Journal
GEOPHYSICAL RESEARCH LETTERS
Volume 42, Issue 7, Pages 2137-2143Publisher
AMER GEOPHYSICAL UNION
DOI: 10.1002/2015GL063384
Keywords
icy satellite; Cassini mission; gravity model; Enceladus ocean
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Funding
- NASA [NNX11AK76G]
- NASA [143050, NNX11AK76G] Funding Source: Federal RePORTER
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Enceladus's degree 2 gravity, determined by Cassini, is nominally nonhydrostatic to 3 sigma (J(2)/C-22=3.38-3.63, as opposed to 10/3). Iess et al. (2014) interpret this in terms of a hydrostatic interior (core) and isostatic (not hydrostatic) floating ice shell. Enceladus's rapid (1.37 d) synchronous spin and tide distorts its shape substantially, though, enough that the predicted hydrostatic J(2)/C-22 is not 10/3 but closer to 3.25. This leads to the following revision to the internal picture of Enceladus, compared with Iess et al.: (1) the satellite's core is somewhat smaller and slightly denser (190km radius and 2450kg/m(3)); (2) the compensation depth (shell thickness) of the global (degree 2) ice shell is approximate to 50km, rather close to the base of the modeled ice+water layer; and (3) the compensation depth (shell thickness) beneath the South Polar Terrain (from J(3)) remains shallower (thinner) at approximate to 30km, independent of but influenced by the degree 2 solution.
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