Andy Weir Says One Thing We’ve Accepted About Matt Damon In The Martian Actually Doesn’t Make Scientific Sense

Project Hail Mary’s first weeks at the box office helps prove there's still a desire for science fiction-based stories. And, if the positive reactions to the book-to-screen adaptation are anything to go off, fans are buying into the science depicted in the flick. Author Andy Weir seems to know how to utilize hard science within his stories, and that's also true of The Martian, of which an adaptation starring Matt Damon was made over a decade ago. However, Weir now says one widely accepted aspect of that story's science isn't logical.

The Martian was a triumph upon its release, and it's still considered one of the best films of 2015. Adapted from Weir's 2011 novel of the same name, the film focuses on astronaut Mark Watney, who's accidentally left on Mars, leading NASA to mount rescue efforts. Scientific practices like growing food in Martian soil and making Mars’ atmosphere breathable abound within this tale. As Weir recently admitted to IMDb , though, one survival method Mark used was unnecessary:

As shown in the Ridley Scott movie, Mark Watney creates water from leftover rocket fuel since rain doesn't fall on the Red Planet and there’s no well. Despite that, one of the fascinating scientific facts to learn from The Martian is that with 35 liters of water in every cubic meter of Martian soil, Mark could have heated up the dirt to make water.

Also, the gravity in the movie wasn’t totally accurate either, as gravity on Mars is 40% of Earth's, meaning Mark would feel much lighter in his new environment. Astrophysicist Neil DeGrasse Tyson actually ripped into that while watching the movie. But, at the end of the day, we have to remember that this genre is called science fiction for a reason. (Emphasis on the fiction part.) In any case, I appreciate Weir being so forthcoming about the inconsistencies in the Oscar-nominated film adaptation.

In the case of Project Hail Mary, at least, DeGrasse Tyson scientifically approved of the science being depicted. That film follows an amnesiac middle school science teacher, who wakes up on a spacecraft and applies real-life scientific logic to survive in space while trying to achieve his mission. Interestingly enough, Andy Weir continued to tell IMDb of a scientific inaccuracy in that book that even he thought was accurate at the time he wrote it:

Of course, it's hard to blame the NY Times best-selling author for writing what he thought was accurate at the time. After all, part of the charm of Project Hail Mary is that the story does include a lot of grounded scientific facts. And, with the film adaptation, directors Phil Lord and Chris Miller -- and by extension, lead actor Ryan Gosling -- sought to keep everything as realistic as possible. (Sure, there's not actually a spaceship-flying rock creature like Rocky, to our knowledge, but still.)

If anything Andy Weir's openness in critiquing his own work is a testament to just how much he respects the true science. I obviously can't speak to how anyone else feels, but these reveals wouldn't stop me from immersing myself in the story and sci-fi thrills presented in The Martian or Project Hail Mary. Check out the more recent of those films, which recently arrived amid the the 2026 movie schedule, in theaters now.