Lonely Planets

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Lonely Planets Page 21

by David Grinspoon


  believe any of these egotistical fantasies, but the reflexive reaction

  against these views can be as illogical as the narrow thinking that

  prompted them.

  Sure, humans have historically overemphasized our role in things and

  foolishly imagined that we were “conquering nature” and running the

  world, where at best we’ve been temporarily mucking it up. Sure, we

  need the microbes more than they need us. If they disappeared from the

  face of the Earth, we would perish. If we disappeared, most of them

  would not notice. But microbes, without us, are not capable of noticing

  anything. Through us the microbes have found a mind, a voice. It is

  foolish to ignore that human evolution represents a new phase in the

  life of Gaia,* a phase with enormous potential and peril. It’s merely a

  matter of perspective whether you regard Earth as planet of the

  microbes or planet of the apes. Each brings essential qualities to our

  *The Gaia Hypothesis, a scientific portrait of a living Earth, has implications for life on other planets that will be discussed in chapter 17.

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  home world. I believe, as Teilhard argued, that mankind is not just

  another species, but an important evolutionary phenomenon—the pre-

  cursor of the psychozoic age.

  L O V E R S O F E X T R E M E S

  Now, having found mind and the beginnings of technological prowess,

  Earth’s biosphere is starting to take a look around, exploring the neigh-

  bor planets for the first time, and searching for life in the bright and

  dark corners of the solar system. Much of this search takes the form of

  self-examination, seeing the home world with new eyes.

  I’ve been describing the history of life as a series of leaps to greater

  complexity and organization culminating, at least so far, in the psy-

  chozoic age. While all this has been going on, over the 4-billion-year

  life of Earth’s biosphere, other evolutionary dramas have been playing

  out. Life has expanded on its bag of chemical tricks to facilitate sur-

  vival in a bewildering array of environments.

  In recent years, we’ve discovered life in the strangest of places: in

  unlikely corners of our planet where no one had thought to search

  because they seemed so obviously uninhabitable. We’ve found bacteria

  thriving in acid so strong that it would dissolve your skin instantly, and

  creatures soaking contentedly in superheated thermal springs above

  two hundred degrees. Some of these hyperthermophiles, or extreme-

  heat-loving organisms, require temperatures above the normal boiling

  point of water to survive. At the opposite extreme are those that sur-

  vive in intense cold. In frigid arctic tundras that appear lifeless, we’ve

  found colonies of bacteria hiding out inside frozen rocks. We’ve even

  found organisms that can survive after being frozen for weeks in liquid

  nitrogen!

  The green plant Welwitschia mirabilis can survive for thousands of

  years in places with only one centimeter of rainfall per year. The Dead

  Sea, it turns out, is alive with salt-loving bacteria and algae. In 1997,

  Japanese scientists discovered a species of marine worm living in an

  ocean trench twenty-one thousand feet beneath the sea at a crushing

  pressure 650 times that of sea level. Bacteria have survived for 3 million

  years in Siberian permafrost at fifteen degrees below zero with no sun-

  light, air, or food. They don’t do very much down there but survive

  simply by waiting, for eons if necessary, until the ground thaws and

  they can resume living at a healthier clip.

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  L o n e l y P l a n e t s

  Large, diverse communities of previously unknown organisms crowd

  the hot, nutrient-rich waters surrounding “black smokers,” volcanic

  vents on the bottom of the sea. The denizens of these recently discov-

  ered ecosystems include sulfur-eating shrimp and giant tube worms up

  to ten feet long. As weird and unearthly as these deep-ocean communi-

  ties seem to us, many scientists are starting to think that our most dis-

  tant ancestors came from just such a place.

  There are even bacteria living a mile underground and eating nothing

  but basaltic rock and water.* In fact, it now seems possible that most

  life on our planet is in the “deep Earth biosphere,” a realm extending

  miles underground whose existence we never before suspected. This

  would be the biological equivalent of “dark matter” in that the major-

  ity of life even on our own planet could as yet be unknown to us. We’ve

  been sharing a planet with these unlikely creatures for billions of years,

  but who knew?

  Our own planet is crawling with “aliens.” We continue to find

  extremophiles (lovers of extremes) that break our conceptual barriers

  of life’s range in temperature, pH, diet, and pressure. They show us that

  life is even more robust, adaptable, and resourceful than we imagined,

  and this encourages us to think that it will find ways to persist in

  diverse and extreme environments on other planets.

  In fact, life may not even need a planet. When the Apollo 12 astro-

  nauts retrieved pieces of the old Surveyor 3 spacecraft, which had been

  sitting idle in a lunar crater fully exposed to the harsh radiation and

  vacuum of space, investigators back on Earth were shocked to find

  viable Streptococcus bacteria that had survived a three-year stay on the Moon. Who is to say that living creatures cannot survive longer spells

  in outer space?

