Mars Water Evidence Excites NASA

Kenneth Edgett, a scientist at Malin Space Science Systems in San Diego, Calif., gestures during a news conference at NASA Headquarters in Washington, Wednesday, Dec. 6, 2006 to discuss the possibility that liquid water flowed on the surface of Mars as recently as several years ago, raising the possibility that the Red Planet could harbor an environment favorable to life. (AP Photo/Caleb Jones) (Caleb Jones - AP)

Scientists said five to 10 pools of water rushed down the craters in each case. In both craters, scientists found bright, light-colored deposits several hundred yards long in gullies that weren't present in the original photos. They concluded that the deposits _ possibly mud, salt or frost _ were left there when water recently cascaded through.

Edgett said a combination of factors, including the shape and color of the deposits, led the team to believe it was recent water action and not dust that slipped down the slope. He said dust would leave dark deposits.

Water cannot remain a liquid on Mars for long because of subzero surface temperatures and low atmospheric pressure that would turn water into ice or gas. But scientists theorize that liquid water is being shot up to the surface from an underground source, like geysers.

Mars formed more than 4.5 billion years ago and scientists generally believe it went through an early wet and warm era that ended after 1.5 billion to 2.5 billion years, leaving the planet extremely dry and cold.

"We're now realizing Mars is more active than we previously thought and that the mid-latitude section seems to be where all the action is," said Arizona State University scientist Phil Christensen, who was not part of the current research.

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On the Net:

NASA: http://www.nasa.gov

Malin Space Science Systems: http://www.msss.com