<p>A Martian rock analyzed by NASA's rover Opportunity contains clays formed in non-acidic water, an environment potentially suitable for the chemistry of ancient life to brew.</p>.<p>The solar-powered Opportunity landed on Mars in January 2004 for what was expected to be a 90-day mission to look for signs there was once water. It, and a twin rover, Spirit, which succumbed to the harsh Martian environment three years ago, had both found rocks altered by highly acidic water.</p>.<p>While acid-loving microbes exist on Earth, scientists suspect the chemical building blocks for life need more neutral conditions to evolve into life.</p>.<p>"The tough thing about an acid environment is that it's very, very hard, we believe, to get pre-biotic chemistry, the kind of chemistry that can lead to the origin of life," Cornell University's Steve Squyres, lead scientist for the Opportunity and Spirit missions, told reporters during a conference call on Friday.</p>.<p>"What's exciting about this discovery is that it points to a neutral pH at a time very, very early in Martian history," he added.</p>.<p>"What we have here is a very different chemistry. This is water you can drink," Squyres said. "This is the most powerful evidence for neutral (non-acidic) chemistry water that has been found by Opportunity," he added.</p>.<p>Opportunity took three years to reach the rim of a large impact basin called Endeavour Crater, where it examined, among other objects, a small rock called Esperance.</p>.<p>It took seven tries before Opportunity got itself positioned properly to scratch the rock's surface and see what lies beneath. Unlike NASA's follow-on Mars rover Curiosity, which landed on the opposite side of Mars in August, Opportunity has no drill or onboard chemistry lab to obtain and analyze samples.</p>.<p>Instead, it uses its instruments to determine basic mineralogy. Esperance, scientists determined, contains aluminum-rich clays, a telltale sign that neutral water flowed through the rock.</p>.<p>Likewise, Curiosity's first analysis of powder drilled from an ancient mudstone showed signs of neutral water, plus elements needed to support microbial life. Results from the rover's second sample analysis are pending.</p>.<p>Opportunity now is making its way south along the Endeavour Crater rim toward an exposed stack of rock that may provide more clues about Mars' transition from a warm and wet world to the cold, dry, acidic desert that exists today.</p>.<p>Scientists are hopeful Opportunity will make it there by August 1, before the start of Martian winter in the southern hemisphere.</p>.<p>"We've been on borrowed time for a while," said project manager John Callas, with NASA's Jet Propulsion Laboratory in Pasadena, California. "How long Opportunity lasts is anyone's guess."</p>
<p>A Martian rock analyzed by NASA's rover Opportunity contains clays formed in non-acidic water, an environment potentially suitable for the chemistry of ancient life to brew.</p>.<p>The solar-powered Opportunity landed on Mars in January 2004 for what was expected to be a 90-day mission to look for signs there was once water. It, and a twin rover, Spirit, which succumbed to the harsh Martian environment three years ago, had both found rocks altered by highly acidic water.</p>.<p>While acid-loving microbes exist on Earth, scientists suspect the chemical building blocks for life need more neutral conditions to evolve into life.</p>.<p>"The tough thing about an acid environment is that it's very, very hard, we believe, to get pre-biotic chemistry, the kind of chemistry that can lead to the origin of life," Cornell University's Steve Squyres, lead scientist for the Opportunity and Spirit missions, told reporters during a conference call on Friday.</p>.<p>"What's exciting about this discovery is that it points to a neutral pH at a time very, very early in Martian history," he added.</p>.<p>"What we have here is a very different chemistry. This is water you can drink," Squyres said. "This is the most powerful evidence for neutral (non-acidic) chemistry water that has been found by Opportunity," he added.</p>.<p>Opportunity took three years to reach the rim of a large impact basin called Endeavour Crater, where it examined, among other objects, a small rock called Esperance.</p>.<p>It took seven tries before Opportunity got itself positioned properly to scratch the rock's surface and see what lies beneath. Unlike NASA's follow-on Mars rover Curiosity, which landed on the opposite side of Mars in August, Opportunity has no drill or onboard chemistry lab to obtain and analyze samples.</p>.<p>Instead, it uses its instruments to determine basic mineralogy. Esperance, scientists determined, contains aluminum-rich clays, a telltale sign that neutral water flowed through the rock.</p>.<p>Likewise, Curiosity's first analysis of powder drilled from an ancient mudstone showed signs of neutral water, plus elements needed to support microbial life. Results from the rover's second sample analysis are pending.</p>.<p>Opportunity now is making its way south along the Endeavour Crater rim toward an exposed stack of rock that may provide more clues about Mars' transition from a warm and wet world to the cold, dry, acidic desert that exists today.</p>.<p>Scientists are hopeful Opportunity will make it there by August 1, before the start of Martian winter in the southern hemisphere.</p>.<p>"We've been on borrowed time for a while," said project manager John Callas, with NASA's Jet Propulsion Laboratory in Pasadena, California. "How long Opportunity lasts is anyone's guess."</p>