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Organics Modify Freezing Processes of Ocean World Ice Shells

Presentation #509.05 in the session Icy Moons Interior and Ice Shell (Oral Presentation)

Published onOct 23, 2023
Organics Modify Freezing Processes of Ocean World Ice Shells

The modeling of the phase fractions in the ice shells of Europa and Enceladus has previously focused on inorganic brines. However, organics have also been detected in Enceladus’s plume. Furthermore, it is anticipated to find organic on Europa as well during the upcoming Europa Clipper Mission, which seeks to constrain the chemistry and habitability of this Ocean World.

The Murchison meteorite is thought to represent a good analog of materials and molecules that could be found in Ocean World cores. Both amino acids and carbohydrates were found on this meteorite. Our hypothesis is that Murchison meteorite organics could behave like uronic acids do in sea ice on Earth and thereby create and maintain microhabitable pore space if they were incorporated into an Ocean World ice shell. Our approach is designed to provide an initial assessment of how organic incorporation may enhance the habitability Ocean World ice shells.

To evaluate the role of organics in enhancing the habitability of Ocean World ice shells, we added organics to non-organic ocean chemistries. The initial ocean chemistries were based on the published modeled geochemistries for Europa (e.g., Zolotov and Shock, 2001) and Enceladus (Glein et al., 2018). We then added amino acids, such aspartic acid, serine, glycine, and beta alanine, and carbohydrates such as glycerol and benzoic acid at concentrations present in the Murchison meteorite. These combined ocean chemistries were the starting point for our models.

We conducted thermodynamic modeling using OLI Studio, which combines equations of state and thermophysical data to model multiphase electrolyte environments and calculate properties such as pH, viscosity, density, and enthalpy. The habitability metrics calculated using OLI Studio will be compared to the published results obtained from the aqueous geochemistry program FREZCHEM. This will be used to validate the use of OLI Studio for this type of applications. The strengths and limitations of the thermodynamic model will also be presented.

Thermodynamic modeling using OLI Studio revealed that the addition of organic compounds to brine will affect the phase volume fraction. These data suggest organics modify the freezing processes of Ocean World ice shells in ways that may maintain habitable conditions within the ice shells.

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