A movie adaptation of a novel can never include everything — some material is too dense or not important to the angle the movie is taking. For the sake of narrative, it’s understandable that a film won’t act out every paragraph, even memorable ones. The film adaptation of Andy Weir’s novel The Martian is no different.

Though The Martian is probably the most realistic sci-fi film in a decade or more (earning high marks from me) and largely faithful to the novel, there was a lot of material that was either left out or changed. And for a film about the triumphs of human ingenuity, many of the sections where that was most on display were left out. But again, this is understandable. Many pages of The Martian novel are devoted to what reads like an xkcd What If? post. These sections would be visually boring, and all that Hollywood talent needed screentime.

So what made the cut? There will be major spoilers for both the novel and the movie below.

The Big Changes

The Ending

The biggest difference between the novel and the film is the film’s ending. In both stories, after Watney straps himself into the Ares 4 Mars Ascent Vehicle that he turned into a “convertible,” the crew aboard the Hermes prepares to literally grab him out of the moving spacecraft. In the novel, everything goes according to plan (except for the part where the crew intentionally breaches the Hermes), and a crew member jets out on a tether, grabs Watney, and returns to the Hermes. There the story ends.

In the film however, things are much more dramatic. After the intentional Hermes breach to correct course, Watney informs Commander Lewis (played by Jessica Chastain) that he knows the distance is still too far, and would like to try an “Iron Man” by poking a hole in the glove of his suit and aiming it like a repulsor. This suggestion happens in the novel too, but it’s a joke. In the film he actually does it, eventually embracing Commander Lewis who is floating at the end of the tether.

Commander Lewis doesn’t make the grab in the novel, nor does Watney ever try the Iron Man. However, the sequence in undeniably thrilling, and Jessica Chastain plays arguably the other lead character, so the change makes sense, at least from a movie making standpoint.

The Epilogue

Though Weir has said that the original version of his novel did have an epilogue after Watney’s rescue, it was cut. “I just didn’t like it,” Weir explained in a Reddit AMA. “Having an 8-month time jump just for one more scene felt lame. Also the epilogue itself wasn’t very good in my opinion.” So the novel ended with Watney back aboard the Hermes, happy but smelling like hot garbage.

The epilogue returns in the film however, showing Watney teaching a bunch of students and making quips about farming with his own poop on Mars. It also shows what each of the characters went on to do after the rescue mission.

Pathfinder

Regaining contact with NASA is what ultimately saves Watney’s life. He does this by finding and resurrecting the Mars Pathfinder spacecraft and its Sojourner rover, hacking their communications systems to run off solar power. Once he’s able to email NASA, rather than send simple picture messages, Watney is on track to salvation. However, right before he makes his journey to Ares 4, he accidentally shorts out Pathfinder with the placement of an improperly grounded drill. He has to make the trek alone, relying on his own modifications to the Ares 3 rovers.

In the film, he never shorts out Pathfinder and maintains contact with NASA all the way to Ares 4.

The Storm

Watney dies if he can’t get to the Ares 4 landing site thousands of kilometers away from where he was stranded. Much of the novel is devoted to his preparations for that journey, and when he finally does attempt it, of course not everything goes according to plan. Unable to contact NASA, in the novel he never hears about a massive dust storm heading his way. If Watney drives right into it, the storm could be big enough to prevent his solar cells from charging, effectively killing him.

Without knowing how big the storm is or in what direction it is moving, Watney must get creative. He rigs up volt meters to solar panels and places them far enough away that the difference in their readings should indicate where the storm is moving, based on how much sunlight it is blocking at each location. Watney avoids the storm with this clever scientific solution.

There is no storm in the film.

The Crater

Before finally making it to the Ares 4 site in the novel, Watney must drive his pimped-out rover into Schiaparelli crater, down a ramp-like structure and into the heart of the formation. It seems easy enough until his entire vehicle assembly digs too far into the dust and flips over. He spends days righting them.

The film shows a long, but safe journey to Schiaparelli.

The Little Things

The Rovers

In the novel, Watney’s only way of getting to his extraction point is to modifiy the two rovers left behind by his crew. Pages and pages detail everything he has to do to them, from how he has to transfer life support from the HAB to how he attaches a bed to the back. One rover drives while the other functions as a trailer. The Martian film only uses a single rover (the other one is destroyed in the storm), with little to no explanation of why or what modifications are made.

The movie also gives the rovers mini cranes, which novel Mark Watney would have killed for, considering all the pain meds he had to take after building a ramp for Pathfinder out of rock and dust.

The Airlock Explosion

The first time we really feel like Watney might be the first human to die on Mars (in both the film and the novel) is when an airlock connected to the HAB ruptures, flinging it, with Watney inside, meters away. The HAB loses all its air, Watney loses all his crops. In the novel Watney spends hours sealing both his suit and the airlock after the accident. He then must flip the airlock like a Mexican jumping bean towards the HAB. But on screen Watney needs only to fix a cracked helmet with duct tape before venturing outside.

The Radioactive Hot Tub

Making sure he doesn’t freeze to death on Mars, Watney digs up and uses a radioactive energy source to provide him with heat in the rover, as well as (in the novel) heat up the gases his life supports generates inside the rovers. It also lets him make a hot tub. With radioactive decay.

Though while shown and used in the film, the radioisotope thermoelectric generator or RTG plays a much more minor role.

The Verdict

The Martian is a great movie. It’s packed with serious talent and jaw-dropping Martian vistas. The action sequences are entertaining, and seeing the positive portrayal of science, engineering, and human resourcefulness (and NASA) is incredibly refreshing. But for a film that makes a lot of the ingenuity of the loneliest human in history, it removes much of the tinkering and problem solving that got the novel noticed in the first place.

If some future scientist or engineer or explorer asked me, however, one movie she should see this year, it would be The Martian.

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IMAGES: 20th Century Fox