Saturn
Sixth planet from the Sun; second-largest gas giant; host of the most extensively studied planetary system in astrobiology after Jupiter, primarily due to the 2004-2017 Cassini-Huygens mission.
Key Cassini-derived facts
- Rotation rate ~10.7 hours — pinned by the 22 proximal orbits of the grand-finale; Voyager could not resolve this. (src-cassini-huygens-ocean-worlds-2026-04)
- Magnetosphere — rotation-dominated and mass-loaded by enceladus-supplied plasma, with its magnetic cusp in the afternoon sector rather than at noon (Xu et al. 2026). Aligns Saturn with Jupiter as a rotation-dominated regime; suggests Earth’s solar-wind-dominated regime may be the special case.
- Ring system precisely characterized in mass and composition.
- Multiple moons of astrobiological interest: enceladus (subsurface ocean, plumes) and titan (methane/ethane hydrology, subsurface water ocean).