Physics
Scientific paper
Dec 2002
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2002agufm.p72a0485j&link_type=abstract
American Geophysical Union, Fall Meeting 2002, abstract #P72A-0485
Physics
3934 Optical, Infrared, And Raman Spectroscopy, 3944 Shock Wave Experiments, 5420 Impact Phenomena (Includes Cratering), 5464 Remote Sensing, 6225 Mars
Scientific paper
We have acquired thermal infrared (3-40 microns) hemispherical reflectance and emissivity spectra of shocked samples of a fine-grained (1-5 mm) albitite from Szklary, Poland to determine the spectral degradation effects of shocked albite as a function of increasing shock pressures (17-56 GPa). Reflectance data were acquired using a Nicolet 5SXC FTIR spectrometer at the HIGP, University of Hawaii, and emission spectra were acquired using a Nicolet Nexus 670 emission spectrometer at Arizona State University. These data complement similar previous measurements of experimentally shocked anorthosite relevant to interpreting spectra provided by the Thermal Emission Spectrometer (TES) on Mars Global Surveyor. The samples were shocked using the 25-mm barrel gun at Johnson Space Center and provided ~400 mg per sample. Large (2-10 mm) chips of recovered material were separated from the samples and washed to remove clinging fines, and the residual was powdered to provide a consistent grain size (~20 microns). Spectra were obtained of both the chips and the powder samples. Results for the chips show a progressive loss of spectral features and contrast compared to unshocked samples, while results for the powders show a reduction in the depth of the transparency feature located near 855 wavenumbers (11.7 microns) with increasing pressure. The albite structure retains its crystalline state to higher pressures than anorthosites, consistent with previous transmission spectra. Additional visible/near-infrared (0.35-2.50 microns) measurements of the powdered albitite and anorthosite samples also were acquired at the RELAB facility. These spectra show a decrease in albedo and a loss of water bands near 1.4 and 1.9 microns with increasing pressure. The broad feldspar absorption near 1.25 microns was not present in the albitite sample (possibly due to its fine original grain size) but was present in the anorthosite sample, where its band depth decreased with increasing shock pressures.
Christensen Paul
Hörz Fred
Johnson Jay Robert
Lucey Paul
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