When Weir wrote the novel The Martian, he strove to present the science correctly and used reader feedback to get it right.[134] When Scott began directing the film, he also sought to make it realistic and received help from James L. Green, the Director of the Planetary Science Division at NASA's Science Mission Directorate. Green put together teams to answer scientific questions that Scott asked.[135] Green said, "The Martian is reasonably realistic", though he said the film's hazardous dust storm, despite reaching speeds of 120 miles per hour (190 km/h), would in reality have weak force.[136] Green also found the NASA buildings in the film to be more stylish than the functional ones NASA actually uses.[137] Film critics picked up the point that the Martian winds could amount to "barely a light breeze" in their reviews,[138][139] and screenwriter Goddard agreed the winds had to be considerably exaggerated in order to set up the situation that sets the story in motion.[140][141][142]
The process used by the character Watney to produce water was accurate and is being used by NASA for a planned Martian rover. The radioisotope thermoelectric generator was also appropriately used for heat.[134] When his rations begin to run low, Watney builds an improvised garden using Martian soil and the crew's feces as a fertilizer. However Martian soil has since been found to be toxic to both plant and animal life, although it is believed that microbial organisms have the potential to live on Mars.[143][144][145] In one scene, the glass face shield on Watney's helmet cracks; as oxygen momentarily drops below the critical level, he quickly patches the helmet with duct tape and avoids suffocation.
Time magazine criticized another duct tape based repair: "When a pressure leak causes an entire pod on Watney’s habitat to blow up, he patches a yawning opening in what's left of the dwelling with plastic tarp and PSA duct tape." Such a repair would not work in an average Martian temperature of −60 °C (−76 °F).[146]
While Martian gravity is less than 40% of Earth's, director Scott chose not to depict the gravitational difference, finding the effort less worthwhile to put on screen than zero gravity.[34] Scott said the heavy spacesuits would weigh the main character enough to make up for not showing the partial gravity.[44] The climate of Mars is also cold enough that it would make Watney's initial plan to disable the rover's heater immediately impractical, since the average temperature is −80 °F (−62 °C); it is cold enough on Mars for carbon dioxide snow to fall at the poles in winter. However, this issue is almost immediately brought up, and is the reason for the plan failing.
The plot key to the eventual rescue plan is gravity assist, a well-known practice that has been used on a number of robotic planetary exploration missions and served as a backup strategy on manned Apollo missions. It would have been one of the first approaches that everyone within NASA would have considered,[146] but in the film, only one JPL astrodynamicist argues for sending the Ares mission back to Mars using gravity assist rather than having a separate mission to rescue Watney.
Ed Finn, director of the Center for Science and the Imagination at Arizona State University, said, "What this story does really well is imagine a near-future scenario that doesn't push too far off where we are today technically."[44] British physicist Brian Cox said, "The Martian is the best advert for a career in engineering I've ever seen."[147]
