[meteorite-list] NASA Rover Helps Reveal Possible Secrets of Martian Life

[Ron Baalke]

November 29, 2005

George Deutsch/Erica Hupp 
Headquarters, Washington 
(202) 358-1324/1237 

Guy Webster 
Jet Propulsion Laboratory, Pasadena, Calif.
(Phone: 818/354-6278) 

RELEASE: 05-415

NASA ROVER HELPS REVEAL POSSIBLE SECRETS OF MARTIAN LIFE

Life may have had a tough time getting started in the ancient 
environment that left its mark in the Martian rock layers examined by 
NASA's Opportunity rover. The most thorough analysis yet of the 
rover's discoveries reveals the challenges life may have faced in the 
harsh Martian environment. 

"This is the most significant set of papers our team has published," 
said Dr. Steve Squyres of Cornell University, Ithaca, N.Y. He is 
principal investigator for the science instruments on Opportunity and 
its twin rover, Spirit. The lengthy reports reflect more thorough 
analysis of Opportunity's findings than earlier papers.

Scientists have been able to deduce conditions in the Meridiani Planum 
region of Mars were sometimes wet, strongly acidic and oxidizing. 
Those conditions probably posed stiff challenges to the origin of 
Martian life. 

Based on Opportunity's data, nine papers by 60 researchers in volume 
240, issue 1 of the journal Earth and Planetary Science Letters 
discuss what this part of the Martian Meridiani Planum region was 
like eons ago. The papers present comparisons to some harsh habitats 
on Earth and examine the ramifications for possible life on Mars. 

Dr. Andrew Knoll of Harvard University, Cambridge, Mass., a paper 
co-author, said, "Life that had evolved in other places or earlier 
times on Mars, if any did, might adapt to Meridiani conditions, but 
the kind of chemical reactions we think were important to giving rise 
to life on Earth simply could not have happened at Meridiani." 

Scientists analyzed data about stacked sedimentary rock layers 23 feet 
thick, exposed inside "Endurance Crater." They identified three 
divisions within the stack. The lowest, oldest portion had the 
signature of dry sand dunes; the middle portion, windblown sheets of 
sand with all the particles produced in part by previous evaporation 
of liquid water. The upper portion corresponded to layers Opportunity 
found earlier inside a smaller crater near its landing site. 

Materials in all three divisions were wet both before and after the 
layers were deposited by either wind or water. Researchers described 
chemical evidence that the sand grains deposited in the layers had 
been altered by water before the layers formed. Scientists analyzed 
how acidic water moving through the layers after they were in place 
caused changes such as the formation of hematite-rich spherules 
within the rocks.

Experimental and theoretical testing reinforces the interpretation of 
changes caused by acidic water interacting with the rock layers. "We 
made simulated Mars rocks in our laboratory then infused acidic 
fluids through them," said researcher Nicholas Tosca from the State 
University of New York. "Our theoretical model shows the minerals 
predicted to form when those fluids evaporate bear a remarkable 
similarity to the minerals identified in the Meridiani outcrop." 

The stack of layers in Endurance Crater resulted from a changeable 
environment perhaps 3.5 to 4 billion years ago. The area may have 
looked like salt flats occasionally holding water, surrounded by 
dunes. The White Sands region in New Mexico bears a similar physical 
resemblance. "For the chemistry and mineralogy of the environment, an 
acidic river basin named Rio Tinto, in Spain, provides useful 
similarities," said Dr. David Fernandez-Remolar of Spain's Centro de 
Astrobiologia. 

Many types of microbes live in the Rio Tinto environment, one of the 
reasons for concluding that ancient Meridiani could have been 
habitable. However, the organisms at Rio Tinto are descended from 
populations that live in less acidic and stressful habitats. If 
Meridiani had any life, it might have had to originate in a different 
habitat.

"You need to be very careful when you are talking about the prospect 
for life on Mars," Knoll said. "We've looked at only a very small 
parcel of Martian real estate. The geological record Opportunity has 
examined comes from a relatively short period out of Mars' long 
history."

NASA's Jet Propulsion Laboratory, Pasadena, Calif., manages the Mars 
Exploration Rover project. Images and information about the rovers 
and their discoveries are available at: 

http://www.nasa.gov/vision/universe/solarsystem/mer_main.html 

	
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