  This possibility was amplified by another recent discovery: bacteria

  such as Deinococcus radiodurans that live happily inside nuclear reac-

  tors, flawlessly reassembling their damaged genomes from hundreds of

  fragments, despite radiation doses a thousand times stronger than those

  that would kill a human. Suddenly, the merciless radiation of space

  seems less of a barrier to survival than it once did. Scientists have also

  revived bacterial spores that had been encased in amber for at least 25

  *Fontenelle anticipated this in the seventeenth century when he wrote about “innumerable small worms, living in imperceptible gaps and feeding themselves by gnawing on the substance of the stone.”

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  million years. Such findings have revived talk, or at least whispers, of

  “panspermia,” the idea that Earth life may not have originated on

  Earth.

  P A N S P E R M I A R E C O N S I D E R E D

  Though Earth’s creatures live in a hugely diverse range of environments

  and power ourselves with an impressive variety of chemical energy

  sources, we all use the same basic chemical operating system. There is

  no “think different.” It’s a complete monopoly.* What is the meaning

  of this?

  A remarkable aspect of Earth’s story is that the planet became inhab-

  ited as soon as it was habitable. Once the sterilizing impacts died down, Earth sprang to life—in less than a couple hundred million years, and

  maybe much faster. Then, a short while after life on Earth started, it

  had already constructed the fantastically intricate, interlaced chemical

  engines of DNA replication, protein transcription,
and a great many

  more standardized cycles and systems that would seem so elegantly

  conceived if only they seemed conceived. Life did not take billions of

  years of evolution to perfect these fine and fertile, far-flung factories.

  Not only the origin but most of the essential chemical evolution of life

  on Earth happened before you could say “evolutionary divergence.”

  Does this mean that, given half a chance, a biosphere with such

  refined chemical machinery is easy to make? A widely accepted inter-

  pretation is that on a planet like ours chemical evolution leads rapidly

  and inexorably to life. This inference is a mainstay of scientific belief in

  a universe with many inhabited worlds.

  Although it is not popular to do so, we could also look at this auspi-

  cious timing as supportive of the theory of panspermia, elaborated by

  Arrhenius in 1903—the idea that Earth life was seeded from elsewhere.

  If space contains spores wafting and waiting for watery worlds, life

  would be expected to spring up instantly as soon as it found a stable

  ocean. The strongest objection is that we cannot imagine spores that

  would survive the drift between star systems. This is a valid argument

  against panspermia, but not a damning one. Time and again, evolution

  has proven more clever than we are at solving survival puzzles. I won-

  der if we really don’t like the idea because it gives us the creeps.

  *Hey, could I be channeling Bill Gates?

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  L o n e l y P l a n e t s

  A far-out variant is “directed panspermia”—the idea that some crea-

  tures from elsewhere in the galaxy have played cosmic Johnny

  Appleseed, deliberately spreading life through the universe. That could

  explain the sudden appearance of chemically sophisticated life. Could

  the first living cells on Earth have been designed by a species with very

  advanced biotechnology?*

  If this strikes you as pure science fiction, consider the biotechnology

  progress (and I use the word loosely) of the last decade. Let’s assume

  for a second that we don’t soon commit high-tech suicide with the

  genetically modified tomato that ate Manhattan. Can you imagine the

  biotechnology and space technology we might possess in just one hun-

  dred years, in one thousand years? It doesn’t stretch the imagination

  much to think that we could soon be able to do some directed

  pansperming ourselves. So why does it seem like such a fantastic notion

  that someone else may have done so?

  We hate the idea of directed panspermia because it demotes us, like

  the Neoterics in “Microcosmic God,” to being the product of someone

  else’s ingenuity. It mocks our current biology and origin-of-life studies,

  to say nothing of our egos and established sense of place in the world.

  Our rational minds whir into action, finding logical objections to safe-

  guard us from the disturbing thought. How ironic if science should

  have slain all obvious creator gods only to find that some godlike aliens

  had created us in their image many billions of years ago.

  This model could actually meld the supposedly inimical theories of

  intelligent design creationism and Darwinian evolution. Life evolved

  elsewhere by natural selection to the point where it could develop

  advanced biotechnology. It then proceeded to spread intelligently

  designed seeds throughout the universe. These took root on Earth,

  where life evolved by natural selection to the point where it is now

  again starting to muck around with intelligent design of organisms.

  This is not a favored explanation, because scientists don’t like these

  kinds of explanations. Some people like them very much. But to us, it vio-

  lates Occam’s razor. It is logically almost the same as invoking a biblical

  miracle, only aliens, unlike gods, are scientifically acceptable creatures.

