Character Analysis
Nerd Alert
Rich Purnell fits just about every nerdy stereotype you've ever heard.
Genius-level IQ? Check. Bad social skills? Check. A Drax the Destroyer ability to completely miss the point of jokes? Oh yes. We're not making fun of him, though, because a nerd like him is exactly what Mark Watney needs right now.
Plus, we just made a Guardians of the Galaxy joke. What do you think that makes us? (The answer is: big ol' nerds.)
Rich Purnell's defining characteristic is his dedication to his work. He slaves over the so-called "Purnell Maneuver" for weeks on end until "empty coffee cups rested on every surface" and "take-out packaging littered the ground" (15.100). This isn't a project handed down to him by his bosses: it's a personal obsession. More importantly, it's an obsession that could save Mark's life.
That being said, the guy is clearly "not good with people" (16.94). Purnell is a supremely logical dude, and while that logic comes in useful when he's doing research, it has a tendency to trip him up in social situations. Luckily for everyone involved—Mark Watney especially—NASA isn't paying him to be a charming fellow. They're paying him to be a nerd.