From: g_d_pusch_remove_underscores@xnet.com   
   Copy: baalke@zagami.jpl.nasa.gov   
   Copy: hkoontz@usgs.gov   
      
   baalke@zagami.jpl.nasa.gov (Ron Baalke) writes:   
      
   > 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.   
   [...]   
   > 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 should be noted that Nili Fossae is a Martian "highland" region, and is   
   further above the martian "lowlands" than Mt. Everest is above terrestrial   
   sea level. One finds very little _liquid_ water on top of Mount Everest,   
   and therefore very little water-induced chemical weathering there. Olivine   
   outcrops on high mountaintops are not unusual.   
      
   Hence, and notwithstanding the slower decrease in atmospheric density   
   with altitude caused by the larger "scale height" of the Martian atmosphere,   
   even during a "warm wet phase," one would =NOT= expect to find liquid water   
   in the Martian "highlands," due to their higher relative altitude and Mars's   
   lower mean temperature. Even if the "lowalnd" pressure were a substantial   
   fraction of a bar, the Martian highland "climate" would still be a very cold,   
   very dry, near-vacuum. Therefore, IMO, this observation says NOTHING AT ALL   
   about the ancient martian lowland climate.   
      
      
   -- Gordon D. Pusch   
      
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