If it's just us in this universe, what a terrible waste of space. For thousands of years, humans have wondered about who and what might be living beyond the confines of our planet: gods, beneficent or angry; a heaven full of sinners long forgiven; creatures as large and strange as our imagination.
Some scientists now are on the cusp of bringing those musings back to Earth and recasting our humanity yet again. "Astrobiology" is the name of their young but fast-growing field, which immodestly seeks to identify life throughout the universe, partly by determining how it began on our planet. The men and women of astrobiology -- an iconoclastic lot, quite unlike the caricatures of geeks in white lab coats or UFO-crazed conspiracy theorists -- are driven by a confidence that extraterrestrial creatures are there to be found, if only we could learn how to find them. Most astrobiologists hold the conviction that if a form of independently evolved life, even the tiniest microbe, is detected below the surface of Mars or of one of Jupiter or Saturn's larger moons, the odds that life does exist elsewhere in our galaxy and, potentially, in billions of others, shoot up dramatically. A solar system that produces one genesis -- ours -- might be an anomaly. A single solar system that produces two or more geneses tells us that life can begin and evolve whenever and wherever conditions allow, and that extraterrestrial life may well be an intergalactic commonplace.