The core mass of Saturn is commonly assumed to be 10–25 M _ { \oplus } as predicted by interior models with various equations of state ( EOSs ) and the Voyager gravity data , and hence larger than that of Jupiter ( 0– 10 \ > M _ { \oplus } ) .
We here re-analyze Saturn ’ s internal structure and evolution by using more recent gravity data from the Cassini mission and different physical equations of state : the ab initio LM-REOS which is rather soft in Saturn ’ s outer regions but stiff at high pressures , the standard Sesame-EOS which shows the opposite behavior , and the commonly used SCvH-i EOS .
For all three EOS we find similar core mass ranges , i.e .
of 0– 20 \ > M _ { \oplus } for SCvH-i and Sesame EOS and of 0– 17 \ > M _ { \oplus } for LM-REOS .
Assuming an atmospheric helium mass abundance of 18 % , we find maximum atmospheric metallicities , Z _ { atm } of 7 \times solar for SCvH-i and Sesame-based models and a total mass of heavy elements , M _ { Z } of 25– 30 M _ { \oplus } .
Some models are Jupiter-like .
With LM-REOS , we find M _ { Z } = 16 – 20 M _ { \oplus } , less than for Jupiter , and \mbox { $Z _ { atm } $ } \lesssim 3 \times solar .
For Saturn , we compute moment of inertia values \lambda = 0.2355 ( 5 ) .
Furthermore , we confirm that homogeneous evolution leads to cooling times of only \sim 2.5 Gyr , independent on the applied EOS .
Our results demonstrate the need for accurately measured atmospheric helium and oxygen abundances , and of the moment of inertia for a better understanding of Saturn ’ s structure and evolution .