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Lonely Planets

Page 29

by David Grinspoon


  how we tweak our climate models. Remember, early on, the Sun was

  significantly dimmer than it is now, and this makes the problem harder

  to solve. We’re working on it, but we haven’t yet found a way to melt

  Mars. Maybe we’re missing something. The other nagging problem is

  that we can’t find the carbonate rocks that should be common on the

  planet everywhere if it once enjoyed a watery climate.

  Even given these puzzling discrepancies with the wet-Mars theory, it

  seems nearly inescapable that Mars had liquid water flowing in the

  *A cautionary aside: In the early nineties Magellan found many riverlike features on Venus. Since conditions on Venus are far too hot for liquid water, this possibility was never seriously considered, so we’ve dreamed up exotic liquids, such as carbon-rich lavas, that might flow under Venusian conditions as easily as water does here. No one anticipated the existence of such strange materials before the observations required that we think them up.

  Venus and Mars

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  past. But running water today? In some of the coldest, most shadowed

  places? It seems wrong.

  Several clever theories have been proposed to explain how the gullies

  could form without violating the laws of chemistry and physics. For

  instance, maybe the runny stuff is actually liquid CO2. If you pressurize

  CO2 to many times the surface pressure on Mars, it condenses into a

  liquid. Liquid CO2 might exist in pressurized underground channels,

  sometimes breaking out and spraying onto the surface, causing loose

  material to run downhill and forming the gullies. Or maybe an under-

  ground heat source is pumping water around, or maybe the water is in

  some exotic mix with frozen carbon dioxide, giving it the right fluid

  properties.

  Now that the cat has been let out of the bag and the president has

  gone back to bed, we are all free to gleefully theorize about these

  recent-looking flow features on Mars. Fresh surface water, if con-

  firmed, would mean that, by the currently accepted rules, Mars should

  have life. It makes Mars, not Europa, Jupiter’s watery moon, the most

  accessible place to test our “water = life” paradigm. It also emboldens

  those who urge manned—I’m sorry, “peopled”—missions to Mars in

  the near term, since an accessible water supply would make it that

  much easier for us to live off the land.*

  S A M E A S T H E O L D M A R S ?

  There is a cyclical quality to our ideas about Mars. Like pilgrims seek-

  ing tears on a stone Virgin, we are ready to announce, at the least

  provocation, that we see water running there still. For over a hundred

  years now, the watery channels of Mars have reappeared in different

  forms. So, when MGS scientist Ken Edgett excitedly exclaimed at the

  press conference, “This is not your mother’s Mars!” I thought, “No,

  but it might be my grandmother’s.”

  I am not convinced that the gullies are evidence for surface water on

  Mars today, but they’ve sure shown us that things are happening there

  that we don’t understand. Mars, viewed with unprecedented detail in

  the MGS camera, has once again showed us new sides of its personality.

  *One of Asimov’s best SF stories, “The Martian Way,” involves the struggles of Martian colonists to achieve water independence from imperialist Earth. They achieve this in the end by mining water from the rings of Saturn.

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  L o n e l y P l a n e t s

  While the hints of current water flow remain provocative and puzzling,

  less controversial are numerous features providing the best evidence yet

  that flowing water really did affect much of the surface in the distant

  past. Numerous old impact craters and other topographic depressions

  contain subtle deposits that look like dried-up lakes. Perhaps most

  striking is the wide occurrence of terrain made of layered, sedimentary

  rocks. With the improved clarity of the MGS cameras, the layered

  structures that have been there all along jump out at us.

  These deposits look familiar to terrestrial geologists, and for that

  matter to any terrestrials who have visited the Grand Canyon or any

  number of places where the layered structure of sedimentary rock dom-

  inates the landscape. Such thick tableaux of layered rocks have been

  laid down over extended periods of geological time, usually by liquid

  Image unavailable for

  electronic edition

  Venus and Mars

  189

  water. Though some have proposed that on Mars these layers could

  have been built up out of wind-borne sediments, they look exactly like

  sedimentary rocks on Earth that we know were laid down beneath

  shallow seas of water. More recently still, the Mars Odyssey spacecraft, which arrived at Mars in October 2001, has revealed vast fields of permafrost, frozen water mixed with dirt, in large areas surrounding both

  poles. The Red Planet may once have been blue.

  But was it ever green?

  Jonathan Eberhart, the superb writer who covered planetary explo-

  ration for Science News and was a fixture at our conferences for years

  until he retired in the early nineties, was also known to many as an excel-

  lent singer/songwriter. We had fun rocking out together at some planetary

  meetings in the eighties: Jonathan sang and played piano, I played guitar,

  planetary geologist Dave Pieri played bass, and Kelly Beatty, the editor of

  Sky and Telescope, played drums. It was the ultimate geek jam, a regular planetary Nerdstock. Jonathan’s song “Lament for a Red Planet” is an

  ode to all the lost visions of a vibrant, comfortable, and living Mars from

  the past of science and science fiction. I first heard him sing it in the press-

  room at the Jet Propulsion Laboratory the week of the Viking 2 landing

  on Mars. In a deep, sea-shanty voice, he sang:

  Ten thousand times a hundred thousand dusty years ago,

  Where now extends the Plain of Gold did once my river flow;

  It stroked the stones and spoke in tongues and splashed against

  my face,

  Till ages rolled, the sun shone cold on this unholy place.

