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Tidal viscosity of Enceladus
(Submitted on 27 Jun 2017)
In the preceding paper (Efroimsky 2017), we demonstrated that under weak libration in longitude most dissipation is due to the gravitational tides (including the additional tides generated by libration). The other three sources of dissipation − which are the alternating parts of the centripetal, toroidal and purely radial deformations − are less important when libration is weak. Whether this is so for large-magnitude libration requires a separate study. In Ibid. it was also shown that in some situations the forced libration in longitude can provide a considerable and even leading input into the tidal heating: 52% in Phobos, 33% in Mimas, 12% in Enceladus, and 96% in Epimetheus.
Equating our expression for the tidal dissipation rate (with the libration-generated input included) to the outgoing energy flux due to the vapour plumes, we estimate the mean tidal viscosity of Enceladus, under the assumption that the Enceladean mantle behaves as a Maxwell body. This method yields a value of 0.4×1014 Pa s for the mean tidal viscosity, which is remarkably close to the viscosity of ice near the melting point. We then demonstrate that, with such a value of the tidal viscosity, the tidal dissipation in Enceladus is too low to influence its orbital evolution. Thus the orbital evolution of Enceladus is defined to a much greater extent by the tidal friction in Saturn.
Subjects: Earth and Planetary Astrophysics (astro-ph.EP)
Cite as: arXiv:1706.09000 [astro-ph.EP] (or arXiv:1706.09000v1 [astro-ph.EP] for this version)
From: Michael Efroimsky
[v1] Tue, 27 Jun 2017 18:28:13 GMT (21kb)