000003989 001__ 3989
000003989 005__ 20190130110945.0
000003989 0247_ $$2DOI$$a10.1016/j.icarus.2017.11.009
000003989 037__ $$aSCART-2019-0112
000003989 100__ $$aBeuthe, Mikael
000003989 245__ $$aEnceladus's crust as a non-uniform thin shell: I tidal deformations
000003989 260__ $$c2018
000003989 520__ $$aThe geologic activity at Enceladus's south pole remains unexplained, though tidal deformations are probably the ultimate cause. Recent gravity and libration data indicate that Enceladus's icy crust floats on a global ocean, is rather thin, and has a strongly non-uniform thickness. Tidal effects are enhanced by crustal thinning at the south pole, so that realistic models of tidal tectonics and dissipation should take into account the lateral variations of shell structure. I construct here the theory of non-uniform viscoelastic thin shells, allowing for depth-dependent rheology and large lateral variations of shell thickness and rheology. Coupling to tides yields two 2D linear partial differential equations of the fourth order on the sphere which take into account self-gravity, density stratification below the shell, and core viscoelasticity. If the shell is laterally uniform, the solution agrees with analytical formulas for tidal Love numbers; errors on displacements and stresses are less than 5% and 15%, respectively, if the thickness is less than 10% of the radius. If the shell is non-uniform, the tidal thin shell equations are solved as a system of coupled linear equations in a spherical harmonic basis. Compared to finite element models, thin shell predictions are similar for the deformations due to Enceladus's pressurized ocean, but differ for the tides of Ganymede. If Enceladus's shell is conductive with isostatic thickness variations, surface stresses are approximately inversely proportional to the local shell thickness. The radial tide is only moderately enhanced at the south pole. The combination of crustal thinning and convection below the poles can amplify south polar stresses by a factor of 10, but it cannot explain the apparent time lag between the maximum plume brightness and the opening of tiger stripes. In a second paper, I will study the impact of a non-uniform crust on tidal dissipation.
000003989 536__ $$aPRODEX/$$c4000120791/$$fPlanetInterior
000003989 594__ $$aNO
000003989 773__ $$c145-174$$pIcarus$$v302$$y2018
000003989 8560_ $$fmikael.beuthe@observatoire.be
000003989 85642 $$ahttps://arxiv.org/abs/1711.08236
000003989 905__ $$apublished in
000003989 980__ $$aREFERD