^1,2Zhan Zhou et al. (>10)
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2025JE009052]
¹Key Laboratory of Planetary Science and Frontier Technology, Institute of Geology and Geophysics, Chinese Academy of Sciences, Beijing, China
²University of Chinese Academy of Sciences, Beijing, China
Published by arrangement with John Wiley & Sons

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.

¹Jessika L. Valenciano,¹Clive R. Neal,²Scott A. Eckley,³Charles K. Shearer, the ANGSA Science Team
Journal of Geophysical research (Planets)(in Press) Open Access Link to Article [https://doi.org/10.1029/2024JE008580]
¹Department of Civil and Environmental Engineering and Earth Sciences, University of Notre Dame, Notre Dame, IN, USA
²Amentum—JETS2, Astromaterials Research and Exploration Science Division, NASA Johnson Space Center, Houston, TX, USA
³Institute of Meteoritics, University of New Mexico, Albuquerque, NM, USA
Published by arrangement with John Wiley & Sons

Double drive tubes 73002 (upper) and 73001 (lower) were collected during Apollo 17 from a landslide deposit at the base of the South Massif in the Taurus-Littrow valley. The drive tubes were opened for the first time as part of the Apollo Next Generation Sample Analysis (ANGSA) project, representing “new” samples from the Moon. Many lithic fragments (>1 mm in size) were extracted from the core during core dissection and preliminary examination (PE), including high-Ti mare basalt clasts. Those >4 mm fragments were three-dimensionally imaged using X-ray computed tomography (XCT). The crystal size distributions of ilmenite were measured in 10 high-Ti mare basalts and within the matrix of an impact melt breccia from drive tube 73002 using thin section “slices” from the 3D XCT scans. Residence times (of the crystals in the melt from which they grew) were estimated using experimental growth rates for each sample with all but 73002,2015 being relatively short (<1 year). Linear (constant) cooling rates were determined, expanding upon data already obtained from other Apollo 17 high-Ti basalts showing that these ANGSA basalt clasts had similar cooling histories to those previously studied. Comparison with ilmenite cooling rate experiments estimated cooling rates of <10°C/h for each clast.