones into the urine; this leaching also puts the astronaut at short-term risk for kidney stones and long-term risk for kidney disease.

And for all that muscle exercise on special treadmills, astronauts still find it difficult to walk or even hold a cup after returning from several months in space. Worse for the muscles is the fact that most can’t be exercised. Workouts focus on the major skeletal muscles that move the limbs and torso. But there are hundreds of other muscles—cardiac, involuntary, smooth, and other skeletal—that cannot be exercised. Gravity is their workout on Earth, and on the ISS, they aren’t getting it. All those tiny muscles in the face and fingers get weaker. Tendons and ligaments also begin to fail in zero gravity. The spine lengthens, and astronauts become one or two inches taller in space, which causes back pain. The Space Medicine Office of the European Astronaut Centre, run by the European Space Agency (ESA), is designing a high-tech, highly tight-fitting “skinsuit” to help astronauts overcome back problems in space. Let’s just say the outfit is very, uh, European.

In the body, much more is going on at a cellular level that depends on 1G. Normally, blood pools in the feet because of gravity. Our circulatory system evolved to push blood upward to the brain, a rather important organ. Without gravity, the circulatory system pushes blood upward like a geyser, unharnessed, leaving your head with a pounding feeling. Your heart starts beating faster to pump blood to lower parts of the body. Your body starts thinking there’s a fluid surplus, asking, where is all this blood coming from? So your kidneys go into overdrive to remove excess water via urine. But now you are dehydrated, and your blood starts to thicken. This, in turn, triggers the body to stop making red blood cells, and thus you slowly become anemic, sluggish, short of breath, and prone to infection. And so on and so on. It’s a holistic medicine nightmare.

The eyes are particularly vulnerable to all this unnatural sloshing of fluids. More than two-thirds of astronauts report having deteriorated eyesight after spending several months in orbit. The fluid pressure flattens the back of the eyeballs, inflames optic nerves, and damages fragile blood vessels. NASA astronaut John Phillips was among the first to report the problem. Gazing out the window, he thought Earth looked blurrier and blurrier with each passing month. NASA tested his sight upon his return and found that his vision had deteriorated from 20 / 20 to 20 / 100 after six months in orbit. The implication is that a crew to Mars needs to pack eye-glasses with various prescriptions to help with each phase of their gradual, inevitable, and permanent vision loss. NASA considers the vision issue to be an astronaut’s top immediate-term health risk.

Like the eye, the entire brain floats in fluid. A study of 34 astronauts for whom MRI images of their brains were captured before and after their missions found microgravity-induced changes that could be permanent: essentially, compression as their brains shifted upward and a narrowing of the brain’s central sulcus, a groove in the cortex near the top of the brain that separates the parietal and frontal lobes. These are the parts of the brain that control fine movement and higher executive function; the longer the time spent on the ISS, the worse these brain changes were.

On Earth, and on the ISS, we are shielded from most cosmic radiation, also called galactic cosmic rays or high-mass, high-charged (or HZE) particles. Occasionally a few slip in, smashing into the upper atmosphere and causing a cascade of secondary and tertiary particles. What usually happens is that the cosmic rays collide with nitrogen and oxygen, the two most abundant atoms in our atmosphere, and break them open, releasing neutrons, electrons, and more exotic stuff such as muons, pions, alpha particles, and even X-rays. But there’s a lot of atmosphere to clear, so the radiation tends to decay or be absorbed before it reaches the surface. In fact, cosmic rays were not detected conclusively until 1912, when Austrian physicist Victor Franz Hess carried electrometers on a high-altitude balloon flight. Jet pilots and, by extension, flight attendants have an elevated exposure to radiation compared with the general population. Most of this is cosmic radiation.

Apollo astronauts have seen the effects of cosmic radiation—quite literally. Frequently a cosmic particle has zipped through their eye sockets, producing a flash. This has since been named cosmic ray visual phenomena. What’s happening at a biological level is not clear. A cosmic ray might be colliding into an optic nerve or perhaps passing through the gel-like vitreous humor, creating a cascade of subatomic particles akin to what happens in the atmosphere. The Apollo astronauts, who traveled beyond the magnetosphere on their way to the Moon, sensed the flashes at a rate of about one every three to seven minutes. The astronauts described the flashes in a variety of ways, which may indicate different physical interactions. The reported shapes of the flashes were spots or dots, stars, streaks or stripes or comets, and blobs or clouds, in order of commonality. Closing your eyes won’t help. The astronauts reported that the flashes occurred even when they were trying to sleep.

