High Quality Content by WIKIPEDIA articles! High Quality Content by WIKIPEDIA articles! In planetary science, planetary differentiation is the process of separating out different constituents of a planetary body as a consequence of their physical or chemical behaviour, whereby the body evolves into compositionally distinct layers; the denser materials of a planet sink to the center, while less dense materials rise to the surface. Such a process tends to create a core and mantle. Sometimes a chemically distinct crust forms on top of the mantle.