Zhao, Bin ; Morard, Guillaume ; Boulard, Eglantine ; Rivoldini, Attilio ; Boccato, Silvia ; Siersch, Nicki ; Guignot, Nicolas ; Henry, Laura ; Antonangeli, Daniele

Talk presented at AGU Fall Meeting 2021, New Orleans, online on 2021-12-16

Abstract: Sulfur and carbon are considered as two dominant light elements incorporated with iron in the Moon's core. Physical properties of liquid Fe-C-S are thus crucial for understanding today’s composition of the Moon's core, as well as the core evolution process since the formation of the Moon 4.5 billion years ago. In this work, the liquid structure and density of Fe-C-S alloys containing up to 12.2 at%C and 8.5 at%S have been studied in situ at high pressure and high temperature (1-5 GPa and up to 1900 K) by combined angle and energy dispersive X-ray diffraction (CAESAR) experiments performed in a Paris-Edinburgh press, and by electron microprobe analysis of the recovered samples. The local structure of liquid Fe-C-S alloys shows no obvious modification from that of iron, suggesting that the Moon's core with low light element content probably retains similar compressibility to pure iron. Density of the alloys has been extracted from the diffuse scattering by minimization of the oscillation in the short distance of the radial distribution function g(r). A thermodynamic model has been developed for the density of the ternary Fe-C-S system as a function of pressure, temperature, and light element content. Obtained dataset and derived model are used to address structure and composition of the core of the Moon.

Keyword(s): Moon, core, Fe-C-S
Funding: 3PRODPLANINT/3PRODPLANINT/3PRODPLANINT