Mars Organic Molecule Analyzer (MOMA) Flight Model Qualification

Abstract : Introduction: The Mars Organic Molecule Ana-lyzer (MOMA) investigation on the 2020 ExoMars rover will examine the molecular composition of samples acquired from depths of up to two meters below the martian surface, where organics may have been protected from radiative and oxidative degradation [1,2]. The clay-rich rock exposures accessible in Oxia Planum, the preferred landing zone, will provide an excellent opportunity to sample ancient material for organics analysis. MOMA incorporates both pyrolysis-gas chromatography/mass spectrometry (pyr-GCMS) and laser desorption mass spectrometry (LDMS) modes of operation, and is designed to work in concert with the other investigations in the rover's Pasteur Payload, particularly the Raman [3] and MicrOmega [4] instruments that analyze common drill samples presented on a carousel. With two modes, MOMA detects compounds over a wide range of molecular weight, volatility, and mineralological association [5]. Implementation of GCMS and LDMS Modes: GCMS mode is operated analogously to the Sample Analysis at Mars (SAM) investigation on Curiosity. Samples are sealed into ovens and heated to 850° C. Analyte gases, entrained in He, flow through the GC system to the MS. The GC includes two cooled hydrocarbon traps (Tenax and Carbosieve) that are opened after major water evolution (above 100° C) but prior to organic thermodesorption (from ~300° C up to > 500° C). Trapped organics are injected onto one of four columns and eluted over a temperature ramp to the MS electron ionization (EI) source. GCMS analyzes compounds of high-to-moderate volatility (enthalpies of vaporization !H V ≤ 50 kJ mol-1) such as alkanes, amines, and lighter carboxylic and amino acids and aromatic species. Derivatization agent present in some ovens enables detection of the higher !H V and polar species over the full GCMS m/z range of 50-500 Da. In LDMS mode, molecules are desorbed and ionized directly from powder samples with a pulsed UV laser (266 nm, 1 ns duration) at Mars ambient pressures. Parent molecular cations, and their fragments, enter the MS through a fast aperture valve that closes
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William Brinckerhoff, Veronica Pinnick, Ryan Danell, Friso van Amerom, Ricardo Arevalo, et al.. Mars Organic Molecule Analyzer (MOMA) Flight Model Qualification. 48th LPSC Lunar and Planetary Science Conference, Mar 2017, Houston, United States. ⟨hal-01815549⟩

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