Physical properties of liquid Fe alloys at high pressure and their bearings on the nature of metallic planetary cores

C. Sanloup (1, 2) , F. Guyot (3) , P. Gillet (1) , Y. Fei

1 ENS de Lyon - École normale supérieure de Lyon
2 UPMC - Université Pierre et Marie Curie - Paris 6
3 IPGP - Institut de Physique du Globe de Paris

Sulfur and silicon are among the expected alloying light elements in planetary liquid iron cores. Structural properties of Fe-27 wt % S and Fe-17 wt % Si liquid alloys at high pressure and high temperature (0-5 GPa/1400-2300 K) are measured by synchrotron X-ray diffraction. Sulfur strongly modifies the local structure of liquid iron whereas silicon has only small structural effects. Fe-27 wt % S melts are indeed poorly ordered which explains a higher compressibility compared to pure liquid Fe. These results point out the necessity to consider the strong effect of S on liquid Fe properties while modeling planetary interiors. They imply a low S content in the Earth's outer core, leaving Si as a strong candidate, and argue for a present-day Martian solid core when combined with previous global chemical models.

Keywords: Geochemistry: Composition of the core; Mineral Physics: High-pressure behavior; Mineral Physics: X ray; neutron; and electron spectroscopy and diffraction; Planetology: Solar System Objects: Jovian satellites; Planetology: Solar System Objects: Mars; core; liquid; iron; X-rays; Mars; Ganymede

Domains: Sciences of the Universe [physics]

C. Sanloup, F. Guyot, P. Gillet, Y. Fei. Physical properties of liquid Fe alloys at high pressure and their bearings on the nature of metallic planetary cores. Journal of Geophysical Research : Solid Earth, 2002, 107, ⟨10.1029/2001JB000808⟩. ⟨insu-03597788⟩