¹Yaozhu Li,¹Phil J. A. McCausland,¹Roberta L. Flemming,¹Callum J. Hetherington,¹Bo. Zhao
Journal of Geophysical Research: Planets Open Access Link to Article [https://doi.org/10.1029/2026JE009662]
¹Department of Earth Sciences, Western University, London, ON, Canada, 2Department of Geosciences, Texas TechUniversity, Lubbock, TX, US
Published by arrangement with John Wiley & Sons

Ureilites are ultramafic achondrites for which the parent body is unknown. Monomict ureilites, consisting primarily of olivine and pyroxene, are thought to represent mantle residues, carrying essential information for their parent body deformation history. All monomict ureilites are found to be shocked variously, complicating the interpretation of their deformation history. In this work, four monomict ureilites, Elephant Moraine 96042, Northwest Africa 2221, Larkman Nunatak 04315, and Alan Hills A81101, are examined using electron backscatter diffraction to study shock-related and post-shock microstructural development in the strained olivine. We calculated the unit segment length (USL) to quantify the subdomain development in those olivine grains, and we further applied a modified misorientation index to study the role of shock in subdomain misorientation. A positive trend of increasing USL with increasing shock level is identified, indicating increased microstructural subdivision and decreasing subdomain size with increasing shock deformation. In LAR 04315 and ALH A81101, the development of low-angle subdomain boundaries defines an apparent foliation, consistent with a non-instantaneous, high-temperature deformation overprint following shock. Together, these results demonstrate that EBSD-derived microstructural metrics provide a robust, quantitative framework for distinguishing shock-related deformation from post-shock microstructural modification in ureilitic olivine.

^1,2Kewei Shen, ¹Panming Xue, ¹Duojun Wang, ¹Rui Zhang, ²Guangchao Chen, ¹Kexuan Zhang, ¹Liang Wei
Icarus (in Press) Link to Article [https://doi.org/10.1016/j.icarus.2026.117132]
¹High Pressure Experiment Science Center, College of Earth and Planetary Sciences, University of Chinese Academy of Sciences, Beijing, China
²College of Materials Science and Optoelectronic Technology, University of Chinese Academy of Sciences, Beijing, China
Copyright Elsevier

The Moon shows marked differences in geophysical and geological properties between its nearside and farside, long attributed to internal thermal state. However, the present-day lunar thermal gradient remains poorly constrained. In this study, we measured the thermal conductivity and diffusivity of lunar mantle olivine under 0.5–4.0 GPa and 298–1273 K, demonstrating that lattice conduction was the dominant heat transport mechanism. Combining with regional variation parameters including crustal thickness, radiogenic heat production, and modeled surface heat flow, we constructed thermal profiles for distinct lunar regions. Our results revealed a significant nearside-farside thermal asymmetry, with temperature differences reaching ~79–180 K at depth. Elevated nearside mantle temperatures suggested that partial melting may still persist at depths greater than ~700 km. This localized partial melting likely contributes to the observed low seismic velocity and high electrical conductivity anomalies, as well as the occurrence of deep moonquakes beneath the nearside.