1CORE FORMATION: A NEW MODELLING APPROACH

Core formation in terrestrial planets is still not well understood although this pro ess is of importan e for our understanding of the thermal evolution of a planet and the history of its magneti eld. Be-ause ore formation is among the earliest pro esses in planet formation and evolution, the initial ondi-tions for thermal evolution models are, to a signi-ant extent, determined by this pro ess. The initial temperature of the ore and its state are determined by the amount of energy dissipated during ore for-mation. One possible s enario for the formation of a planetary ore is the settling of liquid iron from a solid matrix (Stevenson, 1990). Assuming that a planet in the late state of a retion has a magma o ean, there soon will form a layer of molten iron at the bottom of the magma o ean. Sin e the iron has a higher density than the underlying planetary mantle, it will probably sink due to Rayleigh{Taylor instability. A ording to Woidt (1978) the sinking iron will attain the shape of spheres be ause the vis-osity of the liquid iron should be mu h smaller than that of sili ates. We model the Stokes falling of an iron sphere through a sili ate mantle with temper-ature dependent vis osity of the mantle material by using a nite element ode (FEATFLOW) written by Turek (1998). We solve the in ompressible Navier{ Stokes equation oupled with the energy and mass equation. With these models the ee t of the tem-perature dependen e of the sili ate ro k vis osity on the dierentiation rate and the temperature of the ore after ore formation an be estimated. Key words: Core formation, planetary interiors, Computational Fluid Dynami s