NASA said Friday that the Spirit rover has found more evidence that water once existed on the Mars, three days following the announcement that its twin, Opportunity, sits in a region which was soaked by water in the distant past.

The findings came from aggressive study of a rock nicknamed "Humphrey" which Spirit came across en route from its landing site to a big crater named "Bonneville," Ray Arvidson, deputy lead scientist at NASA's Jet Propulsion Laboratory in Pasadena, told reporters.

The rover used its rock abrasion tool to drill a 0.85-inch-deep hole into the rock and examined its interior with instruments to determine its mineral composition.

Scientists working with Spirit deduced that water formed small holes and left mineral deposits in the rock.

"If we found this rock on Earth we would say this is a volcanic rock that has had a little bit of fluid move through it either when it formed or shortly thereafter," Arvidson said.

"The best bet is that water was in the magma. I don't think it was a groundwater percolation but water that came up with the magma," he added.

The amount of water at Spirit's site in Gusev Crater would have been much less than what is indicated at Opportunity's site in Meridiani Planum, according to Arvidson.

NASA scientists are now unable to determine when the water may have been present but the evidence suggests it was during the formation of the planet long ago.

Earlier this month, Spirit's twin Opportunity excited NASA scientists by discovering that the region where it was working was once drenched by water.

However, no evidence of life has been found on the Red Planet's barren surface, but scientists said it once was habitable.

Spirit's next task is to finish a 360-degree panorama of high-definition photos at a hollow dubbed Middle Ground, then to drive 82 feet northeast toward Bonneville Crater.

(Xinhua News Agency March 6, 2004)