Planetary oceanography

[8] In June 2020, NASA scientists reported that it is likely that exoplanets with oceans may be common in the Milky Way galaxy, based on mathematical modeling studies.

[15] The gas giants, Jupiter and Saturn, are thought to lack surfaces and instead have a stratum of liquid hydrogen; however their planetary geology is not well understood.

The possibility of the ice giants Uranus and Neptune having hot, highly compressed, supercritical water under their thick atmospheres has been hypothesised.

[19] A global layer of liquid water thick enough to decouple the crust from the mantle is thought to be present on the natural satellites Titan, Europa, Enceladus, Ganymede,[20][21] and Triton;[22][23] and, with less certainty, in Callisto,[24][25] Mimas,[26] Miranda, and Ariel.

[28] Geysers or fumaroles have been found on Saturn's moon Enceladus, possibly originating from an ocean about 10 kilometers (6 mi) beneath the surface ice shell.

The Cassini–Huygens space mission initially discovered only what appeared to be dry lakebeds and empty river channels, suggesting that Titan had lost what surface liquids it might have had.

Later flybys of Titan provided radar and infrared images that showed a series of hydrocarbon lakes in the colder polar regions.

Titan is thought to have a subsurface liquid-water ocean under the ice in addition to the hydrocarbon mix that forms atop its outer crust.

[37] Exomoons orbiting planets, particularly gas giants within their parent star's habitable zone may theoretically have surface oceans.

[39] There is evidence that the icy surfaces of the moons Ganymede, Callisto, Europa, Titan and Enceladus are shells floating on oceans of very dense liquid water or water–ammonia solution.

[46] Hot Neptunes close to their star could lose their atmospheres via hydrodynamic escape, leaving behind their cores with various liquids on the surface.