NASA's top planetary scientist told us what he thinks of the science in 'The Martian'

Spoiler alert if you haven’t read “The Martian.”

Scientists may have just discovered water flowing on the surface of Mars, but it’s still a pretty inhospitable place to call home.

Yet that’s exactly what Matt Damon’s character, a NASA astronaut stranded on the Red Planet, does in the upcoming film “The Martian,” based on the best-selling novel by Andy Weir.

NASA’s head of planetary science Jim Green was a consultant on the film, which premieres nationwide on Friday October 2. We chatted with Green about just how much science the movie gets right.

“What Andy did is kind of unique in science fiction,” Green told Business Insider, referring to Andy Weir, the author of the book. While a lot of sci-fi centres around things that are not possible in our current understanding of science, “Andy decided to write science fiction about a future which would be bounded by the laws we know.”

Here’s the inside scoop from Green about what’s scientifically accurate in the movie:

Mars’ biggest challenges

1. It’s extremely cold.

The first problem anyone visiting the Red Planet would face is the fact that it is an extremely cold, harsh environment. The temperature swings dramatically, for example, sometimes between as many as 120 and 140 degrees Fahrenheit in a day, said Green.

In the book and film, the main character, astronaut Mark Watney (played by Damon) travels long distances in a solar-powered rover. But he doesn’t have enough power to drive the rover and keep it heated, so to keep himself warm, he uses a generator which produces heat from radioactive decay.

Turns out, NASA has a similar generator, only they use theirs to power the real Curiosity rover. The agency also plans to install one of these on the rover it plans to send to Mars in 2020. The excess heat will be used to keep the rover’s instruments functioning (but it’s risky to use around humans because of the risk of radiation exposure).

2. You can’t breathe the air

Next there’s the problem of oxygen, the life-giving gas we take for granted on Earth. The atmosphere of Mars is very thin, contains mostly carbon dioxide, and has less than 0.15% oxygen, compared with that of Earth, which has more than 20% oxygen.

In the film, Watney’s habitat or “hab” has an oxygenator, a device that sucks in carbon dioxide, zaps it with electricity, and spits out oxygen (for breathing) and carbon monoxide (as waste).

This technology is pretty realistic as well. The International Space Station has an oxygenator that splits water to produce air for the astronauts to breathe. Green said NASA plans to send such an oxygenator to Mars on its 2020 rover as a proof-of-concept that they can convert carbon dioxide into breathable air.

3. There’s no food.

Then there’s the issue of food, and the fact that Mars doesn’t have any crops or livestock.

In the book and film, Watney’s mission was only supposed to last 30 days, but because of a rogue dust storm that causes him to be left behind by his crewmates, he must find a way to survive for more than a year. Being a botanist, he figures out he can grow potatoes in the hab by fertilizing Martian soil with his own faeces and moistening the soil with water generated by burning hydrazine, a flammable liquid from rocket fuel.

This part differs a bit from reality. As it turns out, Green said, NASA is finding that the soil on Mars is much more moist beneath the surface than once imagined, and contains nitrates and other minerals that nourish plants. So Watney may not have needed to go to those lengths to make water and fertilize the soil — he could simply dig up some Martian soil and thaw it out to grow his food.

4. You might get lonely or go crazy

As if the other problems weren’t enough, Watney faces the psychological burden of being stranded on a planet millions of miles from home with virtually no human contact. In the film and book, Watney gets by using his sense of humour, by throwing himself into the work of survival, and by focusing intently on problems as they surface, taking things one step at a time.

The stress and isolation Watney faces are not unlike those faced by real spacefarers. NASA astronaut candidates go through a rigorous selection process, which involves thorough psychological evaluations. And outside of NASA, many people have endured extreme isolation (such as prisoners of war) and survived mentally intact.

So overall, how does the scientific accuracy of “The Martian” compare to other sci-fi films? It’s the only film Green has worked on, but “it’s certainly the most accurate one about Mars,” he said.

NOW WATCH: Matt Damon is left to die on Mars in first trailer for ‘The Martian’

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