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Communication Dans Un Congrès Année : 2021

Gas Chromatograph Mass Spectrometry Performance of the Mars Organic Molecule Analyzer on the ExoMars Rover

Résumé

The goals of the joint ESA-Roscosmos ExoMars mission include the search for potential molecular biosignatures on the martian surface and near subsurface, and the discrimination of the endogenous from the exogenous sources of organics on Mars. The Mars Organic Molecule Analyzer (MOMA) aboard the ExoMars Rosalind Franklin rover will be a key analytical tool in providing chemical (molecular) composition of the solid samples collected with the rover's two-meter drill, with a particular focus on broad characterization of organics over a range of structural classes and molecular weight. The MOMA instrument combines two sources, UV laser desorption/ionization and gas chromatography (GC) with electron ionization, with a common ion trap mass spectrometer. As with the Sample Analysis at Mars (SAM) investigation on Curiosity, the GC-MS mode of MOMA incorporates on-board derivatization, providing unique capabilities to characterize both volatile and non-volatile species, as well as perform chiral analysis. In addition to direct pyrolysis, a subset of MOMA ovens contain capsules with derivatization reagent sealed with a eutectic alloy and released at precise temperatures. The choice between three different derivatization chemistries (MTBSTFA [1], DMF-DMA [2], TMAH [3]) allows specific chemical subgroups to be targeted and results in an increase in the volatility of complex organic species. In order to assess the performance of the MOMA instrument with realistic Mars analog samples, especially in GC-MS mode, while maintaining extreme cleanliness of the flight hardware, tests have been carried out with a high-fidelty Engineering Test Unit (ETU). The ETU results are used to guide future science operation, and to demonstrate the status of the end-to-end performance of GC-MS mode over a range of analyte concentrations and sample "matrices" representative of the planned Oxia Planum landing site. We show that from a technical point of view the MOMA instrument and derivatization experiment is working as desired. From a chemical point of view, we show that the MOMA GC-MS protocols (MTBSTFA, DMF-DMA, thermochemolysis with TMAH, and pyrolysis) work efficiently under Mars operational conditions. Additionally, we demonstrate chiral and isomeric separation with standard samples and organics extracted from the Mars analogues.
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Dates et versions

insu-04466880 , version 1 (19-02-2024)

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Arnaud Buch, Francois Raulin, Daniel Glavin, Caroline Freissinet, Fabien Stalport, et al.. Gas Chromatograph Mass Spectrometry Performance of the Mars Organic Molecule Analyzer on the ExoMars Rover. 43rd COSPAR Scientific Assembly, Jan 2021, Sydney, Australia. ⟨insu-04466880⟩
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