Lonely Planets

  within our own solar system.

  M A D S C I E N C E

  Say what you will about the seventies. Maybe you still think disco sucks,

  but at least we were setting sail for the planets on a regular basis. After

  the stunning successes of planetary probes launched between 1961 and

  1978, planetary exploration lost momentum in the eighties. The Soviets’

  winning streak at Venus continued into the early eighties, as they landed

  more cameras and sent balloon-borne instruments below the clouds, but

  no American planetary craft was launched toward any planet for an

  entire decade. This was due in part to the aftermath of Viking. Though

  the search for life on Mars was considered a long shot by most of the sci-

  entists involved, they had overhyped this angle to sell the mission to

  Congress and the public. As a result, the failure to find life was perceived

  as a failure of the mission, and that added to the difficulty in getting new

  missions funded.

  But there was a larger problem. Whether we like it or not (and many

  of us do not) Cold War competition gave planetary exploration its first

  big push. Our fantastic voyages had largely been funded and supported

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  L o n e l y P l a n e t s

  as part of an elaborate form of saber rattling. The technology needed to

  launch a lunar or planetary probe is not dissimilar to that needed to

  deliver an ICBM. What better way to inspire missile envy than by nail-

  ing another planet? Our science had been enabled by the desire of gov-

  ernments locked in the MAD embrace of the Cold War to show off

  their destructive potential. By the late 1970s these demonstrations had

  served their purpose, and Apollo was only a memory. The governments

  that had supported our science to back up their threats were losing

  interest.

  The most dangerous competition on this planet provided the impetus

  for our first liberating leaps beyond it. That these initial interplanetary

  voyages were financed and driven, financially and technically, by a

  potentially suicidal contest carries with it all of the moral contradic-

  tions of modern science.

  Yet, our first pictures of Earth from space fostered a powerful new

  sense of the unity and rare beauty of our planet. Then the uniqueness of

  Earth was brought home to us with our first photos of the other plan-

  ets. It is almost impossible not to have a global perspective while doing

  planetary science. Even during the height of the Cold War, Russian and

  American planetary scientists cooperated on their exploration plans

  and shared data across the geopolitical fault lines. It doesn’t make sense

  for one planet to have two isolated space programs.

  Along with the planetary perspective comes a realization that many

  of our problems and opportunities are global. The Earth has many

  lands but only one atmosphere, and we are all in it together. Shifts in

  global consciousness must be impossible to perceive accurately while

  they are in progress, but it is not inconceivable that a new planetary

  identity, which might be decisive for long-term human survival, is

  slowly dawning (painfully slowly). Certainly, efforts to communicate

  with intelligent extraterrestrials do not make much sense unless they

  are made on behalf of all humans. Merely contemplating the possibility

  of finding other life makes obvious our deep identification with all

  Earth’s inhabitants.

  It’s ironic that the technology that enables you to beat gravity and see

  your planet whole can also threaten global self-destruction. One won-

  ders if elements of this same drama might not be playing out elsewhere

  in the galaxy. If we are going to anthropocentrically worry about others

  on distant planets hastening their own demise with newfound techno-

  The Planets at Last

  61

  toys, we might also hope that the leap into space will have a similar lib-

  erating and unifying effect on their alien souls.

  W O R L D S B E Y O N D

  Anyway, after a decade-long malaise, having kicked the monkey of

  Cold War aggression off our backs, we’ve now demonstrated that, hot

  or cold, we don’t need war to explore. Planetary exploration was resur-

  rected in the 1990s. In 1989, Magellan and Galileo were both launched toward Venus, where Magellan went into orbit and started its radar

  mapping. Galileo made a close flyby, getting a gravitational kick from

  Venus for its long journey out toward Jupiter.

  The heartbreaking loss of Mars Observer, launched in 1992 (it went

  silent as it reached Mars in August 1993, probably due to a fuel-tank

  explosion), was an inauspicious start to a new series of Mars missions.

  But then, on July 4, 1997, Mars Pathfinder, swathed in air bags, made

  its daring bouncedown to land safely in an ancient flood zone.

  Pathfinder delivered the cute Sojourner rover, which was a scientific and public relations success, as it crawled around in the red dirt, snapping photos and sniffing rocks, showing the world that we were back.

  This triumph was followed by Mars Global Surveyor (MGS), which

  began its orbital mapping in 1998. With the MGS cameras we can see

  surface details a couple of meters across,* and its laser altimeter has

  provided us with fantastically detailed global topo maps that reveal the

  possible sites of ancient Martian oceans.

