formed in non-acidic water, an environment potentially suitable for
the chemistry of ancient life to brew.
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 bothfound rocks altered by
highly acidic water .
While acid-loving microbes exist on Earth, scientists suspect the
chemical building blocks for life need more neutral conditions to
evolve into life.
"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.
"What's exciting about this discovery isthat it points to a neutral pH
at a time very, very early in Martian history," he added.
"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.
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.
It took seven tries before Opportunity got itself positioned properly
to scratchthe 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.
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.
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 therover's second sample analysis
are pending.
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.
Scientists are hopeful Opportunity will make it there by August 1,
before the start of Martian winter in the southern hemisphere.
"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."
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