Speculation was rife on Monday that space scientists were on the verge of announcing they had discovered evidence that Mars was once a wet and warm planet, possibly capable of sustaining microscopic life forms.

Officials with the National Aeronautics and Space Administration announced that Mars scientists from the Jet Propulsion Laboratory in Pasadena, California, were flying to Washington for a "significant" announcement, but shied away from saying what it would be.

"I can't confirm what they are going to say ... just that it's a significant ... finding," by the rover Opportunity, JPL spokesman Guy Webster said.

But in recent days, scientists have openly spoken of their excitement over finding coarse gray hematite at the Opportunity site, and predicted it would lead to an understanding of how the bedrock the rover is studying was formed and whether water was involved.

The scientists and engineers working with Opportunity and its twin, Spirit, have held all their briefings in Pasadena since the robotic geologists landed on Mars in January.

But major developments in NASA programs "are typically announced out of (Washington) headquarters," Webster said.

Scheduled to attend the Tuesday briefing were lead rover scientist Steve Squyres, geologist John Grotzinger, chief space exploration scientist Benton Clark, project scientist Joy Crisp, and Jim Garvin, NASA's lead scientist for Mars and the Moon.

Opportunity landed on Jan. 24 in a small crater on the vast flat Meridiani Planum near the planet's equator. It has spent most of its 36 martian days, or sols, studying finely layered bedrock in the crater's wall.

Scientists have been puzzling over whether the layers were formed by wind, volcanic lava flows or water, and if spherical "blueberries" discovered in the rocks were water-related.

In a briefing last week, the Opportunity team said data gathered by the rover's spectrometers and microscopic imager in a flat area of bedrock nicknamed Charlie Flats suggested the presence of gray hematite, which on Earth can form in oxygenated water.

Opportunity's spectrometers also have detected a large deposit of hematite in the surrounding plains.

The science team had planned to compare the spectral signatures of the martian rocks with Earth samples to confirm that the composition was the same.

Evidence of rocks or soil that formed in water would help validate scientists' theories that for the first half of its 4.6 billion-year existence, Mars had plentiful surface water -- even rain and snow -- and possibly, life.

Opportunity and Spirit, now in sol 57 on the other side of the planet, were designed to search for signs of water for at least 90 days, or as long as their solar-powered batteries last.

(China Daily March 2, 2004)