Shulou(Shulou.com)11/24 Report--

Thanks to CTOnews.com netizens AVIDINTEL and classmates for the clue delivery! CTOnews.com, Sept. 17 (Xinhua) according to a study conducted by the National Space Science Center of the Chinese Academy of Sciences and Peking University, the Chang'e V landing area has experienced at least four volcanic magma eruptions, and the magma eruption flux in the region increased significantly (about two orders of magnitude) in the late lunar volcanic activity (about 2 billion years ago).

(a) optical image, (b) false color band composite image and (c) titanium content distribution map of ▲ Chang'e-5 landing area | figure from the National Space Science Center of the Chinese Academy of Sciences, the same below

China's Chang'e-5 lunar probe landed in the northeast of the lunar frontal storm ocean Kripp in December 2020, according to the National Space Science Center of the Chinese Academy of Sciences. then the lunar surface material near the landing site was sampled and 1731 grams of lunar soil samples were successfully brought back to Earth. The northeastern part of the storm ocean Kripp terrane was chosen as the landing area for the Chang'e-5 mission mainly because it is considered to be one of the youngest basalt units on the lunar surface and is rich in thermogenic elements such as uranium, thorium and potassium. Previous simulation studies based on thermochemistry and kinetics have shown that the rich heat-generating elements in the storm ocean Kripp terrane are the main reasons for maintaining lunar volcanic activity. Therefore, the study on the thickness and eruption rate of basalt in Chang'e-5 landing area will further enhance the understanding of lunar volcanic activity and internal thermal evolution history.

CTOnews.com learned that the results show that the Chang'e-5 landing area has experienced at least four volcanic magmatic eruptions, with median thicknesses of 230m, 70m, 4m and 36m, respectively. From the spatial distribution trend of basalt thickness, it can be found that the thickness of basalt decreases gradually with the distance from Rima and Mairan, which indicates that the crater of Rima and Mairan is the source of basalt eruption in Chang'e-5 landing area. Furthermore, combined with the estimated results of the area and age of each basalt unit, the eruption rate of basalt in Chang'e 5 landing area is calculated. it is found that the magmatic eruption flux in this area increased significantly (about 2 orders of magnitude) in the late lunar volcanic activity (about 2 billion years ago).

▲ (a) the thickness of the underlying basalt units in the Chang'e-5 landing area. (B) the spatial distribution of the sum of the thickness of Em4 and Em3 elements, in which the red curve is Rima and Mairan Yuexi. (C) the eruption rate of basalt magma in the landing area of Chang'e V and other areas on the lunar surface.

Based on the study of thermochemical and kinetic models, it is considered that the rich heat-generating elements in the oceanic Kripp terrane of the lunar frontal storm is the main reason why the late lunar volcanic activity is still active. However, the latest sample study results show that the basalt in the Chang'e-5 landing area is not Krip basalt.

This study puts forward a possibility that the heat-generating elements in the storm ocean Kripp terrane do provide a heat source for the partial melting region of the lunar mantle, but the magma may not have time to fully mix with the Crip composition in the storm ocean Kripp terrane in the process of rising rapidly from the lunar mantle to the lunar surface, resulting in no more Crip material measured in the Chang'e-5 basalt samples.

In addition, the thickness of the lunar crust in the Chang'e-5 landing area is about 25% smaller than the average, and the early impact events in the adjacent Yuhai basin may have formed large-scale fissures in the lunar crust, all of which are conducive to the eruption of magma in the lunar mantle to the lunar surface. The maintenance mechanism of late lunar volcanic activity has always been a hot issue in lunar scientific research, and the further excavation of Chang'e-5 basalt samples (such as the measurement of viscosity and thermal conductivity). It is expected to provide new constraints for the existing lunar thermochemical and kinetic models, thus providing strong evidence for explaining the duration and eruption scale of lunar volcanic activity.

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