Interiors of Uranus and Neptune

Interiors of Uranus and Neptune - not well-defined...

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Interiors of Uranus and Neptune Note that a much larger proportion of these planets is rock and ice, hence their higher average densities. The gas layers have a large fraction of hydrogen and helium, but also contain a larger proportion of other gases than is seen in the outer envelopes of Jupiter and Saturn. These diagrams again represent only models of the planets, of course - we cannot actually "see into" the planets, so we have to try to deduce the internal structure by making up plausible models and then see if they fit the observations we have. Fully separated three-layer models have too small a rotational moment of inertia, whereas homogeneous models have too small a J 2 . There must be a strong radial composition gradient, but probably
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Unformatted text preview: not well-defined interfaces. One "allowed" composition would be to have solar-like H/He with a rocky core. At the other extreme one could enrich all the other elements exceptall the other elements except Hydrogen, which gives 70% He, 20% ice and 10% rock by mass, with Hydrogen only in smaller quantities. This large range of possible models illustrates how difficult it is to "invert" the gravity field data to give a unique solution. Spectra taken from ground-based and space probe observations, and Voyager radio occultation experiments find CH 4 (methane) at 1.4 - 2% in the clouds, but condensation physics makes this measurement difficult. It seems likely there will be enhanced NH 3 (ammonia) too....
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