 When I was up there for a year, I think I felt like at some point I lived my whole life up there. That was former NASA astronaut Scott Kelly, who returned to Earth in March after spending 340 days on the International Space Station. His year in space is a stepping stone for future missions to Mars and deep space, because it's helping NASA understand how long-term spaceflight affects a human body. But how does long-term spaceflight affect the mind? What about the psychological challenges of being in space? In short, what will it take mentally to get to Mars? A mission to the Red Planet will last 2 to 3 years. That means that for 2 to 3 years, astronauts will live in microgravity, isolated and far away from home. They won't have many comforts. They won't be able to just step outside and breathe some fresh air, or pick up the phone and call their loved ones. And they'll be living in a high-risk environment, where they might die if anything goes wrong. Such a stressful situation is likely to have psychological implications. Microgravity can add to the stresses as well, and that can produce some stress and strain maneuvering around. That's Nick Canas, a space psychiatrist at the University of California, San Francisco. Also, the way people look in microgravity, sometimes they look puffy and sometimes kind of angry, and so it can be a stressful issue as well. One of the main reasons for Scott Kelly's year on the Space Station was to understand how his body changed and adapted in space. So, on the Space Station while I was there, there were 400 different experiments, and of those, a lot were life science experiments. You know, most of those are related to understanding our physiology, so we can go further into the Solar System and to Mars someday. We already know some of the physical problems astronauts face. People who spend time in space experience bone loss. Microgravity causes muscles to shrink, making astronauts weaker and less coordinated. And astronauts also eat less than they should, and it's key that they get the right nutrients to stay healthy. But there's a lot we still don't know about the effects of a long space mission on the human mind. For now, we know that astronauts in space sometimes suffer from depression. NASA astronaut John Blaha has admitted to becoming depressed onboard the Russian station Mir in the 90s. Blaha said he turned to a family photo album every night to keep him going and deal with the homesickness. We also know that astronauts often develop sleeping problems in space. Space stations are noisy, and try falling asleep when you're floating. Plus, because a space station zooms around the Earth 16 times a day, there's no real morning and night to tell your body when to be sleepy. It's like feeling jet-lagged all the time. Often, astronauts sleep less than six hours a day in space, and lack of sleep can trigger behavioral problems. We also know that conflicts can rise among crew members and mission control on the ground. Being constrained in a relatively small space with the same people for months on end is challenging, especially when these people come from different backgrounds and speak different languages. Well, you know, you're deprived of so much on Earth, and then you have, you know, all these possibilities. You like your crewmates, but you're, you know, you don't have the variety of people and things and possibilities when you're living in such a confined, closed environment for so long. NASA has guidelines to deal with mental breakdowns in space. If someone has severe anxiety, paranoia, hysteria, or attempts suicide, astronauts are instructed to bind the person's wrists and ankles with duct tape, restrain the body with bungee cords, and administer tranquilizers. The procedure has never been used, and NASA says that no behavioral emergencies have ever been reported during spaceflight, but there are known causes of anxiety and conflict in space. During the Skylab 4 mission in 1973, astronauts got so stressed out that they turned off radio communication with the ground and spent a whole day ignoring NASA. During the Salyut 6 mission, a Russian cosmonauts had a dream of having toothache and started obsessing over it. And he started worrying about, well, gee, what if I really did have a tooth problem here? I couldn't do anything about it. And he just sort of obsessed about it. That's Nick Kanis again. It wasn't critical for the mission in the sense that he was sort of talked down and he was able to continue to function. But it leads to the idea that for some astronauts who experience anxiety of being in the space environment, they will somaticize it, they will perceive of it as a worry about a medical or a physical problem. Sort of almost like a psychosomatic reaction. But it's not all bad. Some astronauts have reported a change of perspective. Seeing Earth from space gives them a better appreciation for people and the environment. So I'm originally from Italy and I moved here five years ago. And I honestly think that being away from home kind of changes you somehow. And you've been on the ISS for a year, which is the farthest you can possibly be. Do you think that your space has changed you in some way? Yeah, absolutely. I think just living on that space station for so long and understanding how difficult it was to build and operate kind of inspired to think that if there's something that we want to do, we can do it if we put our minds to it. Looking out at the Earth over the course of a year and seeing the impacts that our presence have on the environment, especially in certain parts of Asia, makes me feel like there's more that everyone can do, including myself, to make Earth a better place for the future inhabitants. And when you're detached from Earth for so long, you do feel a little bit more empathy for all the bad stuff that goes on down here. Yeah, I mean, how has your year in space changed your idea about the environment and what we should do to preserve the Earth? Well, the atmosphere looks like a thin film over the surface, so it looks really fragile. And it's what keeps us alive, so it's worth protecting. The psychological challenges astronauts will face on a mission to Mars will be even greater. On the International Space Station, crew morale is kept up by sending surprise presents, treats like fruits and vegetables, or by arranging phone calls with favorite movie stars or sports figures. Astronauts can also easily keep in touch with loved ones on Earth through emails and phone calls, and they talk to a psychologist on a regular basis. But on a mission to Mars, astronauts would be more isolated than ever. Communication with Earth would have a 20 to 40 minute delay, so calls with friends and family are out of the question. Crew members also wouldn't be able to rely on mission control to solve emergency situations. And then there's boredom. People's schedules on the International Space Station are packed up with experiments, cleaning, and maintenance. But a journey to Mars will last much longer than the usual six-month stay on the ISS. Scientists are simulating missions to Mars to figure out how people deal with the stress and confinement. In one, funded in part by the European Space Agency, six men were locked up for 520 days in a fake spaceship that simulated a journey to Mars. Some crew members reported being depressed, another one developed insomnia. And the simulation didn't even include microgravity and the actual dangers of space travel. On the International Space Station, one of the favorite activities is to gaze out the window and look at our planet. On a mission to Mars, there'll be a time when our planet will look like a tiny star. No one knows how people might react to that. Right now, there's never been a human being who hasn't had some contact with the Earth visually, either seeing it from the Moon or being on the ground or being in the water. You have a sense of place and a sense of being in contact. Well, on Mars, the Earth will be an insignificant greenish-blue dot in the heavens. And that kind of Earth out of view and everything that's ever been important to you being so distant and so trivial may have an effect psychologically on some of the astronauts as well. So what advice would you have for astronauts that are embarking on a journey to Mars? You mean like a three-year journey? You know, a year is a really long time, so I would say, you know, try to keep that in perspective. Manage your energy and fatigue during the course of your time getting there and then on the surface. One thing I always try to think about is that even on the last day of me being there for a year, I would have to be able to respond to an emergency situation the same as if it was my first day. So I would suggest to them, pace yourselves. Would you ever want to go to Mars? I would, but it's easy for me to say that knowing that I probably won't be able to. But I think in a few years if someone said, hey, we've got a trip to Mars, would you like to go? I'd probably volunteer. Now, I wouldn't go on that one-way trip to Mars. I think those people are, I don't know what's the right word, but I think, you know, having spent a year on the space station, I can't imagine spending the rest of my life in an environment like that where you can't go out and get fresh air. You'd want to come back. Absolutely. I think anyone they send there, if you send someone and they're going to stay there forever, they're going to have a change of heart at some point.