Viscoelastic models of tidal heating in Enceladus
Abstract
Tidal heating in Enceladus is investigated using multilayered viscoelastic models of the satellite. Dissipation in a homogeneous Maxwell model of Enceladus at the current eccentricity can be as large as 920 GW, nearly a factor of 2000 greater than previously thought, reflecting the fact that the dynamic Love number can approach unity the elastic Love number ∼10 -3. The theoretical tidal heating maximum violates an upper bound based on Saturn's Q and models with this much heating are unreasonable. Plausible multilayered models are shown to be thermally stable at the current eccentricity with ∼10 km thick lithosphere and surface heat flow ∼5 mW m -2; the models require a combination of near-surface insulation, subsurface solar heating, or anomalously low lithosphere conductivity to simultaneously fit dynamic and geologic constraints. A two-layer model with a conductive lithosphere over a Maxwell mantle has mantle viscosity of about 10 13 Pa sec and mantle temperature about 210°K. A three-layer model with an internal ocean of accumulated NH 3 · H 2O eutectic melt that decouples the lithosphere from a Maxwell core has slightly lower internal viscosity and slightly higher temperature than the two-layer model. Dissipation in the ocean layer may be significant if the tidally forced flow is turbulent. The models suggest that Enceladus' thermal and dynamical evolution may have been relatively simple, involving only Dione in a 2:1 resonance. The current eccentricity could have been maintained since resonance onset with recurring surface activity due to a thermally active interior.
- Publication:
-
Icarus
- Pub Date:
- March 1989
- DOI:
- 10.1016/0019-1035(89)90071-7
- Bibcode:
- 1989Icar...78...90R
- Keywords:
-
- Astronomical Models;
- Enceladus;
- Orbital Resonances (Celestial Mechanics);
- Viscoelasticity;
- Eccentricity;
- Heating;
- Lithosphere;
- Satellite Surfaces;
- Turbulent Flow;
- SATURN;
- SATELLITES;
- ENCELADUS;
- TIDAL EFFECTS;
- HEATING;
- MODELS;
- LAYERS;
- ELASTICITY;
- DISSIPATION;
- ECCENTRICITY;
- PARAMETERS;
- LITHOSPHERE;
- MANTLE;
- CONDUCTIVITY;
- VISCOSITY;
- TEMPERATURE;
- DYNAMICS;
- EVOLUTION;
- DIAGRAMS