How to find an ocean?
Finding water has always been the first step in the search for life beyond Earth. For instance, exoplanets get more attention when they are found to be in their respective 'habitable zone' in which water can remain in its liquid state. Space exploration has revealed that liquid water can exist in 'habitable islands' way beyond the defined habitable zone where heat generated from radioactive decay and tides can melt the ice and form and sustain subsurface water oceans in icy satellites for as long as the age of the solar system.
So far Galileo and Cassini missions have shown strong evidence for the existence of subsurface oceans in Jovian moons (Europa, Ganymede, and Callisto) and in Saturnian moons (Enceladus and Titan). I will describe
in detail the different remote sensing techniques that were used to detect the presence of these oceans. I will also discuss missions currently under preparation (i.e. JUICE, Europa Clipper) and future potential missions (e.g. Ice giants) that would deepen our understanding of the ocean worlds, as well as, discover new ones.