  A frequent objection to panspermia is that it does not solve the

  origin-of-life problem but simply pushes it out into space. Life still had

  *What if we find out that some multigalactical corporation owns the patent on DNA-protein biochemistry and they come back through our system demanding licensing fees?

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  to get started somewhere. Obviously, this is a lame argument against

  panspermia.

  A much less radical variant that’s come into vogue in the last few

  years is “impact panspermia” or “transpermia.” In the mid-1980s we

  realized that some of the meteorites in our collections are actually

  pieces blasted off of the planet Mars. There are several lines of evidence

  for this, but the clincher is that some of these rocks have bubbles of

  trapped air that exactly match the measured composition of the

  Martian atmosphere.

  Ever since we learned that rocks from Mars have landed on Earth,

  we’ve wondered whether life could stow away and ride between

  worlds. Were meteorites the bees that cross-pollinated the flowering

  planets, carrying the seeds of life across the vacuity of interplanetary

  space? Especially when the solar system was young and unruly, with a

  nonstop demolition derby of planetesimals constantly spraying the

  planets with each other’s shrapnel, any critters that could survive the

  launch and the journey would have had no problem hitching a ride to

  another world. So, we cannot regard the early environments of the

  planets as isolated systems, quarantined by space. Maybe, in their early

  days, the planets were all sneezing on one another, sharing germs, with

  meteorites as the vector. If any of them became infected with life, the

  others would quickly catch it, too. It is conceivable that our earliest

  ancestors lived on Venus or Mars and that we are all descendants of

  interplanetary immigrants—or should I say resident aliens?

  According to this picture, we started out as a multiplanet biosphere

  (a biopolysphere?). Gaia was born as planetary “Siamese triplets”

  joined by meteorites. Then, when the rates of interplanetary transfer

  declined, the three became isolated, and Earth was more or less on its

  own. I will discuss the fate of the other two orphaned biospheres in

  ensuing chapters. Transpermia would have slowed down before it effec-

  tively stopped. In an intermediate stage, perhaps long-lost Martian and

  Venusian microbial cousins occasionally arrived on the shores of Earth,

  after millions of years of isolation, stirring the genetic pot in interesting

  ways.

  Now, fueled by the discovery of possible fossils in one of our Mars

  rocks, we are experiencing a revival of the nineteenth-century idea that

  life might have arrived on Earth in falling meteorites. We are attacking

  the problem from several angles with twenty-first-century science.

  Could anything have survived the impact that launched these rocks into

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  L o n e l y P l a n e t s

  space? We test for that with impact simulations using high-speed guns.

  Could they have survived the journey through space and their fiery

  arrival on Earth? With sophisticated computer models of orbital

  dynamics, we follow the paths of impact shrapnel from Mars (and

  Earth and
Venus) to see how likely they are to reach another planet and

  how long the journey would take. Experiments in space and in terres-

  trial laboratories allow us to study the survival of organisms subjected

  to the hardships of space travel.

  Microbes are much tougher than the rest of us. The damn things are

  hard to kill. Thank Gaia they’re mostly on our side. They’ve survived

  experiments with intense radiation, heat, cold, vacuum, shock pres-

  sures, and that ear-crushing tape of bad rock music that the U.S.

  Marines used to flush out Manuel Noriega. So far no showstoppers

  have been found to affect the survival of microbes in space.

  Even given all of these intriguing alternative possibilities for life’s ori-

  gins, my instincts are in accord with the majority scientific opinion. I

  think that planets, Earth included, probably make their own life. Why?

  Because they can. The steps to life on Earth seem promising without

  any external help or prompting. As for the possibility that life here was

  deliberately seeded, all we can do is smile up at the stars, shrug, and

  keep looking for the missing links in our cosmic genealogy, keep

  searching heaven and earth for our roots.

  So What?

  9

  There is that within us which believes us worthy of

  the stars.

  Image unavailable for

  —SALMAN RUSHDIE, The Ground Beneath Her

  electronic edition

  Feet

  Image unavailable for

  Intelligent life understands the void must be filled.

  electronic edition

  —CONVERSATION BETWEEN TWO VENUSIANS

  I N The Quiet Invasion B Y S A R A H Z E T T E L

  B E T W E E N T H E L I N E S

  We could look at Earth life as a trivial by-product of the immense

  cycles of galactic ecology, something odd that happened on one small

  planet, in a random spiral of a largish but unremarkable galaxy. We are

  that, but we are something much more. Earlier, I described Earth’s bio-

  sphere as the Sun’s way of creating life. Well, our star is a product of

  the Milky Way galaxy, which coalesced from the cooling ashes of the

  big bang. If the universe is a self-tilling orchard slowly cultivating life

  and mind, then we, Earth’s awakening biosphere, are a bright flowering

  of the vine. We strongly suspect that there are others.

  It all really boils down to two questions:

 

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