Dark Primitive Asteroids Account for a Large Share of K/Pg-Scale Impacts on the EarthOPEN ACCESS
David Nesvorny, William F. Bottke, Simone Marchi
Icarus
LINK (Update: 15 July 2021)
“Highlights
• We develop a dynamical model for large near-Earth asteroids to understand the occurrence rate and nature of Cretaceous-Paleogene (K/Pg) scale impacts on the Earth.
• About a half of impactors are found to be dark primitive asteroids.
• This explains why the Chicxulub crater, the third largest impact structure found on the Earth, was produced by impact of a carbonaceous chondrite.
• The impactor that triggered the K/Pg mass extinction 66 Myr ago was a main belt asteroid that quite likely (60% probability) originated beyond 2.5 au.”
“A dynamical model for large near-Earth asteroids (NEAs) is developed here to understand the occurrence rate and nature of Cretaceous-Paleogene (K/Pg) scale impacts on the Earth. We find that 16–32 (2–4) impacts of diameter D>5 km (D>10 km) NEAs are expected on the Earth in 1 Gyr, with about a half of impactors being dark primitive asteroids (most of which start with semimajor axis a>2.5 au). These results explain why the Chicxulub crater, the third largest impact structure found on the Earth (diameter ≃180 km), was produced by impact of a carbonaceous chondrite. They suggest, when combined with previously published results for small (D≲1 km) NEAs, a size-dependent sampling of the main belt. We conclude that the impactor that triggered the K/Pg mass extinction ≃66 Myr ago was a main belt asteroid that quite likely (≃60\% probability) originated beyond 2.5 au. “
