Interior structure of Saturn inferred from Pioneer 11 gravity data

Abstract

The structure of Saturn is studied via a fourth‐order theory for rotating planets and equations of state for the envelope which depend parametrically on the helium abundance, on the starting temperature for the adiabat, and on adopted forms of the pressure‐density curve in the region of transition from molecular to metallic hydrogen. Models are constrained by the values of J2 and J4 obtained from the Pioneer‐Saturn celestial mechanics experiment. Equations of state are tested by computing Jupiter models, which can now be subjected to a more stringent comparison with observed zonal harmonics. We find that Saturn has a low‐density hydrogen‐helium envelope with no evidence for enhancement of H2O, CH4, or other abundant compounds. Such compounds are presumably located near the core. The helium mass abundance for Saturn's envelope appears to be in the range of ∼0.12 to ∼0.19, but this result is very model‐dependent. The helium abundance in the envelope of Jupiter is apparently very similar to that of Saturn.

Similar Amino Acid Sequences: Chance or Common Ancestry?

“…In the first case, the result is a larger protein fashioned at the expense of the preexisting gene product. Many examples of this phenomenon are recognizable in existing protein sequences (2), and there is little doubt that this process has been the major route to larger proteins. In the second case, two independent gene products result, for one of which there ought to be a relaxation of the evolutionary restraints imposed by natural selection.…”

Neptune’s Triton: A Moon Rich in Dry Ice and Carbon?

“…For such a cloud, however, having heavy element abundance Z = Z®, the total mass of rock and ice condensate within the gas rings shed at the orbits of J, S, U, and N are 9.5, 7.1, 5.2, and 3.8 M®, respectively. If the condensate in each ring were to aggregate into a single planetary core, the masses of the cores would fall short of the values measured by Pioneer 11 (Hubbard et al 1980), or deduced from planetary interior models (Hubbard and MacFarlane 1980), by factors of 2.1, 2.6, 2.5, and 4.2, respectively. The same problem occurs in the Galilean system of satellites, where eqn.…”

Constraints on the origin and interior structure of the major planets

“…The literature on the structure of rotating bodies in hydrostatic equilibrium is very extensive; some of the more commonly used schemes are discussed by Tassoul (1978). An approach based upon work by James (1964) and Hubbard et al (1975) has been used by Hubbard et al (1981) to carry out an analysis of the interior structure of Jupiter and Saturn. Hubbard et al (1981) have fitted models to the data of table 1 under the following assumptions.…”

“…An approach based upon work by James (1964) and Hubbard et al (1975) has been used by Hubbard et al (1981) to carry out an analysis of the interior structure of Jupiter and Saturn. Hubbard et al (1981) have fitted models to the data of table 1 under the following assumptions. (a) Both Jupiter and Saturn contain dense central cores of rock and 'ice' in approximate solar proportions.…”