The Martian is a love letter to science, but what does science think of The Martian? It’s time for a report card on what’s dead-on accurate, where the facts are fudged, and what’s plausible for a future that could one day happen.

Beware: Spoilers ahead. Plenty of spoilers. Constant spoilers. Endless, unrelenting spoilers. You know what you’re getting into.

The story: In 2035, astronauts land in the third human mission to Mars. Eighteen days into their mission, a massive sandstorm drives them to evacuate, aborting the mission early. One astronaut, Mark Watney, is left behind. He battles to stay alive while Earth (and the rest of his crew) slowly realize he’s alive and struggle to find a way to bring him safely home.

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Undeniable Mars fact: it has epic vistas. Image credit: Twentieth Century Fox Film Corporation

Mars: A

The Good: From the planet-splitting Valles Marineris to the bulging Olympus Mons, weak gravity makes the dusty red planet home to ridiculously high-relief landscapes. From extensive ergs—sand-seas of rolling dunes textured with tiny ripples—to the sharp edges of fresh craters, Mars is just as dramatic in fact and fiction. Delightfully, both of Mars’ lumpy, potatoish moons Phobos and Deimos make cameos.

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The Bad: The fictional geomorphology doesn’t necessary match up with reality. While Acidalia Planitia is relatively flat, it’s no where near as gentle as portrayed in the story. Our fictional Mars also appears to have selective gravity, acting at Earth-strength on astronauts to keep them walking normally instead of hop-bouncing in a variation of the moonwalk while still permitting steep, towering cliffs.

The Fascinating: Dust builds up on Mars at a rate of 0.5 to 5 millimeters per decade, which is enough to constantly coat solar panels but not enough to completely bury the Pathfinder lander. However, a big storm or migrating sand dunes could’ve plausibly eaten the spacecraft. The coolest finding from the Curiosity Rover is that Mars is red on the outside, but green-grey on the inside. It would’ve been fun to see a few fresh exposures of broken rocks leaping out in those endless seas of red.

A dust devil spotted by the Spirit Rover on Mars. Image credit: NASA

Atmospheric Science: C+

The Good: Mars has beautiful wispy clouds, rowdy dust devils, and even the occasional rare storm charging dust into sparking lightning into the rocks.

The Bad: Dust storms on Mars can be planet-spanning catastrophes with winds up to 160 kilometers per hour. However, they don’t come out of no where, and the thinner atmosphere means those winds would have as much impact as a much milder 18 kilometer per hour wind here on Earth. Even the largest storm isn’t going to fling around pebbles, and it certainly isn’t going to tip over a spacecraft or spear a pole into a hapless astronaut. And Martian sunsets are a beautiful, alien blue, not red.

The Fascinating: Because the Martian atmosphere is so thin, it can have dramatic temperature differences over a distance as short as toes to nose. The planet also has seasonal temperature shifts, so human missions to Mars might require summer and winter pressure suits.

Fictional NASA has so much more money for beautiful structures than real-life NASA. Image credit: NASA

Practice of Science: A+

The Good: Everyone in this story loves their jobs, and are good at them. From Watney knowing to look for the finer sediments for soil sampling to mission control’s Mindy Park immediately noticing something has changed in her patch of Mars and how important it is, everyone is deeply competent. The indomitable problem-solving is equally familiar: commander Melissa Lewis instructing her crew to “work the problem” could be Apollo 13. But the best bit is the real-life cultural differences between the starched and suited government agency NASA, and the more relaxed semi-academic setting of Jet Propulsion Laboratories in sweaty t-shirts and blue jeans.

The Bad: NASA must get a massive funding boost in the future both for their prettier infrastructure and all those gorgeous space-toys. The only way Jet Propulsion Laboratories is looking that swanky in the future is if a space-obsessed Californian billionaire decides to become the facility’s patron.

