Where It All Goes Down
Mars
Mark Watney gets stuck on Mars for almost two years. Two years. That's not a vacation: that's a relocation. Over the course of those treacherous months, Mark becomes acquainted with the red planet on a level that no one ever has before.
Hab on the Range
During that time, the Hab becomes Mark's stand-in home. He sleeps there, works there, and watches oodles of '70 television there. He even calls it his "Little Hab on the Prairie" (3.27). It might not be all that comfortable, but it provides him some much-needed release after spending his days struggling for survival. That being said, the comfort of the Hab makes it all the more difficult to step foot outside.
Of course, it doesn't help that the area surrounding the Hab is a complete wasteland. In fact, Mark panics the first time he loses sight of his temporary home, finally confronted with the realization of "how utterly silent Mars is" (21.167). If the Hab makes him feel connected with his old life, then the barren surface of Mars only emphasizes how alone he truly is.
Martian Road Trip
Instead of hiding out in the Hab, however, Mark undertakes a perilous journey across the Martian surface. This quest shows us how old Mars is, as Mark drives to the Ares 4 site through a valley that "millions of years ago [...] was a river" (20.39) We also get a sense of the planet's scale, with Godzilla-sized craters littering the landscape as far as the eye can see. And that's not even mentioning the dust storm that threatens to derail his progress. All in all, this cross-country provides a crash course in the dangers of life on Mars.
Luckily, this the last time Mark will have to deal with this bully of the planet, because he's going home. After fighting the bleak Martian environment for months on end, Mark is finally able to go back to Earth, where he will presumably take a much-needed bath. Mars is stinky, ya'll. Although Mark will never forget his experiences, we're willing to bet that he won't be planning a return trip anytime soon.