The Role of Clathrate Formation in Europa's Ocean Composition

We use a thermodynamic statistical model to evaluate how the composition of Europa's internal ocean may have been affected by clathrate hydrate formation. Assuming an input of the observed O2 and CO2 from the surface into a mildly acidic ocean (pH < 6), and considering the possibility of con...

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Bibliographic Details
Published in:The Astrophysical journal 2019-11, Vol.885 (1), p.14
Main Authors: Bouquet, Alexis, Mousis, Olivier, Glein, Christopher R., Danger, Grégoire, Waite, J. Hunter
Format: Article
Language:English
Subjects:
Argon
astrobiology
Astrophysics
Carbon dioxide
Comets
Composition
Computational fluid dynamics
Europa
Gas hydrates
Gases
Hydrogen sulfide
In situ measurement
Krypton
methods: numerical
Oceans
planets and satellites: composition
planets and satellites: individual (Europa)
planets and satellites: interiors
Rare gases
Sciences of the Universe
Statistical models
Xenon
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Summary:We use a thermodynamic statistical model to evaluate how the composition of Europa's internal ocean may have been affected by clathrate hydrate formation. Assuming an input of the observed O2 and CO2 from the surface into a mildly acidic ocean (pH < 6), and considering the possibility of contributions by reduced (with CH4 and H2S) or oxidized (CO2-bearing) hydrothermal fluids, we calculate the fractional occupancies in clathrate and deduce the effect on the ocean's composition. The structure of the clathrate formed, and therefore its density and composition is influenced by the relative amount of O2 compared to the other compounds present. We also include a mixture of noble gases-argon, krypton, and xenon-based on cometary abundances measured at comet 67P and find that the Ar/Kr ratio can be affected by almost two orders of magnitude. In most cases, the formed clathrate is likely to become part of the icy crust, with guest molecules possibly accessible to future in situ measurements by the Europa Clipper and JUICE missions.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ab40b0