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J Geophys Res Planets. 2015 Mar;120(3):495-514. Epub 2015 Mar 21.

Organic molecules in the Sheepbed Mudstone, Gale Crater, Mars.

Author information

1
Solar System Exploration Division, NASA Goddard Space Flight Center Greenbelt, Maryland, USA ; NASA Postdoctoral Program, Oak Ridge Associated Universities Oak Ridge, Tennessee, USA.
2
Solar System Exploration Division, NASA Goddard Space Flight Center Greenbelt, Maryland, USA.
3
Department of Earth, Atmospheric and Planetary Sciences, Massachusetts Institute of Technology Cambridge, Massachusetts, USA.
4
Solar System Exploration Division, NASA Goddard Space Flight Center Greenbelt, Maryland, USA ; 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
Solar System Exploration Division, NASA Goddard Space Flight Center Greenbelt, Maryland, USA ; 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 ; Centro de Astrobiología, INTA-CSIC Madrid, Spain.
13
Division of Geological and Planetary Sciences, California Institute of Technology Pasadena, California, USA.
14
Earth Sciences Department, Utrecht University Utrecht, Netherlands.
15
Department of Earth and Environmental Sciences and School of Science, Rensselaer Polytechnic Institute Troy, New York, USA.
16
Solar System Exploration Division, NASA Goddard Space Flight Center Greenbelt, Maryland, USA ; Goddard Earth Sciences and Technologies and Research, Universities Space Research Association Columbia, Maryland, USA.
17
Solar System Exploration Division, NASA Goddard Space Flight Center Greenbelt, Maryland, USA ; Department of Chemistry, Catholic University of America Washington, District of Columbia, USA.
18
Instituto Andaluz de Ciencias de la Tierra (CSIC-UGR) Granada, Spain ; Division of Space Technology, Department of Computer Science, Electrical and Space Engineering, Luleå University of Technology Kiruna, Sweden.
19
Astromaterials Research and Exploration Science Directorate, NASA Johnson Space Center Houston, Texas, USA.
20
Instituto de Ciencias Nucleares, Universidad Nacional Autónoma de México, Ciudad Universitaria México City, Mexico.
21
Department of Astronomy, Cornell University Ithaca, New York, USA.
22
Geophysical Laboratory, Carnegie Institution of Washington Washington, District of Columbia, USA.
23
Department of Earth and Planetary Sciences, University of California Davis, California, USA.
24
Centro de Astrobiologia (INTA-CSIC) Madrid, Spain.

Abstract

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 C2 to C4 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.

KEYWORDS:

MSL; Mars; SAM; chlorobenzene; organic molecules; oxychlorine

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