spacetoday.net: Opportunity finds more evidence of past liquid water on Mars

Posted: Thu, Dec 8, 2011, 1:41 PM ET (1841 GMT)
Mars Exploration Rover (NASA/JPL)

NASA's Mars rover Opportunity has found veins of minerals that scientists say could have only formed in the presence of liquid water. Scientists said the mineral, thought to be gypsum, likely formed when water dissolved calcium from volcanic rocks, which later combined with sulfur to create the gypsum deposits. Scientists said the mineral veins, found near the rim of Endeavour crater, is a "slam-dunk story" showing how liquid water once flowed through fractures in the rock in the region. The finding adds to previous evidence that strongly indicates liquid water existed on Mars early in its history, when the planet had a thicker and warmer atmosphere.