Imagine this: you're stuck on Mars. Everyone -- your crew mates, your parents, your government, literally everyone ever -- thinks you're dead. Your corpse, they expect, will be on Mars forever, perfectly preserved by the Martian climate.

That's the situation astronaut Mark Watney finds himself in in "The Martian," hitting theaters today. Based on the novel of the same name by Andy Weir, "The Martian" is a story of human ingenuity and resilience. The difference between you and Mark Watney, other than you being real and him being fictional, is that you likely are not a botanist who has been trained to handle worst-case space situations. (Space camp does not count.)

So while Mark Watney may be great at devising a way to expand and renew his food supply (spoiler: it involves poop) while not exploding his head on the surface of Mars, you may not find yourself in quite the same privileged position.

So what's the best advice Dr. Jim Green, director of planetary science for NASA, can offer the average person who may find themselves stranded in space? In a chat with MTV News at the Toronto International Film Festival, he said that one quality in particular was very, very important for survival.

"You have to have one quality, and that’s the determination, the ability to not give up," he said. "You see that in Matt Damon's character. All the time, you know, when he gets it and he is in that mode of problem solving. He has this, 'I have to survive this enormous length of time on this planet, how am I going to do it?' It's absolutely overwhelming but when he kicks in that science part of his brain, he breaks it up in little bitty chunks, and he knows he can accomplish each and every one of them. Each of those build on the next that enable him to survive on that planet."

"Math, science, and determination. Those are the big three in my determination."

But even if you're determined, you still have to find a way to survive physically. Green broke down the other top challenges in surviving alone on another planet.

"You've got to be able to breathe, got to find a way to continue to consume calories, those are the elements of life, but you know, there's a psychological aspect to it," he said. "Mark is not free to roam around. It’s a harsh environment, the temperature in on day will change by 120 degrees to 140 degrees in one day. It goes from like 70 below to 50 above, that’s the hottest day on Mars is about 50 degrees Fahrenheit, so that variation is huge. So he's gonna be in suits, he's gonna have to rely on systems that keep him alive, that supply him air, he's got to walk into the habs, he's got to be able to have that kind of protection, because the environment not only has these variations in temperature, but it's not a breathable atmosphere."

Even if you find a way to survive, you'd have to steel yourself mentally.

"The ability to be confined, if you're claustrophobic this might not be the best thing for you to do, there's other things you can do," Green said. "He has to rely on these systems and maintain them, which is shown, you know, [Watney is] really a jack of all trades. You see him doing everything from electronics to chemistry in addition to the botany that he does to survive."

So there you have it: to survive on Mars, you have to want it really bad, plus have the improvisational mind and know-how to build the things you need and keep them running.

Best of luck.

"The Martian" is in theaters now.