Wednesday, December 06, 2006

Changing Mars Gullies Hint at Recent Flowing Water -

By Tariq Malik
Staff Writer
posted: 6 December 2006
1:00 p.m. ET

The changing appearance of gullies on Mars within the last few years has prompted new hopes that liquid water may have flowed recently on the red planet.

"The water thing clearly is a surprise to us," Michael Malin, who led a study that found the gully changes, told "The environment for Mars is not very conducive to water."

Malin and his colleagues used images from NASA's now silent Mars Global Surveyor (MGS) to revisit regions earlier this year where gullies, depression-like landforms on the red planet's surface, were found in 2000.

What they found were new, light-colored deposits that do not appear to have formed from martian landslides, but could be the work of frost, salt deposits or long-sought evidence that water flowed recently on Mars [images].

"Our level of certainty which we can address the question of whether the gully features that we're reporting on were formed by water is high, but not extremely high," said Malin, who has lightheartedly referred to the find as "the squirting gun."

"The evidence is mostly suggestive," he said.

Researchers have known of gullies on the Mars since 2000, when the MGS spacecraft's Mars Orbiter Camera (MOC)—built by Malin's Malin Space Science Systems in San Diego, California—first observed the eye-catching landforms. Found mostly on slopes or ridges, the gullies sparked long-running debates on whether they formed from groundwater seeping out of the martian surface or in dry landslides.

Malin's team also used the MOC instrument in their new study, which compared base images of two regions taken in 1999 and 2001 to more recent images captured in the years since.

In an area known as Terra Sirenum, new light-toned deposits coating gullies in April 2005 were not present in December 2001. Similar changes were seen in a crater etched into the Centauri Montes region of Mars, which apparently changed sometime between August 1999 and February 2004.

"Whether or not water was involved, it means that it is contemporary," Malin said of the findings, which will be detailed this week in the journal Science.

That liquid water once existed on Mars in some form has been known conclusively since 2004, when NASA's Opportunity rover found evidence that the wet stuff permeated rocks in the planet's ancient past.

Mars scientists have long associated the search for liquid water on red planet with the possibility of life, since the two are closely linked here on Earth. The existence of subsurface liquid water on Mars could also serve as a potential supply source for future red planet explorers.

But determining conclusively that the gully changes seen by MGS stem from liquid water is daunting, and will likely require an up-close visit—a challenge due to the risk of contaminating a gully site with Earth microbes or other material.

"Personally, I think you're going to have to go to one [and see]," Malin said, adding that the contaminate hurdle is daunting. "It's something that will not be trivially easy to go to, but something there's a lot of interest in."

Kenneth Edgett, a scientist at Malin Space Science Systems, told that the gully changes seen by MGS may be the first of many to be found by Mars-watching orbiters.

"More of these could happen if we just watch," Edgett said.


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