Outer Solar System A Program for Exploration, Report of a Study (1969) / Chapter Skim
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PLANETARY INTERIORS
PLANETARY INTERIORS
Pages 67-74
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From page 67... ...
In particular Jupiter, the largest planet, accounts for most of the mass and angular momentum of the solar system and may be the most accessible sample of material whose chemical composition is similar to that out of which the system was formed. The study of planetary interiors is a particularly difficult task because of the need for relying on indirect observational evidence and often inadequate theories.
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From page 68... ...
Such information is essential for bracketing the probable values of the heat transport and for evaluating the efficiency and kinetics of convective phenomena. The latter play a paramount role in determining the magnetic fields of the planets, their heat budgets, and in many instances even the motion and configuration of visible surface structures.
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From page 69... ...
HEAT FLUX AND BALANCES The heat "budgets" of Jupiter and Saturn are of great importance. These planets receive heat from the sun, the precise amount being the solar constant appropriately diminished by the inverse square law and by "pure" reflection.
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From page 70... ...
PLANETARY MAGNETISM The discovery, just over a decade ago, and subsequent investigations of radio emissions from Jupiter at decimeter and decameter wavelengths have led to the inference that Jupiter produces a poloidal magnetic field whose strength at the visible surface is tens of gauss. The configuration of the magnetic field inferred from the radio-astronomical data is more complicated than that of a centered axial dipole.
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From page 71... ...
The other major planets -- Saturn, Uranus, and Neptune -- should contain extensive fluid layers that are sufficiently well stirred to produce magnetic fields by the aforementioned "dynamo mechanism," the process thought to be responsible for the magnetism of the two planets known for certain to produce magnetic fields of their own (earth and Jupiter)
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From page 72... ...
PLANETARY DENSITIES The family of outer planets has long been held to comprise two physically distinct genera, containing Jupiter/Saturn and Uranus/Neptune, respectively. The case for this dichotomy, reflecting an alleged substantial difference in mean density between the two genera, has now been somewhat weakened.
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From page 73... ...
Improved diameters of these bodies, which might be obtained during flyby, are a prerequisite for refined planetary models. The terrestrial observations of occultations of these bodies are so valuable and so rare that a determined long-range effort to predict occultation of fainter stars ought to be made so that astronomers will be better prepared for future opportunities.
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From page 74... ...
This information would be of particular significance for Jupiter. These same measurements can be conducted with higher sensitivity in the bistatic radar mode, for example, by using the same groundbased transmitter and a receiver in a spacecraft near the object of study.
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