  In October 2001, Mars Odyssey, a new orbiter, reached the Red

  Planet and detected vast fields of water ice mixed into the upper few

  feet of rock and soil surrounding the polar caps. New infrared images

  from orbit have revealed a complex layered structure in some areas,

  suggesting new complexities to the planet’s past geologic history that

  have not yet been puzzled out. The search for signs of life-supporting

  environments, in the past or even present, is once again the primary

  goal of our entire revamped Mars exploration program.

  In 1997, Cassini, a sophisticated, schoolbus-size spacecraft, departed

  for Saturn. Cassini began orbiting the ringed planet in July 2004 and

  in January 2005 will drop off the Huygens probe at Saturn’s moon

  *As opposed to about a kilometer with Mariner 9 and fifty meters with Viking.

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  L o n e l y P l a n e t s

  Titan. Titan is of special interest for possible extraterrestrial life. Voyager

  revealed abundant signs of interesting organic chemistry beneath Titan’s

  thick, hazy, nitrogen-rich atmosphere. Studying this environment may

  help us understand the origin of life on Earth or, just possibly, reveal a new

  kind of cold-loving biology. Launches planned in the next few years

  include several new Mars missions, new Mercury and Venus orbiters, the

  first flyby of Pluto, and several new missions to study asteroids and

  comets.

  The real planets provided a rude awakening from our dreams of

  Earth-like neighbors, but we’re now learning to love them as they truly

  are. Just the fact that the planets were where we thought they’d be and

  our traveling machines actually reached them and worked has got to be

  the most solid confirmation of the scientific and technological revolu-

  tions of the past four centuries.* The r
esurrection of planetary explo-

  ration, in the decade after the Cold War ended, shows that human

  curiosity and wonder can occasionally transcend the deadly conflicts

  that have so often fueled our greatest bursts of innovation.

  But what about worlds beyond our Sun and planets? Ever since

  Bruno and Fontenelle, most thinkers have concluded that our universe

  contains copious extrasolar planets. Throughout huge transformations

  in knowledge and worldview, scientists have consistently believed,

  without any direct evidence, that the Sun’s family of planets is not

  unique among the overwhelming profusion of stars filling the night sky.

  But people believe all kinds of things, and neither analogy nor consen-

  sus makes it so.

  In 1995 another cherished belief crossed the threshold from reason-

  able conjecture to observed fact: we started to find actual planets

  beyond the solar system. The first definitive detection of an extrasolar

  planet was made around a star called 51 Peg. After the first detection,

  planet hunters stalked their quarry with renewed vigor. Before you

  knew it, distant planets were popping up all over the place. As of this

  writing, in the eight years since the first detection, more than one hun-

  dred extrasolar planets have been found.† This is truly something

  new—a definitive, affirmative answer to an ancient question.

  *Stuff that in your socially constructed pipe and smoke it!

  †Such is the pace of current discovery that whatever number of planets I plugged in here in the final edit of galley proofs will be wonderfully obsolete by publication date.

  The Planets at Last

  63

  Though in some ways the twentieth century saw the end of our astro-

  nomical innocence, the recent confirmation that our galaxy is rich in

  planets has granted us a reprieve. Cosmology and extragalactic astron-

  omy have banished us to the periphery of the universe, and spacecraft

  exploration has replaced naive fantasy with cruel fact for the nearby

  planets of our own system. But these brand-new worlds provide an

  enlarged landscape for our speculative dreams. Like the planets of our

  own solar system after the Copernican revolution and before planetary

  exploration, we know these worlds are there, but we know little about

  them. We can let our imaginations run wild.

  A S T R O B I O L O G Y : N E W H Y P E A N D N E W H O P E

  We tend to think of extraterrestrial life as a modernistic or futuristic

  idea that rests on the findings of twentieth-century science and may

  find verification in twenty-first-century discoveries. We think of it as

  something for which humanity has had to be slowly prepared, while

  gradually getting used to the disorienting and humbling knowledge that

  we are very small and may not be so special in the universe.

  Yet, as I’ve described, it is an old idea. Our seventeenth- and

  eighteenth-century scientific heroes, the people we name spacecraft

  after today, were almost all confirmed believers in a fertile, densely

  inhabited universe. They based this belief on empirical observations of

  other planets combined with metaphysical extrapolations. Today, our

  rationale for believing in life beyond the Earth still involves a mix of

  observation and extrapolation by analogy and plenitude. What is dif-

  ferent now is the data. We’ve pretty much ruled out life on the Moon.

  At one point we had ruled out life on Mars, though it has recently—at

  least temporarily—been ruled back in. The boundary between that

  which we can directly observe and that which we must deduce has

  receded. But we still have to take that leap beyond the top rung of the

  ladder of the known to reach for our conclusions.

  Belief in aliens, among scholars at least, actually suffered some of its

  lowest moments during the twentieth century. The search for extra-

  terrestrial life was a semi-taboo subject among scientists. The public never

  lost interest, but for decades professional astronomers risked disapproval

  or career repercussions if they pursued the question as a major research

  topic. Twentieth-century biologists mostly ignored the question.

