Faint Echoes, Distant Stars_The Science and Politics of Finding Life Beyond Earth Read online

  To Lynn Harper and her colleagues,

  courageous scouts on

  the frontiers of knowledge

  And to the memory of Carl Sagan,

  pioneer and friend

  Either we are alone in the universe or we are not; either way it’s mind-boggling.

  —Lee DuBridge, science advisor to President Nixon

  (Also attributed to the comic-strip character Pogo)

  Contents

  Astrobiology on the Space Station: A Brief Commentary

  The Tides of Titan: A Short Fiction

  Isaac Was Right: N Equals One

  Epigraph

  Prologue: Author to Reader

  SECTION I The Path to Astrobiology

  1 Are We Alone?

  2 Time and the Tide of Opinion

  3 The Three Requirements of Life

  4 The Extreme Road to Astrobiology

  5 The Great Mindshift: Exobiology Becomes Astrobiology

  SECTION II The Path to Life on Earth

  6 The Birth of Our Solar System

  7 The Birth of Our World

  8 Nature’s Enforcers

  9 The Birth of Life

  10 Opportunistic, Tenacious Life

  11 Life’s Impact on Planet Earth

  SECTION III Life in the Solar System

  12 A Model Planet Called Mars

  13 Exploring Mars

  14 Hotworlds and False Assumptions

  15 The Realm of the Giants

  16 The Realm of Ice

  SECTION IV Life Beyond the Solar System

  17 Extrasolar Planets: Good News and Bad News

  18 The Heartbreak of SETI

  19 UFOs, Abductions, and Ancient Astronauts

  SECTION V Tomorrow

  Epilogue: An Agenda for the Future

  Postscript: The Apocalypse to Come

  APPENDICES

  Appendix 1 Units and Conversions

  Appendix 2 Refractors and Reflectors

  Appendix 3 Cosmic Abundances of the Elements

  Appendix 4 Acid and Alkaline: The pH Story

  Appendix 5 Major Planets of the Solar System

  Appendix 6 Radioactive Dating: Nature’s Alchemy

  Appendix 7 DNA and RNA

  Appendix 8 Contamination: Sterilization and the Isolation Ward

  Appendix 9 Death’s Calling Card

  Appendix 10 The Nitrogen Fix . . . and Israel

  Appendix 11 Charles Darwin

  Glossary

  Bibliography

  Searchable Terms

  Acknowledgments

  About the Author

  Fiction by Ben Bova

  Credits

  Copyright

  About the Publisher

  E-Book Extra

  Astrobiology on the Space Station: A Brief Commentary

  by Dr. Ben Bova

  Some astrobiologists believe that biological research could be the salvation of the hard-pressed International Space Station [ISS] program. For example, consider research on kidney disease. Researchers culture samples of kidney cells for study in the laboratory. But on Earth the cells form flat, thin sheets instead of the three-dimensional shape they have in the body. In the weightlessness of zero gravity, cell cultures grow into three-dimensional forms and behave much more as they do in the human body. David Wolfe, of NASA's Johnson Space Center, has developed a rotating wall bioreactor that has been used successfully aboard the Space Shuttle and the ISS. Zero gravity (or microgravity, as the purists call it) offers an ideal environment for studies of cell cultures, and the International Space Station provides a long-term microgravity platform for such studies.

  “We can give the ISS a reason for existence that every taxpayer can appreciate,” says one enthusiastic researcher.

  Copyright © 2003 by Ben Bova

  E-Book Extra

  The Tides of Titan: A Short Fiction

  by Dr. Ben Bova

  You are standing on the shore of Titan's hydrocarbon sea.

  Titan, the giant moon of the ringed planet Saturn, is larger than Mercury, a cold and dark world ten times farther from the Sun than the Earth. Only pale and weak sunlight filters through the clouds and smog of Titan's thick, murky atmosphere.

  Standing on an outcropping of ice, you stare through your spacesuit helmet's visor at the black, oily sea surging across the rough, jumbled ice field below. In the distance, a sooty "snow storm" is approaching; a wall of black hydrocarbon flakes blotting out the horizon as it nears.

  Then the bleak, frozen landscape grows suddenly brighter. You look up, and the breath catches in your throat. The clouds break for a moment and you see Saturn riding high above, ten times larger than a full Moon on Earth, its rings a slim knife-edge slicing across the middle of the gaudily striped body of the planet. There is not a lovelier sight in the entire solar system.

  A voice in your helmet earphones warns you that the tide is coming in. Pulled by the immense gravitational power of Saturn, the hydrocarbon sea is a frothing tidal wave swiftly advancing across the broken landscape of ice, swallowing everything in its path, submerging spires and boulder-sized chunks of ice, covering the frozen ground in hissing, bubbling black oil, flooding the world from horizon to horizon. Soon it will drown even the prominence you are standing on. It will slither halfway across Titan before reversing its course.

  Tomorrow you will return to that sea, equipped to sample it and search for living organisms in the black, oily liquid. For now, it is time to get back to the safety of the base, higher up among the peaks of ice. The clouds have covered Saturn again and the black snow is coming closer. Titan grows darker, colder. And the devouring black sea is lapping at the outcropping on which you stand, stretching its oily waves toward you.

