The Martian: a perfect balance of scientific accuracy and gripping fiction

“I’m going to have to science the shit out of this,” says astronaut Mark Watney, played by Matt Damon, after being stranded on Mars. That pretty much sums up the tone in Ridley Scott’s new film The Martian, adapted from Andy Weir’s novel, which appears in cinemas this week. Many have already commended the movie for its scientific rigour and Scott has said himself that it is as “accurate as we can possibly get it”.

So does the movie live up to its expectations? Well, the mission design and the hardware are based on actual NASA capabilities and an existing plan to get humans to Mars known as Mars Direct. However, there are parts that are less scientifically accurate. But what the story lacks in scientific rigour, it makes up for with great fiction that could inspire new interest in science.

Growing food in space

The main challenge for Watney is to find a way to grow food on the planet in order to stay alive the four years until NASA’s next planned mission to Mars. While this has of course never been done in real life, it is not entirely unrealistic. In August 2015 astronauts on the International Space Station (ISS) ate lettuce that they had grown in space. This was the first time that humankind had grown and eaten food away from home.

In these so-called “VEGGIE” experiments the crew had been provided with everything they needed: soil, seeds, specific lamps tuned to the requirements of the plants. In The Martain, however, Watney had none of this specially-prepared equipment and, crucially, no soil.

The vegetable production system aboard the ISS.

The technical term for loose material covering rock is regolith, which includes the soil that we all know on Earth. Even regolith on Mars is familiar: we have been studying its properties since the 1970s, starting with the Mars Viking missions. NASA’sPhoenix Mars Exploration Rover (MER) has found evidence that the regolith contains crucial minerals for growing plants and is slightly alkaline, suitable for a range of crops – including asparagus and green beans.

Normally potatoes are grown in an acidic soil as this suppresses the effect of pathogens, such as common scab, but also because alkaline soils have a negative effect on the yield of potatoes. Our hero could easily account for this in his calculations for the number of plants required to grow enough food for a set number of days.

But Martian regolith may also contain perchlorates that are not good for human bodies. However, somewhat ironically, they are used as markers for the presence of water. Watney needs additional water for his crops and sets about making this by combining oxygen with hydrogen. To get the hydrogen, Watney catalyses a type of rocket fuel known as Hydrazine, in a somewhat dangerous experiment which would be even more dangerous in real life – as you’d end up with some toxic leftovers.

But exciting new results suggest that water sometimes runs openly on the surface of Mars. So in reality, it would have been safer for Watney to just go and extract it from the regolith itself.

We are seeing the early days of growing food in space. Eventually, if humans are to start living for extended periods on the moon, and eventually Mars, we need to be able to do experiments generating raw materials directly on their surfaces. There are already ideas to test our ability to grow food on the moon in small canisters, including basil and turnips.

Stormy weather

What plunges Watney into peril in the movie is an aborted mission in strong winds. Here on Earth, we use the Beaufort scale to measure wind strength. Gale force winds have speeds up to 74km per hour. To get a sense of what’s that like, imagine putting your head out of a car window when moving at 50 miles per hour. Then try to imagine what it would be like at 100 miles per hour as experienced by Watney and his fellow astronauts on Mars.

On Earth this would be a devastating storm, but not on Mars. The pressure that you feel on your skin when out on a windy day is known as the dynamic pressure. It depends not only on how fast the air is moving, but also on its density. In gale force winds on Earth this pressure is about 250 Pascals. The force this exerts on an average person is about one-third of Earth gravity. This is why you have trouble walking about in gale force winds.

But on Mars, the atmosphere is just 1% of the density of that on Earth, meaning the dynamic pressure is much smaller. Even in Watney’s storm the force on a human being would be tiny — less than one-tenth of Mars’ gravity. The storm that Watney and his crew encounter would only feel like a gentle breeze – not the devastating storm shown in the film.

Dust storms of 2001 observed on Mars by Mars Global Surveyor.
NASA/JPL/Malin Space Science Systems

Despite this, the wind and the sound it produces does actually have an important function in the film – it creates tension and allows us to empathise with Watney and feel his fear.

Finding pathfinder

Even though this is a work of fiction, as a follower of Mars exploration I felt a tingle of excitement as Watney recovered the Mars Pathfinder, buried under a huge pile of dust. Just as NASA follow Watney’s exploits using imaging from orbit in the film, space scientists have also been monitoring the landing sites of Mars spacecrafts, including Pathfinder.

Measurements at the landing site of the Mars lander Phoenix have shown that dust settles out of the atmosphere at a rate of about 0.1 – 1 thousandth of a millimetre per Martian day. Over the 20 years Pathfinder has been on Mars, that only amounts to between 1 mm and 10 mm of accumulated dust. So, in reality, Watney wouldn’t really have needed to do much digging at all. But this dramatic unearthing of Pathfinder pulls at the heart-strings of our exploration of Mars.

Pathfinder’s landing site imaged by Mars Reconnaissance Orbiter
NASA/JPL/University of Arizona

All too often in science fiction the characters are placed in impossible situations from which they can only escape by resorting to a kind of scientific deus ex machina. This is certainly not so in The Martian, in which the story has a logically and physically possible resolution.

