An asteroid impact is another possible cause of the extinction, though a telltale crater has yet to be found.
If that turns out to be from an asteroid impact, it would be the largest crater found on Earth. Ever.
So if you've ever cowered under your covers at the thought of an asteroid impact, lighten up and try to focus on their scientific importance.
He describes the effect of the icy climate and asteroid impact as a "double whammy" that paradoxically led to the "flourishing of exotic plankton and the first macroscopic animals".
