Recent orbital evolution and the internal structures of Enceladus and Dione

✍ Scribed by Ke Zhang; Francis Nimmo

• Publisher: Elsevier Science
• Year: 2009
• Tongue: English
• Weight: 933 KB
• Volume: 204
• Category: Article
• ISSN: 0019-1035
• DOI: 10.1016/j.icarus.2009.07.007

✦ Synopsis

We study the orbital behavior of Saturn's satellites Enceladus and Dione during their passage through the 2:1 mean-motion resonances to constrain their interior structures, parameterized by the quantity k 2 =Q (assumed constant). Enceladus' evolution after escape from the second-order e-Enceladus e-Dione resonance requires that ðk 2 =Q Þ Enceladus < 8 Â 10 À4 , for that Q Saturn > 18; 000. This result is in agreement with [Meyer, J., Wisdom, J., 2008b. Icarus 193, 213-223]. The present-day libration amplitude of Enceladus requires that ðk 2 =Q Þ Enceladus > 1:2 Â 10 À4 , assuming that Q Saturn < 10 5 . Dione's present-day eccentricity indicates that ðk 2 =Q Þ Dione 6 3 Â 10 À4 for Q Saturn > 18; 000. Assuming Maxwellian viscoelastic behavior, we find that for Enceladus a convective ice shell overlying an ocean is too dissipative to match the orbital constraints. We conclude that a conductive shell overlying an ocean is more likely, and discuss the implications of this result. Dione's ice shell is also likely to be conductive, but our results are less constraining.