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# Variation of the recent Martian impact cratering rate from ejecta blanket ages

30/03/2017

Campus Paris-Rive-Gauche

11:00

Séminaires Planétologie et Sciences Spatiales

522, bât. Lamarck

Anthony Lagain

GEOPS (Université Paris Sud)

Ages of geological units of inner solar system bodies are determined from crater counts on their surface and especially depend on impact cratering rate model used. All models assume a constant cratering rate over the last 3 Gyr despite recent evidence for variations of the cratering rate over this period of time. Here, we test this assumption by dating a craters population on Mars and we show that the inferred impact rate is inconsistent with the assumed constant flux. Our data show a twofold decrease of the impact rate between 3 Gyr and 500 Myr and a twofold increase since 500 Myr relative to the assumed constant flux, possibly related to known asteroid breakups. This solution modifies the absolute age boundaries of Martian eras and therefore the temporality of geological events occurred on the red planet. Evidence for fluctuations of the recent impact rate for both Earth and Mars suggests that these results may be extrapolated to all inner solar system objects.