Astrobiology sounds like the stuff of lava lamps and Jetsons reruns. Yet seven years after NASA launched a formal astrobiology research program, scientists of every stripe — geologists, biologists, chemists, paleontologists, oceanographers and astronomers — have rallied to the quest. They've spent as much as $65 million a year trying to solve a mystery that has underpinned religion and inspired thinkers from Seneca to Carl Sagan: How did life on the lonely Earth begin? And is Earth really the only source of life in the universe? With the help of modern tools such as the genome, high-powered computer modeling and...