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A spin-orbit constraint on the viscosity of a Mercurian liquid coreThe escape of Mercury from the stable spin-orbit resonance in which the spin angular velocity is twice the orbital mean motion (2n) requires that the kinematic viscosity of a molten core with a laminar boundary layer be comparable to that of water (0.01 sq cm/s) and the tidal Q be less than about 100. If the boundary layer is turbulent, escape from the resonance is only consistent with a liquid core of low viscosity if the critical Reynolds number for the onset of turbulence is above about 500, the moment difference (B - A)/C is below about 0.00001, and the tidal dissipation factor Q is less than about 40. These conclusions depend on the assumptions that Mercury's obliquity was near 0 deg at the time of resonance passage, that the liquid core was not stably stratified at the time at which Mercury passed through the resonance, that a turbulent boundary layer can be characterized by a turbulent or eddy viscosity coefficient, and that the most important coupling between core and mantle is a viscous coupling at a smooth spherical boundary.
Document ID
19770041328
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Peale, S. J.
(California Univ. Santa Barbara, CA, United States)
Boss, A. P.
(California, University Santa Barbara, Calif., United States)
Date Acquired
August 8, 2013
Publication Date
February 10, 1977
Publication Information
Publication: Journal of Geophysical Research
Volume: 82
Subject Category
Lunar And Planetary Exploration
Accession Number
77A24180
Funding Number(s)
CONTRACT_GRANT: NGR-05-010-062
Distribution Limits
Public
Copyright
Other

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