HR: 17:00h
AN: P54A-05    [Abstracts]
TI: Interiors of the Four Giant Planets
AU: * Anderson, J D
EM: jdandy@earthlink.net
AF: Jet Propulsion Laboratory, 121 S. Wilson Ave., Pasadena, CA 91106-3017, United States
AU: Schubert, G
EM: schubert@ucla.edu
AF: Department of Earth and Space Sciences and Institute of Geophysics and Planetary Physics, University of California, Los Angeles, CA 90095-1567, United States
AB: We apply the method of gravity sounding that we used for Saturn (Anderson and Schubert, Science 317, 7 September 2007) to the solar system's other three giant planets and obtain an empirical equation of state EOS for each. We suggest that each EOS so obtained can be used as a reference model for more detailed calculations that use the physics of materials thought to exist in the four giant planets. As expected the planets fall into two classes. The first for Jupiter and Saturn is characterized by a change in the EOS at about 3 Mbar half way into the planet, where the transition from molecular to metallic hydrogen occurs. In the second class for Uranus and Neptune large cores are inferred from the gravitational data. Even though the outer planets break down into two classes, their bulk properties suggest that they each have unique characteristics related to their formation. The mean densities in units of kg per cubic meter are 1327 for Jupiter, 686 for Saturn, 1177 for Uranus and 1552 for Neptune. The respective mean radii are 69,894 km, 58,255 km, 26,017 km, and 25,066 km. The normalized mean moment of inertia (2/5 for a uniform sphere) can be obtained from the inferred density distribution, along with a mapping of the errors in the three measured zonal gravitational coefficients through the software system used for the gravity sounding. The results are 0.265668(3) for Jupiter, 0.222794(35) for Saturn, 0.216196(4) for Uranus, and 0.230700(250) for Neptune, where the numbers in parentheses indicate the standard error in the last place. The EOS of the planet in the outer envelope of all four planets can be approximated by a polytrope with index of 1.795 for Jupiter, 1.631 for Saturn, 2.023 for Uranus, and 1.842 for Neptune. This EOS is valid to a pressure of about 100 kbar. The pressure at a density level of 100 kg per cubic meter is 28.10 kbar for Jupiter, 19.17 kbar for Saturn, 7.22 kbar for Uranus, and 6.40 kbar for Neptune. Depths at the 100 kbar pressure level, the limit of validity of the polytrope, are 4890 km for Jupiter, 8160 km for Saturn, 5070 km for Uranus and 3885 km for Neptune.
DE: 5714 Gravitational fields (1221)
DE: 5724 Interiors (8147)
DE: 6207 Comparative planetology
SC: Planetary Sciences [P]
MN: 2007 Fall Meeting