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NASA Images Suggest Water Still Flows in Brief Spurts on Mars

NASA
2006-12-07 10:24 4517

WASHINGTON, Dec. 6 /Xinhua-PRNewswire/ -- NASA photographs have revealed

bright new deposits seen in two gullies on Mars that suggest water carried

sediment through them sometime during the past seven years.

(Photo:http://www.prnasia.com/sa/200612071022.gif )

"These observations give the strongest evidence to date that water

still flows occasionally on the surface of Mars," said Michael Meyer, lead

scientist for NASA's Mars Exploration Program, Washington.

Liquid water, as opposed to the water ice and water vapor known to

exist at Mars, is considered necessary for life. The new findings heighten

intrigue about the potential for microbial life on Mars. The Mars Orbiter

Camera on NASA's Mars Global Surveyor provided the new evidence of the

deposits in images taken in 2004 and 2005.

"The shapes of these deposits are what you would expect to see if the

material were carried by flowing water," said Michael Malin of Malin Space

Science Systems, San Diego. "They have finger-like branches at the downhill

end and easily diverted around small obstacles." Malin is principal

investigator for the camera and lead author of a report about the findings

published in the journal Science.

The atmosphere of Mars is so thin and the temperature so cold that

liquid water cannot persist at the surface. It would rapidly evaporate or

freeze. Researchers propose that water could remain liquid long enough,

after breaking out from an underground source, to carry debris downslope

before totally freezing. The two fresh deposits are each several hundred

meters or yards long.

The light tone of the deposits could be from surface frost continuously

replenished by ice within the body of the deposit. Another possibility is a

salty crust, which would be a sign of water's effects in concentrating the

salts. If the deposits had resulted from dry dust slipping down the slope,

they would likely be dark, based on the dark tones of dust freshly

disturbed by rover tracks, dust devils and fresh craters on Mars.

Mars Global Surveyor has discovered tens of thousands of gullies on

slopes inside craters and other depressions on Mars. Most gullies are at

latitudes of 30 degrees or higher. Malin and his team first reported the

discovery of the gullies in 2000. To look for changes that might indicate

present-day flow of water, his camera team repeatedly imaged hundreds of

the sites. One pair of images showed a gully that appeared after mid-2002.

That site was on a sand dune, and the gully-cutting process was interpreted

as a dry flow of sand.

Today's announcement is the first to reveal newly deposited material

apparently carried by fluids after earlier imaging of the same gullies. The

two sites are inside craters in the Terra Sirenum and the Centauri Montes

regions of southern Mars.

"These fresh deposits suggest that at some places and times on

present-day Mars, liquid water is emerging from beneath the ground and

briefly flowing down the slopes. This possibility raises questions about

how the water would stay melted below ground, how widespread it might be,

and whether there's a below-ground wet habitat conducive to life. Future

missions may provide the answers," said Malin.

Besides looking for changes in gullies, the orbiter's camera team

assessed the rate at which new impact craters appear. The camera

photographed approximately 98 percent of Mars in 1999 and approximately 30

percent of the planet was photographed again in 2006. The newer images show

20 fresh impact craters, ranging in diameter from 7 feet (2 meters) to 486

feet (148 meters) that were not present approximately seven years earlier.

These results have important implications for determining the ages of

features on the surface of Mars. These results also approximately match

predictions and imply that Martian terrain with few craters is truly young.

Mars Global Surveyor began orbiting Mars in 1997. The spacecraft is

responsible for many important discoveries. NASA has not heard from the

spacecraft since early November. Attempts to contact it continue. Its

unprecedented longevity has allowed monitoring Mars for over several years

past its projected lifetime.

NASA's Jet Propulsion Laboratory, Pasadena, manages the Mars Global

Surveyor mission for the NASA Science Mission Directorate, Washington. For

more information about NASA and agency programs, visit:

http://www.nasa.gov

Source: NASA
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