Astronomical Ice: The Effects of Treating Ice as a Porous Media on the Dynamics and Evolution of Extraterrestrial Ice-Ocean Environments

Abstract:

With the prevalence of water and ice rich environments in the solar system, and likely the universe, becoming more apparent, understanding the evolutionary dynamics and physical processes of such locales is of great importance. Piqued interest arises from the understanding that the persistence of all known life depends on the presence of liquid water. As in situ investigation is currently infeasible, accurate numerical modeling is the best technique to demystify these environments. We will discuss an evolving model of ice-ocean interaction aimed at realistically describing the behavior of the ice-ocean interface by treating basal ice as a porous media, and its possible implications on the formation of astrobiological niches.

Treating ice as a porous media drastically affects the thermodynamic properties it exhibits. Thus inclusion of this phenomenon is critical in accurately representing the dynamics and evolution of all ice-ocean environments. This model utilizes equations that describe the dynamics of sea ice when it is treated as a porous media (Hunke et. al. 2011), coupled with a basal melt and accretion model (Holland and Jenkins 1999). Combined, these two models produce the most accurate description of the processes occurring at the base of terrestrial sea ice and ice shelves, capable of resolving variations within the ice due to environmental pressures. While these models were designed for application to terrestrial environments, the physics occurring at any ice-water interface is identical, and these models can be used to represent the evolution of a variety of icy astronomical bodies. As terrestrial ice shelves provide a close analog to planetary ice-ocean environments, we truth test the models validity against observations of ice shelves.

We apply this model to the ice-ocean interface of the icy Galilean moon Europa. We include profiles of temperature, salinity, solid fraction, and Darcy velocity, as well as temporally and spatially varying melt and accretion rates. A porous medium is an ideal place for the coalescence of nutrients and the formation of energy gradients, key controllers of biological activity. Understanding the physics that influence ice-ocean exchange is thus essential in assessing the habitability of Europa and its contemporaries.