How living on Mars would warp the human body

Cold, bathed in radiation and far from Earth, life on Mars would strain our mental and bodily limits

By Troy Farah

Staff Writer

Published February 7, 2023 5:30AM (EST)

Mars colony, concept (Getty Images/e71lena)
Mars colony, concept (Getty Images/e71lena)

In July 1969, as the Apollo 11 astronauts prepared to trek to the moon, the Nixon Administration prepped some worst-case-scenario remarks in case this risky mission became deadly — a distinct possibility. Nixon's prepared statement, which was not widely publicized until 1999, was grim. It thanked the astronauts for their brave sacrifice, preceded by a clergyman who would've adopted the same procedure as a burial at sea: commending their souls to "the deepest of the deep," and concluding with the Lord's Prayer.

Thankfully, the mission was a success, but some future president may need to prepare a similar draft speech if humans are ever to travel to Mars, the fourth planet in our solar system. Such an assignment would be even more dangerous, and much, much further away, though the stakes may still make such a journey worth it in the end.

But many questions remain about how to make this trip or how to mitigate certain risks, especially when it comes to how the human body would respond to life on Mars. Changes in gravity, sunlight and intense exposure to radiation are a few of the many lethal elements awaiting any Mars-journeying astronauts. Because this challenge has never been attempted before, there are still a lot of unknown variables.

We do know that trips to the Moon and long periods in space, such as what the crew on the International Space Station experiences, have caused profound alterations to astronaut bodies. Microgravity can trigger muscle atrophy and loss of bone density. Pressure differences between the brain and eye when in space can cause visual impairments, like Spaceflight-Associated Neuro-ocular Syndrome. Away from the Earth's electromagnetic field, ionizing radiation is everywhere, which can not only cause cancer, but also bleeding gums, one's hair falling out, brain damage and reduced immunity. And while astronauts on the International Space Station are shielded from the sun's radiation at least half the time (when the Earth is blocking it), astronauts headed to Mars would have no metaphorical lead apron during the seven-month journey to the red planet.

A review of the carcinogenic effects of space published last October in the journal Neoplasia noted many "unsolved mysteries" surrounding our understanding of space radiation and tumor growth, yet the pace of human space exploration is rising rapidly. "Due to difficulties in simulating the effects of space radiation, the lack of accurate data, and individual differences between astronauts such as age, sex and genetic background, there is great uncertainty in space radiation risk prediction," the authors note.

Our bodies evolved over millions of years in tandem with Earth's gravitational pull. Separating ourselves can cause intense effects on our physiology.

NASA, the European Space Agency, Japan Aerospace Exploration Agency and other space agencies are actively working on the problem, starting with the Artemis series of missions. Among other goals, this space program endeavors to put a space station around the moon, which is seen as a sort of testing ground for exploring other planets.

Dr. Kevin Fong, an anesthesiologist based in London, has worked with NASA's Human Adaptation and Countermeasures Office at Johnson Space Center in Houston, studying long duration human space exploration and the effects on the body. He believes space exploration and bodily health are deeply linked.


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"The same exploration that takes us out across the world in the 20th century, and then out across the stars, is the same exploration that takes us inward to explore the human body. It's just different parts, different disciplines," Fong told Salon, emphasizing that human survival could depend on outer space exploration. "It's obvious that if you want to explore, you must survive. But it's also true that if you want to survive, you must explore."

"Your bones waste, your muscles waste, your heart deconditions to a certain degree ... And then some really weird stuff happens."

In his 2014 book, "Extreme Medicine: How Exploration Transformed Medicine in the Twentieth Century," Fong goes into great detail on what life on Mars would do to the human body. It really comes down to two aspects: the journey there and then the stay on Mars. He says the term "spaceflight" is sort of a misnomer. Like in the movie "Toy Story," traveling between planets isn't exactly flying: it's falling with style.

Weightlessness may sound fun, but our bodies evolved over millions of years in tandem with Earth's gravitational pull. Separating ourselves can cause intense effects on our physiology or how the body organizes its many systems, from digestion to cognition.

"When you're moving between two celestial objects, you're falling between them," Fong explains. "It leaves your physiology to make adaptations, which can later cause you problems. Your bones waste, your muscles waste, your heart deconditions to a certain degree. And then you have problems with balance and coordination. And then some really weird stuff happens with your hematopoietic system, [essentially] your blood-forming organs, your immunity. And all of that is in one way or another seems to be connected to the experience of weightlessness up there."

Most astronauts are only subject to weightlessness for a few weeks, but a one-way journey to Mars would last seven to nine months. Either way, double that travel time if you want to actually come back. And there are a lot of unknowns of what may happen to a human floating in the void out there. "We don't have a great understanding of what the radiation field is like between Earth and Mars," Fong says. "You'd think we would, but it's not that well-known."

Landing on Mars would be a much safer place than the vacuum of space, but with around one-third the gravity of Earth, any Red Planet colonists would still experience weird effects on their bodies from the reduced gravity.

"We don't know what a third of the [gravity] will do for us, we don't know if it'll provide any protection or if you can make use of that to give yourself enough gravitational loading to protect your skeleton and your muscles over time," Fong says. "We don't know, but we suspect that you're going to need some sort of countermeasures."

Mars doesn't have much of an atmosphere, an electromagnetic field or an ozone layer, three things which make life a lot more comfortable on Earth.

That means we'll need to bring lots of medications and drugs to Mars, to anticipate every scenario, because we won't be able to jog down to Walgreens if someone needs heart medications or a sleep aid. Unfortunately, we also don't know much about how these meds might fare in space travel or if they'll act differently in our bodies under the unique conditions of Mars.

Likewise, the psychological effects could be staggering for the first humans in history to completely lose sight of the Earth. This could have unforeseen mental health consequences.

"The suite of threats that presents to you on Mars are unique and poorly understood," Fong says, noting that a day on Mars is about 37 minutes longer than an Earth day. "It's dark out there. It messes with your circadian rhythms because the day is slightly longer. It's just enough out of sync that it really messes you up. And you're very isolated. Psychologically, there's some not insignificant problems."

Mars doesn't have much of an atmosphere, magnetic field or an ozone layer, three things which make life a lot more comfortable on Earth. This means there's still plenty of cancer-causing radiation on Mars (though slightly less than in space). And if you stepped outside sans spacesuit, the extreme cold would freeze you to death while the low atmospheric pressure would cause your blood to boil inside your veins. Life on Mars would be a life spent entirely indoors, unless you count being trapped inside a restrictive spacesuit as "outdoors."

"All of these journeys away from the Earth make you appreciate what you have here on Earth in the first place," Fong quipped.

Given all this, it may seem like going to Mars would be absolutely miserable, coupled with many unpleasant ways to die. But he left off with a gentle reminder that all humans are technically astronauts on spaceship Earth. You don't need to leave the planet to venture into the unknown, though hopefully someone will make it to Mars someday.

"At base level, we're all explorers, in one way or another," Fong says. "It doesn't have to just be the physical projection of yourself into this austere environment. Stephen Hawking was one of the greatest explorers of all time and most of his life he never left his wheelchair. That's the exploration I'm in love with, rather than this slightly Victorian view where you have to be made of certain stuff to project yourself out there. You can do that from your library. And that exploration is just as valuable, just as valid and just as worthwhile."


By Troy Farah

Troy Farah is a science and public health journalist whose reporting has appeared in Scientific American, STAT News, Undark, VICE, and others. He co-hosts the drug policy and science podcast Narcotica. His website is troyfarah.com and can be found on Twitter at @filth_filler

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Artemis Astronomy Health Mars Moon Science Space