Comets,volcanism, the salt-rich regolith,and cycling of volatiles on Mars |
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| Institution: | 1. Southwest Research Institute, San Antonio, TX 78238, USA;2. Department of Earth and Planetary Sciences, Washington University in St. Louis, St. Louis, MO 63130, USA;1. Department of Earth and Planetary Sciences, Johns Hopkins University, Baltimore, MD 21218, USA;2. Applied Physics Laboratory, Johns Hopkins University, Laurel, MD 20723, USA;3. Department of Earth and Planetary Sciences, University of Tennessee-Knoxville, 306 EPS Building, 1412 Circle Drive, Knoxville, TN 37996, USA;4. Department of Chemistry and Biochemistry, University of Northern Iowa, Cedar Falls, IA 50614, USA;5. Arizona State University, Tempe, AZ 85287-1404, USA |
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| Abstract: | Estimates of the total inventory of the volatile elements C, H, O, and N on Mars, based upon atmospheric gas tracers, vary by a factor of 25 among different authors. Accretion of comets as the source of volatiles can account for less than 5% of the actual inventory, assuming the chondritic S/Cl abundance ratio in comets and a Martian outgassing ratio for these two elements no lower than for the estimated excess volatile inventory on Earth. Sulfate salt formation with the igneous minerals in the regolith can be a major sink for H2O, but first will recycle C and N incorporated in carbonate and nitrate minerals back to the atmosphere. Extrusive and shallow intrusive volcanism, at a persistent but decreasing rate, can interfere with this volatile recycling by irreversibly masking much of the incorporated inventory, resulting in the inevitable evolution to a relatively volatile-poor environment at the outermost, observable surface of Mars. |
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