Impact cratering rate consistency test from ages of layered ejecta on Mars. (January 2020)

• Record Type: Journal Article
• Authors: Lagain, Anthony; Bouley, Sylvain; Baratoux, David; Costard, François; Wieczorek, Mark
• Is Part Of: Planetary and space science. Volume 180(2020)
• Publication Date: 2020-01
• Subjects: Impact craters -- Mars -- Impact rate -- Layered ejecta craters; Space sciences -- Periodicals; Atmosphere, Upper -- Periodicals; Sciences spatiales -- Périodiques; Haute atmosphère -- Périodiques; 523
• DOI: 10.1016/j.pss.2019.104755
• Languages: English
• ISSNs: 0032-0633

Abstract

Abstract: Ages of geological units of planetary bodies are determined from impact crater counts on their surface. These ages are model-dependent, and several models largely used in the community assume a constant production function and a constant cratering rate over the last 3 Ga. We have mapped the population of small impact craters (>200 m in diameter) formed over a population of large impact craters (>5 km in diameter) with layered ejecta on Acidalia Planitia, Mars. We have deduced the age of each large impact crater under the assumption of a constant impact rate and constant production function. The impact rate inferred from this set of ages is, however, not constant and show a significant increasing during the last ~1 Ga compared to chronology models commonly used. We interpret this inconsistency as an evidence for temporal variations in the size-frequency distribution (SFD) of impactors in the main belt, consistent with recent studies argued for a late increasing of the large impactor flux on Earth and the Moon. Highlights: We measured the age of a set of Martian craters >5km using the small craters on their ejecta and a constant rate. The impact rate inferred from this set of ages is inconsistent with the constant impact rate model commonly assumed. This inconsistency is interpreted as the result of variations in the large impactor frequency distribution over the last 2Ga. The variation in the size frequency distribution of large impactors could be the result of recent asteroid break-ups.