Planetary surface dating from crater size–frequency distribution measurements: Sequence probability and simultaneous formation. Did the close Chang'E-6 mare units form simultaneously?

The Chang'e-6 lunar spacecraft returned samples from the southern mare of the Apollo basin. This work analyses the likelihood that a set of six close crater dating measurements of sub-units near the sampling site actually represent a single formation event. Using theoretical considerations, we find that the measurements are consistent with a simultaneous formation hypothesis with about 1 in 6 likelihood, so that a close sequential formation is more probable. Results of radioisotope dating of basaltic fragments from the surface scoop sample were recently reported close to 2.8 Ga. Our crater dating of the vicinity suggests that the upper 2–17 m predominantly records an age of μ 1.66 − 0.054 + 0.053 Ga , which points to the samples' formation predating this crater population reset of the surface. • Theoretical basis to test hypothesis of simultaneous formation • Closely associated CE-6 landing-site units more likely formed sequentially • Upper 2–17 m of CE-6 vicinity predominantly shows crater-age of μ 1.66 − 0.054 + 0.053 Ga • Recently reported 2.8 Ga basaltic fragment sample age points to prior formation