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Subsurface Oceans on Europa and Callisto: Constraints from Galileo Magnetometer ObservationsGalileo measured the magnetic field perturbations of Europa and Callisto, which are consistent with dipole fields created by temporal variations of the surrounding jovian magnetospheric field. These fields almost match those expected for perfectly conducting moons. Using a simple shell model, we analyze the implications of these observations for the electrical structure for the interiors of the moons. It is discovered that Europa and Callisto must possess areas where the conductivity exceeds 0.06 and 0.02 S/m at a depth of no more than 200 and 300 km below the surface, respectively. This conductivity is not attainable in ice or silicates, unless large temperature gradients can be maintained below the ice or the ice layer is at least partially molten. A cloud of pick-up ions or an ionosphere are probably insufficiently conductive. Global Earth-like oceans under the surface of both moons could explain the observations if they are at least a few kilometers thick.
Document ID
20020046790
Acquisition Source
Goddard Space Flight Center
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Zimmer, Christophe
(California Univ. Los Angeles, CA United States)
Khurana, Krishan K.
(California Univ. Los Angeles, CA United States)
Kivelson, Margaret G.
(California Univ. Los Angeles, CA United States)
Date Acquired
August 20, 2013
Publication Date
January 1, 2000
Publication Information
Publication: Icarus
Publisher: Academic Press
Volume: 147
ISSN: 0019-1035
Subject Category
Lunar And Planetary Science And Exploration
Report/Patent Number
UCLA-Publ-5422
Report Number: UCLA-Publ-5422
ISSN: 0019-1035
Funding Number(s)
CONTRACT_GRANT: JPL-958694
CONTRACT_GRANT: NAG5-7959
Distribution Limits
Public
Copyright
Other

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