2023/12/10 by Benjamín Idini, F. Nimmo, Idini, Benjamin +1 · 2 citations
Biochemistry, Genetics and Molecular Biology · Physics and Astronomy · #Astro and Planetary Science #Earth and Planetary Astrophysics (astro-ph.EP) #FOS: Physical sciences #Fluid Dynamics (physics.flu-dyn) #Geomagnetism and Paleomagnetism Studies #Scientific Research and Discoveries
paper · pdf · doi:10.48550/arxiv.2312.05723
openalex publication_date 2023/12/10 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
Titan's ice shell floats on top of a global ocean revealed by the large tidal Love number k2 = 0.616±0.067 registered by Cassini. The Cassini observation exceeds the predicted k2 by one order of magnitude in the absence of an ocean, and is 3-σ away from the predicted k2 if the ocean is pure water resting on top of a rigid ocean floor. Previous studies demonstrate that an ocean heavily enriched in salts (salinity S\gtrsim200 g/kg) can explain the 3-σ signal in k2. Here we revisit previous interpretations of Titan's large k2 using simple physical arguments and propose a new interpretation based on the dynamic tidal response of a stably stratified ocean in resonance with eccentricity tides raised by Saturn. Our models include inertial effects from a full consideration of the Coriolis force and the radial stratification of the ocean, typically neglected or approximated elsewhere. The stratification of the ocean emerges from a salinity profile where salt concentration linearly increases with depth. We find multiple salinity profiles that lead to the k2 required by Cassini. In contrast with previous interpretations that neglect stratification, resonant stratification reduces the bulk salinity required by observations by an order of magnitude, reaching a salinity for Titan's ocean that is compatible with that of Earth's oceans and close to Enceladus' plumes. Consequently, no special process is required to enrich Titan's ocean to a high salinity as previously suggested.