Internal structure models of the moon, based in part on petrological and thermal models of a moon of fission origin, indicate that the moon has an iron or iron-rich core with a radius between 200 and 400 km. The derived STP density of the lower mantle (>200-km depths) is between 3.35 and 3.51 g/cm3 and indicates that the Mg' of the lower mantle is between 73 and 88. This result, together with the Mg' of the upper mantle (?70) and of the crust (?70), leads to Mg' between 72 and 84 for the bulk moon (minus the core). The Vp in the mantle of the moon is found to be between 7.6 and 7.9 km/s; this result is in general agreement with that derived from seismic data.