FAINT ECHOES, DISTANT STARS

Best known for a steady stream of space-based science fiction (Saturn, 2003, etc.), the veteran author demonstrates a firm factual grasp in framing the big questions about extraterrestrial life.

Forget about little green men sitting by their radios waiting for a sign from us. Bova builds some serious inquiries for humans to ponder and then, perhaps, prompt governments to fund the search for answers. For example, did life begin on this planet, or did it “arrive” from elsewhere? Recent discoveries enhance both possibilities. On the one hand, long-chain molecules, the basis for the “prebiotic” chemistry of carbon-based life forms, are now known to commonly exist in the vast gaseous clouds of interstellar space. On the other, microbes have been found living deep in the Earth’s crust without either air or water, while more ornate creatures thrive in the super-heated, sulfur-rich, oxygen-deprived flows from rifts in the ocean’s floor. In that same “extremophile” category, we find a tiny bacterium capable of surviving a dose of nuclear radiation a thousand times greater than that required to kill a human being; it simply “re-knits” its shattered DNA. In other words, as Bova stressses, expanding our notions of what organisms are capable of is key to the quest for other life forms. Discussing the disappointing 1970s Mars probe, he notes, “With 20/20 hindsight, it is clear that none of the Viking experiments could have detected truly alien life forms because no one knew what to look for except Earth-type biology.” Perhaps the biggest question of all is whether people can get excited enough about the possibility of extraterrestrial life to pay the high price for its discovery. NASA’s Ames Center in California, for instance, was able to reinvent itself with an “astrobiology” focus in order to escape the budget axe, yet its future is anything but secure.

Inspirational treatise faithful to Carl Sagan’s maxim that “absence of proof is not proof of absence.”