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  L o n e l y P l a n e t s

  Then in the late 1990s the field was revitalized, enjoying newfound

  respect and funding. It even got a new name: what had previously been

  referred to as exobiology, bioastronomy, cosmobiology, xenobiology,

  or exobotany was now rechristened astrobiology. NASA administrator

  Dan Goldin declared that the alien quest should now be the corner-

  stone of our approach for studying the entire physical universe. A

  NASA Astrobiology Institute was founded in Silicon Valley, and the

  money began flowing. Researchers in diverse fields are suddenly discov-

  ering that it pays to consider yourself an astrobiologist.

  Why the official change of heart? Several recent discoveries have

  rekindled hope for a living universe. In August 1996, a year after the

  first extrasolar planet was discovered, President Clinton made a star-

  tling announcement. American scientists had found fossils in an ancient

  meteorite from Mars.* Even though many scientists soon challenged

  this interpretation of the microscopic, wormlike structures, it got us all

  thinking “Why not?” Worldwide front-page headlines gave the field a

  boost that lasted long after serious doubts were raised about the biolog-

  ical origins of the possible Martian microfossils.

  That same year Galileo entered Jupiter orbit and returned sharp pic-

  tures of Europa, providing new circumstantial evidence for a possible

  life-giving underground ocean. Around the same time several new kinds

  of bizarre life-forms were discovered on Earth, living under conditions

  previously thought to be deadly. Our conceptual limits on life’s domain

  widened. This harmonic convergence of discoveries was seized upon by

  advisers and officials at NASA, who were also discovering that casting

  our space research in terms of the search for cosmic company could

  supply a much needed PR lift.

  Thus was born the “astrobiology revolution,” which I will discuss in

  more detail in the next section of this book.

  A C R O S S T H E G R E A T D I V I D E

  Dreams of alien life will not die. Almost as if we need to believe that we

  are not alone in the universe, or even somehow know we are not alone,

  this idea is resurrected in every era in new forms reflecting the attitudes

  and convictions of the day. Today, beliefs about extraterrestrials are

  polarized in a way that mirrors our culture’s divergent attitudes about

  *Shades of the panspermia of Kelvin and Arrhenius.

  The Planets at Last

  65

  science. We scientists view the question as part of our turf, as the proper

  subject of astrobiology. In recent decades, however, another train of

  belief has been gathering steam on a parallel track. Although science

  has been on a roll of confidence and power since the Enlightenment,

  antiscientific voices are increasingly audible on the cultural airwaves.

  Creationism, faith healing, astrology, postmodern relativism, and New

  Age spirituality are among those
beliefs that mainstream science regards

  as dangerous superstitions threatening the rational basis of our society.

  Many adherents of these beliefs view science as equally dangerous,

  threatening our very survival with an amoral, materialistic, antispiritual

  attitude and an out-of-control pursuit of new technology. Nowhere is

  the gulf between expert scientific opinion and popular folk beliefs

  greater than on the subject of aliens.

  Millions of rational adults currently believe that UFOs are alien

  spaceships that have come to Earth and occasionally abducted people,

  perhaps to study us, perhaps to help us out. Astrobiologists and SETI

  scientists are quick to dismiss such opinions, even while adhering to

  their own strong faith in our ability to establish radio contact with like-

  minded aliens. On both sides of this divide, many people nourish the

  fantasy that advanced extraterrestrials with superior wisdom will lead

  us beyond the threat of high-tech self-destruction to a safe and won-

  drous future.

  Ironically, widespread belief in UFO aliens may be partly responsible

  for the strong public support enjoyed by NASA’s astrobiology program.

  Certainly our regular stream of “Life on Mars” headlines has lent com-

  fort to the UFO believers. People think there’s life out there, and they

  want us to find it. Although the science/antiscience divide is wide, both

  sides believe in aliens. Perhaps, deep down, our reasons for believing

  are not so different.

  P A R T I I

  Science

  The Greatest Story

  5 Ever Told

  I believe a leaf of grass is no less than the journey-

  work of the stars.

  Image unavailable for

  —WALT WHITMAN, Song of Myself

  electronic edition

  To punish me for my contempt for

  Image unavailable for

  authority, fate made me an authority myself.

  electronic edition

  —ALBERT EINSTEIN

  May you build a ladder to the stars. May you climb

  on every rung.

  Image unavailable for

  —BOB DYLAN, “FOREVER YOUNG”

  electronic edition

  N E E D T O K N O W

  To assess our universe’s potential to create other life and intelligence,

  we need a framework for understanding our own arrival on Earth.

  What is this place and how did we get here? We need to know, so we