Conventional wisdom holds that the far side of the Moon is more rugged and cratered because it acted as a “shield” to support the impact of meteorites originally heading for Earth. However, recent research on soil samples from the Chang’e 6 mission casts doubt on this long-held assumption, suggesting that impacts are essentially the same on both the near and far sides of the moon.

Based on this discovery, Chinese scientists have developed a new lunar crater age model. This model allows accurate age estimation of unsampled lunar regions using only crater density measurements. The breakthrough, published Thursday in the journal Science Advances, provides a universal framework for scientific research on the Moon.

“The Moon serves as a record of the solar system’s planetary collision process, and its surface age is key to understanding its evolutionary history,” said Yue Zongyu, lead author of the study and a professor at the Institute of Geology and Geophysics, Chinese Academy of Sciences.

Yue explained that for areas of the moon that have not been sampled, scientists estimate their age primarily based on crater density. In other words, the older the surface, the higher the density of impact craters. The core of this method lies in establishing a correlation between the existing accurate radiometric age of a soil sample and its estimated age.

Previous lunar age models have relied on samples taken from the moon’s near side, all of which are less than 4 billion years old, leading to controversy over their reliability. But all that changed when Chang’e 6 brought back a 1,935-gram sample from the far side of the moon. These samples contained norite dating back 4.25 billion years, which is thought to correspond to the age of the Antarctic Aitken Basin, the largest and oldest crater on the moon.

The research team analyzed the radiometric ages of samples from the far side and combined that data with high-resolution remote sensing information. They also developed a new lunar age model, incorporating historical data from the U.S. Apollo program, the Soviet Union’s Moon program, and China’s Chang’e program.

The results showed consistent impact rates between the near and far sides of the moon, with the number of craters formed per unit area and unit time being essentially the same on both sides over the same period of time.

Notably, this model challenges the long-debated “late heavy bombardment” hypothesis, which suggests a major bombardment occurred 3.9 billion years ago, since many Apollo samples are concentrated around that time. New models suggest that these may reflect only local events, rather than global cataclysms. Instead, the Moon’s early impact record shows a steady decline in impact frequency.