Abstract
The ChemCam instrument on the Mars Science Laboratory rover Curiosity will use laser-induced breakdown spectroscopy (LIBS) to analyze major and minor element chemistry from sub-millimeter spot sizes, at ranges of ∼1.5–7 m. To interpret the emission spectra obtained, ten calibration standards will be carried on the rover deck. Graphite, Ti metal, and four glasses of igneous composition provide primary, homogeneous calibration targets for the laser. Four granular ceramic targets have been added to provide compositions closer to soils and sedimentary materials like those expected at the Gale Crater field site on Mars. Components used in making these ceramics include basalt, evaporite, and phyllosilicate materials that approximate the chemical compositions of detrital and authigenic constituents of clastic and evaporite sediments, including the elevated sulfate contents present in many Mars sediments and soils. Powdered components were sintered at low temperature (800 °C) with a small amount (9 wt.%) of lithium tetraborate flux to produce ceramics that retain volatile sulfur yet are durable enough for the mission. The ceramic targets are more heterogeneous than the pure element and homogenous glass standards but they provide standards with compositions more similar to the sedimentary rocks that will be Curiosity’s prime targets at Gale Crater.
Highlights
Mars Science Laboratory (MSL) will begin operations on Mars in the summer of 2012
We describe the preparation and properties of the ceramic targets for ChemCam that will be carried on Curiosity, along with complementary data for the ChemCam shergottite glass standard that is described in Fabre et al (2011)
The aluminous ceramic composition was selected in part for the candidate MSL site at Mawrth Vallis, where abundant aluminous clay minerals are identified from orbit, but such compositions might occur at all of the original candidate sites and the added range in composition is useful for calibration in general
Summary
Mars Science Laboratory (MSL) will begin operations on Mars in the summer of 2012. The MSL mission’s highly-capable rover (Curiosity) will carry ten instruments, four of which will provide chemical data. These issues were common to all of the candidate MSL field sites at the time that calibration targets for ChemCam had to be prepared, but of all candidate sites the Gale Crater location has the most extensive and complex sulfate story. The ceramic targets are similar in chemical composition to an evaporite with mafic silicate detritus and clay minerals As such the ceramics provide a closer chemical approximation of regolith and sediments expected at Gale Crater, they have inherent heterogeneity due to their granular nature. In addition to providing igneous calibration targets, the ChemCam team created additional ceramic targets that include Mars-like clay minerals (nontronite and kaolinite) as well as a sulfate. All the on-board targets will be used in combination with data acquired with ChemCam before launch, as well as data from Curiosity’s other instruments, to examine elemental concentrations in Mars surface materials
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