[meteorite-list] NASA Rover Finds Clue To Mars' Past And Environment For Life

[Ron Baalke]

June 3, 2010

Dwayne Brown      
Headquarters, Washington                      
202-358-1726 
dwayne.c.brown at nasa.gov 

William Jeffs 
Johnson Space Center, Houston 
281-483-5111 
william.p.jeffs at nasa.gov 

Guy Webster 
Jet Propulsion Laboratory, Pasadena, Calif. 
818-354-6278 
guy.webster at jpl.nasa.gov 

MEDIA ADVISORY: 10-131

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

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 which 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 seven 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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