The Fascinating: The idea of international space agency cooperation to save human lives is not entirely implausible from historical precedent, although the logistics and deals would be a lot more brutal than adding an astronaut to the next crewed mission to Mars.

Sun Williams running on the treadmill of the International Space Station. Image credit: NASA

Health: C-

The Good: The Hermes is equipped with extensive exercise equipment. The health impacts of long-term exposure to microgravity are mitigated by spending at least two hours a day exercising. NASA is working hard to come up with ways to keep astronauts healthy—both physically and psychologically—during long-duration missions. Our understanding has dramatically improved over the past few decades; it’s only going to get better.

The Bad: In the epilogue, every astronaut should be dying of cancer. Mars lacks a global geomagnetic field to do more than weakly shelter Watney from cosmic rays, while the crew on the Hermes are even more exposed. Their long stint within the orbit of Venus would up their radiation exposure to between 0.66 and 1 sieverts, zapping them all.

The Fascinating: Could Watney survive on a highly calorie-restricted diet of potatoes and pills, and what would the long-term impacts be? If we kindly assume they’ve got protein mixed with the vitamins in a space-age Soylent knockoff, it’s possible, maybe.

Redundancy? Nah, that sounds like too much work. Image credit: Twentieth Century Fox Film Corporation

Communications: C

The Good: NASA astronauts are accustomed to broadcasting their activities with their own unique personalities, although generally with a G-rated filter.

The Bad: Spirit, Opportunity, and Curiosity can all communicate directly with Earth (and with overhead satellites), so why can’t the Mars Ascent Vehicle or the ground rovers? Considering all the redundancies in play during robotic missions, it’s unthinkable a human mission would have so few redundancies. Also, NASA of the future apparently ignores their own styleguide on human spaceflight, instead reverting to the archaic and inaccurate “manned.”

The Fascinating: Hijacking Pathfinder for parts is delightfully plausible, with a lot of constraints. It probably isn’t buried in meters of sand. We aren’t quite sure why it died—out of juice, internal break, or something else—so it may or may not be fixable once uncovered. It has no cheerful blinking LEDs, and not all the cosmetic details are accurate. It slews, but not that quickly, and would need to constantly reposition to track the Earth. But it might be salvageable. Plus, bonus adorable Sojourner roving within the Hab is just adorable.

Interplanetary gardening isn’t impossible, but it’ll be more complicated than this. Image credit: Twentieth Century Fox Film Corporation

Gardening: B+

The Good: We’re pretty certain we could grow things in Martian soil. Perchlorates wash out easily, so it just needs a bit of supplementing with nitrogen (say, from human urine) and bacteria. Although it’s not good practice to use human waste as fertilizer since it’s far too easy to transmit diseases, it could work in a do-or-die situation. Bacteria can survive desiccation and freezing, although why that same hardy bacteria would then die when exposed to Martian atmosphere is a bit of plot-selective science.

The Bad: The actual details of growing things on Mars will be more complicated, and will require a better greenhouse setup than Watney improvised. Sunlight is dim out by Mars. The most likely trick for Martian gardeners would be to use parabolic reflectors to concentrate sunlight before transmitting it through fibre optics. Alternately, he’d need special grow-lights: the ones on the space station are an eerie magenta. Trying to repurpose Thanksgiving potatoes into seed stock is also a stretch: they should be irradiated for preservation on the journey, making them un-sproutable.

The Fascinating: If we sent a human mission to Mars, it’s incredibly likely we’d experiment with farming while on planet. Our growth experiments on the International Space Station serve dual function of testing locally-sourced food and in providing substantial psychological benefits for their astronaut-caretakers. If an Ares crew contained a trained botanist, it’d be a waste to not stock him with seeds to practice interplanetary farming (although the alkaline Martian soil makes it more likely he’d grow beans and asparagus than acidic soil loving potatoes).

