Mathematics – Logic
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010agufm.p44a..07c&link_type=abstract
American Geophysical Union, Fall Meeting 2010, abstract #P44A-07
Mathematics
Logic
[1000] Geochemistry, [1094] Geochemistry / Instruments And Techniques, [6295] Planetary Sciences: Solar System Objects / Venus
Scientific paper
The extreme Venus surface temperatures (~740 K) and atmospheric pressures (~93 atm) create a challenging environment for surface missions. Scientific investigations capable of Venus geochemical observations must be completed within hours of landing before the lander will be overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing the geochemical science goals without the risks associated with collecting samples and bringing them into the lander. Wiens et al. [1] and Sharma et al. [2] demonstrated that both analytical techniques can be integrated into a single instrument capable of planetary missions. The focus of this paper is to explore the capability to probe geologic samples with Raman - LIBS and demonstrate quantitative analysis under Venus surface conditions. Raman and LIBS are highly complementary analytical techniques capable of detecting both the mineralogical and geochemical composition of Venus surface materials. These techniques have the potential to profoundly increase our knowledge of the Venus surface composition, which is currently limited to geochemical data from Soviet Venera and VEGA landers that collectively suggest a surface composition that is primarily tholeiitic basaltic [3] with some potentially more evolved compositions and, in some locations, K-rich trachyandesite. These landers were not equipped to probe the surface mineralogy as can be accomplished with Raman spectroscopy. Based on the observed compositional differences and recognizing the imprecise nature of the existing data, 15 samples were chosen to constitute a Venus-analog suite for this study, including five basalts, two each of andesites, dacites, and sulfates, and single samples of a foidite, trachy-andesite, rhyolite, and basaltic trachyandesite under Venus conditions. LIBS data reduction involved generating a partial least squares (PLS) model with a subset of the rock powder standards to quantitatively determine the major elemental abundance of the remaining samples [4]. PLS analysis suggests that the major element compositions can be determined with root mean square errors ca. 5% (absolute) for SiO2, Al2O3, Fe2O3(total), MgO, and CaO, and ca. 2% or less for TiO2, Cr2O3, MnO, K2O, and Na2O. Finally, the Raman experiments have been conducted under supercritical CO2 involving single-mineral and mixed-mineral samples containing talc, olivine, pyroxenes, feldspars, anhydrite, barite, and siderite. The Raman data have shown that the individual minerals can easily be identified individually or in mixtures. [1] Wiens R.C., et al. (2005) Spect. Acta A 61, 2324; [2] Sharma, S. K. et al. (2007) Spect. Acta A, 68 , 1036 (2007); [3] Barsukov VL (1992) Venusian Igneous Rocks. In Venus Geology, Geochemistry, and Geophysics (eds. VL Barsukov et al.). Univ. Arizona Press, pp. 165-176. [4] Tucker, J.M. et al. (2010) Chem. Geol., in press.
Barefield James E.
Clegg Samuel M.
Darby Dyar M.
Humphries Stephen
Misra Anupam K.
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