Scientists have exposed 12,900-year-old nanodiamond-rich soil at six North American sites, a discovery which they say adds proof for Earth’s collision with a uncommon group of carbon-and-water-rich comets or carbonaceous chondrites.

A squad at Oregon University has created the rich minute particles of diamond dust in sediments at Murray Springs in Arizona, Bull Creek in Oklahoma, Gainey in Michigan and Topper in California as well as Lake Hind in Manitoba and Chobot in Alberta, Canada.

According to the scientists, the nanodiamonds are formed under high-temperature, high-pressure circumstances produced by cosmic impacts and have been found in meteorites, the ‘Science’ journal reported.

Douglas J. Kennett, who led the team, said: ‘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.’

‘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.’

The Clovis culture of hunters and gatherers was named after hunting gear referred to as Clovis points, first discovered in a mammoth’s skeleton in 1926 near Clovis. The sites then were recognized across the US, Mexico and Central America.

Clovis people maybe entered North America across a land bridge from Siberia. The peak of Clovis era is usually considered to have run from 13,200 to 12,900 years ago. One of the diamond-rich residue layers reported sits openly on top of Clovis materials at the Murray Springs site.