The Global Shape, Gravity Field, and Libration of Enceladus
Ryan S. Park, N. Mastrodemos, Robert A. Jacobson, Alexander Berne, Andrew Vaughan, D. Hemingway, Erin Leonard, Julie Castillo‐Rogez, Charles S. Cockell, J. T. Keane, A. S. Konopliv, F. Nimmo, Joseph E. Riedel, M. Simons, S. Vance
Abstract
Abstract In order to improve our understanding of the interior structure of Saturn's small moon Enceladus, we reanalyze radiometric tracking and onboard imaging data acquired by the Cassini spacecraft during close encounters with the moon. We compute the global shape, gravity field, and rotational parameters of Enceladus in a reference frame consistent with the International Astronomical Union's definition, where the center of the Salih crater is located at −5° East longitude. We recover a quadrupole gravity field with J 3 and a forced libration amplitude of 0.092° ± 0.009° (3‐ σ ). We also compute a global shape model using a stereo‐photoclinometry technique with a global resolution of 500 m, although some local maps have higher resolutions ranging from 25 to 100 m. While our overall results are generally consistent with previous studies, we infer a thicker 25–29 km mean ice shell, a thinner 26–30 km mean ocean thickness, and a mean core density range of 2,290–2,350 kg/m 3 .