P075-05
A Deep Dive into Planetary Abysses: Effects of Pressure, Phase Equilibria and Chemistry on the Structure and Habitability of Icy-Ocean Worlds.
Wednesday, 16 December 2020: 04:16
Virtual
Baptiste Journaux1, J Michael Brown2, Evan Abramson3, Olivier Bollengier4, Penny Espinoza5, Anna Pakhomova6, Ines Collings7, Sylvain Petitgirard8, Steve Vance9, Erica Clinton4 and Tiziana Boffa Ballaran10, (1)University of Washington, Earth and Space Sciences, Seattle, WA, United States, (2)University of Washington Seattle Campus, Seattle, WA, United States, (3)University of Washington Seattle, Seattle, WA, UNITED STATES, (4)University of Washington Seattle Campus, Earth and Space Sciences, Seattle, WA, United States, (5)University of Washington Seattle Campus, Earth and Space Science, Seattle, United States, (6)DESY Deutsches Elektronen Synchrotron, Hamburg, Germany, (7)Empa, Duebendorf, Switzerland, (8)ETH Swiss Federal Institute of Technology Zurich, Zurich, Switzerland, (9)Jet Propulsion Laboratory, California Institute of Technology, Pasadena, United States, (10)University of Bayreuth, Bayerisches Geoinstitut, Bayreuth, Germany
Abstract:
For terrestrial planets the behavior of silicates as the predominant rock-forming constituent is understood and described as petrology. Because silicates remain metastable at Earth’s surface, rocks collected at the surface can be “read” to give their depth and temperature of formation as well as the chemical processes associated with their origins. In the case of icy ocean worlds, ice and hydrates are the dominant solid phases in both the upper crust and in possible layers of high-pressure polymorphs at greater depths. As with metastable silicates on Earth, the preservation of water-rich phases formed at depth is probable on low temperature planetary surfaces through various processes. Therefore, the petrology of icy ocean worlds remains to be explored experimentally and requires a comprehensive thermodynamic and petrological framework to support the scientific returns from past, present and future space missions.
We present here new experimental and theoretical advances, which constrain the thermodynamics of aqueous systems at pressures and temperatures relevant to icy-world hydrospheres. Through X-ray diffraction, new measurements of high-pressure ice polymorphs were combined with statistical physics models to derive new Gibbs surface parameterization for all phases stable in the pure water phase diagram. These have been combined into the SeaFreeze open-source framework (Python and Matlab) to predict water and ice equilibrium thermodynamics up to 10,000K and 2300 MPa, covering the entire range of conditions found in hydrospheres of the Solar system. Based on experimental sound speed measurements, the Gibbs parameterization of (Na,Cl,Mg,SO4)-H2O aqueous solution chemistry has since been investigated and allows to predict melting point depression and ices-solution density inversions. Finally, we discovered and characterized several new hydrate phases in the (Na,Cl,Mg,SO4)-H2O systems that could be major species of icy worlds, strongly influencing the structure and dynamic of their hydrospheres, and potentially detectable on their surfaces.
Acknowledgements: Work supported by NASA SSW grant 80NSSC17K0775, by the Icy Worlds, and Titan and Beyond nodes of the NAI (08‐NAI5‐0021 and 17‐NAI8‐ 2‐017). Part of this work was carried out at the JPL, Caltech, under a contract with NASA (80NM0018D0004).
