From: baalke@zagami.jpl.nasa.gov   
      
   Contact: Heidi Koontz   
   hkoontz@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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   and enhance and protect our quality of life.   
      
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