Characterization of LIBS emission lines for the identification of chlorides, carbonates, and sulfates in salt/basalt mixtures for the application to MSL ChemCam data. Issue 4 (24th April 2017)

• Record Type: Journal Article
• Authors: Anderson, D. E.; Ehlmann, B. L.; Forni, O.; Clegg, S. M.; Cousin, A.; Thomas, N. H.; Lasue, J.; Delapp, D. M.; McInroy, R. E.; Gasnault, O.; Dyar, M. D.; Schröder, S.; Maurice, S.; Wiens, R. C.
• Is Part Of: Journal of geophysical research. Volume 122:Issue 4(2017)
• Page Start: 744
• Page End: 770
• Publication Date: 2017-04-24
• Subjects: LIBS spectroscopy -- carbon -- chlorine -- sulfur -- salts -- Mars Science Laboratory; Planets -- Periodicals; Geophysics -- Periodicals; 559.9
• DOI: 10.1002/2016JE005164
• Languages: English
• ISSNs: 2169-9097

Abstract

Abstract: Ancient environmental conditions on Mars can be probed through the identification of minerals on its surface, including water‐deposited salts and cements dispersed in the pore space of sedimentary rocks. Laser‐induced breakdown spectroscopy (LIBS) analyses by the Martian rover Curiosity's ChemCam instrument can indicate salts, and ChemCam surveys aid in identifying and selecting sites for further, detailed in situ analyses. We performed laboratory LIBS experiments under simulated Mars conditions with a ChemCam‐like instrument on a series of mixtures containing increasing concentrations of salt in a basaltic background to investigate the potential for identifying and quantifying chloride, carbonate, and sulfate salts found only in small amounts, dispersed in bulk rock with ChemCam, rather than concentrated in veins. Data indicate that the presence of emission lines from the basalt matrix limited the number of Cl, C, and S emission lines found to be useful for quantitative analysis; nevertheless, several lines with intensities sensitive to salt concentration were identified. Detection limits for the elements based on individual emission lines ranged from ~20 wt % carbonate (2 wt % C), ~5–30 wt % sulfate (1–8 wt % S), and ~5–10 wt % chloride (3–6 wt % Cl) depending on the basaltic matrix and/or salt cation. Absolute quantification of Cl, C, and S in the samples via univariate analysis depends on the cation‐anion pairing in the salt but appears relatively independent of matrices tested, following normalization. These results are promising for tracking relative changes in the salt content of bulk rock on the Martian surface with ChemCam. Key Points: Chlorine, carbon, and sulfur LIBS emission lines suited for identification and quantification of salts in a basaltic matrix were identified Above the measured detection limits, relative changes in salt content were observed with LIBS through univariate analysis Results are applicable to the investigation of salts dispersed in basaltic rock on the Martian surface with ChemCam and future instruments