BEIJING, (Pakistan Point News - 22nd Aug, 2025) Chinese and international researchers have dated the formation of the Apollo Basin - a major impact basin on the far side of the moon - to 4.16 billion years ago, based on a recent study of lunar samples collected as part of the Chang'e-6 mission last year.
This discovery provides key information that could help explain the apparent early impact flux during the Late Heavy Bombardment (LHB) period of the moon and the solar system. The study was published in Nature Astronomy on Wednesday.
According to China Central Television (CCTV), the giant impact basins scattered across the lunar surface are largely remnants of intensive bombardments by asteroids from the solar system during the early formation stage of the moon, which is known as the LHB.
Due to a lack of precise, sample-backed age data on the moon's key impact basins, scientists have long debated whether the LHB impact flux declined gradually or saw a sudden intensity peak approximately 3.8 billion to 4 billion years ago.
Last year, the Chang'e-6 probe landed and collected samples in the Apollo Basin, located within the South Pole-Aitken Basin, the largest secondary-impact structure in the region. Scientists believe that the Apollo Basin likely formed concurrently with the onset of the LHB, determining its formation date key to unraveling this mystery.
A team from the Chinese academy of Sciences' (CAS') Guangzhou Institute of Geochemistry, led by CAS academician Xu Yigang, worked with other Chinese and international researchers to examine three unusual clasts measuring 150 to 350 micrometers in size, which were among the lunar samples retrieved by the Chang'e-6 mission. The three samples are impact-melt fragments that formed during the formation of the Apollo Basin, meaning they can act as a geological clock for the impact event.
The research team accurately determined the age of the fragments and, by integrating multiple information sources, including remote sensing images and geochemical data, determined that the Apollo Basin formed approximately 4.16 billion years ago.
These findings push back the date at which the LHB began on the moon by at least 100 million years. The study has also revealed that the LHB impact flux followed a trend of gradual decay, a fact which does not support the hypothesis of a sudden surge between 3.8 billion and 4 billion years ago.
This research on the Chang'e-6 samples will continue to drive humanity's developing understanding of the evolution of the Earth-moon system, according to the researchers.