  Your ochered cliffs and rusted sands stand regal and serene,

  But oh my wan and wasted world, I miss your blues and greens.*

  When it comes to life on Mars, we’ve got a feeling we can’t hide. Our

  intuition that Mars holds life is strong, recurrent, and seemingly imper-

  vious to data. Every time we learn a new way that Mars is deadly, it

  represents only a temporary setback for this stubborn belief, until we

  can invent new ways that Mars might, after all, live on. This pattern

  suggests that our persistent belief fulfills needs that go beyond scientific

  evidence. Decade after decade, both before and during the space age,

  *Jonathan’s album Life’s Trolley Ride, which has this song, is available from Folkways Records. Sadly, Jonathan passed away in 2003.

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  our science has been swayed by this hope. The more we learn, the more

  likely that we won’t get fooled again, but if we ever do discover life on

  Mars, one of the lessons might be that we should trust our intuition

  about these things. The picture of Mars that is emerging from our latest

  missions of exploration is oddly re
miniscent of Percival Lowell’s dying,

  dried-out world. Gone are the canal builders, but visions of rebel bacte-

  ria colonies holding out in some underground cave will be much harder

  for our science to rout out. The deeper we probe, the deeper they seem

  to retreat into the bowels of the planet.

  As my planetologist friend (and former office mate at NASA/Ames)

  Kevin Zahnle, a keen observer of the scientific condition, wrote in 2001

  in Nature, “The most interesting information remains right at the limit

  of resolution. . . . Always life on Mars seems just beyond the fields that

  we know.”

  Growing Up with Europa

  12

  All these worlds are yours—except Europa.

  Attempt no landings there.

  Image unavailable for

  —ARTHUR C. CLARKE’S 2010: Odyssey Two

  electronic edition

  Image unavailable for

  Lime and limpid green the sound

  electronic edition

  resounds the icy waters underground.©

  —SYD BARRETT,

  Astronomy Domine

  T H E T R I A L S O F G A L I L E O

  So far our search for alien life isn’t going too well. Although we cannot

  count Venus or Mars out yet, neither looks as promising—at least for

  our kind of life—as many believed when we began exploring. But from

  this we do not conclude that the universe is lifeless.

  We’re not capable of reaching such a conclusion—logically or emo-

  tionally. In this sense, aliens are like gods. No scientific result would

  convince us that alien life does not exist. Yet, the opposite—proof posi-

  tive of life on another planet—would be accepted by everyone except

  those yahoos who think the lunar landing was faked.* The hopes and

  faith we place in our dreams of alien life are not in any danger of being

  dashed by science. At worst, they will be displaced at the pace of our

  exploration. At best, they will be confirmed in a dramatic discovery of

  something unmistakably alive.

  *If you are one of those yahoos, I apologize for my insensitivity.

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  Our reluctant letting go of warm oceans on Venus and Mars simply

  forced us to broaden our definitions of habitability. We widened our

  search, traveling ten times farther afield to other worlds, which seem,

  on the surface, even more exotic.

  Just the idea that there are other worlds has been a difficult and

  painful concept to get into our little carbon-based skulls. Galileo was

  the first to actually find any new worlds, and look what happened to

  him. Recently our search for life has taken us back to the site of that

  first decisive Copernican battle: Jupiter’s Galilean moons.

  We know them as the four lovers of Jupiter: Io, Europa, Ganymede,

  and Callisto.* It only took us four hundred years to progress from dis-

  covery to exploration. Now, we’ve launched ships to cross wider seas

  and explore Galileo’s new worlds. Out there we’ve found unforeseen

  wonders that feed our hopes for a new revolution of Copernican pro-

  portions. Could we possibly find confirmation, among the moons of

  Jupiter, of our suspicion that we are not alone in the universe?

  Our first good look came in 1979 when the two Voyager spacecraft

  whipped through the Jupiter system, frantically snapping pictures as

  they sped by. It all happened fast; each Voyager, with no way of slowing

  down, spent just two days in the vicinity of Jupiter and its moons

  before being gravitationally flung back out into the void toward a ren-

  dezvous with Saturn.

  In the summer of 1979 I was a space-freak college freshman with a

  way-cool summer job: assistant to the Voyager Imaging Team at the Jet

  Propulsion Laboratory (JPL) in Pasadena during the Voyager 2 Jupiter

  encounters. When I wasn’t running off to Grateful Dead shows, I was

  closeted in a big, air-conditioned cubical building with the men and

  women who had planned and built these early ships of deep space,

  delighting in every new picture as the expanding, approaching dots

  became worlds. It was then that Galileo’s four strange moons first took

  on their distinct personalities: the manic volcanic face of Io; the dark

  lines winding like turnpikes across Europa’s bright, icy landscapes; the

  densely grooved terrain of Ganymede; and the ancient, icy, cratered

  surface of Callisto.

