A model for the accretion of planetary bodies from the primitive solar nebula (PSN) in which the rate of accretion is fast relative to the rate at which the PSN cools. The consequence is that each body forms very quickly and consists entirely of material that was in equilibrium with the physical conditions of the PSN over only a very short period of time. According to this model, the layered structures of the planets are entirely of secondary origin. Compare heterogeneous accretion.