22-December-2005, 03:55 AM
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Senior Member
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Join Date: Mar 2004
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University of Colorado: Mars Region Probably Less Watery In Past Than Thought, Says Study
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A region of Mars that some planetary scientists believe was once a shallow lakebed and likely habitable for life may not have been so wet after all, according to a new University of Colorado at Boulder study.
The new study indicates chemical signatures in the bedrock, interpreted in 2004 by the Mars Exploration Rover, or MER, mission team as evidence for widespread, intermittent water at Mars' surface, may have instead been created by the reaction of sulfur-bearing steam vapors moving up through volcanic ash deposits. Known as Meridiani Planum, the region may have been more geologically similar to volcanic regions in parts of North America, Hawaii or Europe, said Thomas McCollom of CU-Boulder's Center for Astrobiology.
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"We think the bedrock was laid down by enormous volcanic ash flows over time that were then permeated by sulfur dioxide-rich steam vapors," said McCollom. "The sulfur dioxide and water combined to form sulfuric acid, which reacted with and altered the bedrock to give it its present chemical composition."
The new scenario does not require prolonged interaction between bedrock and a standing body of surface water as proposed by the MER team, and the process likely occurred at high temperatures, perhaps more than 200 degrees F, said McCollom. "Everything about the site seems to be consistent with our conclusions," he said.
"In our scenario, the water required to support the chemistry in this bedrock would only have had to have been around for months, years or perhaps as much as a few centuries," said Hynek. "This is very different than previous scenarios, which require that a much larger amount of water be present for many millennia."
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Nature: The waters ran shallow
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Surface features at the landing site of Opportunity, the Mars Exploration Rover, have been taken as evidence that liquid water was once abundant on Mars. But two groups now present alternative explanations of the layered structures and mineral compositions of the Meridiani Planum that do not involve a standing body of liquid water. Turbulent flow of rock fragments, salts and ice produced by meterorite impact and deposition of volcanic material followed by reaction with condensed sulphur dioxide- and water-bearing vapours, are offered as alternative explanations for the observations.
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Space.com: New Studies Question Mars Water Assumptions: Popular summary of above reports and articles.
It sounds like the MER folks are sticking to their guns, confident in having more recent data:
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Squyres said a deeper understanding of the situation came when Opportunity examined Endurance Crater, where observations were made of 25 vertical feet of rock outcrops. Those results were published just a month ago, after the two Nature papers had been submitted.
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Last edited by 01101001 : 22-December-2005 at 08:20 AM.
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