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Vincent,
Not to be disrepectful, but you are mistaken. There is nothing about the features in the images you have presented that require an extant aqueous explanation. More importantly, the sub-surface radar instruments aboard Mars Express and MRO have both failed to detect any subsurface aquifers. And, after an exhaustive search, Mars Odyssey failed to find evidence of any extant hydrothermal activity on Mars.
Sincerely,
Algorithms
Vincent,
None of the images you have presented offer any evidence of extant liquid water.
At the present time we have yet to detect the extant presence of liquid water on Mars. You cannot draw the conclusion to the contrary from the images you've shared here.
To be sure, it is entirely possible that liquid water can exist at the surface ephemerally under rare conditions when atmospheric pressure and surface temperature line up. Unfortunately, the places where this is most likely to occur are also most likely dessicated for the very same reasons.
And, it is still possible we may find aquifers of liquid water beneath the surface, but, to date, the search has come up empty-handed. Neither MARSIS, nor SHARAD have detected any such aquifers. In addition, a planetwide survey by Mars Odyssey failed to turn up evidence of any extant hydrothermal activity. Gully features first found by MGS have been determined to be more likely the cause of non-aqueous action.
That's the current best state of the science. Of course, we should keep looking.
Regards,
Algorithms
Well stated, Gregori. That is an important distinction between Mars and Earth. The best possible candidates for finding life on Mars are worse than the worst possible places life can survive in here on earth.
Liquid Water Found On Mars? Not Yet.
http://www.marstoday.com/news/viewpr.html?pid=24893
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, 1-520-626-2126
jdpellet@email.arizona.edu
Alfred McEwen, 1-520-621-4573
mcewen@lpl.Arizona.edu
Related Web pages:
Jon Pelletier
http://geomorphology.geo.arizona.edu
Alfred McEwen
http://www.lpl.arizona.edu/resources/fa ... nom=McEwen
HiRISE
http://hirise.lpl.arizona.edu/
Mars Reconnaissance Orbiter
http://www.nasa.gov/mro
Mars Rovers Sharpen Questions About Livable Conditions
Mars Daily
by Staff Writers
Boston MA (SPX) Feb 18, 2008
Like salt used as a preservative, high concentrations of dissolved minerals in the wet, early-Mars environment known from discoveries by NASA's Opportunity rover may have thwarted any microbes from developing or surviving.
"Not all water is fit to drink," said Andrew Knoll, a member of the rover science team who is a biologist at Harvard University, Cambridge, Mass.
Opportunity and its twin, Spirit, began their fifth year on Mars last month, far surpassing their prime missions of three months. Today, at a meeting of the American Association for the Advancement of Science in Boston, scientists and engineers discussed new observations by the rovers, recent analysis of some earlier discoveries, and perspectives on which lessons from these rovers' successes apply to upcoming missions to Mars.
"The engineering efforts that have enabled the rovers' longevity have tremendously magnified the science return," said Steve Squyres of Cornell University, Ithaca, N.Y., principal investigator for the rovers' science payload. "All of Spirit's most important findings, such as evidence for hot springs or steam vents, came after the prime mission."
Opportunity spent recent months examining a bright band of rocks around the inner wall of a crater. Scientists previously hypothesized this material might preserve a record of the ground surface from just before the impact that excavated the crater. Inspection suggests that, instead, it was at the top of an underground water table, Squyres reported.
Experiments with simulated Martian conditions and computer modeling are helping researchers refine earlier assessments of whether the long-ago conditions in the Meridiani area studied by Opportunity would have been hospitable to microbes. Chances look slimmer. "At first, we focused on acidity, because the environment would have been very acidic," Knoll said.
"Now, we also appreciate the high salinity of the water when it left behind the minerals Opportunity found. This tightens the noose on the possibility of life."
Conditions may have been more hospitable earlier, with water less briny, but later conditions at Meridiani and elsewhere on the surface of Mars appear to have been less hospitable, Knoll said.
"Life at the Martian surface would have been very challenging for the last 4 billion years. The best hopes for a story of life on Mars are at environments we haven't studied yet -- older ones, subsurface ones," he said.
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