HR: 0830h
AN: P21B-0053    [PDF]
TI: Thermal Infrared Spectra of Experimentally Shocked Basalt
AU: * Johnson, J R
EM: jrjohnson@usgs.gov
AF: U.S. Geological Survey, 2255 N. Gemini Dr., Flagstaff, AZ 86001 United States
AU: Horz, F
AF: Johnson Space Center, SN 2 NASA, Houston, TX 77058 United States
AB: We acquired thermal infrared (3-40 microns) emissivity and hemispherical reflectance spectra of experimentally shocked samples of a fine-grained basalt from Grand Falls, AZ to document the spectral effects of shock as a function of increasing shock pressures (17-57 GPa). This sample contains 25% pyroxene, 20% olivine, and 45% feldspar, making it a suitable analog to the Surface Type 1 (basalt) observed in Thermal Emission Spectrometer (TES) data of Mars. Reflectance data (3-14 microns) were acquired using a Nexus 470 FTIR spectrometer at the HIGP, University of Hawaii, and emission spectra (5-40 microns) were acquired using a Nicolet Nexus 670 emission spectrometer at Arizona State University. These data complement similar previous measurements of experimentally shocked plagioclase and pyroxene relevant to interpreting spectra provided by TES. 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 ($\sim$20 microns). Spectra were obtained of both the chips and the powder samples. Results for the chips show a shift in band positions in the 900-1200 wavenumber (wn) region compared to unshocked samples, consistent with the structural degradation of feldspar and subsequent formation of maskelynite and glass. The development of a band near 460 wn at high pressures is also consistent with glass formation in feldspars. Conversely, absorptions related to pyroxene remain present even at high pressures, consistent with previous work. Results for the powders show little variations with increasing pressure except for the loss of minor transparency features in the 800-900 wn region. Additional visible/near-infrared (0.35-2.50 microns) measurements of the powdered basalt samples also will be acquired at the RELAB facility. Future work will include acquisition of thermal infrared and visible/near-infrared spectra of shocked basaltic andesite from SP Flow, AZ. Acknowledgments: The authors thank P. Christensen (ASU), and P. Lucey and V. Hamilton (UH) for assistance with spectra acquisition.
DE: 3934 Optical, infrared, and Raman spectroscopy
DE: 3944 Shock wave experiments
DE: 5420 Impact phenomena (includes cratering)
DE: 5464 Remote sensing
DE: 6225 Mars
SC: Planetary Sciences [P]
MN: 2003 Fall Meeting