Vredefort, Sudbury, Chicxulub: Three of a kind?

Vredefort, Sudbury, and Chicxulub are the largest known terrestrial impact structures. All have been cited as multi-ring basins. The available data indicate that all have some form of multiple-ring attributes, most commonly structural features. Chicxulub, however, is the only example with morphological ring features. There an also commonalities in the structural and lithological features of Vredefort and Sudbury, and it is possible to construct a generalized compilation of the character of 200-300 km diameter impact basins on Earth. It is not clear, however, that any of these structures had the original morphological characteristics of large lunar multi-ring basins. Additional data and synthesis are required to fully characterize these structures in order to realize their potential to constrain large-scale cratering processes. If this is not sufficient incentive for further studies (the environmental effects of Chicxulub aside), the Vredefort, Sudbury, and Chicxulub impact events are also the reason for the existence of world-class mineral and hydrocarbon deposits.