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| Tidal Evolution Of Mimas, Enceladus, And Dione |
| Presentation Time: Monday, 8:40 a.m. - 8:50 a.m. |
Jennifer Meyer1, J. Wisdom1
1MIT. |
| Presentation Number: 02.02 |
The tidal evolution through several resonances involving Mimas and/or Enceladus is studied numerically with an averaged resonance model. We find that, in the 2:1 Enceladus-Dione resonance, Enceladus evolves chaotically in the future for some values of k2/Q. Past evolution in the 2:1 Enceladus-Dione multiplet of resonances is shown to be more interesting than previously thought. In particular, the ee'e'-resonance, ee'-resonance, and a 2:1 secondary resonance are important (where primed refers to the outer satellite), and evolution can apparently be chaotic.
We find that the current anomalously large eccentricity of Mimas can be explained by passage through the 3:2 Mimas-Enceladus resonance. Explanation of the current eccentricity of Mimas through this mechanism implies that the Q of Saturn is below 70,000. Alternatively, the free eccentricity of Mimas can be explained by passage through the 3:1 Mimas-Dione ee'-resonance. This mechanism requires that the Q of Saturn be below 100,000. Resonance escape, in these cases and those mentioned above, occurs by unstable growth of the libration angle, sometimes with the help of secondary resonances.
Though the eccentricity of Enceladus can be excited to moderate values by capture in the 3:2 Mimas-Enceladus e-Enceladus resonance, the libration amplitude damps and the system does not escape. Thus past occupancy of this resonance and consequent tidal heating of Enceladus is excluded.
A coherent history of the tidal evolution of Mimas, Enceladus, and Dione is presented.
This research was supported in part by the NASA Planetary Geology and Geophysics Program. |
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