Impact hypothesis loses its sparkle
The warming that following the last Ice Age was interrupted by a cold snap that killed off megafauna such as the giant ground sloth and the wooly mammoth. Could this crisis have been caused by an asteroid impact or a comet breaking up in the atmosphere? Unfortunately the geological evidence for such a dramatic event has not stood up to scrutiny. In PNAS a group of scientists challenges the catastrophists last, best hope: shock-synthesized nanodiamonds.