Life or Death?

Gleaming low in the western sky for almost two hours after sunset is the planet Venus. Often called the sister of the Earth, Venus is perpetually hidden in clouds. Those clouds were once thought to be mostly water vapor, and it was believed that Venus was a watery world, teeming with life.

That was a dream, shattered by the discovery that these clouds were carbon dioxide, trapping the heat of the Sun, turning the surface of Venus into an inferno. With a surface temperature of over nine hundred degrees, nothing remotely like us could live there. The problem? No oceans.

From the molten interior of all planets, a mixture of carbon dioxide and water vapor constantly belches forth. (This is what fills the clouds coming from a volcano.) On the Earth, this water vapor condensed into the oceans, enabling the carbon dioxide to dissolve. But on Venus, closer to the Sun, it was too hot for this water vapor to condense. The carbon dioxide remained in the atmosphere, causing a runaway greenhouse effect. The Sunšs heat was trapped, and the temperature soared.

We turn the other way. Rising in the east at about 8:00, brighter than any star, is the red planet Mars. Space probes have definitely established the presence of water on Mars. First, there were only signs that water existed billions of years ago, when Mars was still young. But the latest probes report that that precious liquid still exists on Mars. Could some simple form of life have begun and evolved on Mars?

Of course, the answer lies in the world of science fiction, not science fact. But this much is clear. It is water that makes the difference between life and death.

That's why workers at NASA were so excited by the pictures sent back by the spaceship Galileo, -- pictures of Europa, a moon of Jupiter, that seem to show signs of oceans there.

Maybe, just maybe, we aren't alone, and our neighbors are right next door.

(10/07/05)