London Telegraph 
Saturday, Dec 20, 2008
Scientists have found minerals on Mars that suggest the planet was once wet enough to support life.
Deposits of carbonate, formed in neutral or alkaline water, were spotted by NASA’s Mars Reconnaissance Orbiter.
“Obviously this is very exciting,” said John Mustard of Brown University in Rhode Island. “It’s white – it’s a bulbous, crusty material.”
Carbonate is formed when water and carbon dioxide mix with calcium, iron or magnesium. It dissolves quickly in acid, so its discovery counters the theory that all water on Mars was at one time acidic.
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“It would have been a pretty clement, benign environment for early Martian life,” said Bethany Ehlmann, a graduate student at Brown University who led the study published in the journal Science.
“It preserves a record of a particular type of habitat, a neutral to alkaline water environment.”