If you've heard about the Mars One mission, you've probably had one overriding question: what the hell would prompt someone to volunteer for a one-way trip to another planet? Thanks to The Guardian, we now have a clearer answer. The news outlet has just published If I Die on Mars, a documentary that asks three Mars One finalists why they're willing to leave Earth (and everyone they know) behind. In short, they have little to lose and a lot to gain. None of the three candidates has a romantic attachment, and they all feel that they're achieving a higher purpose by settling a distant world. That common response won't be very reassuring to their families, but it does help make sense of a seemingly irrational desire for interplanetary travel.