Mathematics – Logic
Scientific paper
Dec 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009agufm.p31d..07c&link_type=abstract
American Geophysical Union, Fall Meeting 2009, abstract #P31D-07
Mathematics
Logic
[1060] Geochemistry / Planetary Geochemistry, [5494] Planetary Sciences: Solid Surface Planets / Instruments And Techniques, [6295] Planetary Sciences: Solar System Objects / Venus
Scientific paper
The extreme Venus surface temperature (740 K) and atmospheric pressure (93 atm) creates a challenging environment for future lander missions. Scientific investigations capable of Venus geochemical observations must be completed within several hours of landing before the lander is overcome by the harsh atmosphere. A combined remote Raman - LIBS (Laser Induced Breakdown Spectroscopy) instrument is capable of accomplishing 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] have 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 LIBS and demonstrate the quantitative analysis under Venus surface conditions. The LIBS experiment involves focusing a Nd:YAG laser operating at 1064 nm onto the surface of the sample. The laser ablates material from the surface, generating a plasma containing electronically excited atoms, ions and small molecules. Some of this emission is collected with an 89 mm diameter telescope. The light is directed into a Princeton Instruments f/4 0.25 m dispersive spectrometer and recorded with an ICCD detector. The powdered and pelletized samples are placed in a pressure vessel containing supercritical CO2 at 93 atm and at least 423 K and the vessel is placed at least 1.6 m from the telescope and laser. A range of Venus-analog basaltic rock types [3] was chosen for this study to reproduce compositions identified by Soviet Venera and VEGA landers, including several standards: four basalts (BCR-2, BIR-1, GUWBM, JB-2), granite (GBW 07015), andesite (JA-1), carbonate (SARM-40), and Kauai volcanic (KV04-17, KV04-25). We also added a good Venus analog, TAP 04, which is an alkali-rich rock from an olivine minette in the Ayutla volcanic field (Righter and Rosas-Elguera [4]). Our goal was to study samples with a range of abundances for each element of interest so as to optimize the efficacy of the resultant calibration for predicting a range of compositions. Peaks for all required major, minor, and trace elements were well above the noise floor and readily detected. Peak intensities and areas were then used to quantify elemental chemistry. 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. PLS analysis demonstrates that the major element compositions of rock powders acquired at 93 atm/423 K can be determined with better than 10% accuracy and precision. [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, AT Basilevsky, VP Volkov, and VW Zharkov). Univ. Arizona Press, pp. 165-176. [4] Righter K. and Rosas-Elguera J. (2001) J. Petrol. 42, 2333.
Barefield James E.
Clegg Samuel M.
Darby Dyar M.
Humphries Stephen
Misra Anupam K.
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