We already have better maps than Watney used on his roadtrip from Acidalia Planitia to Schiaparelli crater. Image credit: NASA/Fred Calef III

Cartography: D

The Good: We have maps of Mars. Some of those beautiful, high-resolution maps made background appearances. We also have satellites in orbit over Mars, sending home a steady stream of data to the point where we can occasionally spot craters that are not yet even a day old.

The Bad: Our heroes don’t use those maps, instead preferring outdated cartography. Watney relied on a black-and-white sketch map so rough it must be a futuristic elementary school exercise. The Director of Mars Missions Vincent Kapoor lacks faith that his dedicated mappers possess the tools to draw a straight line on a satellite image, instead stealing a picture off the break room walls.

The Fascinating: Why wouldn’t our futuristic rovers be loaded with not just the most detailed maps of Mars, but also tied in to automatically retrieve fresh imagery from overhead satellites? Local crews should have the very best forecasts and maps of Mars, six to twenty minutes earlier than anyone on Earth.

Hi-Seas isolation experiment in Hawaii. Image credit: NASA

Habitats: C-

The Good: We are working on harvesting key materials locally on Mars to minimize how much we need to ship ahead. Curiosity found a way to harvest water from the atmosphere (if it can’t just be mined or found running freely, either way shortcutting the need to synthesize it from rocket fuel), while the Mars 2020 rover is going to try to use local materials to produce oxygen. And duct tape really does work everywhere.

The Bad: An inflatable habitat provides no radiation shielding for squishy, fragile humans or for their delicate electronics. In reality, Martian colonists would be molepeople hiding in caves with habitats thrown on top for easier entry and exit.

The Fascinating: Those future surface structures might plausibly be inflatable. While our hero relied heavily on what looked like plastic sheeting for everything from patching a blown airlock to putting a sunroof on the rover, material science is rapidly advancing to create thin, flexible materials capable of maintaining a pressure differential. We’ll even be testing an inflatable module on the International Space Station in the next few months. (Although why our hero would brave out a storm with flapping sheets instead of retreating to his rover or temporarily donning a spacesuit is an open mystery of masochism.)

Astrophysicist Rich Purnell contemplates a daring way to bring our hero home. Image credit: Twentieth Century Fox Film Corporation

Astrophysics: A+

The Good: Orbital dynamics is a harsh mistress that rewards creativity. The timing of the story is driven by the pull of gravity and conservation of angular moment, immutable constraints that cannot be cheated. Best of all, yes, it’s incredibly important to not just intercept in space but to also match velocities (although more on the details of that later).

The Bad: The original orbit isn’t quite optimized—professional NASA mission planners would trim the trip by 24 days, although this would leave Hermes shy of fuel for making the modified double roundtrip. More bizarrely, why did Rich Purnell plug directly into a supercomputer mainframe instead of submitting a request to the job queue like any other researcher?

The Fascinating: The Rich Purnell manoeuvre could work, but is risky enough to be do-or-die instead of a new faster standard. The double hyperbolic trajectories leave little room for error, and the Hermes spends a terrifying amount of time tucked within Venus’ orbit on its return to Mars.

A dust storm temporarily coated the Spirit Rover’s solar panels. Image credit: NASA/JPL-Caltech/Cornell

Power: B+

The Good: Solar panels on Mars are how we power so many of our landers and rovers; it makes complete sense we’d use the same technology for a human habitat on the red planet. Electrically charged dust is ridiculously sticky, necessitating Watney’s daily panel-cleaning.

The Bad: Radioisotope thermoelectric generators are real and in active use in places where sunlight is too dim to provide steady power. But we’re running out of plutonium to power them, and the shortage is severe enough that researchers of more distant objects are grumpy we loaded one on the Curiosity rover when Mars is close enough for solar power. The problem is only going to get more severe in the future, so it’s unlikely we’d deploy one on a human mission (with a crew capable of daily panel-dusting), and strains plausibility we’d then waste it by burying it in a sand dune.

