dangers in space travel

NASA scientists consider the health risks of space travel

Humans aren't built to live in space, and being there can pose serious health risks . For space administrations like NASA, a major goal is to identify these risks to hopefully help lessen them. 

That was a major theme during NASA’s Spaceflight for Everybody Virtual Symposium in November, a virtual symposium dedicated to discussing current knowledge and research efforts around the impact of spaceflight on human health. During a panel discussion titled “Human Health Risks in the Development of Future Programs” on Nov. 9, NASA scientists discussed these risks and how they are using existing knowledge to plan future missions. 

Each panelist emphasized that the health risks presented by space travel are complex and multifaceted and that all types of risks should be considered closely when planning future missions. 

Related:  Space travel can seriously change your brain  

• Spending time in space can harm the human body — but scientists are working to mitigate these risks before sending people to Mars
• Astronauts Will Face Many Hazards on a Journey to Mars

Five types of risk

When discussing the risks presented by living in space and space travel, there are five main types, the scientists outlined in the presentation. 

Two types of risk, radiation and altered gravity, come simply from being in space, they said. Research has shown that both can have major negative effects on the body, and even the brain . Others, like isolation and confinement as well as being in a hostile closed environment, encompass risks posed by the living situations that are necessary in space, including risks to both mental and physical health. 

Then, there are the risks presented simply by being a long way from Earth. The farther humans get from the Earth, the riskier living in space becomes in almost every way. 

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Everything from fresh food to unexpired medication will be extremely difficult to make accessible with longer journeys farther away. On the International Space Station, astronauts aren’t too far from us, and we can routinely send supplies to the crews in orbit. But a mission to the moon or Mars would pose more problems. 

Communication delays would increase, and there would likely be communication blackouts, said Sharmi Watkins, assistant director for exploration in NASA’s Human Health and Performance Directorate who served as a panelist for this discussion.   She said it would also take longer to get back to Earth if there was a medical emergency. 

"We're not going to measure it in hours, but rather in days, in the case of the moon, and potentially weeks or months, when we start to think about Mars," said Watkins.

Steve Platts, the chief scientist in NASA’s human research program, broke down different levels of risk in space and discussed how NASA uses a "phased approach" when it comes to research on human health. In this approach, initial "phases" include research on the health effects of being in space has also been done in simulated conditions on Earth, from isolation experiments in Antarctica to radiation exposure at Brookhaven National Laboratory in Long Island, New York. Likewise, experiments on the space station will help us to prepare for risk on the moon and Mars — these later phases build on knowledge gained from simulations. 

"We do work on Earth, we do work on low earth orbit and then we'll be doing lunar missions, all to help us get to Mars," Platts said. 

— Deep-space radiation could cause have big impacts on the brain, mouse experiment shows

— Without gravity, the fluid around an astronaut's brain moves in weird ways

— Long space missions can change astronaut brain structure and function

Still, no matter how much we may prepare on Earth, every space mission comes with risk, so NASA has set health standards to minimize this risk for astronauts. 

NASA has over 800 health standards that they’ve developed based on current research. These standards describe everything from how much space astronauts should have in a spacecraft to how much muscle and bone loss an astronaut can experience without being seriously harmed. These standards also include levels of physical fitness and health the astronauts need to meet before going into space. All of NASA’s health standards for astronauts are available online . 

A mission can impact astronauts’ health, but it also works the other way — health troubles with astronauts could impact a mission if they aren’t able to perform mission tasks adequately, said Mary Van Baalen, acting director of human system risk management at NASA and the panel’s moderator. She emphasized the complex interplay between these two types of impacts, both of which NASA scientists must keep in mind when planning missions. 

"Space travel is an inherently risky endeavor," she said. "And the nature of human risk is complex."

You can watch the full recording of the panel discussion and other talks from the symposium here . 

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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].

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].

Rebecca Sohn is a freelance science writer. She writes about a variety of science, health and environmental topics, and is particularly interested in how science impacts people's lives. She has been an intern at CalMatters and STAT, as well as a science fellow at Mashable. Rebecca, a native of the Boston area, studied English literature and minored in music at Skidmore College in Upstate New York and later studied science journalism at New York University. 

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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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Five hazards of human spaceflight.

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Exploration to the Moon and Mars will expose astronauts to five known hazards of spaceflight:

• Space Radiation
• Isolation and Confinement
• Distance From Earth
• Gravity Fields
• Hostile Closed Environments

Watch a playlist of videos to explain each hazard and to learn what NASA’s Human Research Program is doing to protect humans in space.

