A long-sought-after mineral on the martian surface has been spotted by the researchers via the use of a powerful instrument aboard NASA's Mars Reconnaissance Orbiter and with it, unexpected clues to the Red Planet's watery past.

Carbonate minerals were spotted by the scientist while surveying the intact bedrock layers with the Compact Reconnaissance Imaging Spectrometer for Mars, or CRISM. This indicated that Mars had neutral to alkaline water when the minerals formed at these locations more than 3.6 billion years ago. Basically carbonates dissolve quickly in acid. It is therefore suggested that their survival until today on Mars challenges suggestions that an exclusively acidic environment dominated the planet and instead it points to the fact that different types of watery environments existed. If there are more varieties of wet environments, there are more chances that one or more of them may have supported life.

Scott Murchie, principal investigator for the instrument at the Johns Hopkins University's Applied Physics Laboratory in Laurel, Md said, "We're excited to have finally found carbonate minerals because they provide more details about conditions during specific periods of Mars' history."

The findings which were announced at a briefing at the American Geophysical Union's Fall Meeting in San Francisco appear in the Dec. 19 issue of Science magazine.

Bethany Ehlmann, lead author of the article and a spectrometer team member from Brown University, Providence, R. I. said, "The carbonates that CRISM has observed are regional rather than global in nature, and therefore, are too limited to account for enough carbon dioxide to form a thick atmosphere."

"Although we have not found the types of carbonate deposits which might have trapped an ancient atmosphere, we have found evidence that not all of Mars experienced an intense, acidic weathering environment 3.5 billion years ago, as has been proposed. We've found at least one region that was potentially more hospitable to life," she concluded.