Recovery of Fatty Acids from Mineralogic Mars Analogs by TMAH Thermochemolysis for the Sample Analysis at Mars Wet Chemistry Experiment on the Curiosity Rover

Abstract : The Mars Curiosity rover carries a diverse instrument payload to characterize habitable environments in thesedimentary layers of Aeolis Mons. One of these instruments is Sample Analysis at Mars (SAM), whichcontains a mass spectrometer that is capable of detecting organic compounds via pyrolysis gas chromatographymass spectrometry (py-GC-MS). To identify polar organic molecules, the SAM instrument carries the ther-mochemolysis reagent tetramethylammonium hydroxide (TMAH) in methanol (hereafter referred to as TMAH).TMAH can liberate fatty acids bound in macromolecules or chemically bound monomers associated withmineral phases and make these organics detectable via gas chromatography mass spectrometry (GC-MS) bymethylation. Fatty acids, a type of carboxylic acid that contains a carboxyl functional group, are of particularinterest given their presence in both biotic and abiotic materials. This work represents the first analyses of asuite of Mars-analog samples using the TMAH experiment under select SAM-like conditions. Samples analyzedinclude iron oxyhydroxides and iron oxyhydroxysulfates, a mixture of iron oxides/oxyhydroxides and clays,iron sulfide, siliceous sinter, carbonates, and shale. The TMAH experiments produced detectable signals underSAM-like pyrolysis conditions when organics were present either at high concentrations or in geologicallymodern systems. Although only a few analog samples exhibited a high abundance and variety of fatty acidmethyl esters (FAMEs), FAMEs were detected in the majority of analog samples tested. When utilized, the TMAH thermochemolysis experiment on SAM could be an opportunity to detect organic molecules bound inmacromolecules on Mars. The detection of a FAME profile is of great astrobiological interest, as it couldprovide information regarding the source of martian organic material detected by SAM
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Amy Williams, Jennifer Eigenbrode, Melissa Floyd, Mary Beth Wilhelm, Shane O'Reilly, et al.. Recovery of Fatty Acids from Mineralogic Mars Analogs by TMAH Thermochemolysis for the Sample Analysis at Mars Wet Chemistry Experiment on the Curiosity Rover. Astrobiology, Mary Ann Liebert, 2019, 19 (4), pp.522-546. ⟨10.1089/ast.2018.1819⟩. ⟨insu-02073584⟩

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