Authors: Anderson J. D., Jacobson R. A., McElrath T. P., Moore W. B., Schubert G., and Thomas P. C.
Year: 2001
Title: Shape, Mean Radius, Gravity Field, and Interior Structure of Callisto
Journal: Icarus
Volume: 153
Number: 1
Pages: 157-161
Keywords: Jupiter, galilean, planetology, observation, theory, analytical, numerical, spacecraft, analysis
Abstract: Radio Doppler data generated by the Deep Space Network (DSN) from five encounters of the Galileo spacecraft with Callisto, Jupiter's outermost Galilean satellite, have been used to determine the mass (GM) and unnormalized quadrupole gravity coefficients in Callisto's external gravitational field. The results are GM=(7179.292+/-0.009) km3 s-2, J2=(32.7+/-0.8)×10-6, C22=(10.2+/-0.3)×10-6, S22=(-1.1+/-0.3)×10-6, C21=(0.0+/-0.3)×10-6, and S21=(0.0+/-1.6)×10-6. Also, four spacecraft images of Callisto have been used to determine its mean radius. The result is R=(2410.3+/-1.5) km, with no detectable deviation from sphericity. Derived parameters are Callisto's mean density of (1834.4+/-3.4) kg m-3 and axial moment of inertia C/MR2=0.3549+/-0.0042. While the mean density indicates that Callisto is a mixture of rock and ice, the moment of inertia is too small for a homogeneous mixture. Accordingly, we present a suite of possible two- and three-layer interior models that satisfy the given constraints for radius, density, and moment of inertia. While not unique, these models show that Callisto cannot be entirely differentiated, and that there must exist a region of mixed ice and rock-metal, possibly extending to the center of the satellite.
%F: AA(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California. john.d.anderson@jpl.nasa.gov), AB(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California), AC(Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California), AD(Department of Earth and Space Sciences, Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California), AE(Department of Earth and Space Sciences, Institute of Geophysics and Planetary Physics, University of California, Los Angeles, California), AF(Cornell University, Center for Radiophysics and Space Research, Ithaca, New York)
Bibliogaphic Code: 2001Icar..153..157A
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