Icy Moon Surfaces Microstructure through Multiphysics Simulations

Abstract

Water ice has a microstructure shaped by a complex interplay of coupled multi-physics processes. Among them, ice sintering—also referred to as metamorphism or annealing—transports material from ice grains into their neck region, resulting in changes in the mechanical and thermal properties of the ice. Understanding sintering is essential to investigate the properties and microstructure of ice. While the sintering process of snow on Earth has been extensively studied, there is a scarce amount of information regarding the alteration of ice in planetary surface environments characterized by low temperatures and pressures. Here we present a multiphysics simulation model designed to study the evolution of planetary ice microstructure.  Coupled to a heat transfer solver, we have built a new model for the sintering of ice grain  with mathematical refinement to the diffusion process. As changes in ice microstructure affect the thermal properties we have expressed the heat conductivity with a formulation that consider microstructure and porosity which enables a two coupling between sintering and heat transfers. Our simulations of Europa's icy surface spanned a million years, allowing us to thoroughly explore the evolution of ice microstructure. Results show that the hottest regions experience significant sintering, even if high temperatures are only reached during a brief portion of the day. This process takes place on timescales shorter than Europa's ice crust age, suggests that these regions should currently have surface ice composed of interconnected grains. Accurately simulating these highly coupled processes, plays a crucial role in accurately determining the microstructure and quantitative composition of Europa's surface, a key objective for upcoming missions such as JUICE and Europa Clipper.