Turns out Mark Watney jokingly calling himself a space pirate¹, bragging about having colonised Mars, and the like, was one of the most realistic things in The Martian.
In the book. In the film he never lost communication with Earth after reactivating Pathfinder, so he had permission to commandeer the Ares IV MAV, and it wasn’t an act of piracy.
Turns out Mark Watney jokingly calling himself a space pirate¹, bragging about having colonised Mars, and the like, was one of the most realistic things in The Martian.