Discovery of Coesite on the Lunar Farside

Abstract The Moon has been highly shocked as evidenced by numerous impact craters on its surface. High‐pressure minerals are expected to form during these shock events and can be used to unravel the pressure and temperature conditions for the shock events. However, high‐pressure minerals are rarely reported in the lunar returned samples, yielding a discrepancy with the prediction. The lunar soils returned by the Chang'e‐6 (CE6) mission from the South Pole‐Aitken (SPA) basin provide new opportunities to investigate the shock metamorphism of the lunar samples and the shock events on the Moon. Here, we reported the discovery of coesite in a shock‐induced melt pocket from a CE6 mare basalt, which could have experienced a shock event with a peak pressure of ∼24 GPa. The coesite exhibits two types of occurrences, a polycrystalline aggregate in the center and a ring along the margin of a silica clast. The coesite could have been formed by solid‐state transformation followed by partial conversion to silica glass during decompression. The coesite has a higher survival temperature and a slower back‐transformation rate than most other high‐pressure minerals, which are favorable for its preservation under high‐temperature conditions of lunar soils induced by impacts. These findings provide new insights for the preservation of coesite in natural shock events and indicate that more thermal‐resistant high‐pressure minerals could have been formed and preserved in lunar samples than previously thought, providing new targets for studying the shock events on the Moon.