  You turn and begin climbing toward safety, knowing that tomorrow you will come back and begin to search out its secrets.

  Tomorrow.

  Copyright © 2003 by Ben Bova

  E-Book Extra

  Isaac Was Right: N Equals One

  by Dr. Ben Bova

  It’s time for serious science fiction enthusiasts to admit the obvious: there are no intelligent aliens out among the stars.

  Despite more than four decades of radio searches for intelligent signals from the stars, no hint of an alien civilization has been found. The most likely reason is that there aren’t any out there to be found.

  Despite all the scholastic numerology in which the Drake equation has been played like a church organ, there are no other intelligent creatures in the Milky Way except us.

  If N = R*fpneflfifcL is the question, then the answer is, N = 1. We’re it. The late and sadly missed Isaac Asimov was right. In his galaxy-spanning novels of the Foundation and intelligent robots, there are no intelligent aliens. And in the real Milky Way, there are none either.

  Drake’s famous equation was never meant to be holy writ. It was intended as a guide to thinking about the possibility of extraterrestrial civilizations. Since all the factors in the equation are unknowns1 , it can hardly be considered a reliable guide to anything except our own prejudices.

  Freeman Dyson, of the Institute for Advanced Study at Princeton (and no stranger to unorthodox ideas himself), wrote: “I reject as worthless all attempts to calculate...the frequency of occurrence of intelligent life forms in the universe. Our ignorance of the chemical processes by which life arose on earth makes such calculations meaningless.”

  But the situation is actually worse than that.

  It’s not merely the deafening silence from the stars that brings me
to this sad conclusion. Admittedly, our radio telescopes have probed only a tiny fraction of the Milky Way.

  The real problem is that underneath our search for extraterrestrial intelligence lies a basic assumption that today’s biologists find highly questionable: the assumption that wherever life begins, it will eventually achieve intelligence, given enough time and the good luck to avoid total extinction.

  That assumption, modern biologists strongly believe, is just plain wrong.

  Hubris or Narcissism?

  Yet science fiction writers continue churning out stories about intelligent extraterrestrials, alien civilizations, interstellar empires and interspecies wars. Meanwhile, very bright and dedicated scientists - including Frank Drake himself - continue to search the skies for intelligent signals.

  Why? Are they guilty of hubris, the sin of overweening pride, believing that they know somebody’s out there waiting for us to find them, despite the mounting evidence that it just isn’t so?

  No, I think the fault is narcissism: we look out at the stars and see our own reflection.

  We have the been the victims of that false assumption, an assumption buried so deeply in our psyches that we didn’t even realize it was there, coloring our thinking, leading us onward like a siren toward the rocks of bitter disappointment.

  We blithely assume that intelligence is the end-point of biological evolution. As a fundamental part of our world view, we firmly believe that we Homo sapiens are the most complex creatures on Earth, and our splendid intelligence is the secret of our success.

  This leads us to assume that wherever life is found beyond Earth, intelligence will develop quite naturally, inevitably, unless some planet-shaking catastrophe interrupts the progression of local life forms from simple to constantly more complex.

  We are aware that intelligence poses certain dangers, such as nuclear devastation or ecological collapse, but we believe that most (or at least some) intelligent species will be smart enough to avoid those traps and flourish into an interstellar civilization.

  In the April 2002 issue of Analog Robert Zubrin displayed this hidden, almost subconscious assumption:

  “. . . the entire history of life on Earth shows clearly that, once life starts, it exhibits a continuous tendency toward development of greater complexity, activity, and intelligence.”

  Tell it to the bacteria, the most successful form of life on Earth (and probably elsewhere, as well). They’ve been chugging along since before our planet’s crust cooled down, and those single-celled prokaryotes outweigh all the other forms of life on Earth, put together. Bigger life forms come and go, but the bacteria roll on forever.

  Zubrin goes on, “In other words, based on everything we know, life and intelligence should be common in the universe.”

  Alas, he is wrong. We don’t know any such thing. Life in the universe may indeed be as common as bacteria, but intelligence might just happen to be a fluke that happened here and nowhere else. Because it happened here, we naively assume it is an inevitable result of biological forces. ’Tain’t so.

  Harvard paleontologist Stephen Jay Gould points out that although life began on Earth nearly four billion years ago, multicellar life is only about 750 million years old, and intelligence (us) didn’t come onto the scene until a scant few million years ago.

  Considering that the Sun is about halfway through its stable life span of roughly 10 billion years, Gould writes, “If a meandering process consumed half of all the available time to build such an adaptation (intelligence) even once, then mentality at the human level certainly doesn’t seem to rank among the ’sure bets,’ or even mild probabilities, of history.”

  In other words, the existence of life does not automatically lead to the existence of intelligence. Intelligence is most likely a survival trait that has been adapted by only one genus (Homo) of all the countless life forms that have inhabited this planet Earth over the past three-plus billion years. The odds against it happening on another world are, frankly, astronomical.

  Where’s the Evidence?

