Physicochemical Characterization Of Potential Minerals On Titan, Saturn’S Moon

The recently concluded Cassini-Huygens mission, a project instrumental to the physicochemical characterization of Titan, Saturn’s moon, revealed striking similarities between Titan and Earth. Within Titan's dense atmosphere, methane and nitrogen undergo photochemical reactions fueled by energy from Saturn’s magnetosphere and solar radiation, resulting in the synthesis of a rich diversity of hydrocarbons, prebiotic molecules, and potential precursors to methanogenic life. These molecules partake in a seasonal cycling of methane–a process that parallels Earth's hydrological cycle–as they are carried by methane rainfall to the surface, where they dissolve in lakes, seas and rivers of methane and ethane. As methane evaporates during dry seasons, these trace molecules precipitate and solidify as evaporite minerals. Though these evaporite deposits have been directly observed via remote sensing, information on their chemical composition is still limited, as Titan's dense atmosphere and the resolution limits of the instruments pose significant challenges in collecting observational information about the surface. As a result, our current understanding of Titan's surface composition relies heavily on predictions made using atmospheric models. These models in turn rely on experimental data with which to validate their predictions, and thus laboratory studies are a crucial component in the characterization of Titan's surface compounds. However, existing reference data (i.e. spectral libraries) is often limited to pure compounds, and established literature values are often lacking for mixtures and multicomponent species. In addition, most of this data is based on experiments conducted at Earth's surface conditions, which can lead to inaccurate interpretation of observational data collected at Titan's surface conditions (~93 K, 1.45 atm). In this research, we systematically investigate the compositional and structural diversity of the surface of Titan by 1) characterizing phase transitions of pure compounds over the full range of Titan-relevant temperatures, and 2) detailing the phase behavior of binary mixtures within the same temperature range to constrain the resulting effects of impurities and mixtures on the behavior of the pure compounds. In each case, we determine the thermodynamic properties of the system using Differential Scanning Calorimetry (DSC) and Powder X-ray Diffraction (PXRD) to extract structural information relevant to the characterization of the physicochemical properties of these compounds and the interpretation of their geological role as minerals on Titan's surface.