Jupiter and Saturn rotation periods

Abstract: Anderson and Schubert [2007. Saturn''s Gravitational field, internal rotation, and interior structure. Science 317, 1384–1387 (paper I)] proposed that Saturn''s rotation period can be ascertained by minimizing the dynamic heights of the 100mbar isosurface with respect to the geoid; they derived a rotation period of 10h 32m 35s. We investigate the same approach for Jupiter to see if the Jovian rotation period is predicted by minimizing the dynamical heights of its isobaric (1bar pressure level) surface using zonal wind data. A rotation period of 9h 54m 29.7s is found. Further, we investigate the minimization method by fitting Pioneer and Voyager occultation radii for both Jupiter and Saturn. Rotation periods of 9h 55m 30s and 10h 32m 35s are found to minimize the dynamical heights for Jupiter and Saturn, respectively. Though there is no dynamical principle requiring the minimization of the dynamical heights of an isobaric surface, the successful application of the method to Jupiter lends support to its relevance for Saturn. We derive Jupiter and Saturn rotation periods using equilibrium theory to explain the difference between equatorial and polar radii. Rotation periods of 9h 55m 20s and 10h 31m 49s are found for Jupiter and Saturn, respectively. We show that both Jupiter''s and Saturn''s shapes can be derived using solid-body rotation, suggesting that zonal winds have a minor effect on the planetary shape for both planets. The agreement in the values of Saturn''s rotation period predicted by the different approaches supports the conclusion that the planet''s period of rotation is about 10h 32m. [Copyright &y& Elsevier]