Overview of the main differentiation regimes that arise for different assumptions on the proportions of ice and rock (Neumann et al. 2016a). Left: composition is dominated by ice whose melting results in the formation of an ocean. The rock mantle grows from the settling of rock particles in the Stokes regime and their deposition at the bottom of the ocean. Right: composition is dominated by rock. Melting of ice creates a water network within a porous matrix. The ocean grows due to the percolation of water which is driven by the gravity-induced compaction of the matrix (e.g., McKenzie 1984). Differentiation in this regime requires a longer time scale. In general, planetesimals of equal size but with different ice fractions would differentiate on a different time scale and result in structures with different layer dimensions.