Moons of the giant planets
This artist's impression depicts thermal plumes venting from the southern polar region of Saturn's moon Enceladus. The moon's icy shell is thought to overlay a global ocean.
Titan is depicted above, the only moon in the Solar System that has a substantial atmosphere, hydrocarbon seas at the surface, and a subsurface salty ocean.
'Moons of the Giant Planets' is one of the science themes for the Large-class missions in ESA's Voyage 2050 plan.
A mission to one or more of the moons of Saturn or Jupiter would allow us to explore farther the habitability of ocean worlds. Such a mission would search for biosignatures, and study the connection of moon interiors with their near-surface environments, and the implications for the exchange of mass and energy into the overall moon-planet system. This would follow the breakthrough science from the international Cassini-Huygens mission and expected scientific return from ESA's Jupiter Icy Moons Explorer (Juice) launching in 2022.