  The modern search for extraterrestrial intelligence (SETI) began in 1959, when Drake arrived at the spanking-new National Radio Astronomy Observatory (NRAO) in Green Bank, West Virginia. A graduate of Cornell and Harvard, Drake had become intrigued with the possibilities of locating alien civilizations ever since he had been a student at Harvard and had detected a strong radio signal while observing the Pleiades star cluster. The signal turned out to be from a terrestrial source, but that sudden thrill of thinking that maybe, just maybe, he had found an extraterrestrial civilization was a turning point in Drake’s life.

  Few astronomers admitted even to thinking about alien intelligence in those “silent generation” days of the 1950s, but Drake was fortunate enough to hear a lecture by Otto Struve while he was at Cornell. Struve was an astronomer of impeccable international reputation, and the son of a world-famous astronomer, as well. Among his many interests in astronomy was the way that stars spin: Struve believed that slow-spinning stars must be accompanied by planetary systems that have absorbed the star’s angular momentum, as the planets of our solar system have absorbed the Sun’s angular momentum. At that time there was no clear evidence of planets orbiting other stars (that was not to come until 1995), but Struve maintained that stellar spin rates showed that other stars must have planets accompanying them. In those days, hardly any astronomers avowed an interest in whether other stars were accompanied by planets.

  Struve became the first head of NRAO, and Drake joined his staff in West Virginia. Somewhat hesitantly, Drake suggested using the new 26-meter radio telescope to search for possible alien signals. Struve enthusiastically agreed with Drake, but, because the search for alien life was still a touchy subject in academia, and carried a large “giggle factor” among the politicians who decided on NRAO’s funding, Drake’s search was started in secret, “piggybacked” on a legitimate study of the 21-centimeter radiation.

  Meanwhile, two highly-respected physicists from Cornell University, Giuseppe Cocconi and Philip Morrison, proposed using radio telescopes to search for intelligent signals from alien civilizations. Their landmark paper, “Searching for Interstellar Communications,” was published in the British journal Nature in September 1959. It ended with the words:

  The presence of interstellar signals is entirely consistent with all we now know, and if signals are present the means of detecting them is now at hand. Few will deny the profound importance, practical and philosophical, which the detection of interstellar communications would have. We therefore feel that a discriminating search for signals deserves a considerable effort. The probability of success is difficult to estimate, but if we never search the chance of success is zero.

  Drake calculated that his equipment could detect radio signals similar to those being broadcast around Earth out to a distance of little more than 10 light years. He did not expect to find alien messages deliberately beamed toward us; he was hoping to detect the background chatter of a global civilization’s radio and television broadcasts. He picked the two nearest solar-type stars to study: Epsilon Eridani and Tau Ceti, 10.7 and 11.3 light years distant, respectively. He dubbed his “bootlegged” program Ozma, after the queen of L. Frank Baum’s fictional land of Oz, which, in Drake’s words, is “a place very far away, difficult to reach, and populated by exotic beings.”

  The very first day (radio telescopes can operate in daylight) their first look at Epsilon Eridani produced a sharp signal that electrified Drake and his colleagues. But it turned out to be a false alarm: something nearby put out an electrical pulse that the radio telescope picked up. The search was not going to be that easy. Far from it.

  Over the next four decades, more than a dozen radio searches probed the stars with ever-more-sophisticated equipment. NASA became involved, and turned the world’s largest radio telescope, at Arecibo, Puerto Rico, and the Jet Propulsion Laboratory’s Deep Space Network array of radio dishes at Goldstone, California, to the search for intellige
nce.

  Aside from one “Wow!” signal that was picked up by an array at Ohio State University in 1977 - a strong radio pulse that was never repeated and therefore could not be identified - no sign of intelligent communications has been found. There was a brief flurry of intense excitement in 1967, though, when very precise pulsed signals were detected by Jocelyn Bell and Antony Hewish in Britain, but despite a few weeks of wondering whether they had discovered “little green men,” the astronomers found that they had stumbled onto a new type of stellar object, the pulsars.

  SETI became an international affair, with the Russians devoting considerable effort to the search. Thinking about the difficulty of finding an individual star that might be broadcasting messages, Carl Sagan suggested that radio telescopes be turned to some of the nearby galaxies, such as M31, the great spiral in Andromeda, some two million light years distant. His reasoning was that by aiming at a whole galaxy, a single telescope could “see” hundreds of billions of stars. If there were any highly advanced civilizations among that host deliberately beaming out powerful messages, their signals might span the immense distance between us.

  By 1974 Drake was a professor of astronomy at Cornell. Together with Sagan, who by then headed Cornell’s Laboratory for Planetary Studies, he used the Arecibo telescope to beam a simple message at the globular star cluster M13, which contains more than 100,000 stars. British astronomer and Nobel laureate Sir Martin Ryle strongly objected, arguing that no signals should be sent out because they could show possibly hostile and dangerous aliens where we are. Sagan, who grew up reading science fiction, pointed out that since M13 is 25,000 light years away, even if there are evil aliens intent on conquest, they could not possibly trouble us for at least 50,000 years.