Legendary physicist and ET speculator Freeman Dyson thinks dead planets need a human touch. Author and astrophysicist J. Richard Gott, III calls it a simple matter of survival. And author Sid Goldstein figures settling other worlds is all about economics and environmentalism. It’s time to leave this planet, they all agree. Space colonization is not a new idea, but it is one that, despite decades of talk, has yet to be realized. Many promoters of putting humans permanently in space say the first step need not be all that big, with Mars right next door, cosmically speaking. And recent evidence suggests that the Red Planet contains the one key ingredient any practical colonization effort would depend upon: water.