Elastic-plastic flexure and heat flux on icy moons

Abstract

Investigating ice shell flexure observed in elevation data provides one of the few ways to infer the ice shell structure and the thermal evolution of icy moons. Most previous work have relied on the classical elastic plate model to fit observations and infer the elastic thickness of the lithosphere and heat flux at the time of deformation. Here, we show how to compute more realistic elastic-plastic flexural profiles considering ice friction in the upper ice shell and plastic flow at deeper levels. This approach does not rely on the elastic thickness mathematical construct and can be used to directly infer the ice shell heat flux and/or rheology from observed flexural profiles. We show that, under high plate curvature (>10−5 m−1), purely elastic models predict unrealistic oscillations near and in the flexural bulge region, which can bias the estimated elastic thickness and heat flux. Applying our elastic-plastic flexural model to Ariel and Ganymede, we find heat fluxes lower than previous estimates, which has implications for our understanding of the geodynamic history of these worlds. We demonstrate that the maximum curvature of the synthetic elastic plate profile should be used when relating elastic thickness to heat flux, and discuss heat flux estimation on icy moons.