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Science 6 May 1988:
Vol. 240. no. 4853, pp. 779 - 781
DOI: 10.1126/science.240.4853.779
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Articles

The Nature of the Interior of Uranus Based on Studies of Planetary Ices at High Dynamic Pressure

W. J. NELLIS 1, D. C. HAMILTON 2, N. C. HOLMES 2, H. B. RADOUSKY 2, F. H. REE 2, A. C. MITCHELL 2, and M. NICOL 3

1 Physics Department and Institute of Geophysics and Planetary Physics, University of California, Lawrence Livermore National Laboratory, Livermore, CA 94550.
2 Physics Department, University of California, Lawrence Livermore National Laboratory, Livermore, CA 94550.
3 Department of Chemistry and Biochemistry, University of California, Los Angeles, CA 90024.

Data from the Voyager II spacecraft showed that Uranus has a large magnetic field with geometry similar to an offset tilted dipole. To interpret the origin of the magnetic field, measurements were made of electrical conductivity and equation-of-state data of the planetary "ices" ammonia, methane, and "synthetic Uranus" at shock pressures and temperatures up to 75 gigapascals and 5000 K. These pressures and temperatures correspond to conditions at the depths at which the surface magnetic field is generated. Above 40 gigapascals the conductivities of synthetic Uranus, water, and ammonia plateau at about 20(ohm-cm)-1, providing an upper limit for the electrical conductivity used in kinematic or dynamo calculations. The nature of materials at the extreme conditions in the interior is discussed.

Submitted on January 11, 1988
Accepted on March 29, 1988


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