For more than a century, a vigorous scientific debate over what caused the extinction of so many types of large mammals at the end of the last ice age has simmered as scientists subscribe to different hypotheses. One hypothesis argues that a cataclysmic extraterrestrial impact 12,900 years ago contributed to the Younger Dryas cooling which led to the extinction of more than 30 species. Another theory argues that overhunting and disease wiped out species such as mammoths and other behemoths.
Today that debate has reached a boil following the publication of a scientific paper in the International Glaciological Society's Journal of Glaciology documenting the discovery of a layer of nanodiamonds in the Greenland ice sheet. Nanodiamonds are believed to be evidence of an extraterrestrial event. Their presence in the Greenland ice sheet is the first discovery of a heavy concentration of a discreet layer of extraterrestrial matter in the Greenland ice sheet, said University of Maine's Dr. Andrei Kurbatov, lead author on the paper.
"We can link this to events in time and we think it is in proximity to the Younger Dryas," said Kurbatov. "But we cannot yet determine the definitive timing of the event."
The Younger Dryas was an abrupt cooling period with estimated 8- to 10-degree centigrade drop in temperature, which is substantial. During the Younger Dryas era, the climate returned to near glacial conditions of earlier ice ages.
The finding adds credibility to the theory that fragments of a comet struck across North America and Europe approximately 12,900 years ago, said Kurbatov. In 1997, scientists proposed that an extraterrestrial impact caused the Younger Dryas cooling (Firestone et al., Evidence for an extraterrestrial impact 12,900 years ago that contributed to the megafaunal extinctions and the Younger Dryas cooling. PNAS (2007) vol. 104 (41) pp. 16016-16021).
The most recent discovery is further evidence that suggests that sometime before the Holocene, Earth was struck by Extra Terrestrial objects, said Kurbatov.
"There are two possible scenarios: a) This is the same ET event that was reported in numerous North American sites ( See Firestone et al., 1997; Kennett et al. Nanodiamonds in the Younger Dryas Boundary Sediment Layer. Science (2009) vol. 323 pp. 94; or b ) this is another ET event." —Rachel Walker