M2: Composition of metallic cores

Master M2 internship

Telluric planets are differentiated bodies that have metallic cores dominated by iron and iron alloys. Geochemical and mineral physics data show that the major alloying element is nickel. But nickel, being so similar in behavior to iron, has only a minor effect on the physical properties of the core. On the contrary, the presence of various light volatile elements, can tremendously affect the properties of molten iron. They can reduce the density of the melt, influence its structure, change its transport properties.

Consequently, modeling the interior of any planetary telluric body, going from Mercury to Mars, from Vesta to Ganymede, from Venus to super-Earths, requires knowledge of the properties of the iron cores of these objects. Moreover, large planetesimals contributed greatly to the balance of light elements on the Earth, by large and giant impacts during the early history of the Earth, in periods like the late veneer.

Here we use ab initio molecular dynamics simulations to compute the effect of various light elements on the density and physical properties of liquid iron at conditions typical to the core of planetesimals, as well as small and large telluric planets. We characterize the solubility of the volatiles in the melt, the effect on the structural properties of the iron melts, and we estimate the densities of the molten alloys. Then we use the results of these simulations to estimate various properties like core sizes, planetesimal /planet internal structure, and possible amounts of light elements brought to Earth during impacts. 

We will run the simulations on the supercomputers of the TGCC supercomputing center of the CEA. The internship is supported by the ERC IMPACT and the ERC SEPTIM projects. For further information don’t hesitate to contact Razvan Caracas in IPGP at caracas@ipgp.fr or James Badro in IPGP at badro@ipgp.fr.

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