Carbon and Sulfur Isotopic fractionation during Planetary differentiation – CSI-Planet

This project aims to understand the origin of the differences in carbon and sulfur contents and isotopic signatures between Earth and Mars. Thanks to an experimental approach, this project will determine C and S partitioning and isotopic fractionation during planetary core formation and during the degassing of primitive atmospheres, as well as the effect of initial conditions differences during Earth's and Mars' formation ( S and H content, oxygen fugacity, fO2) on these fractionations.
During their formation, both Earth and Mars underwent a magma ocean stage in which they were largely or completely melted. This step was essential because it allowed the segregation of a metal core from the silicate mantle and the formation of a primitive atmosphere by the degassing of the magma ocean. These planetary formation processes have altered the original concentrations and isotopic compositions of volatile elements (H, C, N and S) on Earth and Mars. The evolution of C and S is particularly important for the development of conditions favorable to the emergence of prebiotic molecules and the maintenance of life. This project will determine if the differences in the conditions of formation between the Earth and Mars (the size of the planets, ie the pressure-temperature conditions, P – T; the fO2; the initial contents of volatile elements) can explain the differences observed in C and S contents and isotopic compositions of the Earth's and Mars' interiors.
Using high pressure equipments and advanced analytical techniques at the CRPG, the partitioning and isotopic fractionations of C and S will be determined in between silicate glasses, metal alloys and gas in experimental samples. These new data will be used to reconstruct C and S isotopic compositions of the proto-Earth and proto-Mars (prior to their differentiation) to determine whether or not C and S on Earth and Mars share a common origin.