Mathematics – Logic
Scientific paper
Dec 2006
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2006agufm.p23c0068j&link_type=abstract
American Geophysical Union, Fall Meeting 2006, abstract #P23C-0068
Mathematics
Logic
3934 Optical, Infrared, And Raman Spectroscopy, 3944 Shock Wave Experiments, 5420 Impact Phenomena, Cratering (6022, 8136), 5464 Remote Sensing, 6225 Mars
Scientific paper
Laboratory spectra of experimentally shocked feldspars (anorthosite and albitite rocks) were included in spectral deconvolutions of thermal infrared data acquired from the Thermal Emission Spectrometer (TES) on Mars Global Surveyor. This work expands on previous investigations in Cimmeria Terra in which model results suggested that exposures of shocked feldspars were not necessarily restricted to regions near morphologically fresh impact craters (Johnson et al., Icarus, 180, 60-74, 2006). We used a multiple endmember spectral mixing algorithm (MESMA) to model global TES emissivity data sets at 1 pixel/degree (ppd) resolution (Bandfield, JGR, 107, 2001JE001510, 2002). TES data were restricted to surface temperatures >250 K, atmospheric dust opacities < 0.30, water ice opacities < 0.15, and emission angles < 30 degrees. Data marked with anomalies (e.g., phase inversions) were not used. The emissivity data were further constrained to exclude pixels with TES bolometric albedo values > 0.24 (a proxy for regions with abundant dust cover). MESMA deconvolutions using spectral endmember libraries containing typical minerals and glasses plus atmospheric endmembers (CO2, dust, water ice) were supplemented by separate model runs that incorporated intermediate and highly shocked feldspar spectra (27 GPa, 56 GPa). In the latter models, final results were constrained by selecting only those pixels modeled with > 33% combined surface minerals (i.e., < 67% modeled atmospheric contribution to the TES signal), as well as > 10% shocked feldspar abundances. Models also were constrained to exhibit model root-mean-square errors < 0.0045 that also improved upon inclusion of shocked feldspar spectra. Preliminary results suggest that spatially contiguous regions of shocked feldspars are found in four main regions: Solis Planum, Acidalia Planitia, Syrtis Major Planum, and northern Utopia Planitia. Subsequent work will involve detailed analyses of these regions using higher resolution TES global data sets from Bandfield (2002) (2, 4 ppd) as well as full-resolution TES data for specific regions. In addition, deconvolutions using shocked basalt and basaltic andesite rock spectra will be run separately to compare their spatial distributions to those of shocked feldspars.
Byrnes Jeffrey M.
Johnson Jay Robert
Staid Matthew I.
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