The Cassini space mission that investigated the Saturn system from 2004-2017 made numerous discoveries about its largest satellite, Titan, during 127 targeted flybys. On approximately 2/3 of these flybys, the spacecraft made a closest approach at an altitude &lt; 1500 km (Nixon et al. 2019) – effectively inside the highly extended atmosphere - permitting direct sampling of atmospheric material. On many of these opportunities one or more of Cassini’s three mass spectrometers made direct measurements of gas and particle abundances, revealing the richness of the organic chemical composition. In particular, Cassini’s Ion and Neutral Mass Spectrometer showed a wealth of positive ions at masses up to 100 Da at altitudes down to 950 km, including the protonated forms of many molecules not previously detected in the lower atmosphere by remote sensing techniques (Vuitton et al. 2007). Photochemical modeling has provided predictions of the molecular abundances for many species extending downwards to the surface (Vuitton et al. 2019), but the low abundances and instrumentation limitations have limited the chemical species detected so far in the neutral middle and lower atmosphere to a much restricted version of the range seen in the ionosphere. Since 2012, the advent of the Atacama Large Millimeter/submillimeter Array (ALMA) has revolutionized molecular astronomy, allowing numerous new detections of faint chemical species in astrophysical environments, including dense molecular clouds, circumstellar envelopes, planets and comets in our solar system, and Titan. Two new molecular species have been detected on Titan using ALMA (C2H5CN, Cordiner et al. 2015; C2H3CN, Palmer at al. 2017), and the search continues for further important detections that can be used to refine photochemical models, and our understanding of Titan’s atmospheric chemistry as a whole. In this presentation we describe recent efforts underway by our team based at NASA Goddard Space Flight Center, with European collaborators, to search for new chemical species in Titan’s atmosphere, including the latest measurements, detections and upper limits on molecules and isotopologues.

Search for new chemical species in Titan’s neutral atmosphere with ALMA

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.