Physics
Scientific paper
Dec 2005
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2005agufm.p21c0166m&link_type=abstract
American Geophysical Union, Fall Meeting 2005, abstract #P21C-0166
Physics
5464 Remote Sensing, 5470 Surface Materials And Properties
Scientific paper
The southern margin of Isidis Planitia, one of the four large impact basins on Mars, shows some of the highest values of thermal inertia (>600 J m-2 K-1 s-1/2) on the surface, yet there is no obvious reason for the presence of these high values. We investigated possible mechanisms responsible for the high values of thermal inertia by comparing thermal inertia data, derived from the Thermal Emission Spectrometer (TES) onboard the Mars Global Surveyor (MGS) spacecraft and Thermal Emission Imaging Spectrometer (THEMIS) onboard the Mars Odyssey spacecraft, to a variety of complementary data sets, including albedo and radar data. We also investigated possible processes controlling the distribution of thermal inertia within the Isidis Basin by comparing the thermal inertia data to topographic and visible data and results from mesoscale atmospheric simulations using the Mars Regional Atmospheric Modeling System (MRAMS). The four mechanisms we considered for creating the high thermal inertia were (1) thinning of a dust mantle, (2) unconsolidated, coarse grained material, (3) high rock abundance, and (4) high degree of induration. The albedo and thermal inertia data from TES are inconsistent with a surface dominated by a dust mantle. An unconsolidated material alone cannot achieve the higher values of thermal inertia present in the basin (>500 J m-2 K-1 s-1/2). Comparisons between the radar and thermal inertia data indicate there is no correlation between the thermal inertia and density of the surface, but complications in the radar data do not allow us to completely rule out the possibility that rocks are contributing to the high values of thermal inertia. However, the distribution of thermal inertia in the basin is inconsistent with the pattern of rocks if the rocks were deposited by mass-wasting processes from the rim of the basin, as was suggested by Bridges et al. (2003). An indurated surface is consistent with the thermal inertia, albedo, and radar data and so we conclude the surface of Isidis is most likely an indurated surface and that the regions of high thermal inertia are areas showing a greater degree of induration. We investigated three processes possibly controlling the geographical distribution of thermal inertia, including (1) the influence of topography, (2) mantling by material related to the knobby terrain in the basin, and (3) aeolian scouring of the surface. The comparison of MOLA topography and the thermal data suggest that topography heavily influences the distribution of thermal inertia at the base of the southern rim, but that there is no such influence in the northern reaches of the regions of high thermal inertia. Rings of lower thermal inertia are present in THEMIS data surrounding the conical features that characterize the knobby terrain in the basin and processes related to these features may have mantled a terrain of high thermal that is now only present where the conical features are absent in the basin. Based on the wind patterns modeled by MRAMS, aeolian activity has played a significant role in creating the current distribution of high thermal inertia regions in Isidis. The MRAMS results indicate that winds occurring under non-nominal atmospheric conditions, such as during dust storms or a previous wind regime, may have scoured the areas now showing high thermal inertia. References: Bridges, J. C., et al. (2003), JGR, 108.
Jakosky Bruce M.
Larsen Kristopher William
Mellon Michael T.
Murphy Nathaniel W.
Putzig Nathaniel E.
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