The Fascinating: Hermes is propelled by an ion engine, technology that is in active use on Dawn puttering around Ceres. It’s loaded with a prototype that hasn’t yet been space-tested, but it’s plausible it could work in the future. But the real problem? Poor Hermes needs a magical power supply. The juice to power that engine far exceeds the pretty array of solar panels; it’d need a nuclear reactor roughly the size of the ship’s living quarters. Theoretically, given enough money and major policy changes, it could happen, but the elegant Hermes would need to undergo a refit first for a bigger reactor.

EVA theme: No tethers when they make sense, and tethers when they make no sense at all. Image credit: Twentieth Century Fox Film Corporation

Spaceships: B

The Good: For long duration missions, the only way to go is with smaller spacecraft to get from planet to orbit, then a larger craft to ferry around in deep space. While harsh, Watney’s 12g launch is survivable and would certainly lead to blacking out.

The Bad: Hermes is enormous, gorgeous, and spacious. This is downright luxurious spaceflight. The radiation shielding is also left assumed instead of explained, which is probably a good thing as we have no idea how to keep our astronauts from being nuked en route to Mars.

The Fascinating: Could a spacecraft really be stripped down to a tarp-topped convertible yet successfully launch through the thin Martian atmosphere? Our only experimental data is from our challenges with landing; we haven’t actually attempted to launch back off the surface again. It’s plausible, but it’d be uncertain and risky enough to be a last-ditch do-or-die, not a rational choice made deliberately when any other options are possible.

Bruce McCandless exploring with a nitrogen jet propelled backpack in 1984. Image credit: NASA

Extravehicular Activity: D

The Good: Everyone is wearing a spacesuit, and they’re even wearing the tough, survival-centric bulky deep space version for EVAs instead of more flexible planet-bound pressure suits for exploration.

The Bad: How astronauts behaved in space yet outside their spacecraft was utterly inexplicable. One astronaut goes hopping all over the outside of the Hermes without a tether because it’s more fun that way? The commander spontaneously decides to break protocol and abandon her leadership role, skipping oxygen pre-breathing and tempting the bends. More troubling, she leashes herself to the Hermes despite also wearing a jetpack whose entire purpose is to break free of tethers and manoeuvre freely.

The Fascinating: The most perplexing non-science starts with the “Iron Man” manoeuvre of our intrepid hero deliberately puncturing his suit. Assuming he carefully doesn’t stab himself so coagulating blood doesn’t seal the hole (which is what happened in the only real-life instance), we’re left wondering how to have a leak small enough to keep from depressurizing the suit (giving Watney between seconds and minutes to live) yet big enough to provide substantial propulsion. Even after that, the colliding reunion between Watney and the commander plays mere lip-service to the concept of angular momentum and spinning faster as mass distribution moves closer to the axis of rotation.

Are we done sciencing yet? Image credit: Twentieth Century Fox Film Corporation

The Verdict: A-

The Martian isn’t a documentary of 100% accurate science, but it’s plausible and mostly consistent. A few moments strain credibility to snapping and some science is distinctly plot-triggered, but this is a story where physics plays a starring role and it shows. Don’t rely on The Martian in place of studying for your next exam on human deep space exploration, but you won’t crack your skull from exasperatedly smacking it against the desk in frustration, either.

Science can accept this love letter as a fictional tribute, a story that inspires and celebrates the very best it has to offer. And who knows? Maybe this will pay off with a bump to NASA’s budget, and our big dreams of going to Mars (and beyond!) might have a chance of playing out.

Read more about challenges facing human health in space and farming on Mars in Gizmodo specials later this week! Read about nine NASA technologies from the movie here.

Top image: The fictional rover is aesthetically almost identical to the actual NASA Multi-Mission Space Exploration Vehicle prototype under development. Credits: Twentieth Century Fox Film Corporation/NASA


Contact the author at mika.mckinnon@io9.com or follow her at @MikaMcKinnon.