my country's Chang'e-5 lunar probe landed in the northeastern region of the Cripple Terrain on the front of the moon in December 2020, and then sampled lunar surface materials near the landing site and successfully brought lunar soil samples back to Earth.

The northeastern part of the Ocean of Storms Cripple Terrain 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 uranium, thorium, potassium and other heat generating units element.

Previous simulation studies have suggested that the heat-generating elements rich in the Cripple Terrain of the Ocean of Storms are precisely the main reason for maintaining lunar volcanism.

Therefore, the study of the thickness of the basalt in the Chang'e-5 landing area and its eruption rate will further enhance people's understanding of the lunar volcanic activity and internal thermal evolution history.

　　Recently, researchers from the Key Laboratory of Solar Activity and Space Weather at the National Space Science Center of the Chinese Academy of Sciences, in collaboration with researchers from the Shanghai Observatory of the Chinese Academy of Sciences, Peking University, and Shandong University (Weihai), estimated the thickness of basalt in the landing area of ​​Chang'e-5.

Based on the distribution characteristics of titanium content in the sputtering crater of the Chang'e-5 landing area, and combined with the statistical dating results of the lunar surface impact craters and the radioisotope dating results of the Chang'e-5 basalt samples, the researchers determined the Chang'e-5 landing site and its surroundings. The sequence of formation of regional basalt units.

The research team used multi-source remote sensing data such as optics, topography, spectroscopy, and gravity to estimate the depth of penetrating and non-penetrating impact craters, the topographic evolution process of partially submerged impact craters, and the effective density spectrum that describes the degree of correlation between gravity and topography. The thickness of each underlying basalt unit in the landing area of ​​Chang'e 5 is calculated.

　　The research results show that the Chang'e-5 landing area has experienced at least four volcanic magma eruptions, with median thicknesses of 230 meters, 70 meters, 4 meters and 36 meters, respectively.

Judging from the spatial distribution trend of basalt thickness, the study found that as the distance from Rima and Mairan gradually increased, the thickness of basalt gradually decreased, which indicates that the craters of Rima and Mairan are the landing areas of Chang'e 5. The source of the basalt eruption.

Further, combined with the area and age estimation results of each basalt unit, the study calculated the eruption rate of the basalt in the landing area of ​​Chang'e 5, and found that the magma eruption flux in this area was significantly (about 2 billion years ago) in the late lunar volcanic activity (about 2 billion years ago). about 2 orders of magnitude) enhanced.

　　The study believes that the richness of heat-generating elements in the Crip terrane of the ocean frontal ocean of storms is the main reason for the still active volcanic activity in the late lunar period.

However, the latest sample study results show that the basalt in the Chang'e-5 landing area is not Krip basalt.

The study raises the possibility that the heat-generating elements in the Cripple Terrain of the Storm Ocean did provide a heat source for the partially molten region of the lunar mantle, but the magma may not have time to rise rapidly from the lunar mantle to the lunar surface It is fully mixed with the Krip composition in the Krip terrane of the Ocean of Storms, so that not much Krip material was 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 lunar crust thickness, and the early adjacent Imbrium Basin impact event may have formed large-scale fissures in the lunar crust, all of which are beneficial to the lunar mantle Magma erupted onto the lunar surface.

The maintenance mechanism of late lunar volcanic activity has always been a hot issue in lunar scientific research, and further research on the Chang’e-5 basalt samples is expected to provide new constraints for the existing lunar thermochemical and kinetic models, thus providing new insights into the interpretation of the moon. The duration and scale of volcanic activity provide strong evidence.

　　(Headquarters CCTV reporter Shuai Junquan)