Impact Energy Flux on Earth in the Last 150 Ma as Inferred from the Cratering Records

Abstract

We have used a compilation of 30 well-dated large impact craters on Earth (i.e., diameters larger than 5 km) younger than 150 Ma, their diameters, geochronologic ages, and the corresponding uncertainties to construct a graph summarizing our current knowledge on the influx of the impact energy onto the Earth as a function of time. From the crater diameters, we estimated the corresponding impact energies through suitable scaling laws. Then to each crater we associated a gaussian (bell) function of time centered at its age. Finally, all the bell functions corresponding to different craters were summed up and the resulting curve was plotted. From this curve, it is apparent that the 65 Ma old Chicxulub crater associated with the Cretaceous/Tertiary boundary corresponds to the highest energy influx peak, almost an order of magnitude larger than the next ones, and that there is probably a threshold size of ≈ 3 km for the smallest projectile capable of triggering large-scale extinctions. Although there is no convincing evidence for periodicities in the distribution of the crater ages, a few group of several craters appear to be more closely spaced in time than in a purely random distribution.