We're not the first generation to dream of colonizing Mars. Not even close. But we are the first to at least theoretically have the technology to reach the red planet. And we're not doing so great with the only planet we currently have, so letting billionaires make promises of populating a backup home seems like a pretty good idea. We might as well be ambitious, right? About that... Mars is hard to live on. Like, harder-than-the-Earth-after-nuclear-winter hard to live on. And even in the very best scenarios dangled in popular culture, there are a few things that always get left out. It doesn't mean it will never happen—and we'll send at least a few people, eventually—but it does mean the image of a Mars colony that's in your head is, well, something put there by Hollywood. GUEST: Dr. Katie Mack, theoretical cosmologist, assistant professor, NC State University