An ancient asteroid impact may have caused a global firestorm on Earth that burned every twig, bush and tree on the planet, U.S. researchers say. An asteroid the size of Manhattan that slammed into a region of Mexico in the dinosaur era could have triggered a worldwide firestorm that led to the extinction of 80 percent of all Earth's species, a University of Colorado Boulder study suggests. Computer models show the collision would have vaporized huge amounts of rock and then blown the material high above the atmosphere. The re-entering ejected material would have heated the upper atmosphere enough to glow red for several hours at roughly 2,700 degrees Fahrenheit, possibly killing every living thing not sheltered underground or underwater, the researchers said. The researchers say they detected excess charcoal or soot in sediments dating from the Cretaceous-Paleogene boundary of around 66 million years ago when the asteroid struck. Some researchers have suggested that layer of soot was created by the impact itself, but Robertson and his colleagues say the amount of soot was too high to have been created during the massive impact event and was consistent with the amount that would be expected from global fires. "Our data show the conditions back then are consistent with widespread fires across the planet," researcher Douglas Robertson said. "Those conditions resulted in 100 percent extinction rates for about 80 percent of all life on Earth."