The stark differences in proximity and width between the moon’s near and far sides, along with their topography, volcanism, and crustal structures, offer crucial insights into the moon’s formation and evolution. However, investigations into the mechanisms behind this hemispherical asymmetry have been constrained by the absence of far-side samples. A recent study revealed fragments of rock and soil collected by China’s Chang’e 6 spacecraft from a large crater on the moon last year. Researchers confirmed that these rock samples are approximately 2.8 billion years old, analyzed the chemical composition of the minerals, and estimated that they were formed from lava deep within the moon at temperatures around 1,100 degrees Celsius. Survey results were published in the journal Natural Earth Science.
A global map of Albedo from a 750 nm filter on a UV-VIS camera mounted on NASA’s Clementine spacecraft. This image shows the near and far side of Lambert’s moon, and is an equal area projection. Image credit: NASA.
“The near and far sides of the moon differ significantly, both on the surface and potentially in their internal structures,” said Professor Yang Lee, a researcher at the University of London.
“This is one of the moon’s great mysteries. We refer to it as the two-sided moon. While variations in temperature between the near and far sides have long been theorized, our research presents the first evidence derived from actual samples.”
“These discoveries bring us closer to understanding the moon’s dual nature,” stated PhD candidate Xuelin Zhu from Peking University.
“They indicate that the disparities between the two sides extend beyond the surface, reaching deep within the moon.”
In this research, the authors examined 300 grams of lunar soil assigned to the Beijing Institute of Uranium Geology.
“This sample represents the first collection by the Chang’e 6 mission from across the moon,” commented Dr. Sheng, a researcher at the same institute.
The researchers found the samples were primarily composed of basalt particles and utilized electron probes to map specific areas of the sample, determining their composition.
They analyzed variations in lead isotopes dating back 2.8 billion years.
Several techniques were employed to estimate the sample temperatures at different stages in the moon’s past.
The first method involved analyzing mineral composition and comparing it with computer simulations to estimate the formation temperatures of the rocks.
This was juxtaposed with similar estimates for rocks from the near side, revealing a temperature difference of approximately 100 degrees Celsius.
The second technique delved further into the sample’s history, inferring from its chemical composition to ascertain the heat of the “parent rock” and comparing it with estimates of lunar samples obtained during the Apollo missions.
Once again, a Celsius difference of about 100 degrees was identified.
Due to the limited samples returned, they estimated the parent rock temperature using satellite data from the Chang’e landing sites on both sides, comparing this with similar data from nearby areas, which revealed a difference of 70 degrees Celsius.
On the moon, thermogenic elements like uranium, thorium, and potassium are often found alongside phosphorus and rare earth elements within a material referred to as KREEP (an acronym for potassium (K), rare earth element (REE), and phosphorus (P)).
The leading theory regarding the moon’s origin posits that it formed from debris resulting from a large-scale collision between Earth and a Mars-sized protoplanet, developing from primarily molten rock.
This magma solidified as it cooled, but KREEP elements were compatible with the forming crystals and remained within the magma for extended periods.
Scientists anticipate that KREEP material would be evenly distributed across the moon. In reality, it appears to be concentrated in the near side’s mantle.
The distribution of these elements may explain why the near side exhibited more volcanic activity.
While the current mantle temperatures on the far and near sides of the moon remain unknown due to this study, the temperature imbalances are likely to persist for a considerable duration, as the moon cools very slowly since its formation from a catastrophic impact.
Scientists aim to provide definitive answers to these questions in ongoing research.
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she et al. Chang’e-6 basalt and relatively cool moon facid mantle inferred from remote sensing. nut. Geosci Published online on September 30th, 2025. doi:10.1038/s41561-025-01815-z
Source: www.sci.news
