Exotic clasts in Chang'e-5 regolith indicative of unexplored terrane on the Moon

The 2-Gyr-old Chang'e-5 samples are the youngest lunar basaltic regolith returned to Earth and can provide information on the lithological diversity and regolith gardening processes at young mare regions on the Moon over a hitherto unexplored time window. Here we study the lithology and composition of over 3,000 Chang'e-5 regolith particles less than 2 mm in size and identify 7 exotic igneous clasts: a high-Ti vitrophyric fragment, a low-Ti basalt, an olivine-pyroxenite, a magnesian anorthosite, an evolved lithology, a Mg-rich olivine fragment and a pyroclastic glass bead. We associate them with impact-ejected materials from other regions of the Moon, over 50-400 km away from the Chang'e-5 mare unit. In particular, the pyroclastic bead records a volcanic eruption on the Moon with unique chemical composition, suggesting the presence of additional and yet-unrecognized lunar volcanic eruptions. The significantly lower amount of exotic material in the Chang'e-5 samples (similar to 0.2%) with respect to expectations (similar to 10-20%) might indicate that current modelling of impact ejecta needs to be revisited for young lunar geological units.

Automated summary

The 2-Gyr-old Chang'e-5 samples are the youngest lunar basaltic regolith returned to Earth and can provide new information about lithological diversity and regolith gardening processes on the Moon. Analysis of over 3,000 Chang'e-5 regolith particles revealed 7 exotic igneous clasts, including a pyroclastic glass bead that suggests previously unrecognized volcanic eruptions on the Moon. The lower than expected amount of exotic material in the samples indicates a need to revise current impact ejecta models for young lunar geological units.