LIFE ON MARS?

In a revelation that could clinch the age-old mystery--"Is there life in outer space?"--NASA scientists have reported astonishing new evidence of liquid water on Mars. "The discovery has profound implications for the prospect of Martian life not only in the past but maybe even today," says Ed Weiler, NASA space science chief.

Close-up photos from orbiting Mars Global Surveyor clearly show gullies--trenches chiseled by water--that were probably formed by liquid water seeping right beneath the Martian surface, explains NASA researcher Michael Malin. (New Surveyor images reveal the smallest details ever captured on the Red Planet's surface--about the size of an SUV.) Some seepage could have taken place as recently as several days or as long as thousands of years ago--scientists don't know. But the findings are extraordinary, because until now scientists thought water on Mars could exist solely in frozen form below the soil, in polar icecaps, or as sparse clouds in the meager atmosphere.

Scientists have long speculated that Mars contained oceans billions of years ago. But almost all water vanished as the planet cooled and its atmosphere thinned. For decades researchers have debated where the water went. Now they think they know: "Some water seeped under ground, and maybe it's still there," Malin says.

But since atmospheric pressure at Mars' surface is 100 times less than at sea level on Earth, water would immediately boil and evaporate when exposed at the planet surface. So how can gullies form? A possible explanation: repeated outbursts of water and debris, like flash floods on Earth, carved the gullies. Now scientists will try to sleuth out concrete proof of both liquid water and life on Mars. After all, "we didn't find Martians in a hot tub," says Ed Weiler. Look again.