For decades, the prospect of a crewed mission to Mars has seemed like a real possibility, albeit one that’s always just out of reach. The proposed dates have been continually pushed back, though both the U.S. and China have expressed optimism that such a trip could happen in the 2030s. NASA has even stated that a crewed mission to Mars could take place as early as 2035, with the trip to the Red Planet lasting around seven months, followed by a stay of up to 500 days before the journey home.
Yet even if the technology, funding, and public support aligned to make a voyage to Mars possible, there’s one crucial variable that’s harder to account for: the human body’s ability to cope with the demands of interplanetary travel.
With the proliferation of private and commercial spaceflights in recent years, it’s easy to forget that only 24 people have ever left low Earth orbit: the astronauts of the Apollo program in the late 1960s and early 1970s, for missions that lasted less than two weeks.
A mission to Mars would likely last years and subject the participants to a wide range of physiological effects that can only be theorized and approximated on Earth or even aboard the International Space Station. Although space flight side effects like spine lengthening and muscle and bone wasting are well documented, others can take experts by surprise. For example, it appears that space travel can make certain medications less effective and change the composition of bacteria in the mouth and gut. Additionally, by redistributing more blood flow to the head and neck, blood clots become more likely.
American astronaut Scott Kelly, who spent more than 520 days in space during his career, including a 340-day stint on the International Space Station from 2015 and 2016, reported strange and unprecedented symptoms after his long spaceflight, including painful leg swelling and an unexplained rash.
Perhaps notably, a groundbreaking comparative study between Scott Kelly and his twin brother, Mark (a former astronaut himself who is now a U.S. Senator), revealed troubling findings, including a decline in Scott Kelly’s mental speed and accuracy and off-the-charts levels of inflammation in his blood, indicating extreme stress. His vision had deteriorated, and the walls of his carotid arteries had become inflamed. Thousands of his genes had altered their expression, either temporarily or permanently, likely due to Kelly’s radiation exposure during his mission. Through the Twin Study and other research, scientists discovered that the human brain appears to be particularly vulnerable to the effects of space travel, some of which may be irreversible. In addition to the brain moving higher in the skull and swelling brain cavities, there appears to be an increase in some biomarkers associated with degenerative conditions, perhaps suggesting that there is a limit to the amount of strain the brain can endure beyond Earth.
Mission to Mars:
- NASA recognizes five hazards that need to be overcome for a successful spaceflight: space radiation, isolation and confinement, distance from Earth, gravity, and closed environments.
- Many of these hazards would be significantly amplified on a Mars mission compared to spaceflight in low Earth orbit. For example, the radiation experienced by astronauts on a trip to Mars would be many times greater than for those orbiting the Earth on the ISS, likely approaching NASA’s recommended lifetime radiation limits.
- Built by the Mars Society in the early 2000s, the Mars Desert Research Station in southern Utah is a simulated Mars analog facility that has hosted hundreds of simulated missions to the Red Planet. Participants have had to contend with the social and psychological stress of living in a confined space with a small group of people while carrying out essential tasks and conducting scientific experiments.
