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NASA says a shallow sea once lapped Martian shores

By Charles Piller
Los Angeles

March 25, 2004

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Mars rover Opportunity sits on an ancient seashore. PICTURE: REUTERS
Photo: Reuters

Portions of the Martian surface were once covered with a salty sea, NASA scientists said on Tuesday, announcing a discovery that transforms the image of the now frigid and desolate planet.

Evidence of the body of water, possibly covering hundreds or thousands of square kilometres, was found near the landing site of the Opportunity rover on a plain called Meridiani Planum, near the Martian equator. The rover has been exploring the planet since January 24.

NASA associate administrator for space science Ed Weiler said: "This dramatic confirmation of standing water in Mars history builds on a progression of discoveries about that most Earth-like of alien planets."

NASA scientists announced earlier this month that they had determined that water had once existed on Mars, possibly during the early history of the planet 3 to 4 billion years ago. But they did not know if the water once percolated in underground reservoirs or actually flowed on the surface in lakes, rivers or seas.

They have now determined that the rocks at Meridiani Planum were formed in a standing body of water, long since evaporated from the desiccated landscape of towering canyons and rock-strewn craters.

Although the water may have been quite shallow, it was more likely it was deep enough to swim in and perhaps very deep.

The finding is the strongest evidence yet that Mars once had a habitable environment.

Mission geologist Matt Golombek said that the standing water meant that portions of the Martian environment were once much warmer than today's frozen desert.

The planet's atmosphere is likely to have been much denser because without an atmosphere, the water would have evaporated rapidly, he said.

NASA gathered the new data about two weeks ago, then had it reviewed by outside experts, all of whom concurred with the agency's conclusions.

"I was astonished to see structures like we see on Earth," said Dave Rubin, a geologist with the US Geological Survey and one of the independent reviewers.

He compared the terrain to the salt-encrusted Qaidam Basin in Central China. Other scientists said it resembled Death Valley, which was once full of water.

Scientists do not yet know the extent of the Martian sea but believe it could have been substantial, possibly covering the entire plain. They also are uncertain if other bodies of water existed on the planet. But Mr Golombek said that it is likely that flowing water existed elsewhere since the odds against Opportunity landing at the only sea on Mars were astronomical.

Scientists say the prospect of vast seas or oceans on Mars increased the possibility of determining if life once existed on the planet.

- Los Angeles Times



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