ocean worlds

• bodies with a large liquid-water ocean, usually under an ice shell
• mostly icy moons of the outer solar system (Earth also counts)
• strong cases: Europa (Jupiter), Enceladus and Titan (Saturn)
• Mimas (Saturn): young ocean inferred from its orbital motion (Lainey et al., 2024)
• likely or possible: Ganymede, Callisto, Triton, Pluto
• evidence mostly indirect: gravity, induced magnetic fields, rotation, plumes
• Enceladus plumes: ocean material sampled by Cassini, including phosphates (Postberg et al., 2023)
• salty water, possibly with ammonia (antifreeze)