LL oo nn ee ll yy PP ll aa nn ee tt ss The Natural Philosophy of Alien Life D A V I D G R I N S P O O N For my parents Evelyn Betsy Grinspoon and Lester Grinspoon with love and gratitude Penetrating so many secrets, we cease to believe in the unknowable. But there it sits, nevertheless, calmly licking its chops. —H. L. MENCKEN Contents Epigraph iv Foreword: It Came Out of the Sky viii Preface xx PART I HISTORY 1 1 Spirits from the Vasty Deep 3 2 Plurality of Worlds 19 3 A Wobbly Ladder to the Stars 34 4 The Planets at Last 51 PART II SCIENCE 67 5 The Greatest Story Ever Told 69 6 Earth Birth 88 7 Life Itself 97 8 Childhood 115 9 So What? 135 10 The Lives of Planets 150 11 Venus and Mars 167 12 Growing Up with Europa 191 13 Enter the Exoplanets 205 vii Contents 14 Exobiology: Life on the Fringe 221 15 Astrobiology 237 16 Is It Science Yet? 252 17 Living Worlds 266 PART III BELIEF 287 18 SETI: The Sounds of Silence 289 19 Fermi’s Paradox 310 20 Have You Seen the Saucers? 334 21 Cons, Piracies, Conspiracies 358 22 Believing Is Seeing 374 23 The Immortals 389 24 Astrotheology 408 Notes on Sources and Suggestions for Further Reading 417 Index 423 About the Author Praise Other Books by David Grinspoon Credits Cover Copyright About the Publisher Foreword: It Came Out of the Sky We are all in the gutter, but some of us are looking at the stars. —Oscar Wilde On a tranquil late afternoon in early January 2004, the sky split open and an alien ship dropped out. In a tired, rusty desert land where noth- ing more than a dust devil had stirred for a hundred million years, the monotony was shattered and a thundering, glowing ball of light rushed toward the ground. Suddenly, at about two hundred feet, the visitor inflated like an angry puffer fish, growing to many times its original size, and then, seconds later, landed with a mighty “whump!” bouncing as high as a four-story building. After twenty-eight more bounces— each one raising a fearsome cloud of dust that slowly drifted off—it came to rest on a desolate, sandy plain scattered with worn and broken rocks. Nineteen days later, on the other side of the world, a twin vessel made a similarly strange, bouncing entrance, rolling to a stop in a small crater sunk into a vast flat wasteland of salt-crusted rocks sprinkled with metallic, berrylike spheres. Each visitor quickly began to trans- form itself, deflating its landing cocoon to reveal a small hibernating creature within. Extending wheeled legs, mechanical eyes, and other peculiar sensory limbs, each slowly crawled off its now defunct landing pod. The Martian arrival had begun. Back on Earth, just two months later, in late March 2004, hundreds of scientists pursuing alien life congregated in a hastily constructed NASA facility in northern California—a colossal white tent with semi- translucent siding, illuminated by rows of massive searchlights. Armed government guards checked ID of all who wished to enter. At first glance it resembled some top-secret X Files–type government installa- tion, but a peek inside dispelled that impression. Instead of emotionless ix Foreword: It Came Out of the Sky space-suited functionaries intent on inscrutable experiments, the giant hall was filled with a motley assortment of nerds (myself among them) and student nerds-in-training. Fashions ranged from suits and ties to sandals and shorts. Information-packed posters hung in long rows, displaying the latest scientific results on “astrobiology”—the study of extraterrestrial life. A platoon of headsetted journalists, chasing us around with microphones and cameras, completed the scene. This was the Third Astrobiology Science Conference, held at NASA’s sprawling Ames Research Center, spread along the southwestern shore of San Francisco Bay—a tentful of carbon-based, water-loving, marginally intelligent organisms gathered on the thin skin of planet Earth, to prog- nosticate about the possibilities of life beyond. We had a lot to talk about. NASA’s two Mars Exploration Rovers had made their spectacular bouncing landings only two months prior and had already made fantastic discoveries that had recharged and refreshed the perennial debates about life on Mars. Of course Mars was all the rage, so I was somewhat surprised, but delighted, to have been invited to the conference to speak about one of my pet ideas: “Sympathy for the Devil: The Case for Life on Venus.” It was fun to play Lucifer’s advocate for the astrobiology community and attempt to sell Venus’s overlooked charms to this skeptical but far- reaching audience. In a speculative field like astrobiology, complacency, overconfidence, and unsupported consensus are all serious dangers. After all, our field is still lacking in any actual bona fide extraterrestrial research volunteers. So outside ideas, however ultimately wrong-headed they may prove, are welcomed, as long as they can be supported with plausible argu- ments that don’t break too many of our agreed-upon rules. (What are these rules? Why do we agree upon them? Should we? Read this book.) My conjectures about possible microbial life in the clouds of Venus were deemed to pass this test, and so they were invited into the tent, joining the more “conventional” notions of life underground—in possi- ble Martian hot springs and the buried seas of Jupiter’s icy moons. (See chapters 11 and 12 for more on possible Venusian life.) This gathering under a tent, though perhaps not nearly as exotic as a secret government alien research lab, was definitely not your mom’s sci- ence conference. The two other programs for which I was enlisted that week were a panel called “Ethics of Exploration” and a public debate in which a group of scientists and science fiction writers argued over the