Based on data from China's Chang'e-4 probe, Chinese scientists have determined the thickness of the regolith and revealed the fine subsurface structures and evolutionary history of the probe's landing site on the moon's far side.
The study revealed that the landing area of the probe, located within the largest and oldest impact basin on the moon, had experienced multiple impact events and basalt magma eruptions.
The Chang'e-4 probe, launched on Dec. 8, 2018, made the first-ever soft landing on the Von Karman Crater in the South Pole-Aitken Basin on the far side of the moon on Jan. 3, 2019.
Carrying scientific instruments including a lunar penetrating radar, the rover Yutu-2 has conducted scientific detection on the compositions of lunar surface materials and the subsurface structures.
Scientists from the Institute of Geology and Geophysics (IGG) under the Chinese Academy of Sciences (CAS), the Aerospace Information Research Institute under the CAS, the Macao University of Science and Technology and other institutes have carried out research on the lunar penetrating radar onboard Yutu-2 during the first three lunar days and obtained important findings on the subsurface structure of the landing area.
The results showed that the materials detected by Yutu-2 come from the nearby Finsen impact crater rather than the basalt erupted from the lunar mantle, which filled the bottom of the Von Karman Crater. It was also revealed that the landing area had experienced multiple impact events and basalt magma eruptions.
The new discoveries are of great significance to understanding the evolutionary history of the South Pole-Aitken basin of the moon, as well as to the following exploration and research on the composition and structure of the lunar interior, said Lin Yangting, a researcher with the IGG.
Asteroid impacts are an important driving force for the early evolution of the Earth. However, the long-term geological tectonic activities have erased most of the traces of the impact cratering events on Earth, experts said.
The internal evolution of the moon has long ceased due to its small mass. Therefore, impact craters and the deposit profile of crater ejecta on the lunar surface have recorded the impact history of asteroids in the earth-moon system.
According to Lin, the subsurface structure of the moon recorded the number and scale of large-scale impact events and magma eruptions, as well as their temporal and spatial relationships. However, the fine structure of the moon's shallow layers remains a mystery to humans.
The modification of lunar surface materials by asteroid impacts has a direct influence on the results obtained from orbital observations and landing site reconnaissance, and affects how scientists will implement the lunar sample return missions in the future, Lin said.
The study was published in the latest issue of Nature Astronomy.