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 similar to 20wt % carbonate (2wt % C), similar to 5-30wt % sulfate (1-8wt % S), and similar to 5-10wt % chloride (3-6wt % 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.

We report on efforts to perform theoretical modeling of the emission spectrum measured from a basalt sample. We compare our calculations with measurements that were made to provide standards for the ChemCam instrument on the Mars Science Laboratory. We find that to obtain good agreement between modeling and the measurement, it is necessary to determine atomic and ionic level populations via a multi-element approach in which the free electron density that is created influences all the species within the plasma. Calculations that consider each element separately are found to be in poorer agreement with the measured spectrum, indicating that the ‘matrix effect’ term often used to describe the influence of other species on the emission spectrum from a given element is due to the influence of the global electron density of the plasma. We explore the emission features in both the visible and near-infrared wavelength ranges, and also examine radiation transport effects for some of the most intense features found in the basalt spectrum. Finally, we also provide comparisons of the ChemCam measurement with new high-resolution spectral measurements.

FROM A MARS ANALOGUE SITE. Z. E. Gallegos 1 , H. E. Newsom 1 , A. M. Ollila 1 , N. L. Lanza 2 , R. C. Wiens 2 , S. M. Clegg 2 , R. E. McInroy 2 , G. R. Osinski 3 , P. Lee 4,5 , 1 Institute of Meteoritics, Univ. of New Mexico, Albuquerque, NM, U.S.A. (zachegallegos@gmail.com), 2 Los Alamos National Laboratory, NM, U.S.A., 3 Univ. of Western Ontario, Canada, 4 Mars Institute, 5 NASA Ames Research Center, CA, U.S.A.

Laser‐induced breakdown spectroscopy (LIBS) is an active analytical technique that makes use of a laser pulse to analyze materials of interest at a distance by creating a plasma, which emits photons at characteristic emission line wavelengths. We validate the technique for planetary exploration under vacuum conditions. We review the capability and advantages of the LIBS technique for lunar regolith analysis at 1.5 m distance from a lunar rover, and we characterize its potential for the detection of resources for future exploration, such as the determination of regolith water content. The limits of detection determined for the major elements (typically <1 wt %) help to determine regolith parent material such as feldspathic highland rocks, rocks from the ancient magmatic high magnesian suite (Mg‐suite), Fe‐rich mare basalts or potassium, rare earth element, and phosphorus‐rich (KREEP‐rich) samples. Compositional parameters commonly used to classify lunar regoliths such as TiO2, Al2O3, and K2O abundances are readily determined by LIBS. Certain elements support regolith analysis: For example, Ba and Zr can be used to confirm KREEP‐like composition, while quantifying the Ni and Co content can be used to infer the amount of meteoritic material. Finally, it is shown that the ice content of lunar soil produces strong H emissions with the LIBS techniques at the 25 wt % H2O level, while measurements on altered basalts give a limit of detection of about 1 wt % for H2O content. This demonstrates that the 5.6 wt % water content detected by the recent LCROSS experiment should be easily detectable and quantifiable by LIBS analysis.

Introduction: Spectral data from orbit indicate that phyllosilicates are widespread on Mars, including smectites (with a range of compositions from aluminous to Fe,Mg-rich), kaolin group minerals, chlorites, serpentine, and illite/muscovite [1, 2, 3]. This broad range of detected phyllosilicates indicates a variety of formation conditions and hence the importance of phyllosilicate mineralogy in petrogenetic interpretations for Mars. Many phyllosilicate-depositing systems, especially those associated with lower-temperature aqueous systems, are likely targets for study of potential habitable environments on Mars; all four candidate sites for the 2011 Mars Science Laboratory (MSL) contain claymineral associations of primary interest in this regard [4]. Our goal in this study was to evaluate the operation of Laser Induced Breakdown Spectroscopy (LIBS), as carried on the ChemCam instrument for MSL, against a range of phyllosilicates to define operational parameters and possibilities for characterization. LIBS involves generating a plasma by focusing a high power laser onto the sample surface. The plasma contains electronically excited atoms, ions and small molecules that emit light as they relax to lower electronic states. This emission is collected and used to quantitatively determine the elemental composition and sample identification. Samples: Clay powder samples used in these experiments were NIST chemical standard 97b and Clay Minerals Society (CMS) source clays KGa-2, PFl-1, SHCa1, STx-1b and SWy-2. Table 1 contains XRD determinations of mineralogy for these 6 clay samples. Rock powder samples from the Brammer catalog of standards were also selected as chemical reference materials. The geologic standards were basalts (BCR2, BHVO-2, BIR-1, GBW 07105, GUWBM, MO-14), dolomites (JDo-1, GBW 07217a), andesites (JA-1, JA-