Of course, the eyes are just a tiny part of the body. The existence of cosmic ray visual phenomena implies that the entire body is being pinged by cosmic radiation around the clock; thousands of rays would pass through you every second. Physicist Eugene Parker of the University of Chicago has said that a third of your DNA would be sliced up by cosmic rays every year you spend in interplanetary space. This is far too much damage to be controlled by the body’s own DNA repair mechanisms. We also must remember that we won’t be alone in space. We are carrying billions of bacteria, viruses, and fungi, in the form of our microbiome that plays an important role in maintaining health. Microflora in our gut help digest our food, for example. Cosmic radiation could kill or otherwise cause mutations in our microbial passengers, presenting unknown dangers. Only very thick shielding or some kind of mini-magnetosphere around the craft or base (which I explore below) can stop these cosmic rays from passing through your body in space. This has major ramifications not only for spaceflight but also space living. Bases on the Moon, Mars, and nearly anywhere we set up camp beyond our magnetosphere, regardless of how distant they are from the Sun, will be inundated with cosmic rays unless properly shielded. When outside, you would be forced to live with flashes in your eyes, causing untold damage, let alone with the other ramifications of this radiation exposure. Contrary to the silliest of science fiction tropes, cosmic rays don’t engender super-human strength.

The research results from experiments on rodents and space radiation have been ambiguous. Charles Limoli, a professor of radiation oncology at the University of California, Irvine, School of Medicine, led a NASA-sponsored study that exposed laboratory mice to a level of radiation similar to that expected on a six- month one-way trip to Mars. His team found that the radiation caused significant long-term brain damage, including cognitive impairments and dementia, a result of brain inflammation and damage to the rodents’ neurons. The mice’s brain cells showed a sharp reduction in features called dendrites and spines, like a tree losing its leaves and branches, disrupting the transmission of signals among neurons. The radiation also affected part of the brain that normally suppresses prior unpleasant and stressful associations, a process called fear extinction which, if disabled, can cause anxiety. “This is not positive news for astronauts deployed on a two- to three-year round-trip to Mars,” Limoli told me at the time of his 2016 study.

However, as often seen in animal studies, the dose rate in this experiment—bursts between 0.05 and 0.25 Gy / min—was much higher than what would be expected in a human mission to Mars, in which the estimated total dose for a six-month mission is 1 Gy, or 100 rad, evenly dispersed over time. The scientists weren’t able to place mice in a habitat with constant exposure to space radiation for six months. Instead, mice were bombarded in great bursts of radiation from a particle accelerator at the NASA Space Radiation Laboratory at Brookhaven National Laboratory and then *observed* for six months. But dose rate matters. Drinking six beers in one hour might get you drunk; drinking six beers in six hours, maybe not. Same exposure, different rate. Better-designed studies would be needed to truly test whether astronauts will be sane or “punch drunk from radiation” when they arrive at Mars.

Other researchers have found that proton radiation causes attention deficits and poor task performance in rats in a simulated space environment and that HZE particles caused an increase in amyloid beta plaque growth associated with Alzheimer’s disease. From clinical studies, we know that people who undergo certain kinds of radiation treatment for brain cancer can be cured but have notable declines in their cognitive function. The term is radiation-induced cognitive decline. Upward of half of all patients who receive cranial radiation treatment and who survive their cancer for at least six months will be left with progressive cognitive impairment, particularly in the domains of processing speed (thinking quickly) and memory. But again, this may not translate directly to space: the patients are receiving intense radiation over a period of a few months, whereas in space the radiation exposure on a trip to Mars would be spread out across nearly three years.

What can be done to mitigate the risks? Shielding, lots and lots of shielding. Cosmic radiation is more energetic than solar radiation. Basically, it’s moving faster; and some of those atomic bits, such as iron nuclei, are far heavier than the protons and electrons in the solar wind. An iron nucleus would be hundreds of times more energetic than a hydrogen nucleus, which is what a proton is. Flimsy shielding is worse than nothing at all because of the cascade of secondary particles, like shrapnel. A thin layer of spacecraft metal merely scatters the impact of a cosmic ray, turning one fast bullet into scores of only slightly slower bullets. The ship needs thick shielding, and how thick is a simple matter of physics—and economics.

A few centimeters of lead would do the trick. But that would add hundreds of tons to the mission and hence billions of dollars. Water can act as an effective shield. And we need to bring water anyway. So, engineers are playing around with the idea of a hull encompassing the entire craft filled with water. You’d need a lot of it, though, to protect a spacecraft large enough to take a crew to Mars—that is, much more water than you’d need to drink. You can also use trash as extra protection. Still not enough material, but it helps. One very effective shield with low mass would be hydrogen gas, but you’d need a pressurized chamber to hold it, bringing too much mass back into the equation.

