Chinese lander finds evidence of magmatic structures on the far side of the Moon

In early June 2024, China’s Chang’e 6 lunar probe successfully landed on the far side of the Moon, landing softly near the Moon’s south pole.

His main mission, which he carried out along with various side quests, was to study and return the first ever samples from the far side of the Moon. It did just that, bringing back a whopping 1,935.3 grams (68) of material from the lunar surface on June 25th.

The Moon is tidally locked to the Earth, meaning that the rate at which it rotates on its own axis matches the time it takes to orbit the Earth. This applies to most planet-moon systems, where the planet is much larger than its moon and close enough to it that the rotation speed of the smaller body changes as it orbits the much larger mass planet until they are out of sync.

Often referred to as the “dark side” of the Moon, the far side actually receives about the same amount of sunlight. However, there are notable differences between the two sides, which researchers realized after space travel began. Although the Moon’s far side is littered with craters, it lacks the deep basins and “lunar maria” seen on the near side, and its crust was measured by the Gravitational Recovery and Interior Research Laboratory mission in 2012 to be thicker. seems to be more conductive.

Studying these samples could help clear up some of these mysteries and perhaps tell us a little more about how the Moon formed. Looking at the samples for the first time, geologists from the University of Hong Kong discovered that the Chang’e-6 landing site in the South Pole-Aitken Basin (SPA) is rife with magmatism, where magma cools and hardens to form igneous rock.

“The results of this study provide an important geological basis for the study of plutonic rocks in the Chang’e-6 samples, especially the magnesium suite rocks,” Professor Xianhua Li, an academician of the Chinese Academy of Sciences, said in a statement. “Their petrogenesis and timing are unclear, and this study will greatly contribute to understanding the mechanism of their origin.”

The study, combined with previous studies of the material and observations collected from the near side of the Moon, revealed key volcanic differences between the two sides, likely related to the thickness of the Earth’s crust.

In areas with thick crust, extrusive volcanism (where magma flows over the surface and then cools) predominates.

“For regions with moderate crustal thickness, such as Oppenheimer Crater (…), dikes become trapped beneath the crater’s brecciated floor and propagate laterally to form sills. For regions with thick crust, such as the outer part of the SPA and much of the FS, excess magma pressure cannot support an eruption, and dikes tend to intrude and stall, remaining in the crust,” the team explains in their paper. “Extensive intrusive magmatism within the SPA is consistent with its medium-thick crust (…) comparable to the sea-highland boundaries of the FCT, where most FMCs are located. These results support the hypothesis that cortical thickness is a major factor. in explaining the NS/FS discrepancy in marine volcanism.”

While this is interesting, there are still many questions to be answered, including why the Spa Basin does not contain as much basalt as expected. We hope these questions will be answered as samples are further studied and more material is collected from both sides of the Moon.

The study was published in The Astrophysical Journal Letters.