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Salt water found on Mars could have supported life ; NASA scientists say rocks were formed

Posted on: Wednesday, 24 March 2004, 06:00 CST

PASADENA -- Liquid water once pooled on the surface of Mars, forming an ebbing and flowing body of salt water that could have supported life in the now-frozen planet's distant past, NASA scientists said Tuesday, describing the finding as having profound implications for astrobiology.

National Aeronautics and Space Administration scientists announced earlier this month that the Opportunity rover found evidence that water once soaked the Mars rocks it has spent nearly two months analyzing at its landing site in a vast region called Meridiani Planum. Those initial results left it unclear whether it was ground water or surface water.

Now, new findings reveal those rocks likely formed at the bottom of a gently flowing body of salt water. The rocks contain both ripple patterns and concentrations of salt that scientists consider telltale signs that they formed in standing water.

"If we are correct in our interpretation this was a habitable environment," Cornell University astronomer Steve Squyres, the mission's main scientist, told a televised Washington, D.C., news conference. "These are the kinds of environments that are very suitable for life."

The environmental conditions required to allow a pool of water to persist on Mars confirm the planet once was a wetter and possibly warmer place. Such conditions would be conducive to life, scientists believe.

"If you have an interest in searching for fossils on Mars, this is the first place you'd want to go," said Ed Weiler, NASA's associate administrator for space science.

Weiler noted that a group of outside scientists was brought in to review the rover mission scientists' findings before they were announced.

"This is a profound discovery, it has profound implications for astrobiology," Weiler added.

The water body was shallow, forming a sea, desert basin or salt flat that periodically flooded with water to depths of just a few inches before evaporating.

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

If life did flourish at the site when it was awash in water, the type of rock now found at the site is very capable of preserving evidence of any biochemical or biological material that may have been in the water, he said.

Opportunity, however, does not carry instruments capable of revealing traces of microbial life.

The new findings give NASA impetus to expand its Mars exploration program to learn whether microbes ever lived there and, ultimately, whether people can, Weiler said. NASA intends to send one or more unmanned missions to Mars every 26 months.

In 2009, it plans to launch a rover to Mars capable of prospecting for life. A follow-on mission, slated for launch in 2013, would collect samples of rock and soil and return them to Earth for even more detailed analysis.

President Bush recently proposed a crewed mission to visit the planet but did not set a timeline for such an undertaking, which likely remains decades away.

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 2inches deep, said mission science team member John Grotzinger, of the Massachusetts Institute of Technology. It is estimated that the water flowed over the site at 1 mph, Grotzinger said.

Shallow shoreline or desert basin environments could have currents capable of producing the types of ripples found, he added.

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.

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

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 past water activity.

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