Cratering Records in the Chang'e‐5 Mare Unit: Filling the “Age Gap” of the Lunar Crater Chronology and Preparation for Its Recalibration

The Moon is the cornerstone for dating planetary surfaces as it is the only planetary body that has been sampled multiple times from multiple places. The major deficiencies of the lunar crater chronology function are the somewhat limited number of calibration points and data gaps, especially in the ∼1–3 Ga segment. China's Chang'e‐5 mission recently returned samples from a young nearside mare, whose age is estimated to be in that age gap, providing a long‐awaited opportunity for recalibrating the lunar chronology. Here, we report a direct density measurement of impact craters ≥1 km in diameter of Chang'e‐5 mare unit, as (1.696 ± 0.221) × 10−3 km−2. The Chang'e‐5 mare deposits are estimated as ∼1.3–2.7 Ga old in various lunar chronologies, younger than all collected Apollo/Luna basalts. Accurate radio‐isotopic ages of Chang'e‐5 samples can be combined with our crater density measurement for a recalibration of lunar chronology. Plain Language Summary Measuring the size and number of surface impact craters is the primary technique for dating lunar and planetary surfaces remotely. This technique relies on calibration points provided by sample return missions. The Earth's Moon is the only extraterrestrial body for which samples have been collected from multiple locations, enabling the calibration of cratering rates in the inner solar system and dating surfaces not only on the Moon, but also on Mercury, Venus, and Mars. Drawbacks of this technique are the somewhat limited number of calibration points and data gaps in the ∼1–3 billion years segment. The basalt samples recently returned by China's Chang'e‐5 mission likely lie in such gaps and provide an opportunity to recalibrate lunar crater chronology. In this work, we measure directly the density of impact craters ≥1 km on the basalt unit across the Chang'e‐5 sampling site. From our measurements, the Chang'e‐5 basaltic deposits are estimated as ∼1.3–2.7 billion years old, younger than all lunar basalts previously returned by Apollo and Luna missions. Our results can be combined with the accurate ages of Chang'e‐5 samples measured in Earth laboratory for a recalibration of lunar impact flux and improvement of the crater counting dating technique. Key Points We obtain a direct measurement of density of impact craters ≥1 km (N(1) value) of the Chang'e‐5 mare unit as (1.696 ± 0.221) × 10−3 km−2 The Chang'e‐5 mare basalts are estimated as ∼1.3–2.7 Ga old in various lunar chronologies, younger than all collected Apol