ChemCam activities and discoveries during the nominal mission of the Mars Science Laboratory in Gale crater, Mars

Abstract

At Gale crater, Mars, ChemCam acquired its first laser-induced breakdown spectroscopy (LIBS) target on Sol 13 of the landed portion of the mission (a Sol is a Mars day). Up to Sol 800, more than 188 000 LIBS spectra were acquired on more than 5800 points distributed over about 650 individual targets. We present a comprehensive review of ChemCam scientific accomplishments during that period, together with a focus on the lessons learned from the first use of LIBS in space. For data processing, we describe new tools that had to be developed to account for the uniqueness of Mars data. With regard to chemistry, we present a summary of the composition range measured on Mars for major-element oxides (SiO 2 , TiO 2 , Al 2 O 3 , FeO T , MgO, CaO, Na 2 O, K 2 O) based on various multivariate models, with associated precisions.ChemCam also observed H, and the non-metallic elements C, O, P, and S, which are usually difficult to quantify with LIBS. F and Cl are observed through their molecular lines. We discuss the most relevant LIBS lines for detection of minor and trace elements (Li, Rb, Sr, Ba, Cr, Mn, Ni, and Zn). These results were obtained thanks to comprehensive ground reference datasets, which are set to mimic the expected mineralogy and chemistry on Mars. With regard to the first use of LIBS in space, we analyze and quantify, often for the first time, each of the advantages of using stand-off LIBS in space: no sample preparation, analysis within its petrological context, dust removal, sub-millimeter scale investigation, multi-point analysis, the ability to carry out statistical surveys and whole-rock analyses, and rapid data acquisition.We conclude with a discussion of ChemCam performance to survey the geochemistry of Mars, and its valuable support of decisions about selecting where and whether to make observations with more time and resource-intensive tools in the rover's instrument suite. In the end, we present a bird's-eye view of Cite this:

Visible/near‐infrared spectral diversity from in situ observations of the Bagnold Dune Field sands in Gale Crater, Mars

“…Remote Micro-Imager (RMI) images were acquired as part of ChemCam observations, from which accurate locations for the individual points within a raster could be placed [Wiens et al, 2012[Wiens et al, , 2015Maurice et al, 2012Maurice et al, , 2016Le Mouélic et al, 2015]. Comparison to Mastcam images acquired as part of the ChemCam observations also provided context images for interpreting the passive spectra.…”

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“…LIBS is able to analyze elemental compositions of rocks and soils at distances from 1.5 to 7 m Maurice et al, 2016]. Thirty laser shots are usually performed to investigate a given point.…”

“…This RMI gives context imaging to the chemical analyses performed by LIBS [ Le Mouélic et al ., ]. By acquiring light‐induced emission, the LIBS is able to analyze elemental compositions of rocks and soils at distances from 1.5 to 7 m [ Wiens et al ., ; Maurice et al ., ]. Thirty laser shots are usually performed to investigate a given point.…”