The interior of saturn

A source of uncertainty in Saturn interior models is the lack of a unique rotation rate to be ascribed to the deep (metallic-hydrogen) interior. As a result, models are not uniquely constrained by measured gravitational multiple coefficients. Further uncertainty is associated with the effect of a multiplicity of rotation periods due to zonal flows of unknown magnitude and depth (and therefore unknown mass). Nevertheless, the inference that Saturn has a large core of mass 15-20 M _e (Earth masses) is robust. The equation of state of dense hydrogen-helium mixtures is one area where uncertainty has been much reduced, thanks to new first-principles simulations. However, because there is still uncertainty in Saturn's interior temperature profile, a variety of mantle metallicities and core masses could still fit the constraints, and the question of interior helium separation is still unsettled.