In the wake of the Columbia tragedy, the Internet carried an enormous outpouring of condolence messages, most aimed at the families of the seven astronauts who died over the skies of Texas. But mixed among them were messages written or spoken with an eye to the future. The one I remember most came from a woman who said: “I was watching the news coverage and attempting to explain what had happened to my 6-year- old son. After I got done speaking, and he had confirmed that seven people had died, he looked at me and said he wanted to be the first man on Mars.’