Extraterrestrial cause of sudden climate change disproved

The presence of nanodiamonds and charcoal in the soil of the Netherlands is not evidence of a meteorite impact towards the end of the last ice age. This has been revealed in research conducted by the Energy and Sustainability Research Institute Groningen (ESRIG, University of Groningen) in collaboration with Utrecht University and Leiden University. The results of this research were published on 1 May in Proceedings of the National Academy of Science (PNAS).

In 2007, American researchers pointed to an extraterrestrial impact above the North American ice sheet as the cause of the abrupt cold period known as the Younger Dryas. According to the Americans, the impact caused forest fires across the globe, dispersed the rare element iridium and caused the formation of nanodiamonds. The researchers also saw the impact as a cause for the disappearance of the prehistoric Clovis culture and the extinction of the mammoth.

Evidence in the Usselo horizon

Both the alleged impact and the research on it have been fiercely debated at conferences, in the media and the journal Nature. Researchers from the universities of Groningen, Utrecht and Leiden surveyed the Dutch subsoil near the town of Geldrop. They carefully dated the Usselo horizon, which, according to the American researchers, marks the transition to the sudden cold period, and they examined samples using electron microscopes. ESRIG’s Centre for Isotope Research performed the requisite ¹⁴C datings.

Centuries younger than the impact

The survey of the Usselo horizon revealed that the layer of charcoal is probably the result of a natural forest fire and is hundreds of years younger than the alleged impact. The nanodiamonds are younger too, and likely have another cause. This appears to disprove the extraterrestrial explanation for the sudden change in climate.