NASA: Mars’ Surface Had Pool of Water

PASADENA, Calif. – Mars once had a briny pool of standing water on its surface that could have supported life in the now-frozen planet’s distant past, NASA scientists said Tuesday.

Scientists announced earlier this month that the Opportunity rover found evidence of water long ago on Mars, but it was unclear whether the water was underground or on the surface. The new findings suggest there was a pool of saltwater at least two inches deep.

A rocky outcropping examined by the rover had ripple patterns and concentrations of salt – considered telltale signs that the rock formed in standing water.

The findings add to the growing body of evidence that the Red Planet was once was a warmer and wetter place that may have been conducive to life.

“We think Opportunity is now parked on what was once the shoreline of a salty sea on Mars,” said Cornell University astronomer Steve Squyres, the mission’s main scientist.

Although Squyres referred to the water as a sea, scientists said it was not clear how big the body of water might have been or whether it was a permanent fixture. Instead, the site could have been a desert basin or salt flat that periodically flooded with water.

The evidence also does not indicate when water covered the broad and flat region where Opportunity landed, called Meridiani Planum, or for how long. Nor does it indicate if any organisms actually lived on Mars.

If life did flourish at the site when it was awash in water, the type of rock found there could contain evidence of biological material, Squyres said.

The findings were to be presented Tuesday at a televised news conference at the headquarters of the National Aeronautics and Space Administration in Washington.

NASA has tentative plans to send a robotic mission to Mars in 2013 that would collect samples of rock and soil and return them to Earth for more detailed analysis.

“This result gives us impetus to expand our ambitious program of exploring Mars to learn whether microbes have ever lived there and, ultimately, whether we can,” said Ed Weiler, NASA’s associate administrator for space science.

NASA intends to send one or more unmanned missions to Mars every 26 months. President Bush recently proposed a crewed mission to visit the planet but did not set a timeline for such an undertaking, which probably remains decades away.

For decades, spacecraft in orbit around Mars have shown evidence that large amounts of liquid water once flowed across the surface, carving vast and sinuous networks of channels. The new results provide the first definitive evidence from rocks examined on the surface of Mars that liquid water once pooled on the surface.

Opportunity carried out detailed analyses of the finely layered rocks in an outcrop at its landing site, snapping 152 microscopic images of one feature alone.

The repeated, close-up looks revealed that the sediments that bonded together to form the rocks were shaped into ripples by water that stood at least two inches deep, said mission science team member John Grotzinger of the Massachusetts Institute of Technology. The water flowed over the site at an estimated four to 20 inches per second, Grotzinger said.

The analyses also bolstered previously disclosed evidence that suggested the rocks contained a salt called bromine, which would have precipitated out of the water as it evaporated.

Today, Mars is largely dry and cold. It contains trace amounts of water vapor in its atmosphere and large caps of frozen water at its poles. Spacecraft also have detected significant amounts of ice mixed in the martian soil at high latitudes.

NASA’s Jet Propulsion Laboratory launched Opportunity and its twin, Spirit, on a $820 million mission to probe Mars for evidence of water in its past.

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On the Net: http://marsrovers.jpl.nasa.gov/home/index.html