Scientists: Earth Catastrophic Meteor Theory Wrong

About 12,900 years ago, a very large meteor hurtling through space either slammed into the Earth or exploded in in the atmosphere, obliterating most of North America's wildlife in a catastrophic fire and ultimately leading to a 1,000 year-long cold period.

Proponents of that theory point to physical evidence left over from that epoch, such as nanodiamonds, which they say were formed by intense heat and are evidence of the impact.

But a new study being published in the Geophysical Research Letters, a journal of the American Geophysical Union, offers a counter-theory. The researchers argue that the clues which were put forward as evidence to support the meteor theory are little more than fossilized balls of fungus, charcoal, and fecal pellets, some of which had been exposed to centuries of low-intensity wildfires.

"People get very excited about the idea of a major impact causing a catastrophic fire and the abrupt climate change in that period, but there just isn't the evidence to support it," said Andrew C. Scott of the Department of Earth Sciences at Royal Holloway, University of London, who led the research.

According to the AGU, the researchers analyzed particles from Pleistocene-Holocene sediments and compared them with modern soil samples that had been subjected to wildfires. The materials included "balls of stringy fungal material, called sclerotia, some of which were also subjected to a range of temperatures in a laboratory."

They found that the fossilized matter was unlikely to have been exposed to temperatures above 450 degrees Celsius (842 degrees Fahrenheit). Radiocarbon dating also showed that the particles, taken from several layers, ranged in age from 16,821 to 11,467 years ago. Proponents of the impact theory had reported that the spherules they found in the Younger Dryas sediment layer dated to a very narrow time period of 12,900 to 13,000 years before present.

The term Younger Dryas refers to the abrupt cooling period said to have been set in motion by massive fires in North America and Europe.

Scott noted that these sorts of fungal samples have been common since ancient times and that there was "a long history of fire in the fossil record."

"These data support our conclusion that there wasn't one single intense fire that triggered the onset of the cold period," he said.