BEIJING, Feb. 8 (Xinhua) — Scientists have confirmed for the first time that the impact crater rates on the near and far sides of the moon are basically consistent, laying a solid foundation for establishing a globally unified lunar age system, according to Science and Technology Daily.
A research team led by the Institute of Geology and Geophysics, Chinese Academy of Sciences, has successfully revised a decades-old lunar impact crater age model by analyzing remote sensing images.
Their study reveals a uniform impact flux across both hemispheres and provides evidence that early lunar impact events followed a smooth trend of gradual decline, rather than the dramatic fluctuations previously hypothesized. Their findings were published Thursday in Science Advances.
To understand the moon’s geological evolution, it is important to know the age of the moon’s surface. Scientists have been estimating the age of unsampled areas for decades by counting impact craters, with higher densities indicating older surfaces.
However, existing crater dating methods rely entirely on samples taken from the moon’s near side, and the oldest samples are no more than 4 billion years old. This limitation has stimulated ongoing debate about the Moon’s early impact history, including competing hypotheses such as late heavy bombardment.
A breakthrough occurred in June 2024 when China’s Chang’e 6 mission brought back a 1,935-gram lunar sample from the Apollo Basin, located within the South Pole Aitken Basin on the far side of the Moon.
Analysis of these samples identified two important rock types: young basalt, which formed 2.807 billion years ago, and ancient norite, which formed 4.25 billion years ago.
Norite, in particular, originates from magma that crystallized after the giant impact event that formed the Moon’s largest and oldest impact structure, the South Pole-Aitken Basin. These samples served as important anchor points in reconstructing the Moon’s early history.
The researchers used high-resolution remote sensing imagery to systematically map crater density across the Chang’e 6 landing area and the broader Antarctic Aitken Basin.
We then built a new, more comprehensive lunar impact age model by integrating this new density data with all historical sample data from the Apollo, Luna, and Chang’e 5 missions.
Their results show that crater density data from the far side perfectly match the confidence intervals of the model derived from the near side. “This shows that the impact flux was uniform across the moon, providing a reliable basis for unified global lunar dating,” said Yue Zongyu, lead author of the study and a researcher at the institute.
Yue noted that this study fundamentally advances our understanding of the moon’s impact history and highlights the vital scientific value of the Chang’e 6 samples. The sophisticated chronology will serve as a more precise reference not only for the study of the Moon, but also for dating the surfaces of other planets in the solar system. ■