Even at their closest, when Earth and Mars are approaching one another in their oblong orbits, there are 35 million miles between our blue orb and the red planet. But that distance hasn’t stopped NASA and other space agencies from setting their sights on a human mission to Mars, which would require astronauts to live in space for at least two and a half years. NASA has been working toward the goal of delivering astronauts to Mars by the early 2030s, says Thomas Williams, PhD, a psychologist and chief scientist of human factors and behavioral performance at NASA’s Johnson Space Center in Houston, Texas. In December, President Donald J. Trump signed a space policy directive instructing the space agency to return astronauts to the moon. It’s been nearly 46 years since astronauts last traveled beyond Earth’s orbit, and a fresh moon mission would serve as a pock-marked steppingstone toward a subsequent human mission to Mars.

Getting there requires not only rocket science, but also human science—which can be even more daunting than perfecting propulsion systems and landing gear.

NASA doesn’t take these challenges lightly, Williams says. Scientists are carefully assessing the physiological, psychological and social factors associated with a journey to Mars, with NASA conducting research independently as well as in partnership with experts outside of the agency. “We are concerned about the risks behavioral health and performance would pose to a Mars mission within our current understanding, but we have cutting-edge researchers to help us answer these questions,” he says. “None of this we consider insurmountable.”

Far from home

Scientists have been studying the effects of living in space for decades. Since 1971, astronauts (and their Russian counterparts, cosmonauts) have spent weeks or months inhabiting a series of space stations orbiting Earth. The current iteration, the International Space Station (ISS), welcomed its first crew in 2000 and has been occupied ever since.

Research from the space station has provided useful information about how astronauts respond to the challenges of space, such as microgravity, confinement and isolation, says Nick Kanas, MD, emeritus professor of psychiatry at the University of California, San Francisco, who has long studied space psychology. But interplanetary travel is another story, he says. “Mars is a long way away, and the extreme distance has psychological ramifications.”

Pictured here are crew members (left to right): Dr. Ross Lockwood, Dr. Tiffany Swarmer and neuropsychologist Dr. Ron Williams at the Hawai’i Space Exploration Analog and Simulation habitat.Currently, astronauts spend about six months at a time on the ISS. So far, the longest consecutive period spent in space is 437 days, a record set by cosmonaut Valeri Polyakov aboard the Russian station Mir. A multiyear journey is uncharted territory—and a long time to spend in tight quarters with just three or four other people. “It will be hard to have the kind of social novelty we crave,” Kanas says. And because a Mars expedition would probably be a collaborative effort among countries, those astronauts will have to overcome cultural differences to live and work together.

What’s more, communication between Earth and a Mars-bound ship will be delayed up to 20 minutes each way. If an astronaut asked a question, 40 minutes could pass before he or she received a reply. “We know the ability to talk in real time with family and with the people on mission control is very important to astronauts,” Kanas says. “When you take that away, it creates a real conflict.”

The difficulty of speaking with family members on the ground could contribute to loneliness and psychological problems such as anxiety or depression. Astronauts will also have to be much more autonomous and prepared to handle emergencies on their own, since they won’t be able to rely on real-time advice from mission control. “The communication delay will lead to crews having to take care of their own problems, including medical or psychological emergencies,” Kanas says.

Another concern is how astronauts might react to the experience of being so far from Earth. Many ISS astronauts report that gazing at and photographing the Earth from above is a favorite pastime that can reduce stress and even inspire spiritual or transcendental experiences, as Kanas described in a review of the psychosocial issues related to long-distance space travel (Acta Astronautica, Vol. 103, No. 1, 2014). But that perk won’t be available from 35 million miles away. “Nobody knows the effect of seeing the Earth as a dot in the heavens,” he says. “Maybe it won’t have any effect—but maybe it will.”

Floating questions

The physical challenges of living in space can also have implications for psychological well-being. One top concern is how space radiation will affect the body. Beyond the protective bubble of Earth’s atmosphere, space radiation poses a significant threat to human DNA, cells and tissues. “It can impact the central nervous system and can alter the structure and function of the brain,” says Williams.

In animal studies, NASA scientists are exploring how chronic radiation exposure might affect brain function. Recently, Charles Limoli, PhD, at the University of California, Irvine, and colleagues exposed mice to charged particles that simulated cosmic radiation. They found structural changes in the mice’s brains such as reduced complexity of dendrites, the extensions that branch from neurons. What’s more, the mice also showed behavioral changes, including memory deficits, increased anxiety and deficits in executive function (Science Reports, Vol. 6, No. 1, 2016).

Researchers are also studying factors that might compound or minimize those effects, Williams says. For example, scientists are exploring the concept of cognitive reserve, which posits that education and experience can help protect the brain against physical damage (such as the pathological changes associated with Alzheimer’s disease). NASA scientists are investigating whether cognitive reserve can also protect against radiation in space.

The effect of altered gravity is another active area for space scientists. Floating weightless might look like fun, but it can lead to physical problems including motion sickness, muscle wasting and changes in visual perception. Those changes could have downstream effects on psychological well-being, Williams notes. Getting regular exercise, for instance, is a lot trickier when your feet don’t touch the ground—and physical activity is known to promote positive mental health.

Weightlessness can also contribute to psychological problems in surprising ways. For example, kidney stones are more common in altered gravity environments, and stones can raise the risk of urinary tract infections, Williams says. In some cases, undiagnosed UTIs can trigger confusion or delirium, which could be mistaken for a psychiatric disorder. Researchers’ work to connect the dots among these possible risks is essential for preparing astronauts for life in space. “It’s important to be alert to what medical conditions could occur as a result of these altered environments,” Williams says. “If someone has a medical condition, we don’t want to treat it as a psychological problem.”

