NASA has spent decades tracking the stress of its astronauts, as part of an effort to maximize productivity in space. Crew members who are bored, lonely, or fighting with their fellow travelers won't be as effective.

There's a lot more physical stress in zero gravity than on Earth, said Lauren B. Leveton, lead scientist for behavioral health and performance at NASA's Johnson Space Center in Houston. The human body evolved to cope with gravity and doesn't work as well without it. Space travel disrupts sleep, sinuses, and digestion. Movement feels different. Dinner floats.

And that doesn't even begin to address the emotional burden of blasting off from Earth in an apartment-sized tin can, leaving behind nearly everyone and everything you've ever known.


NASA is particularly concerned about astronaut stress as it begins plans to send a spacecraft to Mars in 2030, Leveton said.

A Mars voyage would be far more stressful than any previous mission, Leveton said, because the trip will take so long — nearly a year each way and another year on the planet. Astronauts won't have the reassuring sight of Earth in their rearview mirrors — it'll look like Mars does to us on Earth. Living spaces will be cramped. There will be no evacuation plan or way to rescue the team.

NASA tends to pick astronauts with positive attitudes who bounce back well from challenges, said Al Holland, senior operational psychologist in behavioral health and performance operations at Johnson Space Center.

Then it trains them in places like Antarctica and undersea laboratories to have realistic expectations of what they will face during space travel. And it monitors them closely during missions.

More research and training will be needed before NASA feels confident sending people on a 30-month mission to Mars. "That's a very different environment," he said.


Holland said that managing crew members' stress has taught him a few things about handling his own. "I like to think I'm more aware of pacing myself and I'm willing to say, 'No,' " he said.

Astronaut Mike Barratt, also an internist, said he gained tremendous perspective during his 199 days on the International Space Station and 13 days on the space shuttle Discovery. Remembering the view and the 16 sunrises and sunsets a day still helps him cope with stress here on Earth.

"I've known a lot of people who got more irritable as they age," Barratt said. Astronauts are "probably the opposite."