Conjugated Silicate Nanodroplets in Lunar Regolith: Unraveling Impact-Driven Phase Separation

Abstract

Meteoroid impacts, a key process of space weathering, significantly alter the structures, compositions and properties of lunar regolith. However, the phase separation phenomena, common in lunar regolith and induced by impact, remain poorly understood. This uncertainty arises from the structural complexity and the scarcity of identified impact-induced phase separation features. Here we report the impact-induced formation of chemically distinct amorphous silicate nanodroplets, including iron-rich droplets within a silicon-rich glass matrix and vice versa, on the surface of a Chang'e-5 lunar regolith grain. These nanodroplets are partially ripened aggregates, and their formation is attributed to metastable liquid immiscibility driven by local chemical heterogeneities and rapid quenching. Additionally, troilite-kamacite remnants and skeletal crystallites of ilmenite and apatite provide direct evidence of impact and fast post-impact quenching, respectively. These findings suggest that quenched impact melts in airless bodies can undergo unmixing, forming immiscible conjugated nanodroplets, and exhibiting diverse behaviors under specific post-impact conditions.