Space visionary Freeman Dyson, the acclaimed emeritus professor of physics at the Institute for Advanced Study in Princeton, New Jersey, recently had a conversation with Robert Zubrin, the world’s biggest cheerleader for human missions to Mars. “Your scheme of Mars missions is excellent,” Dyson said, “but it has one fatal flaw, the fact that you are expecting NASA to do it.” “Ah, but when we give NASA a real challenge like this, it will be a different NASA,” Zubrin replied. “I think he is right,” Dyson said last Thursday. I had asked Dyson and other top scientists about the future of human spaceflight, on a day when worldwide media reports said President Bush might soon announce a major new human space initiative, to the Moon and perhaps Mars.