A study completed by the National Space Science Center of the Chinese Academy of Sciences and Peking University and other units showed that the Chang'e 5 landing area has experienced at least four volcanic magma eruptions , and the magma eruption flux in the area Significant (about 2 orders of magnitude) enhancement occurred during the late lunar volcanism (about 2 billion years ago).
According to the National Space Science Center of the Chinese Academy of Sciences, my country's Chang'e-5 lunar probe landed in the northeastern part of the Cripple Terrain on the front of the moon in December 2020, and then sampled the lunar surface material near the landing site and made a Successfully brought 1731 grams of 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 based on thermochemistry and dynamics believed that the rich heat-generating elements in the Cripple Terrain of the Ocean of Storms was 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 the understanding of the lunar volcanic activity and internal thermal evolution history .
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 . From the spatial distribution trend of basalt thickness, it can be found that the thickness of basalt gradually decreases with the distance from the two moon streams of Rima and Mairan, which indicates that the craters of the two moon streams of Rima and Mairan are the landing areas of Chang'e 5 The eruption source of basalt.
Furthermore, combined with the estimation results of the area and age of each basalt unit, the eruption rate of the basalt in the Chang'e-5 landing area was calculated, and it was found that the magma eruption flux in this area was significantly (about 2 billion years ago) in the late lunar volcanic activity period (about 2 billion years ago). 2 orders of magnitude) enhancement.
Studies based on thermochemical and kinetic models believe that the abundance of heat-generating elements in the Cripple terrane of the ocean frontal storm 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 a large-scale fracture structure in the lunar crust. These factors are all conducive 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 excavation research on Chang'e-5 basalt samples (such as the measurement of parameters such as viscosity and thermal conductivity) is expected to provide information for the existing lunar Thermochemical and kinetic models provide new constraints that provide strong evidence for explaining the duration and scale of lunar volcanism .