At 2:07 p.m. in Beijing on 25 June, the Chang’e-6 spacecraft returned to Earth bearing the first samples collected from the Moon’s farside. The mission, run by the China National Space Administration (CNSA), could help scientists understand the drastic differences in nearside and farside geology, impact history, and evolution.
“The Chang’e-6 mission represents a significant milestone in the history of human lunar exploration, and it will contribute to a more comprehensive understanding of lunar evolution,” Wei Yang, a geochemist at the Institute of Geology and Geophysics of the Chinese Academy of Sciences, told Xinhua News Agency.
Repeating Nearside Success
Chang’e-6 launched on 3 May 2024 from Wenchang, China. A lander and small rover touched down on the Moon’s farside, in the South Pole–Aitken (SPA) basin on 1 June. Because the Moon is tidally locked, its farside cannot be seen from Earth and is therefore more difficult for spacecraft to access.
The lander’s drill and scoop collected subsurface and surface samples and placed them in an ascent module. Then, the ascent module launched from the lunar surface, docked with the awaiting orbiter module, and transferred the sample collection container to the atmospheric reentry module. The craft began its return to Earth on 21 June.
The mission’s design was identical to that of the Chang’e-5 mission—indeed, it was originally built as a backup craft for that mission. Chang’e-5 collected and returned to Earth samples from the Moon’s nearside in 2020. That mission collected more than 1.7 kilograms (3.7 pounds) of lunar material, including a core drilled about 1 meter (3.2 feet) deep.
CNSA announced that Chang’e-6 collected around 2 kilograms of drilled and scooped material. If the agency follows the same procedures as for its nearside samples, a small amount of the farside samples may be made available to international scientists.
The Moon’s south polar region is a key target for exploration because of its water and mineral resources. The Chang’e-6 samples and cores may illuminate the extent and availability of those resources.
Second Farside Landing
“What geologic activity is responsible for the differences between the two sides?”
Chang’e-6 landed in the southern mare of the Apollo basin, an impact crater 537 kilometers (334 miles) across that sits within the older SPA basin. The SPA basin is one of the largest and oldest impact features in the solar system and exemplifies the differences in the Moon’s hemispheres.
“There are significant differences between the farside and the nearside of the Moon in terms of lunar crustal thickness, volcanic activity, composition, etc.,” Zongyu Yue, a planetary geologist at the Chinese Academy of Sciences, said in a recent statement. Yue added that the Chang’e-6 samples “are expected to answer one of the most fundamental scientific questions in lunar science research: what geologic activity is responsible for the differences between the two sides?”
Chang’e-6 was China’s second farside landing, following Chang’e-4, which landed in the SPA basin in early 2019. That mission, which is ongoing, has studied shallow subsurface structure, detected lunar mantle material, and mapped ejecta material.
“My greatest hope is that the [Chang’e-6] samples contain some impact melts,” Yue said. That information would “not only help clarify the role of early lunar meteorite impacts on the Moon’s evolution, but also be of great significance in analyzing the early impact history of the inner solar system.”
You can watch the touchdown sequence here:
—Kimberly M. S. Cartier (@AstroKimCartier), Staff Writer
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