The Fate of Simple Organics on Titan's Surface: A Theoretical Perspective

Abstract

Atmospheric photochemistry on Titan continuously transforms methane and nitrogen gases into various organic compounds. This study explores the fate of these molecules when they land on Titan's surface. Our analytical exploration reveals that most simple organics found in Titan's atmosphere, including all nitriles, triple‐bonded hydrocarbons, and benzene, land as solids. Only a few compounds are in the liquid phase, while only ethylene remains gaseous. For the simple organics that land as solids, we further examine their interactions with Titan's lake liquids. Utilizing principles of buoyancy, we found that flotation can be achieved via porosity‐induced (25%–60% porosity) or capillary force‐induced buoyancy for hydrogen cyanide ices on ethane‐rich lakes. Otherwise, these ices would sink and become lakebed sediments. By evaluating the timescale of flotation, our findings suggest that porosity‐induced flotation of millimeter‐sized and larger sediments is the only plausible mechanism for floating solids to explain the transient “magic islands” phenomena on Titan's lakes.

Surface properties of the seas of Titan as revealed by Cassini mission bistatic radar experiments

“…We can generally rule out issues with the absolute calibration algorithms for the reasons listed in the Methods section. If the seas’ surfaces were covered by an unconsolidated material (e.g., precipitated from the atmosphere 6 ), it could reduce the observed near-surface dielectric constant 16 , 46 – 49 , similar to what was observed for the uppermost layer of the lunar regolith probed by means of bistatic radar 50 or to what was recorded by Viking at the high northern latitudes of Mars during its high incidence angles bistatic radar observations 51 . In particular, values of ε r lower than expected were measured by Viking during the first part of the experiment performed on 25 February 1978, when the bistatic track crossed the region of Planum Boreum.…”

“… 2 – 4 , operating in a dense nitrogen atmosphere e.g., refs. 5 , 6 . Winds in the lower atmosphere move sediments and shape them into vast dune fields that encircle Titan’s equatorial latitudes e.g., refs.…”

Capillary Processes in Extraterrestrial Contexts

“…In the titanian case, other aspects have been also explored. For instance, the hypotheses of floating "pumices," made of very porous organic material to ensure buoyancy, has been proposed (Yu et al, 2024). Laboratory experiments have shown (Farnsworth et al, 2023) that non-coalescing liquid droplets may exist at the surface of methane-rich seas after hydrocarbon rainfalls.…”