According to the official WeChat message of the Lunar Exploration and Aerospace Engineering Center, the lunar rover and lander of the Chang'e-4 mission "Yutu 2" completed sleep settings at 19:14 on July 5 and 6:00 on July 6 respectively, completing the 44th It works during the da

According to the official WeChat message of the Lunar Exploration and Aerospace Engineering Center, the lunar rover and lander of the Chang'e-4 mission "Yutu 2" completed the sleep settings at 19:14 on July 5 and 6:00 on July 6 respectively, completing the first Work on the 44th moon day and sleep on the 44th moon night. The lunar rover has traveled a total of 1,239.88 meters on the far side of the moon.

Image source: Official WeChat of the Lunar Exploration and Space Engineering Center

Chang'e-4 research results reveal the origin of the Antarctic-Aiken Basin composition anomaly area

The Antarctic-Aiken Basin is the largest impact basin on the moon, with a diameter of more than 2,400 kilometers. Studying the Antarctic-Aiken Basin is of great significance for revealing the origin of lunar asymmetry, impact process, early evolution process and deep material composition. Orbital remote sensing observations have shown that there is a composition anomaly area in the center of the Antarctic-Aiken basin. The Shandong University planetary science team analyzed and interpreted the in-situ visible and near-infrared spectrum data of the Yutu-2 lunar rover and found that the lunar crust is the Antarctic-Aiken composition anomaly area. The main material source provides important constraints for the future detection of materials in the Antarctic-Aiken Basin and even deep lunar materials.

The main material components of the lunar surface are pyroxene and olivine . The material composition at the bottom of the Antarctic-Aiken basin is abnormal. The content of mafic silicate minerals and iron content are significantly higher than those in the outer areas of the basin ( figure 1).

Distribution of iron and pyroxene content inside and outside the Antarctic-Aiken Basin. Image source: Official WeChat of the Lunar Exploration and Aerospace Engineering Center

In the past, most studies on the material composition of the Antarctic-Aiken Basin only focused on mafic minerals. Due to the abnormal mafic characteristics of this area, it even triggered questions about the lunar mantle The debate is whether it is peridotite or pyroxenite . Although according to the lunar magma ocean hypothesis, olivine and pyroxene are the main minerals of the lunar mantle, the intrusion of plutonic magma after the formation of the lunar crust can also form rocks rich in olivine or pyroxene in the lunar crust, so it is rich in Peridot or pyroxene are not evidence of origin from the lunar mantle. So far, humans have not obtained samples from the Antarctic-Aiken Basin and returned them to the earth, and it is impossible to know their trace elements and isotope characteristics. Among the material composition information that can be obtained through remote sensing or in-situ detection, the plagioclase content can also distinguish the crust source. and key indicators of mantle-derived rocks.

The content of plagioclase in the Antarctic-Aiken composition anomaly area material sputtered from the Finsen impact crater exceeds the plagioclase content that can be evolved during the impact melt differentiation process. Therefore, the mineralogy characteristics of the composition anomaly area exist. The addition of additional lunar crust material (Figure 2). Numerical simulation studies believe that the lunar crust has been completely stripped off during the Antarctic-Aiken impact excavation process, but in the subsequent modification stage, the instantaneous collapse of the crater wall may cause the lunar crust material to slide to the bottom of the basin. In addition, the impact event in other basins after the Antarctic-Aiken impact event also had a backfilling effect on the bottom of the Antarctic-Aiken basin. The lunar mantle material or impact melt products exposed when the basin was formed may have been diluted by the lunar crust material. . Mineralogy and geochemistry unmixing analysis results show that the surface lunar soil in the composition anomaly area is composed of about 70% lunar crust material and about 30% material enriched in iron and incompatible elements.

Mineral components of the Chang'e-4 landing area and their source reservoirs. Image source: Lunar Exploration and Aerospace Engineering Center official WeChat

(China News Service)