Formation of the outer planets

A discussion is given of a number of physical processes which were probably important during the formation of the outer planets if these formed from a gaseous solar nebula in which magnetic effects were not important. Arguments are given that large-scale gravitational instabilities in the solar nebula did not occur. Qualitative consideration is given to the conditions in which dynamical capture of gas onto a planetary core may take place; this may have played a major role in the formation of Jupiter and Saturn. Because of the great difficulty of fractionating hydrogen from helium in the assembly of the outer planets, it is argued that a new approach should be made to the construction of planetary models. Conditions which may lead to the formation of the regular satellite systems are discussed, and the associated problem of removal of primordial angular momentum from Jupiter, Saturn, and Uranus.This is one of the publications by the Science Advisory Group.