Mars odyssey neutron sensing of the south residual polar cap - art. no. 1677

摘要

1] Measurements from the neutron spectrometer instrument of the Mars Odyssey Gamma-Ray Spectrometer (GRS) package for solar aereocentric longitude between 340degrees and 360degrees are used to estimate the CO2 mass, dust content, and covered area of the south residual polar cap. Two models for the cap are explored; a cap uniformly covered in dust-free CO2 and a "Swiss cheese'' model with an exposed H2O ice substrate and 8m mesas composed of CO2 and dust. A range of 1.0 to 3.0 x 10(17) g is found for the mass of residual CO2 on the cap, or about 3 to 9% of the total CO2 seasonally cycled in and out of the atmosphere. For the Swiss cheese model, if the CO2 is dust-free then 60% of the cap area must be the exposed H2O ice substrate. This area decreases with increasing dust concentration in the CO2. For example, if 45% of the cap area is exposed water ice then 224 g/cm(2) of dust is in the CO2 and for a typical dust deposition rate of 0.9 x 10(-3) g/cm(2)/yr, the dust can be deposited in similar to25,000 yrs. [References: 15