Mars once had sea of water, declares NASA

The Mars rover Opportunity has discovered that potentially life-sustaining waters once soaked the surface of Mars, providing an answer to one of the most provocative questions of modern planetary science. At a news conference on Tuesday in Washington, NASA scientists said that an analysis of rock samples showed that salt-laden sediments were shaped by percolating or flowing water — and may even have been formed by a great Martian sea.

‘‘Opportunity has landed on an area of Mars where liquid water once drenched the surface,’’ said Ed Weiler, NASA’s associate administrator of space science. He called the findings ‘‘a giant leap’’ toward determining whether life may have existed on Mars during a warmer and wetter time in the now frigid planet’s past.

Steve Squyres, a Cornell University geologist and chief scientist for the mission, said one of the key pieces of evidence was the discovery of dense deposits of sulphates — similar to Epsom salts — in an outcropping of bedrock near its landing site. Scientists used a grinding tool to look beneath the surface of the rock to be sure the salty deposits were more than a shallow crust. Then they used an instrument called the alpha particle X-ray spectrometer that shoots radioactive particles to determine their mass and composition.

The rocks were ‘‘full of sulfate salts,’’ up to 40 pc of the mass of the rocks, said Squyres — ‘‘a telltale sign, we believe, of water.’’ —(LAT-WP)