Roanoke Times
                 Copyright (c) 1995, Landmark Communications, Inc.

DATE: THURSDAY, March 31, 1994                   TAG: 9403300037
SECTION: EXTRA                    PAGE: 1   EDITION: METRO 
SOURCE: Joel Achenbach
DATELINE:                                 LENGTH: Medium

HERE'S THE TRUTH, CARBON-BASED CREATURE, ABOUT YOUR ORIGIN

A: As you know, "carbon-based" is the answer to the age-old question, "What kind of woman does Bob Packwood find attractive?"

The big hoo-haw about carbon is in honor of its utility in forming elaborate molecules. If you want to do something as grandiose as construct a living thing, you can't do it with a few dribs of hydrogen and a few drabs of helium. And carbon by itself - pure carbon, graphite, soot, whatever - isn't enough diverse molecules, and carbon's perfect for that job. Carbon has a gift for being the integral element within lots of cool molecules, including those vital amino acids.

We are, in a sense, water-based also. But water is operating on a grander scale than carbon. Water, as a unique solvent, is the medium in which all the other molecules form. Water's like the dance floor where these materials meet and shake their groove thang, as it were.

Now that we've got your rapt attention (chemistry: the subject readers crave!) let's tell you about how the Earth was once frozen. That's right, the Earth was once an ice ball. Actually, this is not a confirmed fact, but is a neat theory, emerging from a NASA-funded study of the origins of life. (NASA wants to know how likely it is that life exists out in space, so first we have to figure out why on earth it's on Earth.)

Here's the deal: It has long been assumed that life formed about 4 billion years ago in the ocean, the proverbial "primordial soup." But there have been some major kinks in that scenario. The sun was dimmer back then and only provided about 70 percent of the radiant energy that Earth receives from the sun today. The ocean easily could have been frozen under those conditions.

But scientists have had trouble stomaching the idea of a frozen ocean back then, because the icy surface would have reflected so much of the sun's energy back into space that the ocean would still be frozen even today. They did the calculations and concluded: Frozen then, frozen now. Hence, it couldn't have been frozen then. Instead, they theorized that there was a lot of carbon dioxide in the atmosphere, creating a "greenhouse effect" to keep the planet warm.

But - there's always another but - carbon dioxide is bad news for the chemistry of life. The planet's carbon gets locked into that CO2 molecule: It can't break free to form the more complex molecules needed for the development of living organisms.

So here's the new scenario, as described to us by Jeffrey Bada, a marine chemist at the University of California at San Diego: There wasn't a thick CO2 atmosphere. No greenhouse effect. Forget that nonsense! The ocean was frozen. But the ice was only about 300 meters thick. There was lots of liquid water underneath, molecularly enriched by volcanic activity. An early form of life (the RNA molecule) formed under that ice sheet.

Then why isn't the ocean still frozen? Because at some point an asteroid pummeled the Earth with such power that it melted all the ice. The Earth, basking under a hotter sun, snapped out of its ice funk. And the sunshine inspired those boring RNA molecules to start photosynthesizing and turn into something more interesting, like trilobites.

One implication of this theory is that if there's another planet with Earth-like conditions (lots of water, etc.) there still may not be any living organisms. "You may have to have some very carefully timed events," says Bada. Washington Post Writers Group