That theory -- advanced by geophysicist Allen West -- posits a comet or asteroid exploded just above the Earth's surface over what is now Canada, setting large parts of the northern hemisphere ablaze.

The new evidence was discovered by University of Cincinnati Assistant Professor Ken Tankersley, working with West and Indiana Geological Society Research Scientist Nelson Schaffer. They said samples of diamonds, gold and silver offers the strongest support yet for the exploding comet or asteroid theory.

Tankersley said he undertook the research to disprove West's theory.

"My smoking gun to disprove (West) was going to be the gold, silver and diamonds," Tankersley said. "But what I didn't know … (was) that the likely point of impact for the comet wasn't just anywhere over Canada but located over Canada's diamond-bearing fields.

"Instead of becoming the basis for rejecting his hypothesis, these items became the very best evidence to support it," he said.

The research is to be incorporated into two television specials -- one for the PBS series "Nova" and a second for the History Channel.