Abstract EANA2024-79

Titan is a unique world in the solar system, being the only moon with a dense atmosphere. This air of nitrogen (N2) and methane (CH4), with little free oxygen, is ripe for enabling organic chemistry to occur. Beginning in the upper atmosphere, methane and nitrogen are dissociated into fragments, which then recombine into a dizzy array of complex chemicals as sampled by Cassini's mass spectrometers (INMS and CAPS). The unique structures of only 24 of these molecules are known via remote sensing spectroscopy – 12 are hydrocarbons ranging up to benzene in size, while 8 are nitriles (cyanides) and the remainder are simple inorganic molecules: N2, CO, H2O and CO2. However, this is but the tip of the iceberg, since the data from the mass spectrometers shows the presence of molecules and particles ranging into the 100s and 1000s of Da in size and beyond. At the largest size, macromolecules become sub-micron sized haze particles that scatter visible light and create the ubiquitous Titan golden haze. Many questions therefore remain open: what other molecules are lurking in Titan’s atmosphere, and to which chemical families do they belong (amines, aldehydes etc)? Into which directions does the chemical complexity evolve, for example are PAHs and PANHs formed? How far and how close does the atmospheric chemistry proceed in the direction of creating molecules of relevance to biology on Earth (amino acids, nucleobases etc)? And how are molecules from the atmosphere modified on the surface and even mixed into the interior ocean? In the post-Cassini era, new discoveries are shedding fresh insights into these questions. These include the detection and identification of new molecular species with ground and space-based telescopes such as ALMA, IRTF and JWST; new laboratory spectroscopy and reaction rate measurements allowing refinement of photochemical models; as well as ongoing analysis of Cassini data. In this presentation I will present the most recent findings about Titan’s atmospheric composition from post-Cassini observations with JWST and other large telescope facilities. I will also summarize the principal open questions and consider how these questions may be addressed in future by telescopic observations, the upcoming Dragonfly and other missions, and other techniques including laboratory and theoretical investigations.