The answer to the shielding problem may be a combination of ideas that makes materials serve double-duty. In this regard, hydrogenated boron nitride nanotubes, or hydrogenated BNNTs, show great promise. These tubes are made of carbon, boron, and nitrogen. They are extremely light, hold up to heat and pressure, and are strong enough to serve as load-bearing primary structures for the entire spacecraft. The tubes could be filled with hydrogen gas or water as a primary radiation shield. Boron is an excellent absorber of secondary neutrons, minimizing the radiation cascade effect. As with carbon nanotubes, BNNTs are prohibitively expensive for now but may come down in price in the near future. If the entire craft can’t have such a shield, perhaps just the sleeping chambers could, which would effectively reduce radiation exposure by a third if the crew spent eight hours a day sleeping or resting. Perfect protection, as we have on Earth, might not be feasible, but partial protection might reduce the health risks enough to relieve everyone’s worries.

Researchers at CERN in Switzerland are working on a magnetic force field to serve as a mini-magnetosphere to naturally deflect the cosmic rays. In 2014, CERN broke a record by creating a current of 20,000 amps at a temperature of 24 Kelvin (about −249°C) in an electrical transmission line comprising a pair of twenty-meter-long cables made of a magnesium diboride (MgB2) superconductor. While that bodes well for cheaper and more reliable power transmission on Earth, CERN also joined the European Space Radiation Superconducting Shield project to apply the technology to a spacecraft and space habitat. The goal is to create a magnetic field 3,000 times stronger than Earth’s own magnetic field, with a ten-meter diameter protecting astronauts within or directly outside a spacecraft. CERN is working on a way to reconfigure the electrical coil for space with MgB2 superconducting tape. All of this—the magic materials and the force field—are years away from application. There’s no solution to the cosmic radiation problem in the near future aside from the hope that it isn’t as bad as the laboratory studies are predicting.

Excerpt adapted from Spacefarers: How Humans Will Settle the Moon, Mars, and Beyond, by Christopher Wanjek, published by Harvard University Press. Copyright © 2020 by the President and Fellows of Harvard College. Used by permission. All rights reserved.

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11 Pros and Cons of Space Exploration

We’ve put boots on the moon. There are plans in the works to put boots on Mars in this generation. Small spacecraft, such as Voyager 1, have traveled more than 138 AU from our planet since launching, with the goal of discovering what interstellar space may have in store. The pros and cons of space exploration let us explore the final frontier that we currently know. It allows us to see what the universe offers beyond on our planet.

Exploring space is also inherently dangerous. Not only is space a vacuum environment that does not support human life without protection, but we do not know what may be lying in wait for us out there. The conflicts we have here at home could be minuscule compared to the conflicts that may be waiting for us in the stars.

Here are some of the key points to think about when looking at this debate.

What Are the Pros of Space Exploration?

1. It provides humanity with hope for the future. Humans are currently confined to a single planet and facilities that orbit it. Should something happen that changes the environment of the planet, it would have the potential of wiping out the entire human species. A large asteroid, the star going nova, or even a shift in the planetary climate could devastate humanity. Space exploration gives us the chance to begin colonizing other locations, giving us hope that our species can survive.

2. It increases our knowledge. There are many secrets lying in wait to be discovered in space. Asteroids or planets may have new materials that we don’t have on Earth. We can discover more about how the universe was created and why it exists in its current state. These discoveries could then help to improve life on our own planet as we seek out others to explore.

3. It drives innovations in numerous fields. According to the 100-Year Starship Program, the technologies that were created for and made possible because of space exploration have helped to shape, permeate, and are an integral part of who we are today. To travel the stars, we must be able to store large quantities of energy. We must develop closed-loop support systems. Advances in agriculture, computing, artificial intelligence, and manufacturing must happen as well. The framework needed to explore space improves the socioeconomic frameworks we have at home.

4. It can be something that we do at home. According to information provided by the Goddard Space Flight Center, there are over 2,200 active satellites in orbit around Earth right now. One of those satellites is the Hubble Space Telescope. This technology has allowed us to explore our solar system from right here at home. In 2017, this telescope discovered that a dwarf planet in the Kuiper Belt, name 2007 OR10, has a moon that was previously unknown.

5. True space exploration requires international cooperation. The foundation of how we explore space was created in 1966 with the Treaty on Principles Governing the Activities of States in the Exploration and Use of Outer Space, including the Moon and Other Celestial Bodies. It’s easier to call it the “Outer Space Treaty.” By 2017, there were 105 countries who had signed onto the treaty and another 24 who have signed, but not yet ratified it. This treaty forbids placing weapons of mass destruction into orbit, installing them on the moon, or any other location in space. The treaty also disallows any nation from claiming a celestial resource as a national appropriation.

6. The political structures of managing space exploration are already in place. According to Wired, a multistate body that is supported by 193 nations approves the orbits of items that are currently in space. It is called the International Telecommunication Union and it has been in place since the 1960s. With their protocols helping to create a push deeper into space, exploration could become a future way of life.

What Are the Cons of Space Exploration?

1. It could allow other civilizations to know about our own. The idea of finding alien life has been a concept explored in the medium of fiction for more than a century. There is something comforting about the idea that humans are not alone in the universe as a species. That knowledge could come with a price. If an advanced civilization encountered one of the gold-plated records on the Voyager crafts and decided they wanted our planetary resources, we might be unable to stop them. There is sometimes more danger in being part of a community than living by yourself without any neighbors.

