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

TL;DR

This paper proposes that sluggish lid convection in icy satellite shells can generate the heat flow and deformation necessary for ridge-and-trough terrain formation, unifying observations across multiple moons.

Contribution

It introduces sluggish lid convection as a key process explaining ridge-and-trough terrains on icy satellites, regardless of shell thickness.

Findings

Sluggish lid convection produces appropriate heat flow and deformation rates.

Surface deformation is driven by tidal and convective stresses.

Tidal cracking patterns influence terrain location.

Abstract

Ridge-and-trough terrain is a common landform on outer Solar System icy satellites. Examples include Ganymede's grooved terrain, Europa's gray bands, Miranda's coronae, and several terrains on Enceladus. The conditions 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$^{-1}$. Our prior work shows that the conditions associated with the formation of these terrains on Ganymede and the south pole of Enceladus are consistent with vigorous solid-state ice convection in a shell with a weak surface. We show that sluggish lid convection, an intermediate regime between the isoviscous and stagnant lid regimes, can create the heat flow and deformation rates appropriate for ridge and trough formation on a number of satellites, regardless of the ice shell thickness. For convection to deform their surfaces, the ice shells must have yield stresses similar in magnitude to the daily tidal stresses. Tidal and convective stresses deform the surface, and the spatial pattern of tidal cracking controls the locations of ridge-and-trough terrain.