The striking contrast between the nearby side and the distant side of the moon in the topography, volcanic activity and the crustal structure provides critical information on lunar training and evolution. However, the absence of eccentric samples has long limited surveys on mechanisms stimulating this hemispherical asymmetry. In new research, scientists have examined the fragments of rocks and soils by the Chinese spaceship China 6 last year from a large crater on the other side of the moon. They confirmed the previous results according to which the rock sample was approximately 2.8 billion years and analyzed the chemical composition of its minerals to estimate that it was formed from lava deeply inside the moon at a temperature of around 1,100 degrees Celsius – about 100 degrees Celcius freshness that existing samples on the near side. The results were published in the journal Nature geoscience.
Global albedo map from the 750 Nm filter of the UV-Vis camera aboard the Clementine Spatial Vaix from NASA. The image shows the nearby side and the distant side of the moon in Lambert, projection of the equal area. Image credit: NASA.
“The nearby side and the distant side of the moon is very different on the surface and potentially inside,” said Professor Yang Li, a researcher at the University College London and at the University of Peking.
“It is one of the great mysteries of the moon. We call it the moon with two sides. A dramatic difference in temperature between the nearby side and the distant side of the mantle has long been supposed, but our study provides the first proof using real samples. ”
“These results bring us closer to the understanding of the two faces of the moon,” said Xuelin Zhu, a doctorate. Student at the University of Beijing.
“They show us that the differences between the near and far side are not only on the surface but go deep inside.”
In the study, the authors analyzed 300 g of lunar soils allocated to the Research Institute for Research of Beijing of Uranium Geology.
“The sample taken by the Chang’e 6 mission is the first on the other side of the moon,” said Dr. Sheng He, researcher at the Beijing Institute of Beijing in Uranium.
The researchers have mapped selected parts of the sample, made up largely of basalt grains, with an electronic probe, to determine its composition.
They have measured tiny variations in lead isotopes using an ion probe to date the rock at 2.8 billion years.
They then used several techniques to estimate the temperature of the sample while at different stages of its past when it was at the bottom of the interior of the moon.
The first was to analyze the composition of minerals and compare them to computer simulations to estimate how hot the rock was formed.
This was compared to similar estimates for the rock side rocks, with a difference of 100 degrees Celsius.
The second approach consisted in returning further in the history of the sample, deducting from its chemical composition to what extent its “ Parental Roche ” would have been hot, comparing this to the estimates for the nearby samples collected by the Apollo missions.
They once again found a difference in Celesius of 100 degrees.
As the returned samples are limited, they estimated the temperatures of parental rocks using satellite data from the Chang’e landing site on the other side, comparing this with equivalent satellite data on the near side, finding a difference – this time of 70 degrees Celsius.
On the moon, elements producing heat such as uranium, thorium and potassium tend to occur together alongside phosphorus and rare earth elements in a material known as Kreep (the acronym derives from potassium with the chemical symbol K, elements of the rare earth (REE) and P for phosphorus).
The main theory of the origin of the Moon is that it has formed from debris created from a massive collision between the earth and a protoplanet of size Mars, and started entirely or mainly in melted rock.
This magma solidified in cooling, but the elements of Kreep were incompatible with the crystals which were formed and therefore remained longer in the magma.
Scientists would expect the Kreep material to be uniformly distributed through the moon. Instead, we think he is grouped in the coat on the nearby side.
The distribution of these elements can explain why the near side has been more volcanically active.
Although the current temperature on the distant side and close to the coat of the moon is not known to this study, any temperature imbalance between the two sides will probably persist for a very long time, the moon cooling very slowly from the moment it has formed from a catastrophic impact.
However, scientists are currently working to obtain a final answer to this question.
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She and al. A relatively cool lunar distant coat deduces from Chang’e-6 basalts and remote sensing. Nat. Gealitypublished online on September 30, 2025; DOI: 10.1038 / S41561-025-01815-Z
