How Grooved Terrain on Icy Moons Formed

A Common Origin for Ridge-and-Trough Terrain on Icy Satellites by Sluggish Lid Convection

Authors:

Barr et al

Abstract:

Ridge and trough terrain is a common landform on icy satellites of the outer solar system. Examples include the grooved terrain on Ganymede, gray bands on Europa, coronae on Uranus's moon Miranda, and ridges and troughs in the northern plains of Saturn's small, but active, moon Enceladus. Regardless of setting, the heat flow and strain rates associated with the formation of each of these terrains are similar: heat flows of order tens to a hundred milliwatts per meter squared, and deformation rates of order 10−16 to 10−12 s−1. Barr (2008) and Hammond & Barr (2014a) have previously shown that the conditions associated with the formation of ridge and trough terrain on Ganymede and the south polar terrain on Enceladus are consistent with solid-state ice shell convection in a shell with a weak surface. Here, we show that sluggish lid convection can simultaneously create the heat flow and deformation appropriate for the formation of ridge and trough terrains on a number of satellites. This conclusion holds regardless of the thickness of the satellites' ice shells. For convection to deform their surfaces, the ice shells must have yield stresses similar in magnitude to the daily tidal stresses exerted by the gravitational pull from their parent planets. This suggests that tidal and convective stresses must act together to deform the surface, and that the spatial pattern of tidal cracking on the surfaces of the moons controls the locations of ridge and trough terrain.