[meteorite-list] Liquid Water Found Flowing On Mars? Not Yet

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Sun, 2 Mar 2008 23:20:53 -0800 (PST)
Message-ID: <200803030720.XAA18457_at_zagami.jpl.nasa.gov>

LIQUID WATER FOUND FLOWING ON MARS? NOT YET
-- (sent by Mari N. Jensen, The University of Arizona, 520-626-9635,
mnjensen at email.arizona.edu)

-- Friday, February 29, 2008
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Editors and Reporters Note: Images available from the researchers
Researcher contact information is at the end of this release
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Liquid water has not been found on the Martian surface within the last
decade after all, according to new research.

The finding casts doubt on the 2006 report that the bright spots in some
Martian gullies indicate that liquid water flowed down those gullies
sometime since 1999.

"It rules out pure liquid water," said lead author Jon D. Pelletier of The
University of Arizona in Tucson.

Pelletier and his colleagues used topographic data derived from images of
Mars from the High Resolution Imaging Science Experiment (HiRISE) camera on
NASA's Mars Reconnaissance Orbiter. Since 2006, HiRISE has been providing
the most detailed images of Mars ever taken from orbit.

The researchers applied the basic physics of how fluid flows under Martian
conditions to determine how a flow of pure liquid water would look on the
HiRISE images versus how an avalanche of dry granular debris such as sand
and gravel would look.

"The dry granular case was the winner," said Pelletier, a UA associate
professor of geosciences. "I was surprised. I started off thinking we were
going to prove it's liquid water."

Finding liquid water on the surface of Mars would indicate the best places
to look for current life on Mars, said co-author Alfred S. McEwen, a UA
professor of planetary sciences.

"What we'd hoped to do was rule out the dry flow model -- but that didn't
happen," said McEwen, the HiRISE principal investigator and director of UA's
Planetary Image Research Laboratory.

An avalanche of dry debris is a much better match for their calculations and
also what their computer model predicts, said Pelletier and McEwen.

Pelletier said, "Right now the balance of evidence suggests that the dry
granular case is the most probable."

They added that their research does not rule out the possibility that the
images show flows of very thick mud containing about 50 percent to 60
percent sediment. Such mud would have a consistency similar to molasses or
hot lava. From orbit, the resulting deposit would look similar to that from
a dry avalanche.

The team's research article, "Recent bright gully deposits on Mars: wet or
dry flow?" is being published in the March issue of Geology. Pelletier and
McEwen's co-authors are Kelly J. Kolb, a UA doctoral candidate, and Randy L.
Kirk of the U.S. Geological Survey in Flagstaff, Arizona.

NASA funded the research.

In December 2006, Michael Malin and his colleagues published an article in
the journal Science suggesting the bright streaks that formed in two Martian
gullies since 1999 "suggest that liquid water flowed on the surface of Mars
during the past decade."

Malin's team used images taken by the Mars Global Surveyor Mars Orbital
Camera (MOC) of gullies that had formed before 1999. Repeat images taken of
the gullies in 2006 showed bright streaks that had not been there in the
earlier images.

Subsequently, Pelletier and McEwen were at a scientific meeting and began
chatting about the astonishing new finding. They discussed how the much more
detailed images from HiRISE might be used to flesh out the Malin team's
findings.

Pelletier had experience in using the stereoscopic computer-generated
topographic maps known as digital elevation models (DEMs) to figure out how
particular landscape features form.

DEMs are made using images of the landscape taken from two different angles.
The Mars Reconnaissance Orbiter spacecraft is designed to regularly point at
targets, enabling high-resolution stereo images, McEwen said.

Kirk made a DEM of the crater in the Centauri Montes region where the Malin
team found a new bright streak in a gully.

Once the DEM was constructed, Pelletier used the topographic information
along with a commercially available numerical computer model to predict how
deposits in that particular gully would appear if left by a pure water flood
versus how the deposits would appear if left by a dry avalanche.

The model also predicted specific conditions needed to create each type of
debris flow.

"This is the first time that anyone has applied numerical computer models to
the bright deposits in gullies on Mars or to DEMs produced from HiRISE
images," Pelletier said.

When he compared the actual conditions of the bright deposit and its HiRISE
image to the predictions made by the model, the dry avalanche model was a
better fit.

"The dry granular case is both simpler and more closely matches the
observations," Pelletier said.

"It's just a test," he said. It's either more like A or more like B. We were
surprised that it was more like B."

Pelletier said these new findings indicate, "There are other ways of getting
deposits that look just like this one that do not require water."

One of the team's next steps is using HiRISE images to examine similar
bright deposits on less-steep slopes to sort out what processes might have
formed those deposits.

---------------
Researcher contact information:
Jon Pelletier, 520-626-2126
jdpellet at email.arizona.edu

Alfred McEwen, 520-621-4573
mcewen at lpl.Arizona.edu

Related Web pages:
Jon Pelletier
http://geomorphology.geo.arizona.edu

Alfred McEwen
http://www.lpl.arizona.edu/resources/faculty/faculty.php?nom=McEwen

HiRISE
http://hirise.lpl.arizona.edu/

Mars Reconnaissance Orbiter
http://www.nasa.gov/mro


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Received on Mon 03 Mar 2008 02:20:53 AM PST