The finding appears to be the best evidence to date that conditions which could have supported life once existed on the now-frozen planet.

JPL announced three weeks ago that the six-wheeled rover -- which landed in a shallow crater on Mars' Meridiani Planum on Jan.24 -- had found evidence that water once "drenched" the area.

At that time, scientists presented evidence "that the rocks at Meridiani Planum had once had water seep slowly through them," said Steve Squyres of Cornell University, principal investigator for the Mars Exploration Rover project.

"What's happened since then is we have found what I believe to be strong evidence that the rocks themselves are sediments that were laid down in liquid water," Squyres said. "It's a fundamental distinction -- like the difference between the water you can draw from a well and water you can swim in."

Squyres said the evidence indicates that Opportunity "is now parked on what was once the shoreline of a salty sea on Mars."

NASA's Ed Weiler, associate administrator for space science, described the finding as a "profound discovery" that has profound implications for astro-biology.

The aim of the 820-million-dollar mission -- which also involves a twin rover named "Spirit" -- was to determine if there ever were life-supporting conditions -- such as abundant water -- on the planet.

Scientists say that so far, neither Opportunity, nor its twin six-wheeled rover, Spirit, have found direct signs of living organisms on Mars.

(Xinhua News Agency March 23, 2004)