Titan Lakes Simulation System (TiLSS): A cryogenic experimental setup to simulate Titan’s liquid hydrocarbon surfaces

Abstract

Titan's hydrocarbon lakes play an important role in the chemistry, geomorphology, and climate of the satellite. Our knowledge of their composition relies mainly on thermodynamic modeling and assumptions based on Cassini Radar and VIMS (Visible and Infrared Mapping Spectrometer) data. Several thermodynamic models have been used to calculate the composition of these lakes, and their results on even the major lake components (methane, ethane, propane, and nitrogen) exhibit large discrepancies. Recent Cassini radar observations revealed an echo from the lake's bottom. A low loss factor of attenuation is needed within the lakes to interpret these observations, and it has been suggested that the lakes are dominated by methane. Cassini VIMS data obtained on the North Pole lakes at three-year intervals showed no detectable surface level change, which is consistent with ethane being their primary constituent. This additional discrepancy between thermodynamic models and Cassini data strongly shows the need for experimental measurements under realistic Titan conditions in order to better constrain the thermodynamic models. We designed and built a cryogenic experimental platform allowing the simulation of Titan's lakes. This facility, named Titan Lakes Simulation System (TiLSS), produces liquid hydrocarbons in equilibrium with a gas phase mimicking Titan's atmosphere. Samples of the condensed liquid are injected directly into a gas chromatograph allowing the direct measurement of its chemical components and their abundances. To test the overall operation of the system, a gas mixture of methane and ethane was condensed under 1.5 bar of nitrogen and analyzed. Results from this proof of concept test are in good agreement with experimental studies previously published.

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