HR: 1340h
AN: P13D-1554    [Abstracts]
TI: Identification and Mapping of Olivine-Rich Basalt Bedrock Outcrops in Ganges and Eos Chasma on Mars
AU: * Edwards, C S
EM: Christopher.Edwards@asu.edu
AF: Arizona State University School of Earth and Space Exploration, Mars Space Flight Facility PO BOX 6305, Tempe, AZ 85287-6305, United States
AU: Christensen, P R
EM: Phil.Christensen@asu.edu
AF: Arizona State University School of Earth and Space Exploration, Mars Space Flight Facility PO BOX 6305, Tempe, AZ 85287-6305, United States
AU: Hamilton, V E
EM: hamilton@higp.hawaii.edu
AF: University of Hawai'i, Hawai'i Institute of Geophysics and Planetology, Honolulu, HI 96822, United States
AB: 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.
DE: 5410 Composition (1060, 3672)
DE: 5460 Physical properties of materials
DE: 5464 Remote sensing
DE: 5470 Surface materials and properties
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting