For the first time, scientists have confirmed that the rates of impact cratering on the near and far sides of the Moon are essentially consistent, laying a solid foundation for establishing a globally unified lunar chronology system.
According to Science and Technology Daily, a research team led by the Institute of Geology and Geophysics under the Chinese Academy of Sciences (CAS) has successfully revised a decades-old model of the chronology of lunar impact craters by analyzing remote sensing imagery.
Their study revealed a uniform impact flux across both hemispheres of the Moon, providing evidence that early impact events on the Moon followed a gradual, downward trend, rather than dramatic fluctuations as previously hypothesized.
Their findings were published in the journal Science Advances on Thursday (5/2).
Knowing the age of the lunar surface is crucial to understanding its geological evolution. For decades, for areas of the Moon that had not yet been sampled, scientists estimated their ages by counting the number of impact craters, with higher densities indicating older surfaces.
However, existing crater chronology methods relied entirely on samples from the near side of the Moon, and the oldest specimens were no more than 4 billion years old.
These limitations fuel ongoing debate about the Moon's early impact history, including competing hypotheses such as the Late Heavy Bombardment, a large surge of asteroid and comet impacts over a relatively short period of time.
A breakthrough was achieved in June 2024, when China's Chang'e-6 mission brought back 1,935 grams of lunar samples from the Apollo Basin, located within the South Pole-Aitken ( SPA) Basin on the far side of the Moon.
Analysis of the mission's samples identified two main rock types: young basalts dating back 2.807 billion years and ancient norites formed 4.25 billion years ago.
The norite, in particular, originates from magma that crystallized after the catastrophic impact event that formed the South Pole-Aitken Basin, the largest and oldest impact structure on the Moon. These samples serve as crucial reference points in reconstructing the Moon's early history.
Researchers systematically mapped crater density in the Chang'e-6 landing area and in the wider South Pole-Aitken Basin region using high-resolution remote sensing imagery.
