Computer Science – Sound
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.p41b1359l&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #P41B-1359
Computer Science
Sound
1221 Lunar And Planetary Geodesy And Gravity (5417, 5450, 5714, 5744, 6019, 6250), 5422 Ices, 5462 Polar Regions, 5470 Surface Materials And Properties, 6225 Mars
Scientific paper
The south polar layered deposits (SPLD) constitute the largest known reservoir of surface water on Mars. Previous studies solved for the best-fit uniform density of the deposit using a forward approach. We invert for the lateral density variations in the layered deposit using gravity data from radio tracking of Mars Reconnaissance Orbiter, topography from MOLA on board Mars Global Surveyor, and radar sounding data from MARSIS on board Mars Express. The gravity was first filtered to remove the effects of Tharsis loading and deformation. The residual gravity anomalies over the SPLD result from a combination of topography along the surface of the crust and Moho, density variations within the crust and mantle, and density variations within the polar layered deposits. We cannot uniquely solve for all of the unknowns, and thus must make assumptions regarding the nature of the gravity anomalies arising from the crust and mantle beneath the SPLD. The gravity and topography outside the cap were used to calculate the best-fit degree of compensation of the surface topography, which was then applied to the crust beneath the cap. Residual gravity anomalies outside the cap that are uncorrelated with the surface topography can arise from within the crust or mantle. We use the gravity anomalies outside the polar cap to construct a Wiener filter, which is applied to the gravitational signature of the cap to remove the short-wavelength anomalies over the SPLD that are spectrally consistent with an origin in the crust or mantle. These corrections attempt to isolate the gravity anomaly associated with the mass of the SPLD. We then use a constrained inversion for the vertically-averaged density within the SPLD as a function of position. The inversion smoothes the density variations and constrains the absolute deviation from the mean reference density. A nominal inversion with a mean density of 1300 kg/m3, yields a total range of approximately 700-1700 kg/m3. Apparent relationships between density and thickness suggest that the density variations within the SPLD are real, and may reflect spatial variations in the dust or CO2 content of the deposits.
Andrews-Hanna Jeffrey
Li Jiying
Phillips Raquel
Plaut Jeffrey J.
Sun Yadong
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