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      Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars

      1 , 2 , 1 , 1 , 3 , 1 , 3 , 1 , 4 , 5 , 6 , 7 , 1 , 8 , 9 , 1 , 6 , 10 , 1 , 11 , 1 , 12 , 13 , 9 , 14 , 1 , 8 , 15 , 16 , 1 , 17 , 1 , 18 , 19 , 20 , 1 , 21 , 22 , 1 , 1 , 12 , 23 , 1 , 24 , 7 , 25

      Journal of Geophysical Research. Planets

      John Wiley & Sons, Ltd

      organic molecules, chlorobenzene, MSL, Mars, SAM, oxychlorine

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          The Sample Analysis at Mars (SAM) instrument on board the Mars Science Laboratory Curiosity rover is designed to conduct inorganic and organic chemical analyses of the atmosphere and the surface regolith and rocks to help evaluate the past and present habitability potential of Mars at Gale Crater. Central to this task is the development of an inventory of any organic molecules present to elucidate processes associated with their origin, diagenesis, concentration, and long-term preservation. This will guide the future search for biosignatures. Here we report the definitive identification of chlorobenzene (150–300 parts per billion by weight (ppbw)) and C 2 to C 4 dichloroalkanes (up to 70 ppbw) with the SAM gas chromatograph mass spectrometer (GCMS) and detection of chlorobenzene in the direct evolved gas analysis (EGA) mode, in multiple portions of the fines from the Cumberland drill hole in the Sheepbed mudstone at Yellowknife Bay. When combined with GCMS and EGA data from multiple scooped and drilled samples, blank runs, and supporting laboratory analog studies, the elevated levels of chlorobenzene and the dichloroalkanes cannot be solely explained by instrument background sources known to be present in SAM. We conclude that these chlorinated hydrocarbons are the reaction products of Martian chlorine and organic carbon derived from Martian sources (e.g., igneous, hydrothermal, atmospheric, or biological) or exogenous sources such as meteorites, comets, or interplanetary dust particles.

          Key Points

          • First in situ evidence of nonterrestrial organics in Martian surface sediments

          • Chlorinated hydrocarbons identified in the Sheepbed mudstone by SAM

          • Organics preserved in sample exposed to ionizing radiation and oxidative condition

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          Most cited references 34

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          A habitable fluvio-lacustrine environment at Yellowknife Bay, Gale crater, Mars.

          The Curiosity rover discovered fine-grained sedimentary rocks, which are inferred to represent an ancient lake and preserve evidence of an environment that would have been suited to support a martian biosphere founded on chemolithoautotrophy. This aqueous environment was characterized by neutral pH, low salinity, and variable redox states of both iron and sulfur species. Carbon, hydrogen, oxygen, sulfur, nitrogen, and phosphorus were measured directly as key biogenic elements; by inference, phosphorus is assumed to have been available. The environment probably had a minimum duration of hundreds to tens of thousands of years. These results highlight the biological viability of fluvial-lacustrine environments in the post-Noachian history of Mars.
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            Detection of perchlorate and the soluble chemistry of martian soil at the Phoenix lander site.

            The Wet Chemistry Laboratory on the Phoenix Mars Lander performed aqueous chemical analyses of martian soil from the polygon-patterned northern plains of the Vastitas Borealis. The solutions contained approximately 10 mM of dissolved salts with 0.4 to 0.6% perchlorate (ClO4) by mass leached from each sample. The remaining anions included small concentrations of chloride, bicarbonate, and possibly sulfate. Cations were dominated by Mg2+ and Na+, with small contributions from K+ and Ca2+. A moderately alkaline pH of 7.7 +/- 0.5 was measured, consistent with a carbonate-buffered solution. Samples analyzed from the surface and the excavated boundary of the approximately 5-centimeter-deep ice table showed no significant difference in soluble chemistry.
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              Mars Science Laboratory Mission and Science Investigation


                Author and article information

                J Geophys Res Planets
                J Geophys Res Planets
                Journal of Geophysical Research. Planets
                John Wiley & Sons, Ltd (Chichester, UK )
                March 2015
                21 March 2015
                : 120
                : 3
                : 495-514
                [1 ]Solar System Exploration Division, NASA Goddard Space Flight Center Greenbelt, Maryland, USA
                [2 ]NASA Postdoctoral Program, Oak Ridge Associated Universities Oak Ridge, Tennessee, USA
                [3 ]Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology Cambridge, Massachusetts, USA
                [4 ]Center for Research and Exploration in Space Science & Technology, University of Maryland College Park, Maryland, USA
                [5 ]Laboratoire de Génie des Procédés et Matériaux, Ecole Centrale Paris Châtenay-Malabry, France
                [6 ]Laboratoire Atmosphères, Milieux, Observations Spatiales, Pierre and Marie Curie University, Université de Versailles Saint-Quentin-en-Yvelines, and CNRS Paris, France
                [7 ]Jacobs, NASA Johnson Space Center Houston, Texas, USA
                [8 ]Center for Research and Exploration in Space Science & Technology, University of Maryland, Baltimore County Baltimore, Maryland, USA
                [9 ]Department of Atmospheric, Oceanic and Space Sciences, University of Michigan Ann Arbor, Michigan, USA
                [10 ]Laboratoire Interuniversitaire des Systèmes Atmosphériques, Université Paris-Est Créteil, Paris VII–Denis Diderot University, and CNRS Créteil, France
                [11 ]Exobiology Branch, NASA Ames Research Center Moffett Field, California, USA
                [12 ]Department of Astronomy, Cornell University Ithaca, New York, USA
                [13 ]Centro de Astrobiología, INTA-CSIC Madrid, Spain
                [14 ]Division of Geological and Planetary Sciences, California Institute of Technology Pasadena, California, USA
                [15 ]Earth Sciences Department, Utrecht University Utrecht, Netherlands
                [16 ]Department of Earth and Environmental Sciences and School of Science, Rensselaer Polytechnic Institute Troy, New York, USA
                [17 ]Goddard Earth Sciences and Technologies and Research, Universities Space Research Association Columbia, Maryland, USA
                [18 ]Department of Chemistry, Catholic University of America Washington, District of Columbia, USA
                [19 ]Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR) Granada, Spain
                [20 ]Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology Kiruna, Sweden
                [21 ]Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center Houston, Texas, USA
                [22 ]Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ciudad Universitaria México City, Mexico
                [23 ]Geophysical Laboratory, Carnegie Institution of Washington Washington, District of Columbia, USA
                [24 ]Department of Earth and Planetary Sciences, University of California Davis, California, USA
                [25 ]Centro de Astrobiologia (INTA-CSIC) Madrid, Spain
                Author notes
                Correspondence to: C. Freissinet and P. R. Mahaffy,, paul.r.mahaffy@ , caroline.freissinet@
                ©2015. The Authors.

                This is an open access article under the terms of the Creative Commons Attribution-NonCommercial-NoDerivs License, which permits use and distribution in any medium, provided the original work is properly cited, the use is non-commercial and no modifications or adaptations are made.

                Research Articles

                chlorobenzene, sam, mars, msl, organic molecules, oxychlorine


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