2. Exploring space is a costly venture. In 1973, the total cost of the Apollo program was reported to the US Congress as being $25.4 billion. The total cost of the space shuttle program, when adjusted for inflation, was $196 billion. Each mission that was flown came at a cost of $450 million. The Mars One mission budget to bring just 4 people to Mars is over $6 billion. Even as technologies advance, the costs of exploring space are far from cheap.

3. We must consume resources to get people or equipment into space. There are high fuel costs required to launch anything into orbit. Using the US Space Shuttle program as an example, the total mass of all propellants was over 3.8 million pounds. Fossil fuels are refined to create these fuels, used in the manufacturing processes to create the equipment or vehicles, and this creates an environmental cost which must be paid at some point.

4. Exploring space means we’re leaving a lot of litter behind. According to information provided by NASA, there are more than 500,000 items of debris that are currently being tracked as they orbit our planet. This space junk is litter that is flying at a speed of over 17,500 miles per hour, which means an impact could do great damage. Now expand the amount of space junk that exists to other planets or solar systems and the amount of litter we would leave behind is quite enormous.

5. No agreements are in place for rich resources that may exist in space. The current treaties which govern space exploration forbid governments from appropriating territories in space. The amount of materials in a single asteroid could be more than $100 billion. Planetary Resources has evaluated an asteroid called “Davida” to be worth $100 trillion or more. Although the US has brought back hundreds of pounds of rocks from the moon without litigation, there would be a greater fight in grabbing resources that are in the hundreds of trillions of dollars.

The pros and cons of space exploration highlight the current rifts we have in society. Governments are restricted and private organizations with the most resources have the chance to make huge profits. If those profits can be funneled toward a mutual good, then humanity can do more than just survive. It could thrive.

An expert offers insight into how space travel impacts the human body

S pace travel is not for the faint of heart. It is a challenging and risky endeavor that requires rigorous training, preparation, and adaptation. The human body is not designed to survive in the harsh environment of space, where gravity, radiation, and isolation can have detrimental effects on health and well-being.

NASA has been studying the effects of space travel on the human body for more than 50 years, through its Human Research Program (HRP). The program aims to understand and mitigate the risks of human exploration, as NASA plans for extended missions on the Moon and Mars.

One of the most ambitious projects of the HRP was the Twins Study, which involved Scott Kelly and his identical twin brother Mark Kelly, both retired astronauts. Scott spent nearly a year in space onboard the International Space Station (ISS), while Mark stayed on Earth as a control subject. The study compared the physiological and psychological changes that occurred in Scott and Mark during and after the mission, providing valuable data on the effects of long-duration spaceflight.

Scott was not the only American astronaut to spend almost a year in space. Christina Koch also completed a 328-day mission on the ISS, setting a record for the longest single spaceflight by a woman. Both Scott and Christina experienced changes in their bodies, such as alterations in gene expression, immune system, microbiome, metabolism, and cognition.

However, spending a year in space is not the same as spending a year on Earth. Space travelers face a number of challenges that can affect their health and performance. One of the first and most common problems is space sickness, which is caused by the lack of gravity on the inner ear. This affects balance, coordination, and spatial orientation, and can also impair the ability to track moving objects.

Another challenge is the loss of muscle and bone mass, which occurs due to the lack of mechanical stress on the body. Astronauts can lose up to 20% of their muscle mass and 1-2% of their bone density per month in space, which can increase the risk of fractures, injuries, and osteoporosis. To prevent this, astronauts exercise for two hours a day on the ISS, using specially designed equipment such as treadmills, bikes, and resistance devices.

A more recent discovery is the effect of space travel on vision. Some astronauts have reported blurred vision, reduced contrast sensitivity, and changes in eye shape after returning from space. This is thought to be caused by the increased pressure on the brain and the eye, which results from the fluid shift in the body due to microgravity. NASA is investigating the causes and consequences of this phenomenon, as well as possible countermeasures.

In addition to the physical effects, space travel can also have psychological and social impacts. Astronauts are exposed to isolation, confinement, monotony, and distance from Earth, which can affect their mood, motivation, and mental health. They also have to cope with the stress of living and working in a hostile and closed environment, where any mistake can have serious consequences. NASA provides astronauts with psychological support, communication, and entertainment to help them deal with these challenges.

NASA is also researching the risks of space travel for future missions to Mars, which are expected to last for several years. These risks are grouped into five categories, related to the stressors they place on the body. These can be summarized with the acronym “RIDGE,” short for Space Radiation, Isolation and Confinement, Distance from Earth, Gravity fields, and Hostile/Closed Environments.

