Tectonic history of Europa: Coupling between internal evolution and surface stresses

Abstract

A stress history in the ice shell of Europa is presented. Europa's surface is ubiquitous in extensional tectonic features such as banded terrains. These surface features suggest that the surface may have been fractured and extended due to tensional stress, and various origins for such stresses have been proposed. We have focused on the solidification of the liquid water layer and the accompanying volume change as one of the dominant sources for such stresses. To estimate the stress state in the ice shell, we first performed numerical simulations of the thermal history. Based on the resulting structural evolution, we calculated stresses in the viscoelastic ice shell due to the solidification of the liquid layer. Europa's liquid layer solidifies slowly and may partially survive at present, and its solidification induces sufficient tensional stress to drive extensional tectonic activity. Consequently, we propose the tectonic scenario that the volume change due to phase change develops the basic amplitude of the stress, while tidal forces work as a trigger to fracture the surface.

Structural and tidal models of Titan and inferences on cryovolcanism

“…Though alternative explanations prefer an exogenic origin [e.g., Moore and Pappalardo , ], the correlation between the tidal stress patterns illustrated in Figure and the surface features seen on Titan may rather suggest an endogenic origin of the latter. The calculated diurnal tidal stresses are on the order of a few tens of kPa, comparable to the magnitude of maximum possible nonhydrostatic deviatoric stresses on Titan [ Gao and Stevenson , ], but the accumulation of tectonic stresses could eventually help exceed the tensile strength of fractured ice [ Kimura et al , ; Smith‐Konter and Pappalardo , ]. True polar wander of the spin axis due to large‐scale redistribution of mass on the surface or within the interior and nonsynchronous rotation of the decoupled shell moving slowly across the satellite's permanent tidal bulge may cause the buildup of long‐term stresses and the formation of geologic surface features on a global scale [e.g., Jara‐Orué and Vermeersen , , and references therein].…”

“…If the local temperature gradient is subadiabatic, k v is zero, the fluid material is stably stratified with respect to thermal convection, and the local Nusselt number equals one. Although this treatment slightly overestimates the heat flux at very low Rayleigh numbers [Abe, 1995], the extended mixing length theory has been successfully applied in previous studies [e.g., Sasaki and Nakazawa, 1986;Abe, 1997;Senshu et al, 2002;Kimura et al, 2007Kimura et al, , 2009Tachinami et al, 2011;Wagner et al, 2012].…”

Experimental Investigations on the Effects of Dissolved Gases on the Freezing Dynamics of Ocean Worlds

“…Faults and fractures may be found on their own or as part of more complicated features such as coronae, tilted blocks, and chaos terrain (e.g., Beyer et al, 2019; Collins et al, 2009; Stephan et al, 2013). It is also important to note that these can form from global (e.g., tidal, despinning, and true polar wander; Collins et al, 2009; Hemingway et al, 2019; Kimura et al, 2007; Nimmo, 2004) or regional and local stresses (e.g., from convective upwellings in the ice layer or from freezing of small liquid reservoirs; Collins et al, 2009; Hemingway et al, 2019; Howell & Pappalardo, 2018). Cryovolcanism on icy bodies can lead to the formation of particulate deposits (from erupting plumes), lobate extrusions, and smooth terrains (Stephan et al, 2013).…”