New insights into temperature-dependent ice properties and their effect on ice shell convection for icy ocean worlds

Abstract

Ice shell dynamics are a critical control on the habitability of icy ocean worlds. Here, we present a systematic study evaluating the effect of temperature-dependent material properties on these dynamics. We review the published thermal conductivity data for ice, which demonstrates that the most commonly used conductivity model in planetary science represents a lower bound. We propose a new model for thermal conductivity that spans the temperature range relevant to the ice shells of ocean worlds. This increases the thermal conductivity at low temperatures near the surface by about a fifth. We show that such an increase in thermal conductivity near the cold surface favors conduction over convection in the ice shell of Europa. Furthermore, we find that including temperature dependent specific heat capacity decreases the energy stored in the conductive lid. Thus, the timescale for ice shell response to thermal perturbations is reduced by approximately one third. An ice shell that is more sensitive to thermal perturbations may help to explain surface features such as chaotic terrains which require large additions of energy to the near-surface ice.