Crater counting is a method for estimating the age of a planet's surface based upon the assumptions that when a piece of planetary surface is new, then it has no impact craters; impact craters accumulate after that at a rate that is assumed known. Consequently, counting how many craters of various sizes there are in a given area allows determining how long they have accumulated and, consequently, how long ago the surface has formed. The method has been calibrated using the ages obtained by radiometric dating of samples returned from the Moon by the Luna and Apollo missions.[1] It has been used to estimate the age of areas on Mars and other planets that were covered by lava flows, on the Moon of areas covered by giant mares, and how long ago areas on the icy moons of Jupiter and Saturn flooded with new ice.
- ^ Che, Xiaochao; Nemchin, Alexander; Liu, Dunyi; Long, Tao; Wang, Chen; Norman, Marc D.; Joy, Katherine H.; Tartese, Romain; Head, James; Jolliff, Bradley; Snape, Joshua F. (2021-11-12). "Age and composition of young basalts on the Moon, measured from samples returned by Chang'e-5". Science. 374 (6569): 887–890. Bibcode:2021Sci...374..887C. doi:10.1126/science.abl7957. ISSN 0036-8075. PMID 34618547. S2CID 238474681.