Re-examining the Martian Crater Chronology by Combining Numerical Model Results with New Crater Counts

Impact craters on planetary surfaces can give insight into a planet’s geological history and formation. Many past works assume that the impactor population of the inner Solar System has remained constant throughout time. In our research, we show that the size-frequency distribution (SFD) of impactors has changed over the age of the Solar System, and that the rate of decline of these impactor populations is size-dependent. We use the crater record from an ancient, heavily-cratered terrain on Mars together with an n-body simulation of early Solar System accretion to demonstrate how the interpretation of the geologic age of this terrain could be affected by a size-dependent impactor population. We selected an early Noachian region on Mars between Tyrrhena Terra and Terra Sabaea as our area of study. Recent work has shown that Mars solidified significantly earlier than the other terrestrial planets, possibly beginning to accumulate craters prior to when the other planets finished forming. This ancient surface may provide a record of the earliest impactor populations in the Solar System. Observational data from crater counts can inform numerical models of Solar System accretion and help to close the gap between models and observations. The results of this research are crucial to our understanding of early Martian cratering and Mars’s geologic history.