Planetary surfaces (Cratering rate)

Abstract

Understanding the evolution of planets in the solar system critically depends on accurate estimates of time and rates at which processes, e.g., volcanism, occur. Absolute time scales for planetary surface evolution in the inner solar system (except the Earth and the Moon) can only be derived by linking the lunar crater frequencies with isotopically dated lunar samples. The crater counting method, the only tool to date in absolute terms planetary surface evolution when samples are not available, is challenged by many observational uncertainties and the great diversity of approaches. Diverse crater–production functions are used to calibrate crater density measurements, which has resulted in a variety of different lunar chronology models. This diversity propagates to other planets such as Mars and adds ambiguity to the related temporal interpretations (e.g., Werner and Tanaka, 2011). Commonly used cratering statistics for planetary surface-age determination assume monotonic cratering rate decay, but other interpretations have been put forward due to the discovery of extrasolar planetary systems. Cratering rates prior to formation of the Nectaris Basin on the Moon are not constrained and therefore debated in the light of solar system evolution concepts (Werner and Ivanov, 2014). Nevertheless, currently cratering statistics are the only method to determine globally and across the solar system relative and absolute ages and rates of planetary surface evolution, until such time as datable samples will become available from other planetary bodies.