Rheological controls on the terrestrial core formation mechanism

摘要: Iron core differentiation of terrestrial planetary bodies is thought to have occurred simultaneously with accretion. The exact mechanisms formation, however, remain incompletely understood. One model proposes that cores are formed from numerous smaller iron predifferentiated planetesimals. To further understand this mechanism for forming Mars- and Earth-sized bodies, we present here systematic numerical simulations. Our models include a non-Newtonian temperature-, pressure- strain rate–dependent viscoplastic rheology. Four different formation regimes being observed in the study, as function activation volume, friction angle, Peierls stress, initial temperature state body. We derive scaling laws, which show importance shear heating localization plastic yielding drive interiors, good agreement Results indicate effective rheology body has major effect on mechanism: while weak generally diapiric mode interior stiff can be fractured or displaced toward surface. On protoplanets, water content seems also significant influence formation. time scale few million years, significantly shorter than expected Stokes sinking Newtonian medium.