[meteorite-list] NASA Images Suggest Water Still Flows in Brief Spurts on Mars

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Wed, 6 Dec 2006 10:48:40 -0800 (PST)
Message-ID: <200612061848.KAA28275_at_zagami.jpl.nasa.gov>

Dec. 6, 2006

Dwayne Brown/Erica Hupp
Headquarters, Washington
202-358-1726/1237

Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
818-354-6278

RELEASE: 06-362

NASA IMAGES SUGGEST WATER STILL FLOWS IN BRIEF SPURTS ON MARS

WASHINGTON - 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.

"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's Mars missions, visit:

http://www.nasa.gov/mars

-end-
Received on Wed 06 Dec 2006 01:48:40 PM PST