Bubbles in Titan's seas: nucleation, growth and RADAR signature

TL;DR

This study investigates the nucleation, growth, and RADAR signatures of bubbles in Titan's hydrocarbon seas, proposing that seabed bubble formation explains observed transient bright features.

Contribution

We applied classical nucleation theory and developed a radiative transfer model to analyze bubble formation and RADAR reflectivity in Titan's cryogenic seas, a novel approach in this context.

Findings

Seabed is the most plausible source of bubbles.

Bubbles can produce RADAR signals matching observations.

Gas leaks from the sea floor can generate bubble plumes.

Abstract

In the polar regions of Titan, the main satellite of Saturn, hydrocarbon seas have been discovered by the Cassini-Huygens mission. RADAR observations have revealed surprising and transient bright areas over Ligeia Mare surface. As suggested by recent research, bubbles could explain these strange features. However, the nucleation and growth of such bubbles, together with their RADAR reflectivity, have never been investigated. All of these aspects are critical to an actual observation. We have thus applied the classical nucleation theory to our context, and we developed a specific radiative transfer model that is appropriate for bubbles streams in cryogenic liquids. According to our results, the sea bed appears to be the most plausible place for the generation of bubbles, leading to a signal comparable to observations. This conclusion is supported by thermodynamic arguments and by RADAR properties of a bubbly column. The latter are also valid in the case of bubble plumes, due to gas leaking from the sea floor.