Space travel is not easy, but it is also not impossible. As we continue to explore the final frontier, we must also continue to learn and adapt, ensuring that our astronauts are as prepared as possible for the journey ahead. Space travel is a fascinating and rewarding endeavor, but it also requires careful planning, innovative thinking, and a commitment to understanding and mitigating the risks involved.

Relevant articles:

– The Human Body in Space – NASA

– The effects of space travel on the human body – BBC

– The Health Risks of Space Tourism: What are They?

As private satellites increase in number, what are the risks of the commercialization of space?

The Global Risk Report says some governments “are encouraging private space activity to further national ‘territorial’ claims. Image:  Unsplash/ NASA

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• Around 11,000 satellites already orbit the Earth, together with tons of space junk.
• Life on the planet increasingly depends on space technology.
• As the risk of collisions grows, is it time to think again about how we use - and govern - space?
• Read the Global Risks Report here .

Space is getting more crowded and more commercialized. This is leading to a growing risk of collisions between satellites and space junk, and means that new regulations on the use of space are urgently needed.

Those are some of the conclusions of the World Economic Forum’s Global Risks Report 2022 , which warns that if satellites fail, whether due to natural or human events, the consequences for life on Earth could be profound.

Global navigation and communication systems are heavily dependent on space technology, the report says, but so too are energy and water supplies, financial infrastructure, broadband internet and television and radio services.

Yet if a single piece of space junk strikes just one satellite, it could cause a cloud of debris that takes out many more and results in a “cascading effect” on critical services. That’s according to one theory, called the Kessler Effect.

“With such possibilities becoming likelier in a congested space, the lack of updated international rules around space activity increases the risk of potential clashes,” the report says.

Crowded space

Around 11,000 satellites have been launched since Sputnik 1 became the first human-made object to orbit the Earth in 1957, but almost seven times that number are planned to join them over the coming decades, the report notes.

There are also an estimated half a million pieces of debris in orbit, presenting a growing threat to our use of space. A piece of space junk even hit the International Space Station (ISS) in May 2021, making a hole in a robotic arm.

Only 3% of those surveyed for the Global Risks Report say that mitigation measures to prevent conflict in space are effective, while 59% think they are still at an early stage and 17% believe they have not even started.

Space regulation falling behind

Since 1967, 110 countries have ratified the United Nations Outer Space Treaty , which bans the stationing of weapons of mass destruction in space. But the report points out that space regulation has not kept pace with evolving technologies and new military threats.

It says there is a “pressing need” for an international body to govern the launching and servicing of satellites, to establish space traffic control and provide common enforcement principles to back them up.

The 1972 Space Liability Convention covers only spacecraft, but the report says that clarity is needed on how to deal with the likes of Sir Richard Branson’s Virgin Galactic ships, which launch from a plane and use wings to help them land.

Virgin Galactic is just one example of a growing trend towards private investment in space technology. Elon Musk’s SpaceX rockets are already delivering satellites and supplies for government agencies such as NASA , including Christmas gifts to the ISS crew.

Early space exploration was the exclusive province of governments. But the Global Risk Report says some governments “are encouraging private space activity to further national ‘territorial’ claims, or to foster the development of high-value jobs … as well as enhancing their military or defence-oriented presence”.

In the United States, SpaceX’s Starship rocket has been selected to carry NASA astronauts to the moon as part of the Artemis programme, which also aims to send humans to Mars. Starship will be the first US-manned lunar mission since Apollo 17 landed in December 1972 .

Increased private investment in space is also driving down the cost of launching satellites into orbit, says the report. Lower costs mean more organizations can launch smaller satellites, opening up the prospect of innovations such as space-based energy generation and even tourism.

Have you read?

The big space clean-up - and why it matters, how many space launches does it take to have a serious climate impact, in pictures: the history of space travel, space arms race.

Among the less welcome aspects of new space technologies is the development of hypersonic weapons – missiles that are so fast and agile they can evade conventional defences. The report says a “hypersonic arms race” is already underway.

“Gaps in space governance render arms races even more likely,” says the report. “New rules are unlikely in the near future, as there is little agreement over key issues such as boundaries, control over space objects, or dual-use systems. Any further decline in cooperation on space governance will only exacerbate risks,” it adds.

Warning that critical space technology is vulnerable to hazards other than space junk, the report calls for space powers to work together to avoid conflict and agree standards and norms for space operations.

“Critically, and like other realms where technology is developing at a faster pace than its regulation, bringing private-sector actors into the agreement processes will help ensure that such pacts reflect both commercial and technical realities,” the report concludes.

Emerging and frontier technologies can help tackle social, economic and health challenges. But designed improperly, they could exacerbate the problems that they are intended to address.

For this reason, the World Economic Forum will launch its inaugural Global Technology Governance Summit on 6-7 April 6-7. The first-ever event will be hosted with Japan to create a collaborative neutral space where senior leaders, CEOs, board members, startups, innovators, entrepreneurs, academics, policymakers and civil society can come together to discuss and share issues related to the governance and protocols critical to new technologies.

