HR: 1340h
AN: P13D-1557    [Abstracts]
TI: Geologic context and characteristics of bedrock exposures in Mare Serpentis: Implications for martian surface evolution
AU: * Rogers, A
EM: adrogers@notes.cc.sunysb.edu
AF: Stony Brook University, 255 Earth and Space Sciences Bldg, Stony Brook, NY 11794-2100, United States
AU: Aharonson, O
EM: oa@gps.caltech.edu
AF: California Institute of Technology, MC 150-21, Pasadena, CA 91101, United States
AU: Bandfield, J L
EM: joshband@asu.edu
AF: Arizona State University, Campus Box 6305, Tempe, AZ 85287-6305, United States
AB: Examining the spatial and stratigraphic relationships, geologic context, and composition of martian surface units contributes to our understanding of martian surface processes, as well as to the reconstruction of geologic history for a given region. Here we report observations on exposures of bedrock and/or blocky materials (hereafter, "high-TI" units) that have been identified in the low-albedo region of Mare Serpentis, Mars. These units occur in intercrater plains as well as crater floors, and exhibit THEMIS-derived thermal inertia values ranging from ~550 to >1200 J m-2K-1s-1/2. They are compositionally distinct from surrounding low TI plains and crater ejecta, with higher pyroxene abundance, and lower plagioclase abundance, than the surrounding plains. Additionally, a few of the high-TI exposures do not appear spectrally-uniform; rather, they exhibit isolated areas of less mafic, lighter-toned material; these unique areas are smaller than can be resolved in TES or OMEGA data. The high-TI exposures commonly superpose the ejecta from large diameter (>40 km) craters, indicating that they are younger than the earliest martian crust in this region. Stratigraphic relationships observed in high- resolution imagery are not clear. In some areas, it appears that plains materials have been transported across the margins of the high-TI units, whereas in others, erosion has removed some of the plains sediment leaving the margin of the high-TI unit apparently overlying the plains. Possible geologic scenarios for the formation of these compositionally distinct materials, and for their relationship to the surrounding plains, are currently being investigated. For example, the low inertia plains materials might be related to the high-TI units through a chemical or physical weathering process. Alternatively, the high-TI units may be unrelated to the surrounding plains, potentially implying a volcanic origin. Evidence for and against each scenario will be presented. Determining the true relationship between these materials may have implications for surface evolution processes here and elsewhere on Mars.
DE: 5410 Composition (1060, 3672)
DE: 5460 Physical properties of materials
DE: 5464 Remote sensing
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting