Interiors of Planets and Satellites Models of Individual Bodies

The models outlined here are of the interiors of the planetary bodies as scientists believe them to be today. The evolution of planetary interiors, from the past to the present, and into the future, is largely deferred to later chapters because of the consequences for surfaces and atmospheres.

Recall from the previous chapter that a model of the interior of a planetary body has, as its basic features, a specification of the composition, temperature, pressure, and density at all radii from the centre. From this basic specification, other things follow, such as internal motions, magnetic fields, and so on. The model is arrived at through applying physical principles to calculate the observed properties of the body, and the model is varied until an acceptable level of agreement with the observations is obtained. It is invariably the case that a range of models can be made to fit the observational data. The range will be wide if the data are uncertain, or if some data are absent, such as seismic data. Therefore, a model is not unique, though for most bodies certain features are beyond reasonable doubt.

In considering individual planetary bodies, it would be a very lengthy task to relate all the various features of a model to the observational and experimental data that underpin it. Therefore, we shall highlight just a few examples where specific data are strongly suggestive of particular model features.

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