The stability against freezing of an internal liquid-water ocean in Callisto

Article

关键词: GALILEAN SATELLITES;    SUBSURFACE OCEANS;    ICY SATELLITES;    OUTER PLANETS;    EVOLUTION;    CONVECTION;    GANYMEDE;    EUROPA;    MODELS;    SHELL;   

DOI  :  10.1038/35086506

来源: SCIE

【 摘 要 】

The discovery of the induced magnetic field of Callisto-one of Jupiter's moons-has been interpreted(1,2) as evidence for a subsurface ocean, even though the presence of such an ocean is difficult to understand in the context of existing theoretical models(3-5). Tidal heating should not be significant for Callisto, and, in the absence of such heating, it is difficult to see how this internal ocean could have survived until today without freezing(1,6). Previous work(3,4) indicated that an outer ice layer on the ocean would be unstable against solid-state convection, which once begun would lead to total freezing of liquid water in about 10(8) years. Here I show that when a methodology(7) for more physically reasonable water ice viscosities (that is, stress-dependent non-newtonian viscosities, rather than the stress-independent newtonian viscosities considered previously) is adopted, the outer ice shell becomes stable against convection. This implies that a subsurface ocean could have survived up to the present, without the need for invoking antifreeze substances or other special conditions.

【 授权许可】

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