Masters Thesis

Study of trailing conduits in high bond number metal-silicate plumes during core formation

Meteorite samples and isotopic studies indicate that large planetary embryos and planetestimals had early core formation and that the segregation of metal happened within 30 Myr of the formation of the Solar System. Previous geodynamic studies hypothesized that violent impacts had provided substantial energy that possibly completely or partially melted impacting objects as well as the upper layer of the early Earth, leading to the formation of the magma ocean during the core formation and differentiation phase. Metal ejecta of the cores of differentiated planetesimals may have formed metal drops, descended through the magma ocean and collected into metal ponds at the base of the magma ocean. Over time, the heavy metallic ponds would become unstable and descend through the primitive mantle, either following cracks and fractures or larger downwelling events involved in convective structures such as Rayleigh-Taylor instabilities or large diapirs. In this research, we perform experiments only in the case of large diapirs from Rayleigh-Taylor instabilities of metal ponds. Once a metal pond descends through the primitive mantle, it creates a conduit behind it which fills with magma ocean material. Using fluid laboratory experiments, we observe the onset time of the high Bond number metal-silicate plume and its size and shape while it descends. We also report the experimental results and present analogous models for the trailing conduit formed after the descent of the metal-silicate plume during core formation and differentiation. Specifically, we study the trailing conduit as it changes its shape and size while descending to the base, the reversal flow due to positive buoyancy, how the conduit collapses, and all the forces involved. Finally, we calculate the constriction time for conduits in different early Earth scenarios by varying the primitive mantle's viscosity, density contrast between the magma ocean and primitive mantle materials, as well as the conduit radius.

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