China’s Chang’e 6 mission, a groundbreaking endeavor in lunar exploration, successfully returned the first-ever samples from the far side of the Moon on June 25, 2024. This historic achievement marks a significant milestone for China’s space program and provides an unprecedented opportunity for scientists worldwide to study the Moon’s less-explored hemisphere. The mission, launched on May 3, 2024, from the Wenchang Space Launch Center, involved a complex sequence of maneuvers, including landing in the South Pole-Aitken (SPA) Basin, collecting approximately 1.9 kilograms of lunar regolith and rocks, and a successful return to Earth in Inner Mongolia.
The initial analyses of the Chang’e 6 lunar samples have already yielded fascinating insights into the Moon’s far side. One of the key findings suggests that the far side regolith has a lower density and a more porous structure compared to samples from the near side, indicating a higher presence of light-colored materials like feldspar and glass, potentially originating from distant impact events. Furthermore, the far-side samples exhibit a lower concentration of KREEP (potassium, rare-earth elements, and phosphorus), which is more abundant on the near side. This asymmetry could be a crucial factor in understanding the fundamental differences between the two hemispheres of the Moon.
More recent studies, published in leading scientific journals, have delved deeper into the geological history and composition of the far-side samples. Notably, analyses of basalt fragments have revealed evidence of volcanic activity on the far side dating back 2.8 billion and 4.2 billion years. The 2.8-billion-year-old basalts represent a unique volcanic event not observed in near-side samples, while the 4.2-billion-year-old fragment is the oldest precisely dated lunar rock returned to Earth. These findings challenge the traditional view that the thicker crust on the far side inhibited volcanic eruptions and suggest that other factors, such as mantle composition, played a significant role.
Another significant discovery from the Chang’e 6 samples concerns the Moon’s ancient magnetic field. Paleomagnetic analysis of the far-side rocks indicates an unexpected resurgence in the strength of the lunar magnetic field around 2.8 billion years ago, following a previously known sharp decline. This challenges the existing theory that the lunar dynamo remained in a low-energy state after its initial decline and provides the first paleomagnetic data from the Moon’s far side, offering critical insights into the evolution of the lunar dynamo.
Furthermore, recent research has explored the implications of the Chang’e 6 samples for the giant-impact theory of the Moon’s formation. Analysis of the water content in the far-side mantle, based on the returned basaltic rocks, suggests a significantly lower water concentration compared to the near-side mantle. This finding aligns with models of the giant-impact scenario, which predict a drier far-side mantle due to the dynamics of the impact event. These initial scientific investigations underscore the immense value of the Chang’e 6 samples in unraveling the Moon’s history, composition, and the processes that shaped its two distinct hemispheres. As research continues, these unique samples promise to yield even more groundbreaking discoveries about our celestial neighbor.
