^1,2,3Qi Sun,^4,5Yu-Yan Sara Zhao,^6,7Kesong Ni,^6,7Zonghao Wang,⁸Wen Yu,⁹Wenqi Luo,⁹Wenbin Yu,⁹Xin Nie,⁹Zonghua Qin,^9,2,5Quan Wan
Journal of Geophysical Research (Planets) Link to Article [https://doi.org/10.1029/2025JE009023]
¹State Key Laboratory of Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
²University of Chinese Academy of Sciences, Beijing, China
³School of Chemistry and Chemical Engineering, Guizhou University, Guiyang, China
⁴Research Center for Planetary Science, College of Earth and Planetary Sciences, Chengdu University of Technology, Chengdu, China
⁵CAS Center for Excellence in Comparative Planetology, Hefei, China
⁶Hypervelocity Aerodynamics Institute, China Aerodynamics Research and Development Center, Mianyang, China
⁷National Key Laboratory of Aerospace Physics in Fluids, Mianyang, China
⁸Center for Lunar and Planetary Sciences, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
⁹State Key Laboratory of Critical Mineral Research and Exploration, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Published by arrangement with John Wiley & Sons

Impact events involving phyllosilicates, whether present in targets or impactors, are highly probable on various celestial bodies. While impact melting is considered the most important metamorphic feature in shocked phyllosilicates, lack of understanding of this process represents a substantial impediment to constraining shock conditions from melted phyllosilicates and to inferring surface evolution of celestial bodies. To investigate shock metamorphism of phyllosilicates, cratering experiments were conducted on clinochlore targets using a light-gas gun at impact velocities ranging from 0.8 to 7.0 km·s−1, and the shocked fragments were characterized with electron microscopy, X-ray diffraction (XRD), Raman spectroscopy and near-infrared spectroscopy. Clinochlore underwent melting at a low velocity of 0.8 km·s−1 due to localized energy concentration at the micron-scale projectile-target interface. With increasing velocity up to 7.0 km·s−1, the shock-generated glasses evolved from semi-parallel nanofilaments to complex agglutinate-like layers, within which abundant vesicles were present due to shock-induced dehydroxylation. Submicroscopic metallic particles were pervasive in the agglutinate-like layers, possibly owing to melting and solidification of micro-jetted metallic fragments. In line with the morphological characterization results, XRD patterns, near-infrared reflectance spectra and Raman spectra of the shocked fragments also collectively reflect the presence and evolution of the impact glasses. Beneath the impact glasses, shock metamorphism may be indicated by decreased basal spacings of clinochlore in the unmelted matrices. Additionally, olivine bearing exogenous iron composition from projectiles crystallized from high-temperature melts during secondary impacts. This work may provide important constraints for regolith evolution and impact history of extraterrestrial bodies.

¹Dijun Guo,^1,2Yeming Bao,¹Xing Wu,³Shuai Li,^1,2,4Yang Liu,¹Yazhou Yang,¹Yuchen Xu,¹Feng Zhang,^4,5Jianzhong Liu,¹Yongliao Zou
Journal of Geophysical Research (Planets)(in Press) Link to Article [https://doi.org/10.1029/2024JE008690]
¹State Key Laboratory of Solar Activity and Space Weather, National Space Science Center, Chinese Academy of Sciences, Beijing, China
²University of Chinese Academy of Science, Beijing, China
³Hawaii Institute of Geophysics and Planetology, University of Hawaiʻi at Mānoa, Honolulu, HI, USA
⁴Center for Excellence in Comparative Planetology, Chinese Academy of Sciences, Hefei, China
⁵Center for Lunar and Planetary Science, Institute of Geochemistry, Chinese Academy of Sciences, Guiyang, China
Published by arrangement with John Wiley & Sons

Ferroan anorthosite, the dominant component of the primordial lunar crust, provides valuable evidence for the lunar magma ocean (LMO) theory. Despite its adjacency to the feldspathic highlands terrane, the identification of pure anorthosite in the Apollo basin has been scarce. Through a comprehensive investigation with high-resolution Kaguya Multiband Imager data over the Apollo basin, we identified numerous outcrops exhibiting definitive diagnostic absorption indicative of the presence of ferroan anorthosite. These anorthosite exposures suggest that crustal material remained after the South Pole-Aitken (SPA) basin impact and that the mafic-rich SPA ejecta was thin in the area, providing significant insights into the excavation process of the SPA impact and subsequent evolution. Our results suggest that the Chang’e-6 mission could potentially bring back the primordial crustal anorthosite from the Apollo basin and offer valuable insights into the LMO theory, alongside the mantle material excavated by the massive SPA impact.

¹Alice C. Quillen,¹Sean Doran
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.70006]
¹Department of Physics and Astronomy, University of Rochester, Rochester, New York, USA
Published by arrangement with John Wiley & Sons

We measure ejecta mass as a function of azimuthal and impact angle for 104 m/s oblique impacts into sand. We find that the ejecta mass distribution is strongly sensitive to azimuthal angle, with as high as eight times more mass in ejecta on the downrange side compared to the uprange side. Crater radii, measured from the impact point, are measured at different impact and azimuthal angles. Crater ejecta scaling laws are modified to depend on azimuthal and impact angle. We find that crater radii are sensitive to both impact and azimuthal angle, but the ejecta mass as a function of both angles can be estimated from the cube of the crater radius without an additional angular dependent function. The ejecta distributions are relevant for processes that depend upon the integrated properties of approximately 100 m/s impacts occurring in the outer solar system and possibly during planetesimal formation.