Did killer comets bring the bling? - January 05, 2009
Nanodiamonds that have been discovered in ancient sediment provide new support for a divisive theory that a giant space rock wiped out humans and animals thousands of years ago.
The ‘Clovis’ culture, which thrived in North America on a diet of mammoth, bison and horse, disappeared suddenly 13,000 years ago. While several theories have been offered to explain this perplexing vanishing act, some two dozen scientists controversially proposed in May 2007 that these people and the beasts they hunted were killed by space rocks that exploded on or above North America, changing the climate. With the discovery of fresh evidence, reported in Science, the debate looks set to continue (press release).
“We've discovered nanodiamonds that are not normally produced through average processes on the surface of the Earth," James Kennett, a geologist at the University of California, Santa Barbara, and an author on the Science paper, told the BBC. "They indicate there was an extra-terrestrial event on Earth 12,900 years ago."
This extra-terrestrial event, which distributed nanodiamonds across several sites in North America and Europe, caused temperatures to plunge — resulting in the extinction of plants, animals and the Clovis people — the authors argue.
Not all are convinced. "I know of no mechanism that would break up a comet and distribute it over North America in the way they suggest," NASA space scientist David Morrison told BBC News. "It violates what we understand about cosmic impacts."
Others — many of whom think that a change in ocean circulation brought about a cooling period that killed off the Clovis people — have different concerns. For instance some researchers argue that a meteor couldn’t have caused the shock waves necessary to create the nanodiamonds, or that the scientists might have misidentified the nanodiamonds, The Times reports.
While the debate rages on, many will sit on the fence. "I'm still in a wait-and-see mode," Jeff Severinghaus, a geochemist who studies ice cores at Scripps Institution of Oceanography, tells the BBC.
Image: "Nanometer-sized diamonds occur at the base a layer of sediment directly above the remains of extinct animals (mammoths, dire wolves, etc.) and artifacts from Clovis culture at the research site in Murray Springs, Arizona." / University of Oregon
Comments
Here is a link to an interesting related paper. The supporting information has fascinating photos of Younger Dryas "Black Mats":
http://www.pnas.org/content/105/18/6520
Posted by: Barrett Hamrick | January 10, 2009 06:22 PM