Titan's Anomalous Atmosphere from Top to Turf

Abstract

Titan, Saturn's largest moon, is the only moon with a substantial atmosphere. Its primary constituents are 94.2\% N$_2$, 5.65\% CH$_4$, 0.1\% H$_2$, and smaller amounts of nitriles, hydrocarbons, and other organics. Though there had been several flybys and ground-based observations of Titan since its discovery in 1659, the Cassini-Huygens mission revealed a world unlike any other. Titan is the only place in the solar system, other than the Earth, to have stable liquid on its surface. Instead of water, Titan has methane lakes and seas, and a methane cycle analogous to the Earth's water cycle. The Cassini-Huygens mission also revealed many interesting phenomena, such as a spectacular detached haze layer, superrotating jets, a large dune desert, and more. Since the finale of the Cassini-Huygens mission, there have been many initiatives to try to understand the mechanisms behind the dynamic and chemical processes taking place on Titan using a combination of computational and observational methods. In recent years there has been an intensification of these efforts as the NASA Dragonfly mission prepares to embark. This thesis is an exploration of Titan's atmosphere, from the thermopause at roughly 1400 km to the surface. I combine a variety of computational techniques with observational input to model various dynamic and chemical processes with the goal of furthering the field's understanding of Titan. I present results from four studies, starting with particle-atmosphere interactions and finishing with troposphere-surface interactions. I also include a review on the current Titan General Circulation models (of which there are very few) to summarize the current computational state of the field, highlighting successes, and discussing the many areas that require improvement, before describing the GCM that I work with and the improvements I have made to the code's incorporation of topography, vertical diffusion calculation, and momentum transfer. To conclude, I summarize each chapter and discuss a few future projects.