  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.
