Evidence mounts for ancient comet.

The article discusses a study by geochemist Morgan of Schaller of Rensselaer Polytechnic Institute on the relationship of impact debris and evidence of widespread wildfires around eastern North America to the start of the Paleocene-Eocene Thermal Maximum (PETM). It notes that large comet shattered the Earth 56 million years ago may have caused global warming and the rise of carbon dioxide levels. Micropaleontologist Megan Fung also proposes that charcoal was formed during the wildfires.