Long-term deformation driven by small ambient tectonic stresses and strong oscillating tidal within Enceladus with analogy to rock behavior near the San Andreas Fault
Norman H. SleepPublished May 31, 2015, SCEC Contribution #2108
Strong tidal stresses brought much of the icy shell of Enceladus into frictional failure at past times of high orbital eccentricity. The frictional behavior of shallow terrestrial rock exposed to repeated episodes of strong seismic waves provides analogy. Frictional failure produces cracks that lower the shear modulus. Seismic regolith develops where the shear modulus increases linearly with depth. Imposed peak strains barely cause frictional failure within self-organized regolith. With regard to Enceladus, eccentricity could continue to build up in the past since little anelastic strain, and hence tidal dissipation occurred within the self-organized regolith and within the underlying cold ice. A frictional instability analogous to the formation of weak major faults on the Earth likely occurred once the regolith was many kilometers thick. The effective coefficient of friction dropped to low levels along major faults within the deep cold ice. Tidal dissipation on these faults heated the ice starting thermal convention within the South Polar Terrain. Once thermal buoyancy produced stresses, the oscillating stresses from tides nonlinearly enhanced the rate of tectonic convection. Warm ice that dissipates tides now exists within Enceladus. The eccentricity will likely decrease and the object will then freeze.
Citation
Sleep, N. H. (2015). Long-term deformation driven by small ambient tectonic stresses and strong oscillating tidal within Enceladus with analogy to rock behavior near the San Andreas Fault. Geochemistry, Geophysics, Geosystems, 16(5), 1670-1686. doi: 10.1002/2015GC005725.