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Money latest: Holiday hack for cheaper internet abroad; the healthiest chocolate you can buy

Our cost of living specialist is back with a money-saving tip for using the internet abroad. Read all today's personal finance and consumer news - and listen to the latest Ian King Business Podcast below.

Friday 10 May 2024 09:54, UK

• Interest Rates
• UK exits recession, official figures show
• Interest rate held at 5.25% | Bank of England: June rate cut 'not ruled out but not fait accompli'
• Gordon Ramsay to open new restaurants on London skyscraper

Essential reads

• Ed Conway on economy:  Britain out of recession with a bang
• How to avoid a holiday data roaming charge (while still using the internet)
• Mortgage rates up again this week - here are the best deals on the market
• How you can turn nightly chocolate into a superfood
• Cheapest 10 European cities for a holiday - and how costs compare
• Listen to the Daily above and  tap here to follow wherever you get your podcasts

Sainsbury's is running a scheme that allows some shoppers to earn easy Nectar card points. 

To earn extra points, shoppers just need to spend £1 across multiple transactions at Sainsbury's. 

The supermarket says the scheme is available to "millions" of customers, though all it would say about the eligibility criteria is that it's "based on a range of factors".

Check if you're eligible

Log into your nectar card app and check to see if you have this message...   

Make sure you opt in once you see the message. 

From there, you simply need to spend £1 or more five times - earning extra points each time. 

The number of bonus points on offer varies for each customer.

The offer runs until 4 June. 

Britain is not just out of recession. 

It is out of recession with a bang.

The economic growth reported this morning by the Office for National Statistics is not just faster than most economists expected, it's also the fastest growth we've seen since the tailend of the pandemic, when the UK was bouncing back from lockdown.

But, more than that, there are three other facts that the prime minister and chancellor will be gleeful about (and you can expect them to be talking about this number for a long time).

First, it's not just that the economy is now growing again after two quarters of contraction - that was the recession. 

An economic growth rate of 0.6% is near enough to what economists used to call "trend growth", back before the crisis - in other words, it's the kind of number that signifies the economy growing at more or less "normal" rates. 

And normality is precisely the thing the government wants us to believe we've returned to.

Second, that 0.6% means the UK is, alongside Canada, the fastest-growing economy in the G7 (we've yet to hear from Japan, but economists expect its economy to contract in the first quarter).

Third, it's not just gross domestic product that's up. So too is gross domestic product per head - the number you get when you divide our national income by every person in the country. After seven years without any growth, GDP per head rose by 0.4% in the first quarter. 

And since GDP per head is a better yardstick for the "feelgood factor", perhaps this means people will finally start to feel better off.

But this is where the problems come in. 

Because while this latest set of GDP figures is undoubtedly positive, the numbers that came before are undoubtedly grim.

GDP per head is still considerably lower, in real terms, than it was in 2022, before Liz Truss's disastrous mini-budget, or for that matter lower than in early 2019.

Raising another question: when people think about the state of the economy ahead of the election (and obviously these new figures are likely to increase the speculation about the date of the election), do they put more weight on the years of economic disappointment or the bounce back after them?

Do they focus on the fact that we're now growing at decent whack or on the fact that their income per head is, in real terms, no higher today than it was five years ago?

These are the questions we will all be mulling in the coming months - as the next election approaches. One thing is for sure: this won't be the last time you hear about these GDP numbers.

The chancellor is speaking to Sky News after the welcome news that the UK has exited a recession. 

"It's encouraging that the UK economy is growing faster over the last quarter, not just than France, Germany or Italy, but actually faster than the United States," Jeremy Hunt says.

"But I think what's more encouraging is the longer-term data that we are now seeing about the economy."

He praises the government's handling of the economy. 

"I think that for families who've been having a really tough time, this is an indication that difficult decisions that we've taken over recent years are beginning to pay off and we need to stick with them."

He nods to the Bank of England governor Andrew Bailey's comments yesterday that inflation is expected to fall to 2% in the coming months: "So we're seeing that inflation is falling faster and I think people recognise it's been a very, very challenging period."

He's then asked whether the UK can compete with the US's economy in the coming years. 

Mr Hunt says he wants the UK to become "the new Silicon Valley" as a route into the tech sector. 

"Tech is the sector that is growing the fastest and will continue to grow the fastest," he says. 

Finally, he's asked when national insurance will be abolished - a recent Tory pledge. 

"We haven't set a date... we'll only do it when it's affordable and when we can do so without impacting on public services."

Our economics editor Ed Conway   is giving his first reaction to the ONS statistics that show the UK is no longer in recession. 

"These are great numbers," he says. 

"Certainly in the context of things, they are close to what we would normally historically call trend growth - a good rate of growth - and that's going back a long time. 

