What to do when alone on Mars? (Image: 20th Century Fox Film Corporation)

Astronaut Mark Watney is left alone on Mars when an explosion forces his crewmates to abandon the planet. To survive, the Martian of Ridley Scott’s new film must push NASA’s innovate-and-improvise philosophy further than ever before. Or as he puts it, “In the face of overwhelming odds, I’m going to have to science the shit out of this.”

At New Scientist, we have a long history of using expletives to convey our love of science – so we can only applaud Watney’s never-say-die spirit and almost genius use of science to solve problems. Here, as a spoiler-lite companion to enjoying The Martian, we offer our own thoughts on the science of survival on Mars.


1. Break down your problem into chunks

Watney clearly has the right stuff. Played by Matt Damon, who has bags of fun with the role, he knows that to tackle an apparently insurmountable problem you have to break it into manageable chunks. In this he reminds me of Joe Simpson in Touching the Void, who survived a horrific accident in the Peruvian Andes by taking it one step at a time.

The film, like the book by Andy Weir, is not interested in the very real psychological impact of being in space, let alone being 225 million kilometres from any other human. This story is about engineering and improvising your way out of trouble, so we’ll gloss over the psychology too.

NASA, of course, has a fine record in conducting emergency space repairs. The most famous example – and Weir’s inspiration for the book – came when an oxygen tank exploded on Apollo 13 during NASA’s fifth crewed mission to the moon, but there are many other examples. Watney, though facing the agency’s worst nightmare, embodies its greatest strengths. Written and meticulously researched without help from NASA, the book and film have won the agency over for their portrayals of how it operates.

2. Check the weather

The crisis in The Martian happens because a monstrous sandstorm threatens to blow over the rocket that the crew intends to use to get home. In real life, this is unlikely because the atmosphere of Mars is so thin – only 1 per cent the density of Earth’s. “If you imagine the most unusually high winds you can for Mars, you’re still talking about something that produces a force comparable to a fresh breeze on Earth,” says planetary scientist Nicholas Heavens at Hampton University, Virginia. “Almost knocking down a rocket strains credulity.”

That didn’t spoil the movie for me, by the way. But dust storms on Mars can still be dangerous: they impair visibility and, crucially, reduce your ability to harvest solar energy. This has been a serious problem for previous Mars rovers Spirit and Opportunity, so Watney has to keep his solar panels clean of dust.

Some commentators are concerned about the exposure to cosmic radiation that Watney faces. Mars doesn’t have much of a magnetic field, but its thin atmosphere does provide protection from radiation, according to measurements made by the Curiosity rover. It’s the long journey to and from the planet where exposure to radiation does the damage. “Being on the surface of Mars is better for that than interplanetary transport,” says Kevin Fong of University College London, who works on space medicine. “There are plenty of places to hide, and the planet is effectively a radiation shield from the sun when it’s between you and that source.”

3. Air to breathe, water to drink

Watney relies on his habitation module to produce oxygen. The mission, set in 2035, probably builds on technology developed for NASA’s next trip to the Red Planet, the Mars 2020 rover. That mission will use equipment that takes carbon dioxide from the atmosphere and breaks it up to make oxygen.

But Watney needs more water than he has left after the storm. Because he’s a capable science hero, he figures out how to extract hydrogen from the hydrazine in rocket fuel to make more water. I’d say don’t try this at home, but here’s a video on how to do just that.

Recently, however, the Curiosity rover has found a possible way to farm water from Martian soil without the risk of blowing yourself up.

4. Get growing

Alone on Mars, Watney is not being arrogant when he calls himself the greatest botanist on the planet. But growing plants on Mars presents particular challenges. First, the sunlight that reaches the surface is too feeble to cultivate plants that evolved on Earth. To get around that, you need to grow them indoors under artificial light. This will also protect them from the sub-zero temperatures on the surface.

Then there’s the soil. In 2008, the Phoenix lander found that samples on Mars had the same basic elements as soil on Earth, including magnesium, sodium, potassium and chloride. Scientists have for years been trying to simulate Martian soil to study how they might grow things in it. Watney fertilises his garden using his faecal waste.

Martian plants would need special care (Image: 20th Century Fox Film Corporation)

Cultivating plants on Mars will probably require genetically modified versions of Earth varieties to allow them to cope with the extreme conditions. But Watney makes do with normal Earth potatoes and vitamin pills. Let’s be generous and assume the pills also contain protein – one cannot survive on spuds and vitamins alone.

5. Rocket science

In the movie, the spacecraft used to transport crews between Earth and Mars – the Hermes – is powered by an ion engine. These are already used in some space missions, harnessing solar power to make an electric field for accelerating ions and thus providing constant thrust.

Watney makes use of a nuclear power source to keep him warm. Space missions often use these radioisotope thermoelectric generators to convert the heat produced when a lump of plutonium decays into electricity.

There’s lots more science – orbital trajectories, hexadecimals and ASCII code, and the challenges of making food for space travel, to name a few.

So will Watney make it? You can see the film to find out, but it’s also worth reading Weir’s book to marvel at just how much science he explores in this tale of extraordinary endeavour.

Like this? Read our review of The Martian – on release in the UK from 30 September and in the US from 2 October