Mars Once Had Shallow Sea of Saltwater, NASA Scientists Say

Mar. 24–WASHINGTON — A Mars rover has confirmed that a shallow sea of rippling saltwater once flowed slowly over at least one place on the surface of the red planet.

The historic discovery by the little robotic explorer Opportunity significantly increases the chances that life may have existed on another world besides Earth, NASA scientists said Tuesday.

“We think Opportunity is parked on what was once the shoreline of a salty sea on Mars,” said Steve Squyres, lead scientist for the rover project.

“This was a habitable environment,” he declared

The latest evidence was found in a rock outcrop, nicknamed “Last Chance,” on the rim of a small crater where Opportunity landed two months ago. The rock was composed of irregular, tilted layers of sandy sediments, called “cross-beds,” which are formed only by ripples in moving water.

“These are sedimentary structures just like we see on Earth along a beach or creek,” said Dave Rubin, an independent expert at the U.S. Geological Survey in Santa Cruz, Calif., who was asked to review the NASA scientists’ findings.

John Grotzinger, a member of the rover team from the Massachusetts Institute of Technology in Cambridge, Mass., said the Martian sea must have been at least two inches deep, possibly much deeper, and flowed at the rate of about one mile per hour.

Just three weeks ago, rover scientists announced that Opportunity had found evidence that a rock called El Capitan had once been soaked with water. At that time, however, they could not tell whether the water had been sitting on the surface of the planet for some time, or was merely moisture percolating through underground rocks and soil.

“It’s the difference between water in a well and water you can swim in,” said Squyres, a planetary scientist from Cornell University in Ithaca, N.Y.

The new evidence settles that question, but still does not show how deep or wide the sea was, how long it lasted, and whether such bodies of water existed elsewhere on Mars. The scientists hope Opportunity, its twin, Spirit, which is working on the other side of the planet, and future Mars missions will provide some answers.

Opportunity is already moving to a larger, deeper crater, named Endurance, where the team hopes to get a look at 10 or more layers of ancient sediments, instead of just the one it has examined so far.

“It will be like looking into Grand Canyon,” said Squyres. “We’ll be able to see much further back in time.”

The scientists acknowledged that the presence of a sea does not prove that life ever arose on Mars. But they pointed out that sedimentary rocks can contain traces of past biological activity.

“These rocks are good at preserving evidence of microbial life,” Squyres said.

NASA will launch a Mars Science Lander in 2009 that will carry more advanced instruments able to detect fossil microbes. Because of the success of the rovers, the future lander will probably return to the same region, an Oklahoma-sized plain known as Meridiani Planum.

‘If you’re interested in searching for fossils on Mars, this is first place you’d want to try,” said Ed Weiler, NASA’s associate administrator for science.

The rover scientists were rapturous over their findings. “The stuff of dreams,” exulted James Garvin, lead scientist for NASA’s proposed missions to the moon and Mars.

“The results go beyond our wildest expectations,” said Weiler.

Asked when the question whether life ever existed on Mars, Weiler predicted: “We’re going to know the answer in this century.”

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(c) 2004, Knight Ridder. Distributed by Knight Ridder/Tribune Business News.