Scientists Find 'Missing' Mineral and Clues to Mars Mysteries

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

Steve Cole 202-657-2194
NASA Headquarters, Washington
dwayne.c.brown@nasa.gov

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

News release: 2008-239 December 18, 2008

Scientists Find 'Missing' Mineral and Clues to Mars Mysteries

PASADENA, Calif. -- 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, 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 researchers report clearly defined carbonate exposures in bedrock layers surrounding the 1,489-
kilometer-diameter (925-mile) 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 666 kilometers (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. JPL, a division of the California Institute of Technology, Pasadena,
manages the Mars Reconnaissance Orbiter mission for the NASA Science Mission Directorate in Washington.
Lockheed Martin Space Systems, Denver, is the prime contractor for the project and built the spacecraft. For
more information about the Mars Reconnaissance Orbiter, visit: http://www.nasa.gov/mro .

Additional public affairs contacts: Richard Lewis, Brown University, Providence, R.I., 401-863-3766 or
richard_lewis@brown.edu. Rachel Prucey, NASA Ames Research Center, Moffett Field, Calif.
650-604-0643 or rachel.l.prucey@nasa.gov .

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