This should put a stopper in critics who said that the impact was not large enough to have caused the mass extinction at the end of the Cretaceous. Impacts are still occurring. Astronomers say comet Shoemaker-Levy 9 fragments will impact on Jupiter this July. Its nucleus is fragmented into about a dozen pieces. Callisto indicates that similar fragmented comet impacts have occurred before.
Nobody can dispute that the impact occurred, and an impact that large HAD to cause chaos.
In my humble opinion, the evidence for dinosaur decline prior to the KT boundary layer is due to sampling effects. The other theories, eg. Dinosaurs encompassed very diverse groups of animals, and to think that a disease completely and selectively wiped out all dinosaurs, pterosaurs, and sea reptiles without affecting the animals is too much to swallow. It has to explain not only this extinction event, but other mass exinction events. He was a friend of Louis and Walter Alvarez, two of the men who proposed the impact theory.