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Geophysical investigations of habitability in ice-covered ocean worlds

Vance, Steven D. and Panning, Mark P. and Stähler, Simon and Cammarano, Fabio and Bills, Bruce G. and Tobie, Gabriel and Kamata, Shunichi and Kedar, Sharon and Sotin, Christophe and Pike, William T. and Lorenz, Ralph and Huang, Hsin-Hua and Jackson, Jennifer M. and Banerdt, Bruce (2018) Geophysical investigations of habitability in ice-covered ocean worlds. Journal of Geophysical Research. Planets, 123 (1). pp. 180-205. ISSN 2169-9097. http://resolver.caltech.edu/CaltechAUTHORS:20171204-091454210

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Abstract

Geophysical measurements can reveal the structures and thermal states of icy ocean worlds. The interior density, temperature, sound speed, and electrical conductivity thus characterize their habitability. We explore the variability and correlation of these parameters using 1-D internal structure models. We invoke thermodynamic consistency using available thermodynamics of aqueous MgSO_4, NaCl (as seawater), and NH_3; pure water ice phases I, II, III, V, and VI; silicates; and any metallic core that may be present. Model results suggest, for Europa, that combinations of geophysical parameters might be used to distinguish an oxidized ocean dominated by MgSO_4 from a more reduced ocean dominated by NaCl. In contrast with Jupiter's icy ocean moons, Titan and Enceladus have low-density rocky interiors, with minimal or no metallic core. The low-density rocky core of Enceladus may comprise hydrated minerals or anhydrous minerals with high porosity. Cassini gravity data for Titan indicate a high tidal potential Love number (k_2 > 0.6), which requires a dense internal ocean (ρ_(ocean) >1,200 kg m^(−3)) and icy lithosphere thinner than 100 km. In that case, Titan may have little or no high-pressure ice, or a surprisingly deep water-rock interface more than 500 km below the surface, covered only by ice VI. Ganymede's water-rock interface is the deepest among known ocean worlds, at around 800 km. Its ocean may contain multiple phases of high-pressure ice, which will become buoyant if the ocean is sufficiently salty. Callisto's interior structure may be intermediate to those of Titan and Europa, with a water-rock interface 250 km below the surface covered by ice V but not ice VI.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.1002/2017JE005341DOIArticle
http://onlinelibrary.wiley.com/doi/10.1002/2017JE005341/abstractPublisherArticle
https://arxiv.org/abs/1705.03999arXivDiscussion Paper
ORCID:
AuthorORCID
Vance, Steven D.0000-0002-4242-3293
Panning, Mark P.0000-0002-2041-3190
Stähler, Simon0000-0002-0783-2489
Cammarano, Fabio0000-0003-3475-9448
Tobie, Gabriel0000-0002-4494-0294
Kamata, Shunichi0000-0003-1226-9966
Pike, William T.0000-0002-7660-6231
Lorenz, Ralph0000-0001-8528-4644
Huang, Hsin-Hua0000-0002-1115-2427
Alternate Title:Geophysical tests for habitability in ice-covered ocean worlds
Additional Information:© 2017 American Geophysical Union. Received 4 MAY 2017; Accepted 15 OCT 2017; Accepted article online 30 NOV 2017; Published online 25 JAN 2018. We thank Jurrien Knibbe and an anonymous reviewer for thoughtful and detailed reviews that improved the quality of this paper. The PlanetProfile model and applications described in this work are available online (Vance, 2017). Support for its use may be obtained from SDV via email. Work by JPL co-authors was partially supported by strategic research and technology funds from the Jet Propulsion Laboratory, Caltech, and by the Icy Worlds node of NASA's Astrobiology Institute (13-13NAI7_2-0024). G. T. acknowledges supports from CNES for the ESA JUICE mission and the NASA Europa Clipper mission and for the project ANR OASIS. R. L. acknowledges the support of NASA Outer Planets Research grant NNX13AK97G “Physical Processes in Titan's Seas.” S. C. S. was supported by grant SI1538/4-1 of Deutsche Forschungsgemeinschaft DFG. S. D. V. acknowledges the support of NASA Outer Planets Research grant NNH12ZDA001N “Solution Thermochemistry Relevant to Outer Planets and Satellites.” No conflicts of interest are identified associated with this work. A part of the research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Group:Seismological Laboratory
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
NASA13-13NAI7 2-0024
Centre National d'Études Spatiales (CNES)UNSPECIFIED
NASANNX13AK97G
Deutsche Forschungsgemeinschaft (DFG)SI1538/4-1
NASANNH12ZDA001N
Record Number:CaltechAUTHORS:20171204-091454210
Persistent URL:http://resolver.caltech.edu/CaltechAUTHORS:20171204-091454210
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:83657
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:13 Dec 2017 05:12
Last Modified:04 Sep 2018 17:04

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