Diamond dust shows comets hit 12,900 years ago: study

Soil rich in diamond dust discovered across North America reinforces a theory that falling meteors caused the extinction of mammoths and other animals, said a study in the journal Science.
“These discoveries provide strong evidence for a cosmic impact event at approximately 12,900 years ago that would have had enormous environmental consequences for plants, animals and humans across North America,” said Douglas Kennett of the University of Oregon, who led the research.
The findings appear to bolster the theory set out in 2007 that several comets hitting the Earth triggered a 1,300-year-long ice age, causing the extinction of several species of animals and fragmented the prehistoric human Clovis culture.
The Clovis people lived off of hunting and gathering in an area across what is now the United States, Mexico and Central America.
The peak of the Clovis era was from 13,200 to 12,900 years ago and scientists say the Clovis may have entered North America across a land bridge from Siberia.
One of the diamond-rich sediment layers found by the researchers is located directly above Clovis materials at a site in Murray Springs, Arizona, the researchers said.
The nanometer-sized diamonds are produced under high temperatures and high pressure from cosmic impacts that have been found in meteorites.
The sediments full of diamond dust were also found at digs at five other sites, in Bull Creek, Oklahoma; Gainey, Michigan; and Topper, South Carolina in the United States and Lake Hind, Manitoba; and Chobot, Alberta in Canada.
Nanodiamonds can be produced on Earth but only as a result of high-explosive detonations or chemical vaporization.
The study appears in the January 2 edition of the journal Science.

Copyright AFP (Agence France-Presse), 2009