Recently, the world’s first mineralogical analysis report on a sample from the lunar far side’s ’magnesium ring’ was released at Shandong University. This achievement focuses on a special area called the ’magnesium-rich pyroxene ring’ within the South Pole-Aitken (SPA) basin on the Moon. With the Chang’e 6 mission bringing lunar regolith samples from the vicinity of this area back to Earth, researchers have been able to unveil the true nature of this mysterious location for the first time. The relevant paper has been published in Communications Earth & Environment, a journal of Nature group.
The SPA basin, the largest and oldest impact basin on the Moon, is believed by the scientific community to potentially expose deep lunar materials. The magnesium-rich pyroxene ring refers to a ring-shaped area within the SPA basin that is believed to contain a significant amount of magnesium-rich pyroxene minerals; it is referred to as the “magnesium ring” for short. In the past, scientists could only indirectly infer the composition of this area using remote sensing technology, lacking physical evidence. Now, researchers have obtained the first real mineral composition data from this area, which is akin to conducting a “deep X-ray scan” of the Moon, revealing the deep structure and material composition of the lunar crust.
Recent research indicates that approximately 31%–40% of the lunar regolith returned by Chang’e 6 originates from an impact crater within the SPA basin—Chaffee S. Ejecta from the impact were scattered to the Chang’e 6 landing area. According to the paper’s first author, Dr. Cao Haijun, a postdoctoral researcher at Shandong University, the magnesium-rich ring material of the SPA basin is primarily composed of subcalcic ferroan augite, a rock consisting of plagioclase (63%–67%) and low-calcium pyroxene (25%–27%). The plagioclase proportion is significantly higher than that found in initial impact melt rocks. This characteristic suggests that the SPA basin underwent extensive mixing (approximately 61%–63%) and remolding of lunar crustal material in the later stages of the impact event, ultimately forming a unique magnesium- and plagioclase-rich ring structure. This finding provides crucial evidence for understanding the mixing of lunar deep-seated materials and impact evolution mechanisms.
A planetary science team from Shandong University identified 16 major minerals in the samples using Raman spectroscopy. They found the lunar regolith contains virtually no olivine or ilmenite, indicating a different origin than the Chang’e 5 samples from the lunar nearside. The team also proposed a lunar regolith evolution model depicting the regolith’s formation process from magma eruption and long-distance impact to repeated pulverization, weathering, and cementation.
This testing report represents not only the world’s first research findings on the mineral composition of lunar magnesium rings based on lunar samples from the far side of the Moon, but also provides crucial support for understanding the Moon’s internal structure and composition, its impact and thermal evolution history, and the calibration of lunar orbital remote sensing data.