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arXiv · 1610.00548

Enceladus's and Dione's floating ice shells supported by minimum stress isostasy

Mikael Beuthe·Attilio Rivoldini·Antony Trinh
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Abstract

Enceladus's gravity and shape have been explained in terms of a thick isostatic ice shell floating on a global ocean, in contradiction of the thin shell implied by librations. Here we propose a new isostatic model minimizing crustal deviatoric stress, and demonstrate that gravity and shape data predict a $\rm{38\pm4\,km}$-thick ocean beneath a $\rm{23\pm4\,km}$-thick shell agreeing with -- but independent of -- libration data. Isostatic and tidal stresses are comparable in magnitude. South polar crust is only $7\pm4\rm\,km$ thick, facilitating the opening of water conduits and enhancing tidal dissipation through stress concentration. Enceladus's resonant companion, Dione, is in a similar state of minimum stress isostasy. Its gravity and shape can be explained in terms of a $\rm{99\pm23\,km}$-thick isostatic shell overlying a $\rm{65\pm30\,km}$-thick global ocean, thus providing the first clear evidence for a present-day ocean within Dione.

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Mikael Beuthe, Attilio Rivoldini, Antony Trinh. 2016-10-03. Enceladus's and Dione's floating ice shells supported by minimum stress isostasy. https://doi.org/10.1002/2016gl070650

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