Has the impact flux of small and large asteroids varied through time on Mars, the Earth and the Moon?

1Anthony Lagain,2Mikhail Kreslavsky,3,4David Baratoux,5Yebo Liu,1Hadrien Devillepoix,1Philip Bland,6,7Gretchen K.Benedix,5Luc S.Doucet,8Konstantinos Servish
Earth and Planetary Science Letters 579, 117362 Link to Article [https://doi.org/10.1016/j.epsl.2021.117362]
1Space Science and Technology Centre, School of Earth and Planetary Sciences, Curtin University, Kent St, Bentley, 6102, WA, Australia
2Earth and Planetary Sciences, University of California – Santa Cruz, CA, USA
3Géosciences Environnement Toulouse, University of Toulouse, 14, Avenue Edouard Belin, Toulouse, 31400, France
4University Félix Houphouët-Boigny, UFR des Scinces de la Terre et des Ressoures Minières, Cocody, Abidjan, Côte d’Ivoire
5Earth Dynamics Research Group, The Institute for Geoscience Research (TIGeR), Department of Earth and Planetary Sciences, Curtin University, Kent St, Bentley, 6102, WA, Australia
6Planetary Sciences Institute, Tucson, AZ, USA
7Department of Earth and Planetary Sciences, Western Australian Museum, WA, Australia
8CSIRO – Pawsey Supercomputing Centre, WA, Australia
Copyright Elsevier

The impact flux over the last 3 Ga in the inner Solar System is commonly assumed to be constant through time due to insufficient data to warrant a different choice for this range of time. However, asteroid break-up events in the main belt may have been responsible for cratering spikes over the last ∼2 Ga on the Earth-Moon system. Due to its proximity with the main asteroid belt, i.e., the main impactors reservoir, Mars is at the outpost of these events with respect to the other inner planets. We investigate here, from automatic crater identification, the possible variations of the size frequency distributions of impactors from the record of small craters of 521 impact craters larger than 20 km in diameter. We show that 49 craters (out of the 521) correspond to the complete crater population of this size formed over the last 600 Ma. Our results on Mars show that the flux of both small (> 5 m) and large asteroids (> 1 km) are coupled, does not vary between each other over the last 600 Ma. Existing data sets for large craters on the Earth and the Moon are analyzed and compared to our results on Mars. On Earth, we infer the formation location of a set of impact craters thanks to plate tectonic reconstruction and show that a cluster of craters formed during the Ordovician period, about 470 Ma ago, appears to be a preservation bias. On the Moon, the late increase seen in the crater age signal can be due to the uncertain calibration method used to date those impacts (i.e. rock abundance in lunar impact ejecta), and other calibrations are consistent with a constant crater production rate. We conclude to a coupling of the crater production rate between kilometer-size craters (∼100 m asteroids) and down to ∼100 m in diameter (∼5 m asteroids) in the inner Solar System. This is consistent with the traditional model for delivering asteroids to planet-crossing obits: the Yarkovsky effect slowly pushes the large debris from asteroid break-ups towards orbital resonances while smaller debris are grinded through collisional cascades. This suggests that the long-term impact flux of asteroids > 5 m is most likely constant over the last 600 Ma, and that the influence of past asteroid break-ups in the cratering rate for D > 100 m is limited or inexistent.

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