In 2035, the crew of the Ares III mission to Mars is exploring Acidalia Planitia on Martian solar day (sol) 18 of their 31-sol expedition. A severe dust storm threatens to topple their Mars Ascent Vehicle (MAV). In the ensuing evacuation, astronaut Mark Watney is struck by debris and presumed dead. With the MAV on the verge of toppling, the remaining crew takes off for their orbiting vessel, the Hermes, leaving Watney behind.
Watney awakens after the storm, injured and with a low-oxygen warning. He returns to the crew's surface habitat ("Hab") and treats his wound. As Watney recovers, he begins a video diary. Unable to communicate with Earth, his only chance of rescue is the next Mars mission; in four years, Ares IV will land 3,200 kilometers (2,000 mi) away at the Schiaparelli crater, the Ares IV MAV has already arrived on the site in preparation for the mission. Watney's immediate concern is food; being a botanist, he creates a garden inside the Hab using Martian soil fertilized with the crew's bio-waste and manufactures water from leftover rocket fuel. He then cultivates potatoes using whole potatoes reserved for a special Thanksgiving meal. He also begins modifying a crewed rover for the journey to the Ares IV MAV.
On Earth, NASA satellite planner Mindy Park, reviewing satellite images, notices moved equipment and realizes Watney must be alive. NASA director Teddy Sanders releases the news to the public but decides not to inform the Ares III crew en route to Earth, over flight director Mitch Henderson's strong objection.
Watney takes the rover on a one-month journey to retrieve the Pathfinder probe, which fell silent in 1997. Using Pathfinder's camera, he establishes visual contact with NASA. NASA transmits a software patch to link the mission's rover with Pathfinder, enabling communication by text. Sanders finally allows Henderson to inform Watney's crewmates.
The Hab's airlock blows out, injuring Watney and destroying the potato crops; although Watney repairs the airlock, he is again threatened by starvation. Mars missions director Vincent Kapoor and Jet Propulsion Laboratory (JPL) director Bruce Ng prepare a resupply to deliver enough food for Watney to survive until Ares IV's arrival. Sanders orders routine safety inspections bypassed to expedite the mission, but an oversight causes catastrophe as the resupply spacecraft disintegrates shortly after launch.
The China National Space Administration decides to offer a launch vehicle — originally intended for the Taiyang Shen space probe — to resupply Watney, in exchange for getting a Chinese astronaut on the next Ares mission. Astrophysicist Rich Purnell devises an alternative plan: have the Taiyang Shen launcher rendezvous with and resupply the Hermes, which will then use Earth's gravity to "slingshot" back to Mars two years earlier than Ares IV. Sanders rejects the idea, considering it too risky for the Hermes crew. Henderson surreptitiously sends Purnell's proposal to the crew; they unanimously vote in favor and divert the Hermes. Sanders is forced to support them publicly, but demands Henderson's resignation after Watney is rescued.
Watney begins the 90-sol journey to Schiaparelli, where the MAV for Ares IV is pre-positioned. He must use it to rendezvous with the Hermes, but it needs to be lightened considerably. After takeoff, when the MAV runs out of fuel, its velocity relative to the Hermes is too fast for Watney to be picked up. Commander Lewis quickly improvises, using an explosive to breach a forward airlock, resulting in air escaping violently and slowing down the Hermes. It is still not enough; using a tethered Manned Maneuvering Unit, Lewis is unable to reach Watney. Watney pierces his pressure suit, using the escaping air to propel himself to Lewis, ending his 561 sols alone on Mars.
After returning to Earth, Watney becomes a survival instructor for astronaut candidates. Five years later, as the Ares V is about to launch, those involved in Watney's rescue are seen in their current lives.
Mark Watney's route on Mars
