In Situ Micro-XRD Methods For Identifying Glass And Minerals In Extraterrestrial Samples

Abstract

: Glass or amorphous state materials are vital components of lunar regolith and have attracted considerable attention. The analytical data on the texture and structure of glassy and crystallized materials can be used to reconstruct the geological history of the Moon. However, it is often challenging to distinguish glass from crystals based on morphology and elemental composition, especially in complex extraterrestrial samples that have been subjected to significant impact and metamorphism. In this study, micro-X-ray diffraction (µXRD) techniques were used to identify crystalline minerals and glassy phases in lunar breccia samples extracted in the Chang'e-5 mission. The samples were processed using different operating methods to identify a technique that would minimize damage to their original appearance and structure and yield optimal results. The diffraction results, which possessed two-dimensional patterns were classified into dominant dispersion halos, concentric diffraction rings, independent diffraction spots, and coexisting rings and spots. The results correspond to four types of sample states, namely, the amorphous material, polycrystal, single crystal, and a mixture of polycrystals and single crystals. By identifying the crystallization state and phases of various samples in a non-destructive and intuitive manner, µXRD can facilitate in situ analysis of special samples generated during important geological events, thereby promoting the understanding of complex origins and evolution of extraterrestrial bodies.