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Entrainment and Dynamics of Ocean-derived Impurities within Europa's Ice Shell
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  • Jacob Buffo,
  • Britney Elyce Schmidt,
  • Christian Huber,
  • Catherine Colello Walker
Jacob Buffo
Dartmouth College, Dartmouth College, Dartmouth College

Corresponding Author:jacob.j.buffo@dartmouth.edu

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Britney Elyce Schmidt
Georgia Institute of Technology, Georgia Institute of Technology, Georgia Institute of Technology
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Christian Huber
Brown University, Brown University, Brown University
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Catherine Colello Walker
Woods Hole Oceanographic Institution, Woods Hole Oceanographic Institution, Woods Hole Oceanographic Institution
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Compositional heterogeneities within Europa’s ice shell likely impact the dynamics and habitability of the ice and subsurface ocean, but the total inventory and distribution of impurities within the shell is unknown. In sea ice on Earth, the thermochemical environment at the ice-ocean interface governs impurity entrainment into the ice. Here, we simulate Europa’s ice-ocean interface and bound the impurity load (1.053-14.72 g/kg (parts per thousand weight percent, or ppt) bulk ice shell salinity) and bulk salinity profile of the ice shell. We derive constitutive equations that predict ice composition as a function of the ice shell thermal gradient and ocean composition. We show that evolving solidification rates of the ocean and hydrologic features within the shell produce compositional variations (ice bulk salinities of 5-50% of the ocean salinity) that can affect the material properties of the ice. As the shell thickens, less salt is entrained at the ice-ocean interface, which implies Europa’s ice shell is compositionally homogeneous below ~ 1 km. Conversely, the solidification of water filled fractures or lenses introduces substantial compositional variations within the ice shell, creating gradients in mechanical and thermal properties within the ice shell that could help initiate and sustain geological activity. Our results suggest that ocean materials entrained within Europa’s ice shell affect the formation of geologic terrain and that these structures could be confirmed by planned spacecraft observations.
Oct 2020Published in Journal of Geophysical Research: Planets volume 125 issue 10. 10.1029/2020JE006394