Titan's strong tidal dissipation precludes a subsurface ocean

Area of Science:

• Planetary Science
• Geophysics
• Astrobiology

Background:

• The Cassini mission provided extensive data on Saturn's moon, Titan.
• Titan's tidal response to Saturn suggested a subsurface ocean, but this was not fully explained.
• Previous models could not reconcile Titan's observed tidal response with geophysical data.

Purpose of the Study:

• To reanalyze Cassini radiometric data to investigate Titan's tidal dissipation signature.
• To determine if Titan's gravity field is consistent with a subsurface ocean.
• To develop a model explaining Titan's geophysical measurements.

Main Methods:

• Reanalysis of Cassini radiometric data using improved techniques.
• Detection and analysis of tidal dissipation signatures in Titan's gravity field.
• Modeling of tidal dissipation within Titan's interior.

Main Results:

• The detected tidal dissipation signature is inconsistent with a subsurface ocean.
• Substantial energy dissipation (3-4 TW) occurs in Titan's interior, with a tidal quality factor Q≈5.
• A model with dissipation concentrated in a high-pressure ice layer near melting point explains the data.

Conclusions:

• The presence of a subsurface ocean on Titan is precluded by the new findings.
• Titan's geophysical state is explained by a model involving a slushy high-pressure ice layer, potentially with liquid water pockets.
• This model reconciles Titan's rotational state, gravity field, and tidal dissipation, awaiting further testing by the Dragonfly mission.