Comet Impact May Have Left Layer of Nanodiamonds Across Earth

About 13,000 years ago, a cosmic impact caused a period of global cooling, called the Younger Dryas Period. Now, scientists have taken a closer look at this impact and have examined the character and distribution of nanodiamonds, one type of material produced during this collision.

In this case, the researchers investigated nanodiamonds at 32 sites in 11 countries across North America, Europe and the Middle East. They found an abundance of these tiny diamonds distributed at the Younger Dryas boundary (YDB), a thin, carbon-rich layer that's usually visible as a thin black line a few meters below the surface.

"We conclusively have identified a thin layer over three continents, particularly in North America and Western Europe, that contain a rich assemblage of nanodiamonds, the production of which can be explained only by cosmic impact," said James Kennett, one of the researchers, in a news release. "These are exotic conditions that came together to produce the diamonds from terrestrial carbon; the diamonds did not arrive with the incoming meteorite or comet."

In fact, the scientists determined that the majority of the materials in the YDB samples are nanodiamonds and not some other type of minerals. This indicates that a major cosmic impact did occur at this time period, and may be to blame for the mass extinction of megafauna across North America.

"The evidence we present settles the debate about the existence of abundant YDB nanodiamonds," said Kennett. "Our hypothesis challenges some existing paradigms within several disciplines, including impact dynamics, archaeology, paleontology and paleoceanography/paleoclimatology, all affected by this relatively recent cosmic impact."

The findings are published in the Journal of Geology.