The Effect of Propane on Two Liquid Systems in Titan's lakes

Titan's lakes and seas are predominantly composed of methane, ethane, and dissolved atmospheric nitrogen. Additionally, trace species such as propane may have dissolved from the atmosphere and their effects on the ternary system (CH4-C2H6-N2) are not well-studied. Our research looks to understand what can occur at depth in Titan's seas with these hydrocarbons. Studies suggest that at depth, and therefore a higher pressure, it is possible for Liquid-Liquid-Vapor equilibrium (LLV) to form. To address this, we conducted a series of experiments in the Astrophysical Materials Lab at NAU on the quaternary system (CH4-C2H6-C3H8-N2) with different mixing ratios, varying temperatures, all at 2.0 bar to simulate ~50m depth. Our preliminary results show that in methane rich environments (80:20 CH4:C2H6) and propane rich mixtures (>60%), LLV forms in colder environments (~86 K), where propane poor mixtures form at ~87 K. For equal amounts of methane and ethane, LLV forms at 85 K regardless of the propane concentration. And for ethane rich systems (20:80 CH4:C2H6), LLV tends to form in even colder environments than the other two cases (84 K). This knowledge improves our understanding of Titan's unique hydrocarbon-based hydrological cycle and gives us a picture of the chemical processes that occur in the Titan seas.

This work was sponsored by NASA SSW grant #80NSSC21K0168, NASA grant NNH19ZDA001N-FINESST, NSF REU grants #1950901 and #2349774, the Lowell Observatory Slipher Society, and a grant from the John and Maureen Hendricks Charitable Foundation.