Lonely Planets Read online

  L o n e l l

  y

  P l a n e t s

  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

  P A R T I

  H I S T O R Y

  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

  P A R T I I

  S C I E N C E

  6 7

  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

  P A R T I I I

  B E L I E F

  2 8 7

  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

  Foreword: It Came Out of the Sky

  x

  possibility and desirability of “Terraforming Mars” (the future engineer-

  ing of Mars to be more like Earth).

  Now hold on. Science fiction? Ethics? At a science conference? Yes, if

  the science is astrobiology. In addition to the “strictly physical” ques-

  tions we wrangle with—such as making life to begin with, transporting

  it between worlds, and keeping it alive in a wide range of planetary

  environments—questions about life in the universe inevitably spill over

  into other realms. Intellectually, astrobiology itself is a rather big tent,

  somewhat hastily constructed, in which the Earth, space, and life sci-

  ences commingle with wild speculation, a dash of philosophy, and even

  a splash of spirituality.

  The most eagerly awaited moment of the weeklong conference came

  Tuesday afternoon, when Steve Squyres, principal scientist for the Mars

  rovers, gave us an update on the activities of his two little Martian robot

  geologist puppies, Spirit and Opportunity. There was an air of celebra-tion at this session, as a community that has known recent and repeated

  failure enjoyed a great success. This cockamamie bouncing–on–air bags

  landing scheme had worked once before with the Sojourner rover in

  1997, but we all had a lot more riding on this attempt than just the

  equipment. During the weeks prior to the landings, there had been

  a palpable nervousness, fueled by the fact that we still weren’t sure

  what went wrong with our last attempt to land on Mars in 2000

  and tempered somewhat by the thought that this time we were sending

  two identical, carefully tested rovers and at least one of them ought to

  work.

  This time they both did. Each survived the bouncy landing without

  a hitch, and at the time of the Astrobiology Science Conference, each

  was inching across one of the thousand unexplored deserts of Mars,

  scratching and poking among the ruddy dirt and ancient rocks, shaking

  loose buried secrets, snapping pictures all the while.

  Squyres—rail-thin, angular, and as always sporting jeans over cow-

  boy boots—was looking very bright-eyed for someone who’d been liv-

  ing on Martian time for the last three months. As far as I could tell, he

  hadn’t changed a bit since we first crossed paths in the summer of 1978

  as students at Cornell. I ran into him in the hallway before his talk, and

  though at that moment he was the coolest person in the solar system,

  he didn’t act with one ounce of self-importance. He recounted the latest

  rover findings and the fun he was having, as if he were just an old col-

  league at a meeting telling me about his latest pet project. Which he

  xi

  Foreword: It Came Out of the Sky

  was, but . . . his pets were on Mars, and they were on the move. Steve

  took the stage, to thunderous applause, meant for the triumphant little

  robots as well as for their driver. These are the moments we live for. It is

  thrilling to be back on Mars.

  He began with a spirited recap of the rovers’ initial forays on Mars

  and a preview of their possible futures. Then he got right to the good

  stuff—the possible stuff of life on Mars. What had we found? When I

  think about it I still get so excited I can hardly talk—or type. All my

  life, and my professional career, I’ve been enthralled with the possibil-

  ity that through planetary exploration we can learn something defi-

  nite about whether we have living company in the universe beyond

  Earth. Well, the universe had just dropped us a big hint. We found

  rocks on Mars that were formed of sulfate salts. The only way we

  know of to make that kind of rock is through the evaporation of salty

  seas from a place that must have been soaking wet for significant peri-

  ods of time.

  Why are we so hyped-up about finding sea-formed rocks on Mars?

  Well, as far as we know at present, life needs water. On Earth, where

  there is water there is life. Over the last few decades, circumstantial evi-

  dence had been building for large quantities of surface water in the

  Martian past. Orbital photographs revealed shapes strongly suggestive

  of watery rivers and lakes. Yet, there has always been the nagging possi-

  bility that we were searching so hard for signs of the familiar that we

  were misinterpreting the photos and maps, mistaking the action of lava,

  wind, ice, or some other unknown carver for the work of our beloved

  water. But the rocks don’t lie. Now, at last, we’ve sampled the ground

  itself, and the evidence is no longer circumstantial. We’ve found the

  smoking gun (which in this case is a dripping Super Soaker) of past hab-

  itability. We now know there was other wet ground, beyond the Earth,

  in our solar system. Right next door. Buckets of rain once ran like salty

  tears over the face of our little red brother Mars. This discovery proves

  that Mars is indeed an important place for astrobiology exploration—a

  place where many kinds of Earth life could once have survived—so why

  not Martians? The idea that we might really find fossils of bygone crea-

  tures on the Red Planet can no longer be regarded as far-fetched.

