2007Icar__191_

Authors: Nimmo F., Thomas P. C., Pappalardo R. T., and Moore W. B.
Year: 2007
Title: The global shape of Europa: Constraints on lateral shell thickness variations
Journal: Icarus
Volume: 191
Number: 1
Pages: 183-192
Keywords: Jupiter, galilean, planetology
Abstract: The global shape of Europa is controlled by tidal and rotational potentials and possibly by lateral variations in ice shell thickness. We use limb profiles from four Galileo images to determine the best-fit hydrostatic shape, yielding a mean radius of 1560.8+/-0.3 km and a radius difference a?c of 3.0+/-0.9 km, consistent with previous determinations and inferences from gravity observations. Adding long-wavelength topography due to proposed lateral variations in shell thickness results in poorer fits to the limb profiles. We conclude that lateral shell thickness variations and long-wavelength isostatically supported topographic variations do not exceed 7 and 0.7 km, respectively. For the range of rheologies investigated (basal viscosities from 10¹⁴ to 10 Pas) the maximum permissible (conductive) shell thickness is 35 km. The relative uniformity of Europa's shell thickness is due to either a heat flux ?7 mWm from the silicate interior, lateral ice flow at the base of the shell, or convection within the shell.
%F: AA(Department Earth and Planetary Sciences, University of California Santa Cruz, 1156 High St, Santa Cruz, CA 95064, USA), AB(Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853, USA), AC(Geophysics and Planetary Geosciences Group, Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109, USA), AD(Department of Earth and Space Sciences, University of California Los Angeles, 595 Charles Young Drive E, Los Angeles, CA 90095, USA)
Bibliogaphic Code: 2007Icar..191..183N

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