Chang’e-4 Enters 18th Lunar Night, Data Reveals Composition of Lunar Soil

Chang’e-4 lunar surface photo. (Credit: China National Space Administration)

BEIJING (China National Space Administration PR) — The Chang’e 4 lander and the Yutu 2 lunar rover completed their eighteenth day and night work at 17:00 and 7:15 on May 29, respectively, and completed the moon night mode setting according to the ground instructions, and entered the moon night sleep.

During the eighteenth day of the month, “Yutu 2” gave way to Tianwen 1 and cooperated with the adaptive transformation of the ground deep-space observation and control station of China’s first Mars exploration mission. The scientific load carried by “Yutu 2” was not turned on. In the case of limited communication capabilities, only lunar surface neutrons and radiation dose detectors on the Chang’e 4 lander were turned on for routine detection. At present, the renovation project of the deep-space observation and control station is nearing completion. Upon completion, it will provide more stable and stronger support for the subsequent scientific exploration work of the Mars exploration and Chang’e-4 project planned for July.

Although Yutu No. 2 did not move during this day and night, the ground science team continued to conduct in-depth research and analysis of the scientific data obtained, and constantly made new scientific achievements and scientific discoveries. Dr. Qian Sheng, State Key Laboratory of Remote Sensing Science, Institute of Aerospace Information Innovation, Chinese Academy of Sciences, member of the Center for Excellence in Comparative Planetary Innovation, Chinese Academy of Sciences and Pilot Project Leader, State Key Laboratory of Remote Sensing Science, Institute of Aerospace Information Innovation, Chinese Academy of Sciences Researcher Yue Zongyu and his collaborators used Yutu-2 to measure the spectral data in place to carry out lunar soil mineral composition analysis and space weathering effect research in Chang’e-4 landing area, and discussed the origin and maturity of lunar soil.

The South Pole-Aitken Basin on the back of the moon is the largest, deepest and oldest impact basin in the known solar system, and may expose the lunar mantle material, providing a natural window for detecting the deep lunar material. On January 3, 2019, Chang’e-4 successfully landed in this area (Figure 1), realizing the first lunar back soft landing and patrol detection by human detectors.

Figure 1. Background image of Chang’e-4 landing zone. (Credit: China National Space Administration)

As of May 29, 2020, the Chang’e-4 probe has been working efficiently on the moon’s back for 18 months and days. The “Yutu 2” lunar rover has accumulated 447.68 meters and obtained a large amount of scientific exploration data. Among them, the lunar soil hyperspectral image and infrared spectrum data obtained by infrared imaging spectrometer support the scientific team to obtain the fine spectrum of lunar soil in the landing area (Figure 2), providing scientific exploration data for the study of lunar soil’s mineral composition and space weathering, etc. Promote human research and understanding of the evolution of lunar soil in the landing zone.

Figure 2. The spectrum acquired by the infrared imaging spectrometer before September. (Credit: China National Space Administration)

Spectral analysis showed that the lunar soil in the landing area contains magnesia-rich olivine and magnesia-rich rhodochrosite minerals (Figure 3), and their relative contents are basically equal. The analysis of topographical characteristics shows that the lunar soil in the landing area mainly comes from the splash of Finsen impact crater. Based on the composition of mafic minerals and the spatial location of the Fenson impact crater, the team further analyzed that the lunar soil in the landing area may have originated from the impacted molten foreign matter or a set of magnesium-rich rocks formed by the Anken Basin impact event. The research results were published in “Icarus” with the title of “Forsteritic olivine and magnesium-rich orthopyroxene materials measured by Chang’e-4 rover”.

Figure 3. Results of in-situ measurement spectrum analysis at LE303. (Credit: China National Space Administration)

The team also found that the lunar soil, which originated mainly from the spatters of the Finsen impact crater, had matured. Compared with the immature lunar soil in the Chang’e 3 landing zone, the microscopic metal iron content in the lunar soil in the Chang’e 4 landing zone did not change significantly with the distance between the lunar rover and the lander, indicating that the lunar soil in the Chang’e 4 landing zone is fast The formation process fully mixes the most mature lunar soil at the outermost layer. The research results were published in “Earth and Planetary Science Letters” with the title of “In situ spectral measurements of space weathering by Chang’e-4 rover”.