Space conventions are the sort of place where you meet men with too many pins in their lapels and wide eyes. On my first evening in DC, last Thursday, I met a man in the lobby who was convinced that there are trees on Mars... or at least some sort of foliage. "It's in the pictures!" he explained, his eyes widening. He also seemed to think that there was some kind of alien base on the far side of the Moon. You have been warned.