[S-GC33] Solid Earth Geochemistry, Cosmochemistry

[SGC33-P02] Laser ultrahigh-pressure experiment on Chondrite-Type Allende meteorite

*Yusuke Nakanishi¹, Norimasa Ozaki^1,2, Takayoshi Sano², Yusuke Seto³, Naotaka Tomioka⁴, Ryosuke Kodama^1,2 (1.Graduate School of Engineering Osaka University, 2.Institute of Laser Engineering, Osaka University, 3.Graduate School of Science Osaka Metropolitan University, 4.Japan Agency for Marine-Earth Science and Technology Kochi Core Center)

Keywords:Laser shock, Meteorite, Inhomogeneous structure, Shock wave

Celestial body collisions are a necessary process in the formation of planets in the Solar System, and the current terrestrial planets are thought to be the result of the repeated growth of microplanets a few kilometers in diameter through collisions and mergers. During such collisions, astronomical objects sometimes experience extreme pressure exceeding several hundred of gigapascals, making the study of extraterrestrial materials very important for understanding the history of the Solar System. Scientists have used spacecraft to collect samples of extraterrestrial materials for study, but this is expensive and time-consuming, and samples are not readily available. On the other hand, meteorites are easily accessible and provide many mineralogical and petrological specimens for study. Scientists have used scanning electron microscopy (SEM) and transmission electron microscopy (TEM) to study high-pressure minerals in meteorites and to investigate the impact history of these space rocks. In addition, since the 1970s, shock experiments have been conducted to study the impact evolution of small bodies, thus simulating meteorite samples.[1] However, because a gas gun was used as a shock driver, it was only possible to simulate impacts up to several km/s. On the other hand, laser shock ultrahigh-pressure experiments have made it possible to reach giant-impact class impact pressures. In planetary science, impact compression properties of homogeneous single crystals simulating planetary materials such as olivine have been frequently investigated, but few experiments have been conducted on natural meteorites themselves, which have heterogeneous structures [2,3]. In this study, we performed the world's first laser impact compression experiment on a thin Allende meteorite sample. We investigated the shock wavefront shape, temperature distribution, and other properties of the sample due to compositional and structural heterogeneity under conditions equivalent to a meteorite impact of several hundred GPa.

[1] Sugita, S. et al., Science 310, 274 (2005).
[2] T. Okuchi et al.: Nat. Commun., 12, 4305 (2021).
[3] B.A. Chidester et.al., Earth Space Sci., 48, 8 (2021).