A Raman Spectroscopic and Microimage Analysis Perspective of the Chang'e-5 Lunar Samples

Abstract

The Chang'e-5 (CE-5) materials represent the youngest returned lunar samples. We performed a detailed Raman spectroscopic survey (1259-point Raman modal analysis) to evaluate the mineralogical characteristics of CE-5 soils, constraining the source materials and shock effects of these unique samples. The mineral chemistry (e.g., Mg#3-60 for mafic minerals) and modal abundance (first distinguishing basaltic and feldspathic glasses) of CE-5 mare soils are different from those of Apollo high- and low-Ti basalts, possibly representing an intermediate-Ti mare basalt. The occurrence of minor Mg-rich materials (Mg# > 70) provides evidence of contamination from ∼5% to 7% exogenous materials, possibly related to Mg-suite rocks. The microimage analyses suggest that the CE-5 soils are fine-grained, mature, and unimodal particle-size distribution, highlighting that micrometeorite reworking dominates the CE-5 regolith evolution with minor mixing from nonmare materials. The pressure-sensitive minerals (quartz and maskelynite) indicate that 17–25.8 GPa shock pressures might be the higher limit in a relatively young lunar terrain.