Titan
Titan is the largest Saturnian satellite and is unique in that it has a dense atmosphere and liquid lakes and seas on its surface. In many ways it is akin to Earth, but rather than a hydrological cycle it has a methanological (methane-based) cycle. Our goal in the lab is to understand how the primary ternary system, methane-ethane-nitrogen, creates what we see in the liquid and solid phases on the satellite's surface. In the future, we will add more hydrocarbons to our experiments to see how minority species further perturb the system.
The Stability of Trace Species in the Lakes
Titan's polar surfaces host stable bodies of liquid, with methane (CH4), ethane (C2H6), and dissolved atmospheric nitrogen (N2) making up the bulk of their compositions. In addition to this ternary system, the lakes and seas also likely host trace species that dissolve into the liquids from the atmosphere. The effects of these trace species are not well-studied or understood. Thus, we are conducting studies that investigate the effects of trace species on the ternary system's stability and solubility.
Currently, we are adding propane to methane-nitrogen and ethane-nitrogen binary mixtures, with the purposed of gaining insight into how each molecule interacts with one another.
Image credit: ESA
Methane–Ethane–Propane System +Dissolved Nitrogen
It is suspected there could be a range of 0.8–8.5% propane (C3H8) that resides in the lakes, in addition to methane, ethane, and nitrogen. It may find its way to the lakes either by falling directly into them or being transported by fluvial processes. This study investigates the changes in freezing point temperatures and physical properties of the methane–ethane–nitrogen system when 0–10% propane is added.
The overarching goal of the current experiments is to provide a deeper understanding of the coupled chemical-dynamical behavior of Titan’s lakes. The results may aid in identifying scenarios in which ice could form alongside the surface liquid.
Methane–Ethane System +Dissolved Nitrogen
With the help of our collaborator, Sugata Tan (PSI), we are both modeling and experimentally exploring the methane-ethane-nitrogen phase diagram at 1.5 bar to determine the temperatures at which various multi-phase equilibria form. It is anticipated that the results will add to our understanding of Titan's surface, particularly in and around the polar lakes.
Methane–Ethane Binary Phase Diagram
Although much work as been done in mapping methane and ethane in the gas phase, little has been added to the phase diagram in the liquid and solid phases. Here, we add to the binary system at conditions relevant to Titan's lakes.
Two-Liquid System in Lakes
Given the right pressure, temperature, and ratio of methane-ethane-nitrogen, a two liquid system forms where the top layer is ethane-rich and the bottom layer is nitrogen-rich. These conditions may be obtainable at depths in Titan's lakes, indicating that the two-liquid system may form in them.