Lunar chronology models are built by associating the radiometric ages of samples returned by the Apollo and Luna missions measured in the laboratory with compiled crater distributions of those sites. Such models have not only been widely used to determine the absolute ages of various regions on the Moon(1-6), but have also been generalized to date the surfaces of the rocky bodies of the inner Solar System(7-12). However, there is a gap in lunar samples ages between 3.0 Gyr ago and 1.0 Gyr ago(13), which occupies almost half of the history of the Moon. Chang'e-5, the first lunar sample return mission since the Luna 24 lander in 1976, brought back basalt material from a young mare area that has been dated to the centre of this gap at 2.030 +/- 0.004 Gyr old(14). Using this radiometric age, we updated the most widely used chronology models, focusing in particular on the Neukum model(13). We found that the updated model is consistent with a combination of an exponential decrease and a linear rate. The updated chronology gives older ages with respect to the Neukum model for most of the lunar history, with a maximum difference of 0.24 Gyr at 2.55 Gyr ago. Differences from other models are of comparable magnitude or greater. These results have important implications for the chronology and impact history of the inner Solar System.

The lunar samples brought back by the Chinese Chang'e-5 mission have an age of 2.030 +/- 0.004 billion years, providing valuable new constraints on the cratering chronology used to date most Solar System surfaces. Here an updated chronology model is presented and compared with other models currently in use.

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