"They're better than expected... this is definitely some good news."

The UK economy is no longer in recession, according to official figures.

Gross domestic product (GDP) grew by 0.6% between January and March, the Office for National Statistics said.

A recession, which is defined as two consecutive three-month periods where the economy contracts, was declared in February.

The previous set of figures showed that GDP, a major measure of economic growth, shrank 0.3% between October and December. It followed a contraction of 0.1% in the three months from July to September.

The slump was blamed on reduced consumer spending power as inflation and energy bills stayed high. Months of wet weather also contributed to keeping shoppers at home, commentators said.

Jeremy Hunt, the chancellor, was buoyant about the figures: "It has been a difficult few years, but today's growth figures are proof that the economy is returning to full health for the first time since the pandemic." 

By Megan Harwood-Baynes , cost of living specialist

When my plane touched down on the runway of Manila airport, I was welcomed to the country with a text. Coming from Sky Mobile, the message informed me that using my phone abroad would incur hefty charges - including £2.16 for every megabyte (MB) of data I used.

One MB is equivalent to a short WhatsApp voice note message, and given my average monthly data allowance is 20GB (20,000MB), I would be quickly bankrupted if I continued to use my phone as normal. And while I love switching off from work while I am away, for me, the internet is as much a holiday essential as toothpaste and a hairbrush. 

From the ability to check Google Maps when out and about, or do a quick search to check I am not being scammed, it is now something I always factor into my holiday budget.

Welcome to the world of eSims

An eSim is an industry-standard digital SIM card that allows you to activate a mobile plan on your phone without the need to install a physical SIM into your phone.

TLDR - it means you can activate a short, temporary internet plan while on holiday for a fraction of the price it would cost you through your network provider.

I used an app called Global Yo (other providers are available, but this is the one I used), which has 24-hour plans from as little as 99c (71p) for 1GB. 

Once downloaded from the App Store, you can scroll through the list of countries to select your destination. Select the plan you want - while in the Philippines, I paid around £7 for a weekly plan that would give me 5GB of data. It is cheaper to do it day by day, but that also means you have to remember to top up each morning.

Once purchased, you are sent a QR code to scan - this will help you install the eSIM. The process varies by phone, but once installed, you go into the SIM manager settings on your phone. You can then toggle the settings so your calls and texts come via SIM 1 (your primary phone number), but mobile data uses the eSIM. This means you won't miss any vital text messages that come through to your phone number while on holiday.

The downsides

Not every network, or mobile phone, supports eSIMS, so check with your network provider before you shell out, and make sure your phone is unlocked. My sister, who lives in Hong Kong, wasn't able to install the eSIM on her phone but only realised this after paying £7.99 for a week's worth of data. 

We also had some difficulty installing it on my mum's iPhone, but that could be because we are all Android users.

You also have to be connected to WiFi /the internet to install the eSIM in the first place, so make sure you do it while at your hotel in the morning. A few times while I was paying each day I would forget this, head out and be without internet for the day. 

This wasn't exactly a hardship, but did mean I couldn't share with my Instagram followers what a great time I was having.

It can be hard to balance eating well without spending a lot.

In this series, we try to find the healthiest options in the supermarket for the best value - and have enlisted the help of Sunna Van Kampen , founder of Tonic Health, who went viral on social media for reviewing food in the search of healthier choices.

In this series we don't try to find the outright healthiest option, but help you get better nutritional value for as little money as possible.

Today we're looking at chocolate - and why, before sugar and dairy is added, it's a superfood, in Sunna's view. 

A superfood is anything with a very high "nutritional density" - or lots of nutrients for few calories. 

Superfoods need a high concentration of antioxidants - molecules which neutralise unstable molecules that can harm your cells.

You can get antioxidants by purchasing expensive "greens" powders, but Sunna says plenty of supermarket options can be classified as "superfood".

"Chocolate is not unhealthy, it is actually a superfood - it's the sugar we added to it that is the problem," he says.

"Chocolate in the supermarkets tends to come in at only £27.50/kg, which is almost half the price of your cheapest greens powder." 

Sunna points out that cacao, from which chocolate is made, is in its own right a superfood and has more antioxidants than blueberries, acai berries and cranberries - well-known superfoods. 

"Cacao actually has more than 40x the antioxidants of blueberries in its raw form," he says. 

But, as he says, the added sugar is where the problems come in. 

Sunna's guide to buying chocolate

Sunna recommends picking chocolate that contains a high proportion of cocoa solids - which brings down the sugar content. 

Here's how the different kinds of chocolate stack up:

• Milk – 25% cocoa solids, 54g of sugar per 100g.
• Dark – 47% cocoa solids, 49g of sugar per 100g.
• 70% dark - 70% cocoa solids, 29g of sugar per 100g
• 85% dark - 85% cocoa solids, 15g of sugar per 100g
• 90% dark - 90% cocoa solids, 7g of sugar per 100g

"A typical milk chocolate only contains 25% cacao solids, and the first two ingredients are actually milk and sugar," Sunna says. 

