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Title: Characterization of LIBS emission lines for the identification of chlorides, carbonates, and sulfates in salt/basalt mixtures for the application to MSL ChemCam data: LIBS OF CL, C, S IN SALT-BASALT MIXTURES

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. Here, 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. The data then 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 matrixmore » 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. Our results are promising for tracking relative changes in the salt content of bulk rock on the Martian surface with ChemCam.« less
Authors:
ORCiD logo [1] ; ORCiD logo [1] ; ORCiD logo [2] ; ORCiD logo [3] ; ORCiD logo [2] ;  [1] ; ORCiD logo [2] ;  [3] ;  [3] ; ORCiD logo [2] ; ORCiD logo [4] ; ORCiD logo [5] ;  [2] ;  [3]
  1. California Inst. of Technology (CalTech), Pasadena, CA (United States)
  2. Inst. for Research in Astrophysics and Planetology (IRAP), Toulouse (France)
  3. Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
  4. Mount Holyoke College, South Hadley, MA (United States). Dept. of Astronomy
  5. German Aerospace Center (DLR), Berlin (Germany)
Publication Date:
Report Number(s):
LA-UR-17-27680
Journal ID: ISSN 2169-9097
Grant/Contract Number:
AC52-06NA25396; DGE-11444469
Type:
Accepted Manuscript
Journal Name:
Journal of Geophysical Research. Planets
Additional Journal Information:
Journal Volume: 122; Journal Issue: 4; Journal ID: ISSN 2169-9097
Publisher:
American Geophysical Union
Research Org:
Los Alamos National Lab. (LANL), Los Alamos, NM (United States)
Sponsoring Org:
National Aeronautics and Space Administration (NASA)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY; 58 GEOSCIENCES; Planetary Sciences
OSTI Identifier:
1396140