Metal-silicate differentiation in early-accreted small bodies of the Solar System : a multidisciplinary approach
Many early-accreted small bodies of the Solar System experienced metal-silicate differentiation. This process caused the metal and silicate to separate and may have led to the formation of a metallic core. This PhD focused on understanding the physical processes that drove this differentiation and their consequences on the materials found in the meteoritic record. In order to provide the most plausible models, a joint experimental and modeling approach was used. A three-phase experimental system was designed to be representative of natural samples undergoing differentiation and analyzed using computed 3D X-ray microtomography and electronic techniques. Metal-silicate differentiation mostly occurs though the percolation of an interconnected metallic network. However, significant extraction of the silicate melt is required to allow the formation of such a network. Differentiation remained partial in primitive achondrites due to late accretion and low silicate grain sizes that did not allow complete melting of the iron-rich phases or efficient melt extraction. Complete differentiation occurs for bodies accreted earlier that experienced a magma ocean stage. Models suggest that a significant fraction of the silicates does not melt (corresponding to the rheological threshold), preventing the metal particles from settling. At the end of the magma ocean phase, compaction and efficient extraction of the melts favors differentiation and the formation of achondrites (pallasites, stony and iron meteorites).