Physics
Scientific paper
Dec 2007
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2007agufm.p13d1554e&link_type=abstract
American Geophysical Union, Fall Meeting 2007, abstract #P13D-1554
Physics
5410 Composition (1060, 3672), 5460 Physical Properties Of Materials, 5464 Remote Sensing, 5470 Surface Materials And Properties
Scientific paper
An extensive olivine-rich basalt unit has been identified and mapped in Ganges and Eos Chasma on Mars using Thermal Emission Imaging System (THEMIS) and Thermal Emission Spectrometer (TES) data. A 100 m/pixel THEMIS decorrelation stretch mosaic was created using bands 8, 7, and 5 (11.79 μm, 11.04 μm, and 9.35 μm respectively) as the olivine-rich unit has a deep absorption in THEMIS band 7 data. These outcrops were mapped spatially using this mosaic and were found to extend for more than 1,100 km in length. In addition to the THEMIS data, TES data were used to constrain the composition and abundance of the olivine. By using spectral ratios of the unit and of the surrounding canyon floor material, it is possible to determine that the olivine abundance of this unit is ~10-15% and its composition is estimated to have a Mg/(Mg+Fe) ratio of ~68. In addition to compositional data, this unit has been characterized using elevation data from the Mars Orbiter Laser Altimeter (MOLA). By using MOLA elevation data in conjunction with the compositional data, constraints on the continuity, extent, dip, and orientation of this layer can be made. These data indicate that this unit lies on a nearly uniform surface, dipping slightly (~0.013 degrees) to the northeast. They also indicate that it persists through topographically high areas and outcrops only in predicted locations. Estimates of the thickness of this unit were made utilizing MOLA data, with thickness ranging from ~40 m to ~110 m, illustrating that this layer is thin in comparison to the ~4.5 km of overlying material. High-resolution imagery from the Mars Orbiter Camera and the High Resolution Imaging Science Experiment provide insights into the small-scale morphologies associated with these outcrops, which appear rough, pitted, and largely unmantled with a slightly higher albedo than the surrounding materials. These observations are consistent with THEMIS thermal inertia for an in place rocky unit, with values of >~300-600 JK-1m-2s-1/2. One of the largest in situ, stratigraphic layers identified on Mars has been mapped and characterized using a variety datasets. Several possible emplacement mechanisms for this unit include a basaltic sill, a rifting event, or more likely large flood lavas or a volcaniclastic deposit.
Christensen Per Rex
Edwards Christopher S.
Hamilton Victoria E.
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