Mathematics – Logic
Scientific paper
Dec 2011
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2011agufm.p33c1777w&link_type=abstract
American Geophysical Union, Fall Meeting 2011, abstract #P33C-1777
Mathematics
Logic
[5470] Planetary Sciences: Solid Surface Planets / Surface Materials And Properties, [6225] Planetary Sciences: Solar System Objects / Mars
Scientific paper
The MSL rover, Curiosity, uses a novel remote-sensing instrument, ChemCam, which combines laser-induced breakdown spectroscopy (LIBS) with a high resolution remote micro-imager (RMI). ChemCam uses a focused, pulsed laser beam at targets up to 7 m away to excite a light-emitting plasma. Spectral analysis identifies elements present and provides rapid semi-quantitative analyses. Repeated laser pulses remove dust and weathering coatings from rock samples to depths >0.5 mm and ~0.4 mm in diameter. The RMI, with ~20x20 mrad field of view, provides a broad-band image with 100 μm resolution. LIBS yields abundances of H, Li, Be, B, C, N, O, F, Na, Mg, Al, Si, P, Cl, K, Ca, Ti, V, Cr, Fe, Ni, Zr, Rb, Sr, As, Ba, and Pb. Interference from atmospheric constituents raises the detection limits of C, N, and O (e.g., >2% wt for C). LIBS is very sensitive to alkali and alkali earth elements, with some detection limits to ~1 ppm at close range. Conversely, LIBS is insensitive to F, Cl, S, P, and N, with detection limits of several wt. %. Pointing accuracy is ~3 mrad, however relative pointing accuracy is better, so line scans and rasters will enable analyses of targeted features to ~1 mm. At Gale Crater, determination of elements not previously analyzed in-situ, i.e., H, Li, Rb, Sr, and Ba, along with other elements will constrain aqueous, hydrothermal and vapor geochemical transport processes. Initial analyses after landing will characterize air fall dust and weathering coatings on local rocks, and profile the soil and surfacial materials including bedforms to investigate compositional differences in near-surface layers. Targets within the landing ellipse include fan and inverted channel deposits derived from the crater rim, which may contain alteration minerals produced by impact hydrothermal processes. Enigmatic deposits with bright fracture fill could represent lake sediments modified by injection of deposits from groundwater. During the drive to the Gale mound, ChemCam will provide daily assays of soil composition and morphology, looking for changes en route. A scarp defining the boundary between low and high thermal inertia regions in the ellipse will be another target. Small craters may expose the stratigraphy of the fan. Near the mound ChemCam will study the transition from the fan to the basal unit of the mound to determine whether it contains lithified bedforms. What is the cementing material and what can we learn about the temperature history or depth of burial? At the mound, ChemCam will study chemostratigraphy, correlating elemental compositions against textural fabrics and cross-bedding geometries, and assessing the petrographic heterogeneity of sedimentary and/or diagenetic grains. ChemCam will also investigate questions such as: What are the hydration states of phyllosilicates and salts, including diurnal variability? What fraction of the material is phyllosilicates and how are they distributed? What characterizes the transition from phyllosilicates to sulfates? ChemCam will play a key role in unraveling the geologic history recorded in Gale Crater.
Barraclough Bruce L.
Blaney Diana L.
Bridges Nathan T.
Clark Ben C.
Clegg Samuel M.
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