El lado visible de la Luna (izquierda) y la cara oculta, captado por la misión Clementine. NASA

The stark contrast between the Moon’s nearside and farside in topography, volcanic activity and crustal structure provides critical insights into lunar formation and evolution. However, the absence of farside samples has long limited the investigations into the mechanisms driving this hemispherical asymmetry. The Chinese Chang’e-6 mission recently returned the first rock samples from the lunar farside, offering a unique opportunity to probe its volcanic processes and thermal history. Here we investigate the petrology and geochemistry of the returned lunar basalt fragments. The farside Chang’e-6 basalts dated at 2.8 billion years ago (Ga) reveal that their mantle potential temperature is about 100 °C lower than those recorded by nearside basalts returned by the Apollo and Chang’e-5 missions. Geochemical modelling based on remote sensing data for the 2.8 Ga basalt unit at the Chang’e-6 landing site also yields a ~70 °C lower mantle potential temperature compared with a contemporaneous nearside basalt unit. Collectively, our findings demonstrate that the lunar farside mantle was relatively colder than the nearside mantle, consistent with the hemispherical differences in crustal thickness and heat-producing element distribution, and provide constraints on the thermal evolution of the Moon and the origin of its global asymmetry.

Nature: A relatively cool lunar farside mantle inferred from Chang’e-6 basalts and remote sensing