Opportunity finds signs of life-threatening conditions on Mars.

By Irene Klotz
Cape Canaveral, Florida, June 7 (Reuters) A Martian rock analyzed by the Opportunity Mars rover contains samples of clay formed in non-acidic water, an environment potentially suitable for the chemistry of ancient life to develop.

The solar-powered Opportunity rover landed on Mars in January 2004 for what was expected to be a 90-day mission to search for signs that there was once water on the planet. It and a second rover, Spirit, which succumbed to the harsh Martian environment three years ago, had found rocks altered by highly acidic water.

Although there are microbes on Earth that thrive in acidic conditions, scientists suspect that the chemical building blocks of life need more neutral conditions to evolve and develop into life.

"The difficult thing about an acidic environment is that we believe it's extremely difficult to achieve prebiotic chemistry, the kind of chemistry that could lead to the origin of life," Steve Squyres of Cornell University, principal scientist for the Opportunity and Spirit missions, told reporters during a teleconference on Friday.

"What's interesting about this discovery is that it points to a neutral pH at a very early point in Martian history," he added.

"What we have here is a very different chemistry. This is water we can drink," said Squyres. "This is the strongest evidence of pH-neutral (non-acidic) water that has been found by Opportunity," he added.

It took Opportunity three years to reach the rim of a crater called Endeavour Crater, where it examined, among other objects, a small rock called Esperance.

It took seven attempts before Opportunity was able to position itself properly to scratch the rocky surface and see what lay beneath. Unlike NASA's Curiosity rover, which landed on the far side of Mars in August, Opportunity has no drilling equipment or chemical laboratory on board to obtain and analyze samples. 

Instead, he uses his instruments to research basic mineralogy. Scientists have discovered that Esperance contains aluminum-rich clays, a telltale sign that neutral water has flowed over the rock.

Opportunity is now heading south along the rim of Endeavour Crater toward a pile of rocks that could provide more clues about Mars' transition from a warm, wet world to the cold, dry, and acidic desert it is today. Scientists expect Opportunity to arrive there by August 1st.

(jpveiga@uol.com.br)