Interior structure of Saturn

The principal observational data that constrain interior models of Saturn are summarized, and why they are relevant is explained. The behavior of hydrogen, Saturn's major constituent, at pressures on the order of 0.1 to 10 Mbar and temperatures on the order of 10,000 K, is discussed. Possible behavior and distributions of minor constituents are also considered, along with processes for their transport. Saturn's external gravitational and magnetic fields are interpreted in terms of interior structure, and the relationship between atmospheric zonal flows and the deep interior is discussed. The constraint imposed by tidal evolution considerations is evaluated. Calculations for the thermal evolution of Saturn are presented, both with and without consideration of possible gravitational unmixing. Possible scenarios for Saturn's mode of origin and their implications for presently observed atmospheric abundances are discussed.