Percolative core formation model in planet interiors

The percolation of liquid iron alloy through crystalline silicates potentially played an important role during core formation in planetary bodies of the early solar system. In order to test the feasibility of percolative core formation, the effects of pressure, composition and mineral assemblage on the dihedral angle between Fe-O-S liquid and mantle minerals have been investigated from 1.5 to 23.5 GPa. Texturally-equilibrated dihedral angles increase from 54 to 106° over this pressure range. The dihedral angle increases with pressure and closely related to the oxygen content of Fe-O-S phase, which decreases with increasing pressure, because oxygen reduces the interfacial energy of Fe-S melt. However, the effect of mineral assemblage on the dihedral angle seems to be negligible. Therefore, percolation is likely to have been the dominant core formation mechanism in small relatively-oxidised planetary bodies with a radius less than abogt 1300 km.