Does Titan have a global liquid ocean or a slushy interior?
In plain words
Cassini measured how much Titan, Saturn's largest moon, is squeezed by Saturn's tides, and the large response was first read as a sign of a hidden global ocean. A 2025 reanalysis argues instead for a slushy layer of ice with pockets of water.
Precise statement
Determine from Titan's tidal Love number $k2$, the tidal phase lag and the rotation state whether its interior contains a global liquid water ocean decoupled from the ice shell or a high-pressure-ice layer containing partial melt, and constrain the hydrosphere structure. An answer is an interior model that matches $k2$, dissipation and obliquity data and excludes the alternative.
What would settle it
Independent measurements of Titan's tidal response and dissipation, for example from Dragonfly geophysics, together with consistent rheological models.
Status in the literature
Unverified note
Petricca et al. 2025 (Nature) argued that strong tidal dissipation in Cassini data precludes a global subsurface ocean.