Five Hazards of Human Spaceflight Playlist

Spending time in space can harm the human body − but scientists are working to mitigate these risks before sending people to Mars

Professor of Applied Physiology & Kinesiology, University of Florida

Disclosure statement

Rachael Seidler receives funding from the National Aeronautics and Space Administration, the Translational Research Institue for Space Health, the National Science Foundation, the National Institutes of Health, and the Office of Naval Research.

University of Florida provides funding as a founding partner of The Conversation US.

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When 17 people were in orbit around the Earth all at the same time on May 30, 2023, it set a record. With NASA and other federal space agencies planning more manned missions and commercial companies bringing people to space, opportunities for human space travel are rapidly expanding.

However, traveling to space poses risks to the human body. Since NASA wants to send a manned mission to Mars in the 2030s, scientists need to find solutions for these hazards sooner rather than later.

As a kinesiologist who works with astronauts, I’ve spent years studying the effects space can have on the body and brain. I’m also involved in a NASA project that aims to mitigate the health hazards that participants of a future mission to Mars might face.

Space radiation

The Earth has a protective shield called a magnetosphere , which is the area of space around a planet that is controlled by its magnetic field . This shield filters out cosmic radiation . However, astronauts traveling farther than the International Space Station will face continuous exposure to this radiation – equivalent to between 150 and 6,000 chest X-rays .

This radiation can harm the nervous and cardiovascular systems including heart and arteries , leading to cardiovascular disease. In addition, it can make the blood-brain barrier leak . This can expose the brain to chemicals and proteins that are harmful to it – compounds that are safe in the blood but toxic to the brain.

NASA is developing technology that can shield travelers on a Mars mission from radiation by building deflecting materials such as Kevlar and polyethylene into space vehicles and spacesuits . Certain diets and supplements such as enterade may also minimize the effects of radiation. Supplements like this, also used in cancer patients on Earth during radiation therapy, can alleviate gastrointestinal side effects of radiation exposure.

Gravitational changes

Astronauts have to exercise in space to minimize the muscle loss they’ll face after a long mission. Missions that go as far as Mars will have to make sure astronauts have supplements such as bisphosphonate , which is used to prevent bone breakdown in osteoporosis. These supplements should keep their muscles and bones in good condition over long periods of time spent without the effects of Earth’s gravity .

Microgravity also affects the nervous and circulatory systems. On Earth, your heart pumps blood upward, and specialized valves in your circulatory system keep bodily fluids from pooling at your feet. In the absence of gravity, fluids shift toward the head.

My work and that of others has shown that this results in an expansion of fluid-filled spaces in the middle of the brain. Having extra fluid in the skull and no gravity to “hold the brain down” causes the brain to sit higher in the skull , compressing the top of the brain against the inside of the skull.

These fluid shifts may contribute to spaceflight associated neuro-ocular syndrome , a condition experienced by many astronauts that affects the structure and function of the eyes . The back of the eye can become flattened, and the nerves that carry visual information from the eye to the brain swell and bend. Astronauts can still see, though visual function may worsen for some. Though it hasn’t been well studied yet, case studies suggest this condition may persist even a few years after returning to Earth.

Scientists may be able to shift the fluids back toward the lower body using specialized “pants ” that pull fluids back down toward the lower body like a vacuum. These pants could be used to redistribute the body’s fluids in a way that is more similar to what occurs on Earth.

Mental health and isolation

While space travel can damage the body, the isolating nature of space travel can also have profound effects on the mind .

Imagine having to live and work with the same small group of people, without being able to see your family or friends for months on end. To learn to manage extreme environments and maintain communication and leadership dynamics, astronauts first undergo team training on Earth.

They spend weeks in either NASA’s Extreme Environment Mission Operations at the Aquarius Research Station , found underwater off the Florida Keys, or mapping and exploring caves with the European Space Agency’s CAVES program . These programs help astronauts build camaraderie with their teammates and learn how to manage stress and loneliness in a hostile, faraway environment.

Researchers are studying how to best monitor and support behavioral mental health under these extreme and isolating conditions.

While space travel comes with stressors and the potential for loneliness, astronauts describe experiencing an overview effect : a sense of awe and connectedness with all humankind. This often happens when viewing Earth from the International Space Station.

Learning how to support human health and physiology in space also has numerous benefits for life on Earth . For example, products that shield astronauts from space radiation and counter its harmful effects on our body can also treat cancer patients receiving radiation treatments.

Understanding how to protect our bones and muscles in microgravity could improve how doctors treat the frailty that often accompanies aging. And space exploration has led to many technological achievements advancing water purification and satellite systems .

Researchers like me who study ways to preserve astronaut health expect our work will benefit people both in space and here at home.

• Magnetosphere
• Cardiovascular health
• European Space Agency (ESA)
• Nervous system
• Artemis program
• International Space Station
• blood-brain barrier

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