Mars was once swept by a "horizon to horizon" flood at least 100,000 times faster and more intense than the spring 1997 deluge in Grand Forks, N.D., scientists with the Mars Pathfinder mission said Monday.

The exact height and force of the flood remain unknown. It may have been hundreds of yards deep, said Michael Malin, a scientist speaking at a press conference Monday at Jet Propulsion Laboratory in Pasadena.

"Clearly this was a catastrophic flood with enormous volumes of water," Pathfinder scientist Matthew Golombek said at the press conference.

Scientists also reported what appeared to be a dried puddle left over from the deluge.


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They discovered the puddle by analyzing photos from Pathfinder - which landed Friday - and its rover vehicle, Sojourner, which spent much of Monday photographing and examining rocks.

Monday's press conference marks the first time scientists have reported what amounts to smoking-gun evidence of ancient water on Mars.

For the scientists, who are still recovering from the near-perfection of the probe's landing, the rush of scientific discoveries is emotionally overwhelming.

"The question I've been asking (myself) is: "When am I going to wake up?' " said James Bell of Cornell University, a scientist working with the Pathfinder team.

"I feel we've won the World Series," said project scientist Brian Muirhead.

Atmosphere a key

Since the 1970s, NASA scientists have suspected that massive floods swept the surface of Mars hundreds of millions of years ago, based on their scrutiny of photos from satellites orbiting the planet. Those photos showed what appeared to be dried riverbeds and floodplains.

But Monday's press conference reported crucial new clues, including the dried puddle, that apparently clinched the case for water.

"This wondrous flood," said Golombek, "was almost certainly liquid water."

Previously, some experts had speculated that the so-called riverbeds and floodplains had been carved by glacial ice or other geologic forces.

The apparent confirmation that water once flowed on Mars immediately raises a tantalizing question: Could creatures have inhabited the water?

Some scientists suspect the puddle may be but one of many such ponds that endured long after most of Mars' water either evaporated into space or soaked into the interior of the planet. If so, then microbes or other creatures could have evolved within the ponds.

That question probably can't be answered until many more robotic probes travel to Mars, and perhaps not until humans explore the planet, perhaps sometime in the early 21st century.

A key question is: Was the flood a transient event that occurred at a time when Mars' atmosphere was still as thin as it is today - that is, less than a hundredth as dense as Earth's air? If so, then life may have had trouble forming in such thin air.

But if the Martian atmosphere was once denser and warmer than it is today - as many scientists believe - then life could have thrived beneath those Noahic waves.

Malin, who has studied the effects of devastating floods on the Earth, said the Martian flood might have been as cataclysmic as the one that had filled the Mediterranean - formerly a desert - in ancient times.

Series of clues

On Monday, scientists described findings that included:

*The puddle. Malin said it appears to be a dried patch of ground that might mark where salt, silicates (like sand) and clay-like materials precipitated from ancient water.

A key next step, Malin said, is to send the six-wheeled rover to examine the puddle. The rover carries a TV camera and a device, the alpha proton X-ray spectrometer, that can assess the chemical composition of rocks and soil.

Close-up analysis of the puddle "is high on the list of things to go look at," Malin said.

To which his colleague Golombek added, with a laugh, "We have too many things that are high on our list."

The puddle appears to have been cracked when the Pathfinder lander's air bags retracted. The probe landed Friday nestled inside a cluster of inflated air bags.

When the air bags were retracted, they scratched and deformed the ground around the lander, cracking the puddle and exposing subsurface rock previously obscured by wind-blown dust.

*The suspicious orientation of rocks around the Pathfinder. Malin noted that the rocks appeared to be pointed "20 degrees west of south," as if a flood had nudged them in that direction.

Some rocks were also bunched, as if banged together by a flood, Malin said.

He also said that by analyzing the distributions of rocks, specifically their distances apart, scientists hoped to estimate exactly how deep the water had been.

The larger rocks are on the order of 3 feet across, a size

"typical of the late stages of a flood," Malin said.

The scientists already have given some of these rocks friendly names, such as Barnacle Bill and Yogi.

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