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

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu, 18 Dec 2008 12:52:10 -0800 (PST)
Message-ID: <200812182052.MAA15835_at_zagami.jpl.nasa.gov>

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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Received on Thu 18 Dec 2008 03:52:10 PM PST