NASA scientists have found enough evidence on Mars to believe that the area around the Opportunity rover was once "drenched" with water.

"Opportunity has landed in an area of Mars where liquid water once drenched the surface," NASA associate administrator Ed Weilertold a news conference at Washington DC Tuesday. "Moreover, this area would have been good habitable environment."

Evidence of water is a critical factor in whether life may have arisen on Mars, and the availability of water may be important in any future manned exploration of the Red Planet.

The geologic signs of Martian water include Opportunity's discovery that its nearby outcrop was full of sulfate salt deposits arranged in layers, with spherical particles that can be formed by liquid water.

More convincing were closer observations with two instruments on the rover arm, the Moessbauer and alpha particle X-ray spectrometers, as well as the mast-mounted miniature thermal emission spectrometer. Those instruments found a pattern of salt deposition found in the slow evaporation of water.

What is still unanswered is how long the liquid water lasted and whether any remains today, scientists said.

(Xinhua News Agency March 3, 2004)