The Martian is one of an increasing number of Hollywood films that explore the human soul and spirit of humanity while still grounded in science. Another example is how Christopher Nolan and Kip Thorne used Einstein’s theory of General Relativity to tremendous effect in Interstellar. However, The Martian uses science in a different way. It shows what it is to be a scientist. It shows Watney building scientific arguments, doing calculations, facing the outcome of making an error in reasoning – his answers aren’t in the back of the book. This engages audiences with compelling science.

One could easily be critical of the science shown in fiction. But in a push to reflect “real science” in the cinema we shouldn’t surrender strong narratives for the sake of scientific accuracy. To do so denies us the opportunity to tell stories and to show science in action and in unfamiliar settings.

Meteorite may solve Martian mystery

A meteorite reveals clues to how Mars lost its thick, carbon dioxide-rich atmosphere and became a cold, rocky desert, researchers say.

They say the Lafayette meteorite shows signs of carbonation – where minerals absorb CO2 in a reaction with water.

Mars lost its protective blanket about 4 billion years ago, perhaps because of the loss of its magnetic field, space impacts, or chemical processes.

Carbonation may be the key factor, they write in Nature Communications.

Carbonation could be the main force that turned Mars to stone”

Dr Tim Tomkinson Scottish Universities Environmental Research Centre

The process occurs naturally on Earth – and has been proposed as a technique for mitigating climate change, by capturing CO2 from the atmosphere.

The 4.5cm Lafayette meteorite was discovered in Indiana, US in 1931, having plummeted to Earth about 3,000 years ago.

It formed in the Red Planet‘s crust about 1.3 billion years ago, and was ejected from the surface by a massive impact.

A team from the Scottish Universities Environmental Research Centre (SUERC) performed microscopic analysis on a section of the rock – borrowed from the Natural History Museum in London.

A Scotland-based team of researchers study a meteorite from Mars in the hope of learning how we can deal with climate change here on Earth

They found that silicate minerals, such as olivine and feldspar, had interacted with CO2-rich liquid water to form siderite crystals.

The team says their discovery suggests liquid water was present on Mars more recently than some had thought.

They also say it represents the first direct evidence for carbonation on the Red Planet – and ties in with the discovery of carbonates by Nasa’s Curiosity Mars rover.

“Carbonation could be the main force that turned Mars to stone,” said lead author Dr Tim Tomkinson, of SUERC.

“We can’t say for certain it’s the dominant cause – the loss of Mars’ magnetic field may also have led to the stripping of its atmosphere by the solar wind. And CO2 is also frozen in the poles of Mars.

“But carbonates do seem to be very abundant on the Martian surface.”

False colour microscopic image of Lafayette meteorite showing evidence of carbonation, with siderite (orange) replacing olivine (blue).
Microscopic image shows evidence of carbonation with siderite (orange) replacing olivine (blue)

The loss of its carbon dioxide cloak is likely to have caused Mars to cool. So understanding how the CO2 was removed “could provide vital clues to how we can limit the accumulation of carbon dioxide in the Earth’s atmosphere and so reduce climate change” said Dr Tomkinson.

Mineral carbonation is widespread on Earth. For example, in Oman’s Samail mountains, weathering of peridotite rocks has been estimated to bind more than 10,000 tons of CO2 per year.

Speeding up this natural process – by fracking rocks and pumping in purified CO2 – has been proposed as a technique for carbon capture and storage.

“From our analysis of the meteorite, it seems that carbonation occurs in certain orientations – we see amazing saw-tooth edges, all lining up,” Dr Tomkinson told BBC News.

“It could be for example that if you wanted to frack rocks and introduce CO2 you should do it from a certain angle.”

Dr Caroline Smith, curator of meteorites at the Natural History Museum, said: “These findings show just how valuable meteorites from collections like those we have here really are.

“There is so much important and useful scientific information locked away in these rare rocks.

“Our study shows that as we learn more about our planetary next door neighbour, we are seeing more and more similarities with geological processes on Earth.”

Images of Lafayette meteorite section
Images of a Lafayette meteorite section, highlighting different minerals

The Long and Arduous Quest to Find Flowing Water on Mars May Be Over.


Discoveries of water on Mars are now so common that the subject has become the butt of jokes among planetary scientists: “Congratulations—you’ve discovered water on Mars for the 1,000th time!”

Most of these findings have involved either visual evidence for ancient, long-gone water or evidence for present-day ice, vapor or hydrated minerals. The discovery of actual liquid water on the surface, in the present day, could change the course of Mars exploration. Where there is water on Earth, there is almost always life. Confirming the existence of water on Mars would therefore greatly improve the prospect of finding extraterrestrial life. This is the story of continuing efforts to uncover what role, if any, liquid water plays on Mars today.

In Brief

  • High-resolution orbital imaging over multiple Martian years is revealing all manner of surface changes, some of which may involve liquid water.
    • Surface features known as gullies were once thought to require the presence of water, but recent evidence suggests otherwise.
    • A newly discovered class of features on warm slopes may mark the flow of salty water. These sites could be the best places to look for microbial life on Mars.