Constraints on the mass fractions of heavy elements in the molecular 
envelope ($Z_{\rm mol}$), and in the metallic envelope ($Z_{\rm met}$) 
of Jupiter and Saturn. The
$Z_{\rm mol}=Z_{\rm met}$ relations are shown by diagonal dotted
lines. Additional arrows not included in Fig.~\protect\ref{fig:mcore}
show the changes due to a 1-$\sigma$ increase in the surface helium
mass mixing ratio (``$Y^{\rm mol}$''), and in the case of Jupiter, of
an increase in surface temperature from 165 to 170K (``$T_{\rm
1bar}$''). The mixing ratios are in solar units ($Z_\odot=0.0192$; see
Anders \& Grevesse 1989). {\it Inset}: closeup view of the solutions
and assumed uncertainties for Jupiter models calculated with the
PPT-EOS.
(From Guillot 1999; Plan. Space Sci. 47, 1183)