  Among other things, this will be a major shot in the arm for our

  desires and plans for future missions, providing the encouragement

  (and most likely the funding) we need to keep going, to send new

  machines there that can look for fossils or chemical traces of past life.

  Foreword: It Came Out of the Sky

  xii

  Soon we will want to return Martian samples to Earth. With the right

  Mars rocks in our own laboratories, we will be able to more defini-

  tively test the idea that life once graced our red planetary neighbor.

  The raised prospect of new missions to—and from—Mars height-

  ened the exigency of our ethical discussions, topics that just a year ago

  seemed more academic. How much should we care about—and spend

  to guard against—the possibility that we might contaminate Mars with

  microbes from Earth, or even the slight but disquieting chance that we

  could bring something back from Mars that might enjoy snacking upon

  our own biosphere? John Rummel, NASA’s planetary protection officer,

  was at the conference, addressing these issues.

  Does the news that Mars once had the conditions for life increase the

  threat of contamination? Perhaps not. Many of us believe that what-

  ever biology once graced this rusty world disappeared long ago, along

  with the sputtering geology and the evaporating seas. The Mars rovers

  are wandering places where almost nothing has happened in uncount-

  able eons. Seen up close, these landscapes verify our belief that the sur-

  face of Mars is incredibly ancient. There is nothing in the new photos

  to suggest any recent action, beyond the frequent bursts of dusty winds.

  Most of the geological activity is long gone, leaving a surface freeze-

  dried, ossified, and sculpted in places into bizarre forms not see
n on

  Earth, because you couldn’t find a place on our planet that has been left

  to the wind alone for a billion years. The rovers haven’t found much

  that changes our views of present-day circumstances on Mars. Their

  biggest discoveries are about conditions in the deep past, including the

  enticing possibility of ancient life.

  Even the finding of once-soggy ground, as spectacular as it is, is not

  revolutionary. It doesn’t overturn our current notions about Mars—in

  fact, it confirms them. Yet, while the rovers were grabbing all the atten-

  tion, about a week before the conference, another report had come in

  from Mars that could have truly revolutionary implications. The

  European Space Agency’s Mars Express, which arrived in Mars orbit

  on Christmas Day 2003, had caught a whiff of something in the air.

  Something that didn’t belong there. Something that might indeed be a

  sign of life there today. The announcement received much less press

  attention than the rovers, which, after all, were taking cool pictures. On

  board the orbiter, an infrared spectrometer—which precisely dissects

  the radiation leaking from the planet into a million distinct colors—had

  detected a most unexpected trace gas in the Martian air. Feeble signs of

  xiii

  Foreword: It Came Out of the Sky

  methane had been found on Mars. Methane is CH4, a carbon bonded

  to four hydrogens.

  Chemically, it is out of place in an atmosphere like that of Mars,

  which is composed almost completely of carbon dioxide (CO2). Finding

  methane on Mars is like finding a gazelle strolling unnoticed through a

  pack of hungry lions.

  To me this announcement was shocking, and it seemed even more

  unreal than any of the strange postcards sent home by the rovers. I used

  to say that methane on Mars would be one finding that could change my

  mind about that planet being a perfectly dead world. Why? Because as

  life evolves on a planet, the atmosphere evolves along with it. Chemically,

  the two become intimately coupled. On Earth, the oxygen we breathe,

  the protective ozone layer, and, yes, the trace of methane in the air are all

  chemical by-products of 4 billion years of biology. Life in turn has

  molded its chemistry to cleverly utilize the atmosphere pervading our

  world. It may be this way on all planets with life and air. If so, then a

  close study of a planet’s air will always reveal life or the lack of it.