Titan’s spin state as a constraint on tidal dissipation

Abstract

Tidal dissipation in satellites affects their orbital and rotational evolution and their ability to maintain subsurface oceans. However, a satellite’s dissipation rate, parameterized by k 2 /Q , is hard to measure and is only known for the Moon and Io. Here, we use Titan’s measured departure from its expected rotation state to infer k 2 /Q and its boundary layer dissipation parameter K/C s . Over the likely range of ocean and ice shell thicknesses, we infer a K / C s of 6.3 × 10 −14 s −1 to 2.4 × 10 −10 s −1 , a k 2 /Q of 0.058 to 0.12, and a minimum dissipation factor Q ≈ 5 . Titan’s dissipation parameters are one to two orders of magnitude larger than the Moon’s and suggest an interior with a low effective viscosity. Titan’s dissipation rate implies that its eccentricity and inclination are damping rapidly, consistent with an excitation within the last ~350 Myr. The forthcoming Dragonfly lander could measure Titan’s tidal response, and JUICE could use our approach to determine Ganymede’s k 2 /Q .

Topics & Concepts