Mental health on mars

Prolonged weightlessness is hard to study on Earth, where it’s impossible to cancel out the effects of our planet’s gravity. But many other features of an extended space mission can be recreated in so-called space analog studies conducted in confined and isolated environments.

U.S. Air Force Reserve Officer Casey Stedman served as commander for the second mission of the Hawai’i Space Exploration Analog and Simulation project.The largest such study to date was the Mars500 project, led by the Institute of Biomedical Problems of the Russian Academy of Sciences in 2010–11. For 520 days, six healthy male participants from several countries lived inside an enclosed module in Russia designed to mimic the feel and function of a Mars shuttle. Crew members had military and engineering backgrounds, similar to the traditional backgrounds of astronauts and cosmonauts. During the simulation, the crew members performed routine maintenance and scientific experiments, were isolated from Earth’s light-dark cycles and experienced communication delays just as they would on a flight to Mars.

That experiment raised some concerns, says David Dinges, PhD, a psychologist at the University of Pennsylvania who researches chronobiology and has studied astronauts on the ISS and in space analog environments. He and his colleagues recorded psychological and behavioral changes among the Mars500 participants. One crew member experienced mild to moderate symptoms of depression during most of his time in confinement, they found. Two others experienced abnormal sleep-wake cycles, while another reported insomnia and physical exhaustion (PLOS One, Vol. 9, No. 3, 2014).

In the same study, he and his colleagues also found that the two crew members who had the highest rates of stress and exhaustion were involved in 85 percent of the perceived conflicts with other crew members and mission control. A single stressed-out astronaut, in other words, might cause problems that affect the entire mission.

In a different study, Dinges and colleagues looked more closely at the sleep and activity habits of the Mars500 crew. They found that as the months stretched on, crew members became increasingly sedentary when awake. They also spent more time sleeping and resting, which the researchers characterized as a kind of behavioral “torpor” to conserve energy. Four of the six crew members experienced sleep problems during their 520 days in pseudospace, including disrupted sleep-wake schedules, reduced sleep quality, a shift to more daytime sleep and performance deficits related to chronic sleep loss (PNAS, Vol. 110, No. 7, 2013).

Some of those problems can be addressed by optimizing lighting to more accurately mimic the 24-hour cycle and UV spectrum of sunlight on Earth, Dinges says. “We are a circadian species, and if you don’t have the proper lighting to maintain that chronobiology, it can create significant problems for crew members,” he explains. Other elements, such as stress or operational factors related to crew work schedules, might also be to blame, he says. But more research is needed to fully understand those factors.

Coping skills

Dinges is among a large team of scientists working to understand and prevent psychosocial problems that might arise in space. In a new NASA-supported project, he and colleagues at institutions across the country are looking for biological indicators that offer clues about a person’s emotional, social and cognitive resilience. “We know there are substantial individual differences in how people cope with different kinds of stressors, but we don’t understand why that is—and more importantly, how to identify ahead of time how people might cope, or how to help them do it,” he says.

NASA already employs a comprehensive physical and psychological screening process to identify astronauts likely to thrive under the stressful conditions of spaceflight. Biomarkers of resilience could add a new dimension to that evaluation. However, selecting biologically superior astronauts isn’t necessarily the goal, says Dinges. Instead, he envisions such biomarkers being used in research to identify and test medications or behavioral strategies that could boost resilience.

“Biomarkers could be used to determine how to maximize those countermeasures,” he says. “Behavioral issues are serious, and the challenge isn’t just to figure out who can optimally cope, but also how to provide help for those who need it.”

It’s too soon to say whether scientists will succeed in finding a blood test to measure resilience. But with or without such a test, a Mars mission requires a strategy to help astronauts manage stress and maintain emotional well-being.

Raphael Rose, PhD, a psychologist at the University of California, Los Angeles, is among the scientists contributing to that effort. He has studied a stress management program among participants in the Hawai’i Space Exploration Analog and Simulation (HI-SEAS) project, a study led by the University of Hawai’i at Mānoa. During the fifth installment of the project in 2017, six men and women spent eight months living and working in an isolated compound on the rocky, otherworldly landscape of Mauna Loa.

During that project, participants used Rose’s program, the Stress Management and Resilience Training for Optimal Performance (SMART-OP). The program involves a variety of self-guided modules, such as video demonstrations of conflict-resolution strategies and a biofeedback game that helps the user practice regulating his or her breathing and heart rate. Rose says NASA is reviewing the findings, which have not yet been released to the public. But he’s optimistic the program shows promise. “The participants found the program really useful and helpful, which is a good sign that it’s something people would actually use, and something that could be integrated into future trainings or missions.”

“These crews contain rather remarkable people who are already quite resilient to start with,” Rose says. “But we can lower the risk of any behavioral health concerns by addressing things in advance through training and providing people with an avenue to address any issues that come up.”

Studies such as Mars500 and HI-SEAS are important, but can’t answer all of the questions about life in space. Sample sizes are tiny. And participants know they’re not actually hurtling through the void of space. Of course, there’s that pesky thing called gravity.

Yet while a true trip to Mars might have unique stressors, it is also likely to be filled with excitement and wonder. For people who have long dreamed of exploring the next frontier, those benefits are likely to outweigh the potential risks. “The reality is it would be pretty exciting for astronauts to actually be the first to walk on Mars,” Williams says.