The "Dagwood Sandwich" Moon. Earlier models of Ganymede's oceans were based on the assumption that the existence of salt didn't change the nature of liquid very much with pressure. However, Dr. Vance and his colleagues found, through laboratory experiments, that salt does increase the density of liquids under the extreme conditions hidden deep within Ganymede and similar icy moons with subsurface bodies of water. Imagine adding table salt to a glass of water. Instead of increasing in volume, the liquid will actually shrink and become denser. The reason for this is that salt ions lure water molecules.
But there is an important difference. On our own planet, lakes and seas are flowing with water, while Titan's lakes and seas are filled primarily with methane and ethane, that slosh around within these liquid reservoirs. In this never-before-seen cycle, the hydrocarbon molecules evaporate and condense into clouds that send an exotic "rain of terror" back down to this strange moon-world's carbon-slashed surface.
"We are just beginning to try and figure out quantitatively how all this might smooth a surface," Dr. Thomas said in the May 17, 2013 New Scientist.