Past exam of the short options paper shared by Prelims and Parts A and B of the physics course of the University of Oxford / 2016 / S29 / 3 / 4 / Solution

A qualitative sketch has molecular hydrogen/helium outside, increasing pressure into a conducting metallic-hydrogen-rich interior, and centrally enhanced heavy elements, possibly distributed rather than confined to a sharp solid core. Saturn's lower mass produces different pressure/temperature transitions and a larger relative role for central concentration. Both can have compositional gradients and helium separation; the moment alone does not decide whether any boundary is sharp.