[meteorite-list] Green Mineral Indicates Mars Is Dry

From: Ron Baalke <baalke_at_meteoritecentral.com>
Date: Thu Apr 22 10:28:35 2004
Message-ID: <200310232338.QAA17571_at_zagami.jpl.nasa.gov>

Contact: Heidi Koontz
hkoontz_at_usgs.gov
303-202-4763
United States Geological Survey

Green mineral indicates red planet is dry

The presence of a common green mineral on Mars suggests that the red planet
could have been cold and dry since the mineral has been exposed, which may
be more than a billion years according to new research appearing in the Oct.
24 edition of Science.

Todd Hoefen, a U.S. Geological Survey (USGS) geophysicist, led a team of
researchers from USGS, Arizona State University and NASA, that found
abundant quantities of olivine on Mars. They based their conclusions on data
obtained from a Thermal Emission Spectrometer (TES) carried by the Mars
Global Surveyor (MGS).

Olivine, a transparent green-colored mineral found in many mafic rocks, is
susceptible to chemical weathering and readily alters to other minerals such
as iddingsite, goethite, serpentine, chlorite, smectite, maghemite and
hematite in the presence of water. Except for trace amounts of hematite,
which gives Mars its red color, none of these other weathering products have
been found.

The team detected a 30,000 square kilometer area rich in olivine, in the
Nili Fossae region of Mars. Nili Fossae has been interpreted as a complex of
grabens and fractures related to the formation of the Isidis impact basin,
where post-impact faulting exposed the abundant olivine. They have also
found smaller deposits of olivine all over the planet, all indicating a
surface dominated by volcanic processes.

The fact that so much olivine is exposed at the surface indicates that there
has been little to no weathering due to water, thus no liquid water-mineral
chemical reactions. The age of the surface is somewhat uncertain but is
probably over 3 billion years old.

It took approximately three years for the MGS spacecraft and the TES
instrument to gather the data for the analysis, and scientists another year
to analyze the results. The MGS spacecraft is healthy and continues to map
Mars.

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The USGS serves the nation by providing reliable scientific information to
describe and understand the Earth; minimize loss of life and property from
natural disasters; manage water, biological, energy, and mineral resources;
and enhance and protect our quality of life.
Received on Thu 23 Oct 2003 07:38:07 PM PDT