Origin of Chlorobenzene Detected by the Curiosity Rover in Yellowknife Bay: Evidence for Martian Organics in the Sheepbed Mudstone?

Abstract : The Sample Analysis at Mars (SAM) instrument on the Curiosity rover is designed to determine the inventory of organic and inorganic vola-tiles thermally evolved from solid samples using a combination of evolved gas analysis (EGA), gas chromatography mass spectrometry (GCMS), and tunable laser spectroscopy [1]. The first solid samples analyzed by SAM, a scoop of windblown dust and sand at Rocknest (RN), revealed chlorinated hydrocarbons derived primarily from reactions between a martian oxychlorine phase (e.g. perchlorate) and terrestrial carbon from N-methyl-N-(tert-butyldimethylsilyl)-trifluoroacetamide (MTBSTFA) vapor present in the SAM instrument background [2]. Chlorobenzene (CBZ) was also identified by SAM GCMS at RN at trace levels (~0.007 nmol) and was attributed to the reaction of chlorine with the Tenax polymers used in the hydrocarbon traps [2]. After the RN analyses, Curiosity traveled to Yellowknife Bay and drilled two separate holes designated John Klein (JK) and Cum-berland (CB). Analyses of JK and CB by both SAM and the CheMin x-ray diffraction instrument revealed a mudstone consisting of ~20 wt% smectite clays [3,4], which on Earth are known to aid the concentration and preservation of organic matter. In addition, higher abundances and a more diverse suite of chlorinated hydrocarbons in CB compared to RN suggests that martian or meteoritic organic sources may be preserved in the mudstone [3]. Here we discuss the SAM EGA and GCMS measurements of volatiles released from the Sheepbed mud-stone. We focus primarily on the elevated CBZ detections at CB and laboratory analog experiments conducted to help determine if CBZ is derived from primarily terrestrial, martian, or a combination of sources.
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Daniel Glavin, Caroline Freissinet, J. Eigenbrode, K. Miller, M. Martin, et al.. Origin of Chlorobenzene Detected by the Curiosity Rover in Yellowknife Bay: Evidence for Martian Organics in the Sheepbed Mudstone?. 45th LPSC Lunar and Planetary Science Conference, Mar 2014, The Woodlands, Texas, United States. ⟨hal-01815497⟩

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