"For chocolate to be a superfood, it has to be dark chocolate - at a minimum of 70% dark ideally."

A couple of pieces after dinner each night means you'll be consuming 200g of superfood chocolate a week for £5.50.

"If you're a milk chocolate fan, don't fret," Sunna says. "It is possible to retrain your taste buds in just 10 days to get the superfood benefits of 70% and above."

That might sound easier said than done, but Sunna says the trick is to start with the lower percentages and work your way up to the higher ones. 

"Get to a level you are comfortable with and then make sure you have a piece of chocolate every night for 10 days straight," he says. 

"The more you train the taste buds, the less sugar you consume."

The switch from milk chocolate to 70% dark will save you 2.6kg of sugar a year, while working your way up to 90% will save you more than 4.8kg of sugar a year (assuming 200g consumption per week). 

"Small chocolate changes - and a bit of work to train your tastebuds - can lead to huge sugar savings that are worth it not just for the reduction in sugar, but also the increase in antioxidants," Sunna concludes. 

Read more from this series... 

Every Friday we get an overview of the mortgage market with independent experts from  Moneyfactscompare.co.uk .  Today, finance expert Rachel Springall outlines what's been happening with mortgages this week, before honing in on the best rates for remortgaging…

Fixed-rate mortgage repricing has quietened down this week, but a couple of prominent lenders have made tweaks, such as Virgin Money increasing selected fixed by up to 0.2% and Barclays reducing by up to 0.39%. 

This comes off the back of a busy week for repricing, as lenders reacted to rising swap rates. 

The Bank of England's next rate decision will be in June, but it's uncertain whether a rate cut will happen, with some economists predicting no change until the last three months of the year.

Week on week, the overall average two and five-year fixed rates rose to 5.93% and 5.51%.

Looking at remortgaging, this week the lowest two-year fix for customers with 40% equity comes from The Co-operative Bank, priced at 4.76%, which comes with a £1,999 fee and offers borrowers £250 in cashback and provides a free valuation and free legal fees incentive package. This is available to those who borrow a minimum of £750,000.

Those looking to fix for longer will find the lowest five-year fixed remortgage deal comes from NatWest this week, available to those with 40% equity. Priced at 4.32%, this deal carries a £1,495 fee and offers a free valuation and free legal fees incentive package.

Best buy alternatives

As a remortgage customer, it's possible you are looking to save on the upfront cost of any deal. You might also want a deal to cover a valuation or legal fees. A best buy mortgage could be the most cost-effective choice in this instance.

This week the top packages on a two-year fixed remortgage deal at 60% or 75% loan-to-value come from First Direct, priced at 4.83% and 4.98% respectively, both of which come with a free valuation and free legal fees incentive package and charge a £490 product fee. 

If you want to borrow more, then there is a best buy deal priced at 5.19% from Suffolk Building Society at 80% loan-to-value, which carries a free valuation and free legal fees incentive package and charges a £1,198 product fee.

A five-year fixed mortgage may be more appealing for you to guarantee your monthly repayments for longer.

Vernon Building Society has a deal priced at 4.49%, and charges a product fee of £999 but does not carry any incentives. If you are borrowing at 75% loan-to-value, then Cumberland Building Society has a best buy package priced at 4.58% for five years, which includes a free valuation and free legal fees incentive package and charges a £999 product fee.

Looking for some longer Money reads for your evening/commute/lunch break?

Here's four from the last few months you might like...

Should you offer kids cash rewards for good grades? The psychologist's view

As exam season gets under way, some parents are putting hundreds of pounds aside to reward their children if they achieve certain grades. 

While some parents lambasted the idea as "absolute potatoes", others told Sky News they saw their children's focus increase after offering up to £250 for the top results.

We also spoke to teachers and a psychologist...

What can I do if flexible working request declined?

Every Monday we put your financial dilemmas or consumer disputes to industry experts. A few weeks ago Sky News reader AJ2024 asked...

"While on maternity leave my employer rejected my flexible work request and told me to pick from four new shift patterns or take redundancy if they didn't suit me. All new shifts were full working hours. No support as a new mother and ruined my last few precious weeks. What are my rights?"

We got an employment lawyer to answer...

'£2,000 landed in my account' - The people who say they're manifesting riches

Money blogger Jess Sharp spoke to people who swear they've made money from manifestation - before finding herself meditating under a tree to see if she could get in on the action...

The world of dark tourism - what is it, is it ethical, and where can you go?

Interest in a phenomenon known as "dark tourism" has been steadily rising in recent years - but what is it?

To find out, we spoke with tourism academic  Dr Hayley Stainton  and renowned dark tourist and author Dr Peter Hohenhaus, who runs a  dark tourism website ...

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