[S-IT22] [EE] Interaction and Coevolution of the Core and Mantle in the Earth and Planets

[SIT22-41] Thermoelastic properties of iron-carbide melts under high pressure: implication for carbon in the lunar interior

*Yuta Shimoyama¹, Hidenori Terasaki¹, Satoru Urakawa², Yusaku Takubo¹, Tetsu Watanuki³, Akihiko Machida³, Yoshinori Katayama³, Tadashi Kondo¹ (1.Dept. Earth&Space Science, Osaka University, 2.Graduate School of Natural Science and technology, Okayama University,, 3.Natural Institutes for Quantum and Radiological Science and Technology)

Keywords:Moon, Outer core, liquid, sound velocity, density, bulk modulus

Carbon is one of the possible light elements in lunar interior. Thus, it is important to understanding the effect of density and sound velocity of liquid Fe at high pressure in order to evaluate the presence of carbon in lunar core. Simultaneous measurements of P-wave velocity and the density of liquid Fe-C have been conducted up to 3.4 GPa and 1850 K. Addition of carbon decreased the V_P of liquid Fe by about 2% at 3 GPa and 1700 K and reduced Fe density by about 2% at 2 GPa and 1700 K. The V_P of liquid Fe-3.5 wt% C decreased linearly with increasing temperature at constant pressure. The bulk modulus of liquid Fe-C and its pressure (P) and temperature (T) effects were precisely determined from directly measured r and V_P data to be K_0,1700K = 83.9 GPa, dK_T/dP = 5.9(2), and dK_T/dT = −0.063(8) GPa/K. The effect of carbon in the Birch (r–V_P) plot decreases with increasing pressure. Based on the directly measured V_P and r of liquid Fe-C, elastic properties, such as K, dK/dT, and dK/dP, were determined precisely. These properties can explain differences in dV_P/dT of Fe-C, Fe, and Fe-S.