Introduction: The ChemCam instrument, selected for the Mars Science Rover, includes a remote laserinduced breakdown spectroscopy (LIBS) instrument that will probe samples up to 9 m from the mast [1, 2, 3]. The LIBS technique focuses a high-powered laser onto a sample thereby generating a plasma on the surface which contains electronically excited species. The excited species emit photons at wavelengths characteristic of the elements present in the sample. Some of the emitted photons are collected and recorded by the ChemCam spectrometers. Because of the ablating nature of the technique, it can also remotely remove, with multiple laser shots, dust and/or rind from targeted rocks. This technique has been shown to be enhanced by Mars surface conditions [4, 5]. The focus of this paper is the development of a LIBS elemental spectral library under ChemCam’s 7 m operating conditions. Geologic samples measured using the LIBS technique yield complex spectra, rich with elemental emissions such as the spectrum of basalt GBW 07015 in Figure 1. Interpretation of such spectra is complicated by chemical matrix effects and depends on the incident optical flux [W/cm]. To facilitate elemental identification in data returned by ChemCam, a spectral library is being assembled of simple molecular forms (oxides, chlorides, etc) of elements likely to be encountered during the mission. Table 1 contains a list of the samples probed thus far under ChemCam experimental conditions. The resulting spectra are simpler than those from geologic samples and the elemental emission lines are much easier to assign. Experimental Setup: The experiment involves a laboratory simulation of the ChemCam instrument. An Nd:YAG laser operating at 1064 nm and generating 17 +/-1 mJ of energy per pulse was focused on the samples with a 250 μm diameter (FWHM) spot size. This is compared to the 15 20 mJ and 300 μm spot size of ChemCam [6] Samples were placed in a chamber filled with 7 Torr CO2 to simulate the Martian surface pressure. Optical emissions from the ablated samples were collected using an 89 mm diameter telescope, which is smaller than the 110 mm diameter ChemCam telescope [6]. An optical demultiplexer, similar to the one on ChemCam, was used to split the collected light onto three spectral channels. Three commercial Ocean Optics HR 2000 spectrometers were used which cover 223.40-325.97 nm (UV), 381.86-471.03 nm (VIS) and 494.93-927.06 nm (VNIR) spectral regions. SpecTable 1: Analyzed samples (> 99.9% pure), in atomic order, with Chemical Abstracts Service (CAS) registry number and molecular form. Element CAS Formula Form Hydrogen 129-00-0 C16H10 powder Lithium 7447-48-8 LiCl powder Boron 1303-86-2 B2O3 powder Carbon 129-00-0 C16H10 powder Oxygen various Sodium 7647-14-5 NaCl powder Magnesium 7439-95-4 Mg metal Aluminum 1344-28-1 Al2O3 powder Silicon 7831.86-9 SiO2 powder Phosphorus 7723-14-0 P powder Sulfur 10544-50-0 S8 powder Chlorine various Potassium 7447-40-7 KCl powder Calcium 10043-52-4 CaCl2 powder Titanium 7440-32-6 Ti plate Chromium 10025-73-7 CrCl powder Manganese 1317-34-6 Mn2O3 powder Iron 1309-37-1 Fe2O3 powder Nickel 1313-99-1 NiO powder Copper 1317-38-0 CuO foil Zinc 7440-66-6 Zn powder Rubidium 7991.11.9 RbCl powder Strontium 1633-05-2 SrCO3 powder Barium 1304-28-5 BaO2 powder Lead 7439-92-1 Pb powder