How much of the science did 'The Martian' get right?

Ridley Scott’s fictional space adventure film “The Martian” has had a stellar first couple of weeks at the box office, grossing more than $108 million since its release and getting big thumbs up from the space geek community.

Matt Damon stars in this Robinson Crusoe story set in the early 2030s, millions of miles away from Earth, as astronaut Mark Watney is left marooned on the surface of the Red Planet and is forced to figure out a way to survive. A big part of what is drawing rave reviews from scientists and space nerds is that this ambitious film based on the bestselling novel gets the big things right – like the fact that the Mars environment allows explorers, with access to the right technology, to survive and that the planet actually has the basic ingredients for supporting life.

Adding to the excitement for the film is NASA’s recent big announcement that they have stumbled across the hardest evidence yet for seasonal flowing wateron Mars. They have spotted dribble-like streaks that darken the soil that are 5 metres across and about 300 metres long, down the steep slopes of craters, that appear to form during warm summer months and then disappear during winters.

This sighting is so exciting because it directly impacts our expectations of finding present day microbial life on Mars, since water is considered a key ingredient in the recipe for life as we know it. The discovery also holds great hope for future human expeditions to the Red Planet where the briny water could be purified and used for drinking and farming, or processed to extract hydrogen and oxygen for rocket fuel and breathing within habitats. The robotic rover being readied now for its exploration of Mars in 2020 will demonstrate a method for making rocket fuel from atmospheric air.

In the movie “The Martian” the water generation method that Matt Damon’s character was using involved chemical reactions converting existing rocket fuel in a complicated and dangerous process. But now these scenes would need to be changed due to last week’s discovery. That’s because if we add up all the recent water findings by NASA spacecrafts, both orbiters and rovers, they show that in some regions the Martian soil may actually hold up to 35 litres of water ice per cubic metre.

For some Mars experts like Edwin Kite, assistant professor of planetary science at the University of Chicago, the astronaut’s ingenuity and MacGyver-like inventions are what makes the movie particularly appealing. You can’t help but admire how deep into science the marooned astronaut has to actually dig in order to keep himself alive, says Kite.

“The Mark Watney character has a scientific attitude – I'd want him working in my lab!” says Kite. “Watney's always thinking, ‘what's the most important problem that I need to solve right now?’, and [he] intelligently uses the resources in his environment to solve it.”

One of the biggest examples of this inventiveness is when Watney is forced to figure out how to survive for up to four years before a rescue mission can be launched, in a habitat designed to be livable for only a month. The trained botanist comes up not only with making drinking water, but also with a plan to grow crops of potatoes within his habitat, by planting sprouts in Martian soil fertilized with his own waste.

It turns out that farming in Martian soil might be possible despite the iron-rich, nutrient poor soil. However with the new discovery of briny water – with its salts called perchlorates – would either make the plants difficult to grow or perhaps even toxic. But this can easily be remedied by simply rinsing the soil and washing out the salts before use.

One glaring scientific foible in the movie is that even the general public most likely catches on to the absence of the reduced surface gravity of Mars – which is about one-third of Earth’s. In reality the lower gravity of the Red Planet would have some affects on Watney’s physical condition – especially have after being stranded for hundreds of days.

“Humans have evolved to live in Earth gravity and astronauts who have spent several months in space [we know from work on the International Space Station] can experience muscular atrophy despite regular exercise. NASA continues to research how to keep astronauts fit in low gravity environments, but it may be an issue,” says Nicholas Heavens, a Mars scientist at Hampton University in Hampton, Va.

But Heavens believes what may be a bigger problem in terms of deep space human missions like what we see in “The Martian” is long-term exposure to space radiation.

“Anyone living on Mars would expect radiation doses similar to those of astronauts living on the International Space Station, but by sandbagging [to shield] habitats and minimizing outdoor activities, those doses could be reduced. The bigger risks of radiation to astronauts however would come from the [six to nine month-long] journey to Mars itself, especially in solar storms,” adds Heavens.

Beyond the glaring omission of the smaller planet’s lower gravity, showing untethered astronauts, and the use of flimsy tarps for protection, perhaps how the film portrayed the Martian winds may be the most far-fetched of all.

While there is no doubt that there would be hazards associated with reduced visibility, the reality is that the strongest winds top out at about 100 km per hour, and the air is just too thin for winds to directly tip over an astronaut or heavy machinery. However winds can kick up such large dust storms that they can last for weeks and can even be spotted through Earthbound backyard telescopes.

“Mars has global dust storms that shroud the whole planet, but their effect in most places is to just coat the surface with a very fine layer of dust,” explains Kite.

While space experts admit there are some small technical faults, the story has a great blend of education and entertainment value, while also being inspirational too.

“[The Martian] is a far more uplifting story than most movies about Martian exploration,” said Heavens.

“As a scientist, any movie that would inspire people to explore Mars, despite the challenges, is a positive thing.”