A novel method for simultaneous analysis of particle size and mineralogy for Chang’E-5 lunar soil with minimum sample consumption

Kenan CAO 1, Mingtan DONG 2, Zhenbing SHE 1,*, Qian XIAO 1, Xinyi WANG 1, Yuqi QIAN 3, Yiheng LI 3, Zaicong WANG 3, Qi HE 3, Xiang WU 3, Keqing ZONG 3, Zhaochu HU 3, Long XIAO 3

The successful return of lunar soil samples from the northern Oceanus Procellarum by the Chang’E 5 (CE-5) mission has provided unprecedented ground-truth information for the previously unexplored region of the Moon. Determining the mineral components of lunar soils and their characteristics are critical to understanding the source materials that have contributed to the soil, as well as to interpreting remotely sensed data.

Since the 1970s, various techniques have been used to determine the mineral modes and particle size of the Apollo and Luna soil samples. However, most of these methods require either a relatively large sample size or specific sample preparation, which are sometimes not possible because investigators are often required to work with exceptionally small amounts of samples, typically at the milligram level. Moreover, particle size information and mineral modes are usually independently obtained with different instruments, and are difficult to be correlated.

With a Raman-based particle analysis system, a research team led by Prof. Zhenbing She and Zaicong Wang at China University of Geosciences (Wuhan) show that the particle size properties and mineral constituents of the CE-5 soil can be simultaneously determined with a small sample size (ca. 30 µg). The CE-5 sample scooped from the lunar surface has an overall small size between 0.4 µm and 73.9 µm (mean = 3.5 µm), and mainly consists of pyroxene (39.4 %), plagioclase (37.5 %), olivine (9.8 %), Fe-Ti oxides (1.9 %), glass (8.3 %) and other minor or trace phases. The results are consistent with previous analyses with larger sample sizes. In addition to minimum sample consumption, this method requires very little sample preparation, and can rapidly build a large database with each particle precisely traceable. Therefore, this novel technique is particularly suitable for the analysis of future returned soil samples from extraterrestrial bodies.

This research was supported by the pre-research project on Civil Aerospace Technologies funded by CNSA, the National Natural Science Foundation of China and the State Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences. PhD candidate Kenan Cao at the School of Earth Sciences is the first author.