Mass spectrometry is commonly regarded as a powerful analytical technique for compositional analysis for planetary exploration. Mass spectrometers have been employed for exploration of multiple planetary targets, including Saturn and its moons, Mars, and Earth’s moon. Mass spectrometry measures the mass-to-charge ratio of ions, which can be used to identify molecules and their fragments and is often coupled with separation techniques such as gas chromatography. Recently, the Sample Analysis at Mars (SAM) instrument suite, which uses pyrolysis and gas chromatography coupled with a quadrupole mass spectrometer, detected organic molecules in 3.5 Ga mudstones (Freissinet et al. 2015, Eigenbrode et al. 2018). These organics are consistent with both indigenous Mars sources and exogenous materials from meteoritic infall. The detections show that organic molecules are preserved in ancient Mars materials, despite surface exposure to destructive galactic cosmic rays and powerful oxidants. Furthermore, these detections were made despite the presence of perchlorate in the sample, which, when heated, can oxidize organic matter. SAM has also recently performed experiments to derivatize selected samples to volatilize organics such as amino acids and fatty acids.<br/><br/>While surface sediments such as the Gale mudstones appear to preserve organic molecules, the ExoMars mission launching in 2020 will be able to access sediments at 2 m depth using a drill at the landing site within the clay-rich Oxia Planum region, increasing the potential of detecting organics below the reach of damaging cosmic rays. The Mars Organic Molecule Analyzer, or MOMA instrument, will employ ion trap mass spectrometry in the search for organics on Mars. In addition to pyrolysis and derivatization, MOMA will use laser desorption to introduce sample to the mass spectrometer, minimizing potential destruction of organics by any perchlorate present, and keeping molecular signatures intact. A similar instrument is in development for the Dragonfly mission to Titan, a planetary body presenting a very different challenge of detecting organics of pre-biotic interest in an organic- and water-rich matrix.

Mass spectrometry as a tool for detecting organics on Mars (and beyond)

ACS Spring Meeting 2021

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