Resolving age discrepancies in lunar crater-counting chronology: Insights from Chang'e-5 benchmark and digital twins

Crater-counting chronology represents the primary means of inferring the age distribution of the lunar surface. However, even within a single, broadly continuous and compositionally homogeneous mare basalt unit, such as the Chang'e-5 landing area, prior studies report widely discrepant model ages varying up to 1 billion years, sparking intense debate on whether these discrepancies stem from methodological artifacts or local complex, episodic volcanism. Crucially, sample analysis from the Chang'e-5 mission has confirmed that the regional basalts were sourced from a single magmatic event. This definitive sample-based evidence establishes a rare, ideal benchmark that creates, nonetheless, a critical inter-methodological discrepancy: why the crater-counting chronology estimates across small sub-areas yield conflicting ages for an undeniably synchronous unit? To resolve this apparent conflict, we partitioned the Chang'e-5 landing area into multiple small sub-units and evaluated their age distributions using sequence probability analysis, and developed a digital twin Monte Carlo simulation to benchmark these observations. Our results reveal that smaller sub-units exhibit an apparent low probability of simultaneous formation, seemingly contradicting the sample-based evidence. However, our digital twin simulations demonstrate that this apparent contradiction is not a reflection of real, separate volcanic episodes, but rather an expected manifestation of inherent statistical variance exacerbated by small counting areas and low crater counts. Furthermore, the mean model age of these small sub-areas of the entire landing area aligns closely with the dating result. These findings thus bridge a critical gap between crater-counting and radiometric chronology and caution the isotope community against over-interpreting small-area remote-sensing ages while urging the crater-counting community to recognize the statistical constraints of the method. We recommend utilizing the largest possible counting area (strictly provided that the geological homogeneity of the unit is confirmed) to integrate statistical noise and obtain the most precise and robust model ages. The principles outlined in this study provide practical guidelines for optimizing crater counting area selection on geological units.