Titan is the largest moon of Saturn, with a thick (1.45 bar) atmosphere composed primarily of molecular nitrogen and methane. Photochemistry results in the production of a wide range of organic molecules in Titan's upper atmosphere, including hydrocarbons, nitriles, aromatics and species of possible pre-biotic relevance. Titan's atmosphere is therefore an important environment for testing our understanding regarding the evolution of chemical complexity in carbon and nitrogen-rich planetary atmospheres throughout the Galaxy. Results will be presented from our ongoing studies of using ALMA data obtained during the period 2012-2015, including detection and mapping of emission from HCN, HNC, C2H5CN, HC3N and CH3CN. In addition, combining data from multiple ALMA Band 6 observations, our spectra have reached an unprecedented sensitivity level, enabling the first spectroscopic detection of C2H3CN (vinyl cyanide) on Titan. Liquid-phase simulations of Titan's seas indicate that vinyl cyanide molecules could combine to form (pre-biotic) vesicle membranes, and the astrobiological implications of this discovery will be discussed. ALMA observations provide instantaneous (snapshot) mapping of Titan's entire Earth-facing hemisphere for gases inaccessible to previous studies, and provide the opportunity to continue Cassini's legacy for studying Titan's climate and chemistry in the coming years. Our observed, seasonally variable, spatially resolved molecular maps provide new insights into photochemical production and transport in primitive planetary atmospheres, particularly at stratospheric and mesospheric altitudes.

Climatological variations in Titan’s atmospheric chemistry mapped using ALMA

254th National Meeting (2017)

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