NASA Rover Finds Clue to Mars' Past and Environment for Life

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Guy Webster 818-354-6278
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William Jeffs 281-483-5111
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Dwayne Brown 202-358-1726
NASA Headquarters, Washington
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NEWS RELEASE: 2010-189 June 3, 2010

NASA ROVER FINDS CLUE TO MARS' PAST AND ENVIRONMENT FOR LIFE

The full version of this story with accompanying images is at:
http://www.jpl.nasa.gov/news/news.cfm?release=2010-189&cid=release_2010-189

PASADENA, Calif. -- Rocks examined by NASA's Spirit Mars Rover hold evidence of a
wet, non-acidic ancient environment that may have been favorable for life. Confirming this
mineral clue took four years of analysis by several scientists.

An outcrop that Spirit examined in late 2005 revealed high concentrations of carbonate,
which originates in wet, near-neutral conditions, but dissolves in acid. The ancient water
indicated by this find was not acidic.

NASA's rovers have found other evidence of formerly wet Martian environments. However,
the data for those environments indicate conditions that may have been acidic. In other cases,
the conditions were definitely acidic, and therefore less favorable as habitats for life.

Laboratory tests helped confirm the carbonate identification. The findings were published
online Thursday, June 3 by the journal Science.

"This is one of the most significant findings by the rovers," said Steve Squyres of Cornell
University in Ithaca, N.Y. Squyres is principal investigator for the Mars twin rovers, Spirit
and Opportunity, and a co-author of the new report. "A substantial carbonate deposit in a
Mars outcrop tells us that conditions that could have been quite favorable for life were
present at one time in that place."

Spirit inspected rock outcrops, including one scientists called Comanche, along the rover's
route from the top of Husband Hill to the vicinity of the Home Plate plateau that Spirit has
studied since 2006. Magnesium iron carbonate makes up about one-fourth of the measured
volume in Comanche. That is a tenfold higher concentration than any previously identified
for carbonate in a Martian rock.

"We used detective work combining results from three spectrometers to lock this down," said
Dick Morris, lead author of the report and a member of a rover science team at NASA's
Johnson Space Center in Houston."The instruments gave us multiple, interlocking ways of
confirming the magnesium iron carbonate, with a good handle on how much there is."

Massive carbonate deposits on Mars have been sought for years without much success.
Numerous channels apparently carved by flows of liquid water on ancient Mars suggest the
planet was formerly warmer, thanks to greenhouse warming from a thicker atmosphere than
exists now. The ancient, dense Martian atmosphere was probably rich in carbon dioxide,
because that gas makes up nearly all the modern, very thin atmosphere.

It is important to determine where most of the carbon dioxide went. Some theorize it
departed to space. Others hypothesize that it left the atmosphere by the mixing of carbon
dioxide with water under conditions that led to forming carbonate minerals. That possibility,
plus finding small amounts of carbonate in meteorites that originated from Mars, led to
expectations in the 1990s that carbonate would be abundant on Mars. However, mineral-
mapping spectrometers on orbiters since then have found evidence of localized carbonate
deposits in only one area, plus small amounts distributed globally in Martian dust.

Morris suspected iron-bearing carbonate at Comanche years ago from inspection of the rock
with Spirit's Moessbauer Spectrometer, which provides information about iron-containing
minerals. Confirming evidence from other instruments emerged slowly. The instrument with
the best capability for detecting carbonates, the Miniature Thermal Emission Spectrometer,
had its mirror contaminated with dust earlier in 2005, during a wind event that also cleaned
Spirit's solar panels.

"It was like looking through dirty glasses," said Steve Ruff of Arizona State University in
Tempe, Ariz., another co-author of the report. "We could tell there was something very
different about Comanche compared with other outcrops we had seen, but we couldn't tell
what it was until we developed a correction method to account for the dust on the mirror."

Spirit's Alpha Particle X-ray Spectrometer instrument detected a high concentration of light
elements, a group including carbon and oxygen, that helped quantify the carbonate content.

The rovers landed on Mars in January 2004 for missions originally planned to last three
months. Spirit has been out of communication since March 22 and is in a low-power
hibernation status during Martian winter. Opportunity is making steady progress toward a
large crater, Endeavour, which is about 11 kilometers (7 miles) away.

NASA's Jet Propulsion Laboratory, Pasadena, manages the Mars Exploration Rovers for the
agency's Science Mission Directorate in Washington. For more information about the rovers,
visit: http://www.nasa.gov/rovers.

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