Gliese 581g awaits

If you've been staying at all awake, you sense the excitement. Astronomers have announced the discovery of a new planet, one that may be capable of supporting life as we know it. Actually, it isn't the planet that's just been discovered: it's the relatively benign conditions on that planet, based on data from observatories in Chile and Hawaii.

The planet -- known, somewhat unimaginatively, as Gliese 581g because it's a planet in orbit about the red giant star Gliese 581 -- is 20 light years from earth. As cosmic distances go, this is remarkably close. Even so, it would take a photon of light 40 years to make a round trip. With present technology, it would take you and your descendents considerably longer. If you did have a rocket ship that was cool enough to reach relativistic speeds, you might not age all that much while gone, but you would find that a frighteningly long period of time had elapsed here on Earth once you returned. You know about relativistic effects, right? Don't blame me; I'm just the messenger. Blame Einstein.

Our sun will someday be a red giant, just like Gliese 581. It will become much cooler (hence the change in color, like watching bright yellow embers in a campfire cool down to a dull red), and its perimeter will expand out to the present orbit of Mars. (Even though engulfed by a mere red giant, there will be plenty hot times here on Earth.) It's a sad fate for a star, kind of like watching a young athlete slow down and bloat up as he ages. So Gliese 581 has seen better years, as stars go, but he still has the pleasure of having reached the perfect condition to support his child, Gliese 581g.

Anyone living on Gliese 581g will experience a fast year. The planet zooms around its sun in only 37 days, less than one-third of Mercury's very short orbital period. And like Mercury, Gliese 581g's revolution on its axis is coordinated with its orbit, so that it keeps the same side always facing the sun. The average temperature for the whole planet is about the same as that of Antarctica, but with one side much too hot and the other much too cold. There would be a zone between the two in constant twilight, however, where the temperature would be "just right" -- temperate enough to permit water to exist in liquid form, a necessary pre-condition for development of life.

Moreover, the mass of the planet -- about three or four times that of Earth's -- would be sufficient at the temperatures predicted to hold a terrestial-like atmosphere.

One of the astronomers announcing the discovery said that the chances of life in some form existing on the planet were "almost 100 percent."

He's talking about bacteria or lichen, but you know how these things go. One day it's protozoa, and the next day, you've got fish crawling out of the sea on tiny feet. Before you know it -- ZOWIE!! -- you've got dinosaurs roaming about.

The idea of life existing a not-impossibly-distant 20 light years away reminds me of an old Ray Bradbury story I read as a kid, one of the short stories that comprise The Martian Chronicles. In "Mars is Heaven," an expedition to Mars is greeted by a bucolic farming community scene right out of the American Midwest. Furthermore, each of the crew members discovers deceased relatives living on Mars, living in houses and farms identical to those they recall from childhood. The crew appears to have discovered heaven. And they like it a lot.

Until one night, one of the crew members -- after a warm and convivial evening reliving old times around the dinner table with his wonderful relatives -- realizes some odd discrepancies. As he lies in bed, he begins to suspect that Martian aliens are using telepathic powers to make themselves and their environment resemble people and places that they find in the crew members' memories. He tries to sneak back to the rocket ship in the middle of the night, hoping to radio a warning back to Earth, but runs into one of his "relatives" as he tries to leave the "farmhouse."

The Martian reads his mind, of course, and knows that the jig is up. Before the Earthling's eyes, he changes into his true, Martian form. Not a pleasant sight, at least by Earthly beauty standards. It all ends quite unpleasantly for the crew, and the members of Earth's Expedition to Mars disappear from history. As mysteriously as did the Roanoke colonists in Virginia, I suppose.

Anyway, that's what can happen when one civilization finally meets up with another. Ask the Aztecs and the Incas all about it, if you're not convinced by Ray Bradbury.

Life on other planets? Be careful what you wish for.