Characterization of Organic Molecules in the Glen Torridon Region of Gale crater, Mars, by the SAM Instrument Aboard Curiosity - INSU - Institut national des sciences de l'Univers Accéder directement au contenu
Communication Dans Un Congrès Année : 2021

Characterization of Organic Molecules in the Glen Torridon Region of Gale crater, Mars, by the SAM Instrument Aboard Curiosity

Caroline Freissinet
Cyril Szopa
James Lewis
  • Fonction : Auteur

Résumé

The Sample Analysis at Mars (SAM) instrument on board Curiosity is searching for organic molecules in near surface samples in order to uncover clues about Mars habitability. To do so, SAM performs in situ evolved gas analysis (EGA) and pyrolysis-gas chromatograph-mass spectrometry analysis (pyro-GCMS). In addition, SAM is able to analyze less volatile organics using wet chemistry reagents (MTBSTFA and TMAH). To evaluate whether organic molecules were preserved within the minerals of the Glen Torridon (GT) clay-bearing unit, SAM performed five pyro-GC-MS experiments, two MTBSTFA derivatization experiments, and a TMAH thermochemolysis experiment on six samples in total. Results revealed the highest diversity and abundance of organic molecules ever detected on Mars. EGA indicated high molecular weight compounds including aromatics, suggesting the presence of a complex mixture of compounds consistent with recalcitrant organic materials. The CO2 evolutions in EGA were consistent with oxidized organic carbon (e.g., oxalate salts) but CO2 evolved at temperatures above 360oC possibly results from carbonate decomposition. GCMS analyses showed the presence of N- and O-bearing organics which could be derived from the MTBSTFA background present in SAM and/or fragments of oxidized organics and larger parent N-bearing molecules. Background level chlorohydrocarbons may have been produced from reactions between HCl from martian chloride and organics from SAM internal sources. The highest diversity and abundance of S-bearing organics yet detected in Gale crater were also observed, including dimethylsulfide and thiophene as well as new detections including dithiapentane, dithiolane, and trithiane. Pathways of formation of the S-bearing and aromatic compounds are under investigation with laboratory experiments to ascertain their likely source(s). Possibilities include indigenous recalcitrant organic materials (as some were released above 600°C), organic fragments modified upon thermal release in the oven, and the SAM internal background.
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Dates et versions

insu-04460759 , version 1 (15-02-2024)

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Maeva Millan, Amy Williams, Amy Mcadam, Jennifer Eigenbrode, Caroline Freissinet, et al.. Characterization of Organic Molecules in the Glen Torridon Region of Gale crater, Mars, by the SAM Instrument Aboard Curiosity. AGU Fall Meeting 2021, Dec 2021, New Orleans, United States. pp.id. P24A-07. ⟨insu-04460759⟩
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