[meteorite-list] Scientists Find 'Missing' Mineral and Clues to Mars Mysteries

[Ron Baalke]

Dec. 18, 2009

Steve Cole 
Headquarters, Washington 
202-657-2194 
stephen.e.cole at nasa.gov 

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

Jennifer Huergo 
Johns Hopkins University Applied Physics Laboratory, Laurel, Md. 
240-228-5618/443-778-5618 
jennifer.huergo at jhuapl.edu 

RELEASE: 08-331

SCIENTISTS FIND 'MISSING' MINERAL AND CLUES TO MARS MYSTERIES

SAN FRANCISCO -- Researchers using a powerful instrument aboard NASA's 
Mars Reconnaissance Orbiter have found a long sought-after mineral on 
the Martian surface and, with it, unexpected clues to the Red 
Planet's watery past. 

Surveying intact bedrock layers with the Compact Reconnaissance 
Imaging Spectrometer for Mars, or CRISM, scientists found carbonate 
minerals, indicating that Mars had neutral to alkaline water when the 
minerals formed at these locations more than 3.6 billion years ago. 
Carbonates, which on Earth include limestone and chalk, dissolve 
quickly in acid. Therefore, their survival until today on Mars 
challenges suggestions that an exclusively acidic environment later 
dominated the planet. Instead, it indicates that different types of 
watery environments existed. The greater the variety of wet 
environments, the greater the chances one or more of them may have 
supported life. 

"We're excited to have finally found carbonate minerals because they 
provide more detail about conditions during specific periods of Mars' 
history," said Scott Murchie, principal investigator for the 
instrument at the Johns Hopkins University Applied Physics Laboratory 
in Laurel, Md. 

The findings will appear in the Dec. 19 issue of Science magazine and 
were announced Thursday at a briefing at the American Geophysical 
Union's Fall Meeting in San Francisco. 

Carbonate rocks are created when water and carbon dioxide interact 
with calcium, iron or magnesium in volcanic rocks. Carbon dioxide 
from the atmosphere becomes trapped within the rocks. If all of the 
carbon dioxide locked in Earth's carbonates were released, our 
atmosphere would be thicker than that of Venus. Some researchers 
believe that a thick, carbon dioxide-rich atmosphere kept ancient 
Mars warm and kept water liquid on its surface long enough to have 
carved the valley systems observed today. 

"The carbonates that CRISM has observed are regional rather than 
global in nature, and therefore, are too limited to account for 
enough carbon dioxide to form a thick atmosphere," said Bethany 
Ehlmann, lead author of the article and a spectrometer team member 
from Brown University in Providence, R.I. 

"Although we have not found the types of carbonate deposits which 
might have trapped an ancient atmosphere," Ehlmann said, "we have 
found evidence that not all of Mars experienced an intense, acidic 
weathering environment 3.5 billion years ago, as has been proposed. 
We've found at least one region that was potentially more hospitable 
to life." 

The article reports clearly defined carbonate exposures in bedrock 
layers surrounding the 925-mile diameter Isidis impact basin, which 
formed more than 3.6 billion years ago. The best-exposed rocks occur 
along a trough system called Nili Fossae, which is 414 miles long, at 
the edge of the basin. The region has rocks enriched in olivine, a 
mineral that can react with water to form carbonate. 

"This discovery of carbonates in an intact rock layer, in contact with 
clays, is an example of how joint observations by CRISM and the 
telescopic cameras on the Mars Reconnaissance Orbiter are revealing 
details of distinct environments on Mars," said Sue Smrekar, deputy 
project scientist for the orbiter at NASA's Jet Propulsion Laboratory 
in Pasadena, Calif. 

NASA's Phoenix Mars Lander discovered carbonates in soil samples. 
Researchers had previously found them in Martian meteorites that fell 
to Earth and in windblown Mars dust observed from orbit. However, the 
dust and soil could be mixtures from many areas, so the carbonates' 
origins have been unclear. The latest observations indicate 
carbonates may have formed over extended periods on early Mars. They 
also point to specific locations where future rovers and landers 
could search for possible evidence of past life. 

The Applied Physics Laboratory led the effort to build the Compact 
Reconnaissance Imaging Spectrometer for Mars and operates the 
instrument in coordination with an international team of researchers 
from universities, government and the private sector. NASA's Jet 
Propulsion Laboratory manages the Mars Reconnaissance Orbiter mission 
for NASA's Science Mission Directorate in Washington. 

For more information about the Mars Reconnaissance Orbiter, visit: 

http://www.nasa.gov/mro  
	
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