It isn’t a new field: Carl Sagan was arguing for the plausibility of other worlds — and other life — way back in 1966. But astrobiology, in recent years, has seen a rebirth. The rapid-fire discovery of a few dozen extrasolar planets will do that. Ditto the finding of what could be fossil bacteria in a hunk of Martian meteorite. Then there are the fresh insights about life here at home. Who knew, 15 years ago, that there was more of it embedded in rocks beneath Earth’s surface than there is above ground? Or that living things thrive in boiling hotsprings and Antarctic wastes?