  I will never forget the heart-stopping moment when the first close-up

  pictures of Europa arrived on Earth. On the morning of July 9, we—the

  imaging team and assorted students, assistants, and hangers-on—were

  *Jupiter is bisexual. There is a lot of him to love.

  Growing Up with Europa

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  stuffed into a small, dimly lit room, staring up at a dark screen in com-

  munal, nervous anticipation. It was as if we were all riding along on the

  spaceship and gathered together to stare out of a porthole near the

  bow, awaiting our first glimpse of an unknown shore. A film crew from

  Cosmos was crammed in there as well, adding to the suspenseful air.*

  As the face of Europa began to appear on the screen, slowly, in thin,

  vertical strips, gasps of disbelief erupted from this crowd of generally

  reserved scientists. Never before and never since has our knowledge of

  another world taken such a great leap in a few brief revelatory

  moments.

  Our theories predicted an ancient, dead, cratered landscape on the

  small ice-planet. Instead, we saw a smooth, bright surface crisscrossed

  by strange dark lanes. The immediate impression was of a fresh, active

  world. At first nobody spoke. The appearance of Europa was so truly

  unexpected that no one, in a room full of verbose rocket scientists,

  could offer anything intelligent. The first to speak was Carl Sagan:

  “Percival Lowell was right!” he exclaimed. “Only, the canals are on

  Europa!”

  While they’re not canals, those enigmatic markings might be signs

  pointing to life. This took a while to sink in. The Voyagers’ trajectories

  were not optimized for Europa viewing. Each ship had a date with

  Saturn that dictated its hurried path through the environs of Jupiter.†

  On a flyby you only get one chance, so coverage of Europa was spotty

  and incomplete. We saw only half the planet in photos taken from

  thousands of miles away, leaving us with only imagination and theories

  to fill in what we could not glimpse.

  We had to wait nearly two decades to get back to Jupiter. During that

  time I finished college, moved out West, toured with a reggae band, cut

  off my Afro, and became a comparative planetologist funded by NASA.

  In 1989, the year I got my Ph.D., a spacecraft bearing Galileo’s name

  was launched toward the moons that he had first seen on a cold

  January night in 1610.

  Even before its launch, Galileo was a hard-luck spacecraft. Always at

  the edge of disaster, it has at times seemed jinxed. The spacecraft has

  *I actually appear briefly here in the television show: I’m the skinny geek sporting an improbably huge Afro, wide-eyed in the back of the room.

  † Voyager 1’s path through the system four mont
hs earlier had not permitted any close-up pictures of Europa.

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  L o n e l y P l a n e t s

  followed a tortuous path and faced trials that rival those of the man for

  whom it’s named. Budget-cutters in Congress threatened repeatedly to

  cancel the mission. Protesters tried to derail the launch over concerns

  about the fifty pounds of plutonium that it carried for power at Jupiter.

  In December 1986, the Challenger blew up, killing seven brave explor-

  ers and shutting down the space shuttle program for three years.

  Galileo had been slated for the very next launch.

  The irrepressible craft finally made it off the ground in October

  1989. Upon reaching deep space, its twelve-foot-diameter main

  antenna, folded tight for launch, was supposed to spread open like a

  metallic beach parasol. But when the moment came, it just sat there,

  stuck stubbornly in the folded position. Ground controllers tried to jar

  it loose by running its motor in various stop-and-start sequences. They

  tried spinning the spacecraft in hopes that it would fling itself free.

  Months went by, and increasingly desperate efforts failed to open the

  umbrella, which we needed to establish a communications link between

  Jupiter and Earth. Gradually the reality set in that it would not open.

  The main antenna, vital portal for all the riches expected at Jupiter,

  remained in a crumpled-up, completely useless configuration for the

  entire mission. Imagine the frustration. We had the most sophisticated

  spacecraft ever built finally sailing toward Jupiter, able to photograph

  the mysterious moons in unprecedented detail, but we had no way to

  send the pictures homeward.

  Houston, we had a problem.

  NASA engineers marshaled all of their legendary, save-the-day inge-

  nuity and found solutions. A puny “low-gain” antenna, not designed

  for this kind of work, was pressed into service—a little like finding that

  your new high-speed modem is dead and being forced to settle for two

  tin cans and a piece of string. The expected rushing stream of data was

  reduced to a feeble drip. The mission never fully recovered from the

  main-antenna failure, but clever work-arounds, combined with

  Galileo’s stubborn longevity, allowed us to get 10 percent of the origi-

  nally planned pictures of Jupiter and its moons.

  After suffering enough technical glitches to give the most even-

 

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