Cosmic nanodiamonds – Science Spot

Tiny particles of crystalline carbon found in sediments at six sites in North America dating back almost 13000 years, suggest that a swarm of carbon-and-water-rich comets smashed into the Earth triggering extinctions of large mammals, including the woolly mammoth, across the globe.

The nanodiamonds from these carbonaceous chondrites are formed under high-temperature and high-pressure conditions created at impact and have been found in meteorites in similarly aged sediments at Murray Springs, Arizona, Bull Creek, Oklahoma., Gainey, Michigan, and Topper, South Carolina, as well as at Lake Hind, Manitoba, and Chobot, Alberta, in Canada. Their existence represents evidence for the cause of a severe cold snap that last 1300 years known as the Younger Dryas period.

Douglas J. Kennett

The Clovis culture of hunters and gatherers was named after hunting tools referred to as Clovis points, first discovered in a mammoth’s skeleton in 1926 near Clovis, New Mexico. Researchers later identified Clovis sites later across the American continent. The Clovis people presumably reach the Americas via a land bridge from Siberia and their culture is thought to have peaked around 10,900 years to 12,500 years ago. The Younger Dryas period is thought to have fragmented the prehistoric Clovis culture and led to mass extinctions of many animals across North America.

In 2007, a 26-strong research team from sixteen institutions proposed that a cosmic impact event, possibly due to multiple airbursts of comets was the trigger for the Younger Dryas. Now, a team led by the University of Oregon’s Douglas Kennett, a member of the original research team, report the discovery of billions of nanometre-sized diamonds concentrated in sediments in the same six locations. One of the diamond-rich sediment layers reported sits directly on top of Clovis materials at the Murray Springs site.

The nanodiamonds that we found at all six locations exist only in sediments associated with the Younger Dryas Boundary layers, not above it or below it, explains Kennett. 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.

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