[S-IT25] Planetary cores: Structure, formation, and evolution

[SIT25-05] In situ observation of Rayleigh–Taylor instability growth of liquid Fe-Si using laser shock

*Hidenori Terasaki¹, Tatsuhiro Sakaiya¹, Keisuke Shigemori², Hiroki Kato², Yoichiro Hironaka², Tadashi Kondo¹ (1.Graduate School of Science, Osaka University, 2.Institute of Laser Engineering, Osaka University)

Keywords:Core formation, Rayleigh–Taylor instability, liquid Fe-alloy

Rayleigh–Taylor instability occurs at the interface between two fluids with different densities when a heavy fluid overlies a light one in a gravitational field. The RT instability is considered as one of the important core formation mechanism beneath the magma ocean. This mechanism has been discussed from simulations (e.g., Honda et al. 1993, Ricard et al. 2009) and analog experiment (e.g., Olson and Weeraratne, 2008). However, experimental approach using liquid Fe-alloys for this mechanism has never been performed under high pressure. In this study, we applied the laser-shock technique to observe in situ the Rayleigh–Taylor instability of liquid Fe-Si alloy under high pressure. The growth of the Rayleigh–Taylor instability was successfully observed using in situ x-ray radiography under shock compression. The growth rate of the Rayleigh–Taylor instability was estimated to 0.3 ns⁻¹. The present results provide useful information to constrain the time scale of the Earth’s and planetary core formation.