[meteorite-list] Water May Not Have Formed Mars' Recent Gullies

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Mar 16 18:08:42 2006
Message-ID: <200603161943.k2GJhPS26351_at_zagami.jpl.nasa.gov>

WATER MAY NOT HAVE FORMED MARS' RECENT GULLIES
>From Lori Stiles, UA Office of University Communications, 520-621-1877
 
- Thursday, March 16, 2006

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Contact Information
Gwendolyn Bart 520-626-5065 gwenbart_at_lpl.arizona.edu
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If you're a scientist studying the surface of Mars, few discoveries could be
more exciting than seeing recent gullies apparently formed by running water.

And that's what scientists believed they saw in Mars Orbital Camera (MOC)
images five years ago. They published a paper in Science on MOC images that
show small, geologically young ravines. They concluded that the gullies are
evidence that liquid water flowed on Mars' surface sometime within the last
million years.

A word of caution, though: The moon has gullies that look like that, a
University of Arizona Lunar and Planetary Laboratory researcher has found.
And water certainly didn't form gullies on the waterless moon.

Gwendolyn D. Bart is presenting the work today at the 37th Lunar and
Planetary Science Conference in Houston.

"We'd all like to find liquid water on Mars," Bart said. "That would be
really, really exciting. If there were liquid water on Mars, humans wouldn't
have to ship water from Earth when they go to explore the planet. That would
be an enormous cost savings. And liquid water near the surface of Mars would
greatly increase the chances for native life on Mars."

The 2000 Science paper was provocative, Bart said. "But I was skeptical. I
wondered if there is another explanation for the gullies."

Then last year she heard a talk by Allan Treiman of the Lunar and Planetary
Institute. Treiman suggested the martian gullies might be dry landslides,
perhaps formed by wind and not formed by water at all.

Recently, Bart was studying the lunar landscape in high-resolution images
taken in 1969, prior to the Apollo landings, for her research on processes
that modify the lunar surface.

"Totally by accident, I saw gullies that looked strikingly like the gullies
on Mars," she said.

"If the dry landslide hypothesis for the formation of martian gullies is
correct, we might expect to see similar features on the moon, where there is
no water," she said. "We do."

Gullies in the moon's 10-mile-diameter (17 kilometer) crater Dawes are
similar in structure and size to those in a martian crater that MOC
photographed. Micrometeorites hitting the smooth slopes and crater on the
airless moon could easily trigger small avalanches that form gullies, Bart
said.

However, the martian gullies also resemble gullies on Earth that were
formed by water, she noted.

"My point is that you can't just look at the Mars gullies and assume they
were formed by water. It may be, or may be not. We need another test to
know."
Received on Thu 16 Mar 2006 02:43:25 PM PST