Groundbreaking Insight into the Moon’s Hemispheric Dichotomy
The Moon’s far side has always intrigued scientists with its stark differences from the side facing Earth. A collaborative effort involving the Beijing Research Institute of Uranium Geology, the China National Nuclear Corp, Peking University, and Shandong University has produced a landmark finding: the lunar mantle on the far side is cooler than the near side. Published in Nature Geoscience on Sept. 30, this discovery advances our understanding of the Moon’s thermal history and the origins of its hemispheric dichotomy.
how the discovery was made
Researchers analyzed lunar dust samples retrieved from the far side by the Chang’e 6 mission. By examining the mineral composition, including clinopyroxene and plagioclase in lunar regolith basalt, they calculated crystallization temperatures and pressures using three independent thermobarometers. To ensure robustness, they also simulated the crystallization process with a petrological model tailored to the Chang’e 6 samples. The results were consistent across methods, pointing to a far-side basalt crystallization temperature around 1,100°C, about 100°C cooler than near-side basalt.
What the temperature difference implies
Beyond crystallization temperatures, the team reconstructed the original chemical makeup of the Moon’s magma and inferred the mantle’s potential temperatures. They concluded that the far side’s mantle potential temperature sits roughly 100°C lower than the near side. This thermal dichotomy aligns with existing observations of crustal thickness variations and the distribution of heat-producing elements, offering a coherent picture of why the Moon evolved with distinct hemispheres.
Broader significance for lunar science
These findings contribute to a more nuanced narrative of lunar evolution. A colder far-side mantle would influence the style and vigor of ancient volcanic activity, the composition of erupted materials, and the long-term cooling of the Moon. The study also provides critical data to test models of how heat-producing elements are distributed across the lunar crust and mantle—a key factor in shaping the Moon’s thermal and geological history over billions of years.
Cross-disciplinary achievement
The Nature Geoscience publication marks another milestone for China’s multidisciplinary collaboration between nuclear and space sciences. Building on earlier discoveries, such as the identification of Changesite-(Y) mineral in 2022, the new research demonstrates how combining nuclear geoscience techniques with planetary exploration can yield robust insights into planetary interiors.
The Chang’e 6 mission: a pivotal step
Launched in May 2024 from Wenchang Space Launch Site in Hainan, Chang’e 6 represents the world’s first mission to return samples from the Moon’s far side. After 53 days of complex maneuvers, the mission delivered 1,935.3 grams of lunar material. The far-side samples opened a new window on the Moon’s interior, enabling direct comparisons with near-side materials and strengthening tests of thermal evolution theories.
What this means for future exploration
Understanding the temperature gradient between the Moon’s hemispheres informs the design of future missions and instrumentation. It helps in predicting mantle dynamics, the timing of early volcanic episodes, and the distribution of valuable rock types that can unlock planetary formation puzzles. As researchers continue to unfold the data from Chang’e 6, the Moon’s far side may reveal more secrets about its past and its place in the solar system’s formation saga.
Global context and Earth’s parallels
Scientists see a broader value in these findings for comparative planetology. Studying how planetary interiors cool and differentiate enhances our grasp of Earth’s own evolution and how once-formed bodies diverge in thermal histories. Each new data point from the Moon sharpens the scientific consensus on how terrestrial bodies evolve in isolation, away from our blue planet—yet still connected through shared cosmic origins.
