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New Study Challenges Martian Water Theory

Posted on: Thursday, 22 December 2005, 09:00 CST

New study challenges Martian water theory

LOS ANGELES, Dec. 21 (Xinhua)-- A region of Mars that some scientists believe was once a shallow lakebed and likely habitable for life may not have been so wet, according to a new study released on Wednesday.

The Meridiani Planum on the red planet had been listed as evidence of widespread, intermittent Martian environment after NASA 's Mars rover Opportunity had explored the region last year.

But the new study, conducted by researchers at the Colorado University, indicated chemical signatures in the bedrock on the Meridiani Planum may have been created by the reaction of sulfur- bearing steam vapors moving up through volcanic ash deposits.

The region may have been more geologically similar to volcanic regions in parts of North America, Hawaii or Europe, according to Thomas McCollom, the the lead researcher of the study appearing in the Dec. 22 issue of the journal Nature.

"Our study indicates it was probably more like parts of Yellowstone, Hawaii or Italy than something like the Great Salt Lake," he said. "We think it was far less favorable for past biological activity than other scenarios that have been proposed."

A series of scientific papers, published in 2004 by the rover scientific team and based on data gathered by Opportunity, concluded that the Meridiani Planum region once probably had a large sea or huge lake that may have waxed and waned over eons.

The authors proposed that the evaporation of surface and subsurface water over time left behind various chemical precipitates, predominately sulfate salts that they interpreted as evidence for a watery environment that would have been conducive for life to exist.

McCollom's paper argued that, if the sulfate was the result of precipitation from an evaporating brine of surface and subsurface water as has been proposed, the bedrock should be enriched with a large amount of positively charged atoms, known as cations, from minerals like iron, calcium and magnesium.

But it is not, the researchers said. Instead, the bedrock might have been laid down by enormous volcanic ash flows over time that were then permeated by sulfur dioxide-rich steam vapors.

"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 researchers described the geology of the region as " solfatara-like," featured with vapor-emitting vents. The size of the suspected Meridiani Planum volcanic deposits appears much larger than any similar deposit on Earth, they said.

But the researchers are cautious to exclude the possibility of Martian life. Etreme environments on Earth such as solfataras host microbes that use sulfur for sustenance, they noted.

"My view is that there is a good possibility there is life on Mars, probably in the subsurface," McCollom said. "We know from examples on Earth that life can exist in extreme places, and Mars seems to have the necessary ingredients for that."

Source: Xinhua News Agency - CEIS

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