In a landmark achievement for lunar science and planetary exploration, China’s Chang’e-6 mission has successfully returned pristine samples from one of the Moon’s most enigmatic regions—the South Pole–Aitken (SPA) basin, located on the Moon’s farside. This accomplishment marks the first time in human history that material from this ancient, colossal impact basin has been brought back to Earth, opening unprecedented windows into the Moon’s geological past and, potentially, its deep interior. As scientists worldwide eagerly anticipate detailed laboratory analyses, the key to unlocking the secrets of these precious lunar samples lies in understanding their complex origin, evolution, and the processes that shaped the regolith at the landing site.
The SPA basin is one of the largest and oldest known impact structures in the solar system, spanning an immense 2,500 kilometers in diameter and reaching depths of up to 12 kilometers. Its farside location has made direct geological investigations challenging until recently. The Chang’e-6 mission’s successful touchdown and sample retrieval have allowed researchers to conduct the first integrative study aimed at tracing the provenance of the collected material, encompassing global, regional, and local scales of lunar geology. Such comprehensive investigations are crucial because the regolith—the layer of loose, fragmented rock and dust—is a dynamic record of impact bombardment, volcanic activity, and solar wind influence that has modified the lunar surface over billions of years.
To decipher the origin of the Chang’e-6 samples, researchers employed a systematic approach, cataloguing a total of 1,674 major impact craters within and surrounding the SPA basin. These craters, ranging in size and impact depth, have collectively contributed ejecta materials—broken rock fragments and finer dust—that blanket the Chang’e-6 landing site to a depth of approximately 53.4 centimeters, with an uncertainty margin of ±15.7 cm. Notably, these ejecta materials originated from depths of up to three kilometers beneath the surface, implying that the returned samples contain components excavated from considerable lunar depths, reflecting the complex stratigraphy of the lunar crust.
Detailed compositional modeling indicates that the bulk of the returned samples are dominated by about 93.3% local lunar basalts. These basalts represent volcanic material that solidified from molten lava flows, revealing prolonged mare volcanism and geological activity within the SPA region. Intriguingly, about 6.1% of the materials are attributed to the SPA basin itself, including substances that are likely sourced from the deeper mantle layers beneath the lunar crust. This small but significant presence of mantle-derived materials provides an unparalleled opportunity to characterize the Moon’s subsurface composition without the complexity of direct mantle sampling, which would require prohibitively deep excavation.
In addition to local basaltic and SPA basin materials, about 0.6% of the returned samples comprise feldspathic highland materials. These components originate from sources external to the SPA basin and are characteristic of the ancient lunar highlands, composed predominantly of anorthosite-rich crustal rocks. The trace admixture of these exotic materials encapsulates the intricate history of impact mixing and regolith migration, painting a geological mosaic in the area surrounding the Chang’e-6 landing site.
Furthermore, scientists constructed elemental abundance depth profiles to map the vertical distribution of these distinct material components within the regolith. Their modeling revealed that exotic materials—the mantle-like and highland contributions—are primarily concentrated between depths of 2.5 to 3 meters, but crucially, some fraction of these materials exists within the uppermost 1 meter, which aligns with the sampling depth capabilities of the Chang’e-6 drilling tools. This vertical stratification suggests a complex interplay of impact excavation, ejecta deposition, and regolith overturning processes that have transported diverse materials to accessible depths for sample collection.
A deeper understanding of the temporal dimension of the lunar surface’s exposure to space weathering processes was also achieved. By estimating the exposure time of the surficial seismic scooped samples at a depth of just 1 millimeter, researchers proposed a relatively young age of approximately 2.1 million years, with a margin of error spanning from 1.2 to 3.2 million years. This timeframe corresponds well with established lunar regolith turnover rates driven by micrometeorite bombardment and solar wind irradiation, two key agents of surface weathering. Notably, exposure durations for deeper drilled samples are estimated to be even shorter, reflecting their more shielded locations below the surface layer.
The implications of these findings extend beyond mere sample cataloguing. Understanding the sources and maturation history of the lunar regolith in the Chang’e-6 landing region equips scientists with an essential framework for interpreting the geochemical and isotopic signatures laboratory analyses will soon reveal. The complex admixture of local basalts, ancient mantle-derived fragments, and exotic highland materials provides high-resolution context for revealing planetary differentiation, volcanic evolution, and impact-driven mixing processes that have shaped the lunar farside’s geological architecture over billions of years.
Moreover, this multi-scale provenance study highlights the dynamic processes governing lunar regolith mobility. Continuous bombardment by meteoroids redistributes materials over time, homogenizing the surface but also allowing for pockets of distinct composition at varying depths. The solar wind continuously modifies the uppermost regolith, implanting ions and altering mineral surfaces, a phenomenon known as space weathering, which affects remote sensing signatures and sample chemistry alike. The measured exposure timeline is integral for calibrating these modifications, enabling deconvolution of primary geological signals from secondary alteration effects.
Beyond advancing lunar science, the Chang’e-6 findings enhance our understanding of solar system processes. The SPA basin, due to its age and scale, is a natural laboratory for investigating impact cratering dynamics and planetary crust-mantle interactions. The mission’s success underscores the value of farside explorations, which complement prior near-side Apollo and Luna missions that delivered samples from geographically limited locations with distinct geochemical backgrounds. It is precisely the farside’s ancient, largely unaltered nature that makes the SPA basin samples scientifically precious.
Looking ahead, the integration of remote sensing data, in situ geochemical measurements, and laboratory analyses of the Chang’e-6 samples will undoubtedly illuminate the Moon’s volcanic evolution, revealing temporal variations in mantle melting, crust formation, and impact gardening processes. The mission’s insights into regolith evolution under the continuous influence of space weathering will also inform future human and robotic exploration strategies, aiding site selection, resource assessment, and hazard evaluation for upcoming lunar endeavors.
Importantly, these findings set the stage for a new era of comparative planetary geology, enabling detailed cross-referencing with meteorite collections, Apollo and Luna samples, and ongoing missions such as NASA’s Artemis program. The Chang’e-6 sample provenance study establishes a blueprint for interpreting complex regolith assemblages on other planetary bodies, including Mars and asteroids, where impact-ejecta mixing and space weathering are pervasive.
The success of the Chang’e-6 mission and the sophisticated regolith modeling efforts exemplify how international space exploration efforts increasingly rely on interdisciplinary collaboration—melding planetary geology, geochemistry, impact physics, and space environment science to decode extraterrestrial surfaces. As the first samples from the Moon’s farside SPA basin become accessible, they herald transformative scientific revelations about the origin and evolution of our celestial neighbor, deepening humanity’s cosmic perspective.
Ultimately, the legacy of Chang’e-6 lies in delivering not only lunar materials but also a detailed contextual understanding that empowers the global scientific community to unlock secrets buried beneath the Moon’s dusty veneer. With each grain of returned lunar soil, the echoes of billions of years of planetary processes become clearer, guiding us toward a comprehensive narrative of lunar history and, by extension, the solar system’s formative epochs.
Subject of Research: Provenance and evolution of lunar regolith at the Chang’e-6 sampling site.
Article Title: Provenance and evolution of lunar regolith at the Chang’e-6 sampling site.
Article References:
Zhang, M., Fa, W. & Jia, B. Provenance and evolution of lunar regolith at the Chang’e-6 sampling site. Nat Astron (2025). https://doi.org/10.1038/s41550-025-02525-7
Image Credits: AI Generated
