Life on Earth

(Richard Thompson)

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By Joel Achenbach
Sunday, November 12, 2006

Recently, the Mars rover "Opportunity" completed a long, slow journey across the surface of the planet and reached the rim of a crater. What it beheld was a stunning vista that looked like the American Southwest. Here were vertical cliffs, craggy rock faces, a violent and parched landscape, a very real place where you could imagine bounding around with a miner's pick and a hand lens.

These new views of Mars are an amazing technological feat, especially when paired with an image taken by an orbiter from above the same crater, showing the rover as a little dot on the rim. To use the scientific term: pretty neat.

Previous images of Mars from robotic landers and rovers had also been interesting, but you could make the case, at the risk of being called a cynic, that we were looking at a mighty drab landscape. There were rocks and . . . more rocks. There were boulders and there were pebbles. Scientists gave some rocks special names, as though they were pets. They made a fuss when one rock seemed to have, inscribed on its face, the letter B. (Had it had a B and then an O and another O, that would have been intriguing.)

Of course, if you look hard enough, you can see anything. A 1970s image from an orbiting spacecraft showed a structure that looked like a face. An elaborate mythology grew, incorporating tales of Martian cities, destructive wars, even colonization of Earth by the beings who built the Face. But in more recent images, the Face looks like a face only if you examine the image out of the corner of your eye while hanging upside down in a dark room after about nine beers. (And then, oddly, it looks exactly like Gertrude Stein.)

So now we have these new images to ponder, and invariably they will once again generate speculation about Martian life. Life beyond Earth is probably the biggest unknown in science, even bigger than why we can feel when someone is staring at us. The universe is so humongously big. Life seems to be made of ordinary stuff, such as hydrogen and nitrogen and carbon, among the most common elements in the cosmos. There has to be life out there. But how much? What's it like? Are there intelligent beings? (And could they possibly understand why the chicken-crossing-the-road joke is funny even though it's not actually, you know, funny?)

And yet we've found not a single alien life form. It's all astronomy and planetary geology out there, but, so far, no biology. The good news is that the people who study extra-terrestrial life, known as exobiologists or astrobiologists or bioastronomers or whatever else they think will keep their funding from being cut, have made great gains in understanding exotic life forms right here on Earth. Life, scientists have discovered, is ingenious, pernicious, rambunctious.

"Extremophiles" are organisms that thrive below ice sheets, in parched deserts, around hot vents at the bottom of the sea, or in boiling sulfuric springs. Every time scientists find more extremophiles on Earth, they announce that this could mean there's life on Mars. It's almost like a nervous reflex. Examination of the Martian surface by space probes indicates that water long ago flowed freely. A warmer, wetter Mars might well have had at least some microbial life, if not anything as ostentatious as a bunny rabbit. Mars is also considered by scientists to be an "Earthlike" planet, meaning it's a rocky world more conducive to life, and not a gas giant such as Jupiter or Saturn (note heroic restraint in not making Rush Limbaugh joke).

But let's go back to the new images from Opportunity. Keep looking. They're actually a bit haunting. Because, while desert-like, Mars doesn't really look like the American Southwest.

There is not even the faintest hint of anything alive. No cactus, no sidewinder, not even a little touch of slime. It's pure geology. It appears, at least on the surface, to be an utterly sterile world. It's a crime scene we're looking at. Call in the CSI unit.

Mars is a prime example of the aphorism that bad things happen to good planets. It suffered cascading failures. Its atmosphere was blasted away by meteor and comet impacts. It lacked the volcanic activity that could recycle carbon. Warm, wet Mars became cold, dry and, by all appearances, dead.

Obviously, it is asking too much to expect Opportunity to glimpse Road Runner speeding away from Wile E. Coyote. But as we admire these images of Mars, it's impossible not to appreciate the blue planet that we call home.

Read Joel Achenbach weekdays at washingtonpost.com/achenblog.


© 2006 The Washington Post Company

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