The interests of the Mars Society—an organization with the overarching goal of colonizing Mars—tend to elicit snickers from non-space fans. Why talk about building homes on Mars when we have problems on Earth like war, bird flu, AIDS and global warming? To the Mars enthusiast, these scourges simply count among the reasons to ditch this rock and head for the Red Planet. Robert Zubrin, the founder of the Mars Society, likes to point out that Columbus encountered similar resistance from noobs when he pointed across the Atlantic. But Zubrin isn’t a seafarer—he's a scientist, with calculations that say people could...