Space Weathering Properties of Chang’e-6 Soils and Implication for Regolith Evolution of Young Lunar Maria

Abstract

Lunar soil samples from young maria (formed <3.0 billion years ago (Ga)) preserve key records of recent space weathering history in the Earth–Moon system. China’s Chang’e-6 mission returned the first farside soil samples from a young mare (∼2.8 Ga) at the northeastern South Pole–Aitken basin. We present preliminary results on the space weathering properties of the Chang’e-6 soils. The glassy agglutinate content in the Chang’e-6 soils is approximately 30%, significantly lower than the 50%–70% observed in the mature Apollo soils from older maria (>3.0 Ga) and higher than the ∼21% found in the Chang’e-5 soils from younger mare (∼2.0 Ga). However, our spectroscopic study reveals that the Chang’e-6 soils are well developed, with high maturity, weak absorption, and a red-sloped continuum, similar to the characteristics of the mature soils from the Apollo and Chang’e-5 landing sites. Orbital observations indicate more mature surface than in the returned samples from young mare regions, likely due to the destruction of an optically mature veneer by spacecraft. The optically mature veneer reveals deficiencies in remote sensing and emphasizes the importance of sample return missions. The thinner optically mature veneer and lower abundance of glassy agglutinate in younger maria suggest reduced gardening cycles and changes in impactor properties (such as rate and size) after 3.0 Ga. This is important for understanding how the relative contributions of space weathering agents change over time and the evolution of impactors in the inner solar system.