The Influence of Permeability and Melt Rate on Melt Extraction Times in Europa’s Ice Shell
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Pierce-Walker, Chazerae
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Abstract
Jupiter's moon Europa is a promising candidate for studying habitable environments in our solar system. Sustained chemical disequilibrium created by a combination of reactants in the ocean and oxidants sourced from the surface may be a key ingredient for habitable conditions on Europa. However, there needs to be a way to transport those oxidants through the ice shell to the ocean. Previous researchers have suggested that Darcy-like two-phase flow may be able to transport materials through the ice shell, but assumptions made about the permeability laws governing fluid transport make the results of these models difficult to compare. This masters thesis examines two-phase flow as a potential transport mechanism for oxidants, and investigates the effects of different permeability models on melt extraction times to assess the efficiency of this method. The results of this thesis show that permeability laws depending on different grain sizes/geometries and different power law relationships with porosity result in melt extraction times ranging from several hundreds of years to several millions of years. These uncertainties make assessing the viability of two-phase flow difficult. Additionally, simulations varying melting and freezing rates in the ice shell were run to explore how sensitive ice shells of different permeability are to changes in melt volume over time. While simulations with high permeability always resulted in significantly faster extraction times than those with low permeability regardless of the melting or freezing rate, low-permeability simulations were far more sensitive to melting and freezing rates than high-permeability simulations. Even very low rates of phase change ($0.0001$ kg/$m^3$/yr) were able to substantially shorten or lengthen the extraction timescale by thousands of years. This suggests that the effect of an emplaced plume or other heating scenario may promote very efficient transport of surface materials even with low melt generation. A lack of information about the permeability of Europa's ice shell creates substantial uncertainty about the possible timescales involved in melt extraction. In the future, this may be improved by more measurements from NASA's Europa Clipper mission and further modeling of Europa's ice shell that incorporates more complex processes such as solid-state ice convection and the inclusion of salts.
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2025-12
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Thesis (Masters Degree)