Debate Heats Up Over Meteor's Role in Ice Age

Debate Heats Up Over Meteor's Role in Ice Age
New evidence taken from fossils like this one suggests that the Younger Dryas era (known as the Big Freeze) 12,900 years ago was not caused by a meteor, scientists now suggest.
(Image: © AGU)





Still, proponents of an impact theory are not backing down.



Organic matter normal, not melted




"After the carbon spherules, only one credible piece of supporting evidence remains — the so-called nanodiamonds purportedly found in 12,900-year-old deposits," Pinter said. "Impact proponents are putting all of their remaining eggs in the nanodiamond basket."

Debate not over

Nanodiamonds are micron-scale fragments of diamond thought to have come  to Earth by comets or meteors or formed in the extreme pressure that radiates from their impact.

Considered by the Younger Drays impact proponents as a strong indication of an extraterrestrial event, very small diamonds are found "in the millions to billions" in any sample at the beginning of the Younger Dryas period, as opposed to very small amounts in the background of other periods, geologist James Kennett at the University of California told

An active member of the school of thought that supports the impact theory, Kennett contested Pinter's claim that carbon spherules are illegitimate evidence.

"He's saying that all carbon spherules are fungal sclerotia, a type of spore that fungus produces," Kennett said. "Our argument for that is that he has not made a compelling case for that at all. There's a whole range of carbon spherules. We can produce these through biomass burning."

A whole family of carbon-rich spherules exist that range beyond sclerotia and show a "striking peak" in sediment layers also rich in nanodiamonds, he said.   

"There's no other way of explaining the presence of these diamonds except through extraterrestrial impact," said Kennett. "But there's not only diamonds, there's a range of spherules, a family of spherules that correspond with the nanodiamonds."

The debate may heat up when both sides, including Pinter and Kennett, participate in a public debate at the University of Wyoming Aug. 14.
