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
. Rachel Prucey, NASA Ames Research Center, Moffett Field, Calif.
650-604-0643 or email@example.com
Media contacts: Guy Webster
Jet Propulsion Laboratory, Pasadena, Calif.
Steve Cole 202-657-2194
NASA Headquarters, Washington
Jennifer Huergo 240-228-5618/443-778-5618
Johns Hopkins University Applied Physics Laboratory, Laurel, Md.