Dynamic viscosity, $\eta_i$ $10^{-1}$           $10^{-2}$          Pa.s
               Diffusion coefficient, $\kappa_i^c$ $10^{-9}$           $10^{-9}$          m$^{2}$.s$^{-1}$
                 Thermal conductivity, $\lambda_i$ 4                   $10^2$             W.m$^{-1}$.K$^{-1}$
                   Thermal diffusivity, $\kappa_i$ $10^{-6}$           $10^{-5}$          m$^{2}$.s$^{-1}$
                          Surface energy, $\gamma$ 0.5                 0.5                J.m$^{-2}$
                               Reynolds number, Re $10^{12}$           $10^{14}$          -
          Thermal Péclet number, $\mathrm{Pe}_{T}$ $10^{14}$           $10^{12}$          -
    Compositional Péclet number, $\mathrm{Pe}_{C}$ $10^{17}$           $10^{17}$          -
                  Thermal Ohnesorge number, Oh$_T$ $10^{-12}$          $10^{-10}$         -
            Compositional Ohnesorge number, Oh$_C$ $10^{-15}$          $10^{-15}$         -
                                   Bond number, Bo $10^{15}$           $10^{15}$          -
                                  Weber number, We $10^{15}$           $10^{15}$          -
  ------------------------------------------------ ------------------- ------------------ ----------------------

  : Typical parameters of a metallic impactor’s core falling into a magma ocean. Modified after @solomatov_2015 and @deguen_2011. Dimensionless numbers are calculated for a 100 km impactor’s core.

\[tab:parameters\_magma\]

The *iron rain* scenario is based on the assumption of rapid fragmentation of the impactor cores into centimetric drops. Whether this is realistic remains an open question. Differentiation of terrestrial planets started early and most of the Earth was accreted from large differentiated planetesimals and embryos (100 to 1000 km) [@rubie_2015]. Whether the huge volumes of metal delivered by these impacts were indeed able to fragment into cm-scale drops is unclear [@dahl_2010; @deguen_2014; @kendall_2016; @landeau_2014; @wacheul_2014]. Liquid fragmentation is a well studied problem of fluid mechanics and the key mechanisms are 