Asteroid impact caused extinction during last ice age

Researchers have found further evidence supporting the theory that an extraterrestrial body such as an asteroid or a comet may have crashed into the Earth almost 13,000 years ago, and caused the extinction of many large animals, and a likely decline in the early human population.

The study, published in the journal Scientific reports, noted that an asteroid or a comet hit the Earth, or blew up in the atmosphere 12,800 years ago, causing a period of extreme cooling that may have led to the extinction of more than 35 species including giant sloths, sabre-tooth cats, and mammoths in what is called the Younger Dryas climate event.

The researchers, including those from the University of South Carolina (UofSC) in the US, found further evidence of a cosmic impact based on research done at White Pond near Elgin in the US.

The new study adds to the discovery of platinum spikes -- an element associated with cosmic objects like asteroids or comets -- in multiple places across the world, including North America, Europe, western Asia, and recently in Chile and South Africa.

"First, we thought it was a North American event, and then there was evidence in Europe and elsewhere that it was a Northern Hemisphere event. And now with the research in Chile and South Africa, it looks like it was probably a global event," said study co-author Christopher Moore from UofSC.

Archeologists continue to find evidence of an asteroid or comet impact pertaining to this time period, the study noted.

"There have been numerous papers that have come out in the past couple of years with similar data from other sites that almost universally support the notion that there was an extraterrestrial impact or comet airburst that caused the Younger Dryas climate event," Moore said.

The researchers said that the extinction event got its name from a cold-tolerant wildflower, Dryas octopetala, that suddenly became common in parts of Europe 12,800 years ago.

Scientists believed that the extinction event was caused by the failure of glacial ice dams that allowed a massive release of freshwater into the north Atlantic, affecting oceanic circulation, and causing the Earth to plunge into the ice-age, the study noted.

The Younger Dryas hypothesis, on the other hand, claims that the cosmic impact was the trigger for the meltwater pulse into the oceans, the researchers said.

The researchers drilled and extracted sediment samples from underneath White Pond in South Carolina in the US and found that the layers in the sediment pertaining to the initial time period of the Younger Dryas contained a large platinum anomaly, consistent with findings from other sites.

The study noted that a large soot anomaly was also found in sediment cores from the site, indicating that large-scale regional wildfires happened in the same time interval.

The researchers also found that there were decreased quantities of fungal spores associated with the dung of large herbivores at the beginning of the Younger Dryas period.

They suggested that this was evidence of a decline in population of large animals beginning at the time of the impact.

"We speculate that the impact contributed to the extinction, but it wasn't the only cause. Over hunting by humans almost certainly contributed, too, as did climate change," Moore said.

According to him, some of these animals may have survived after the event, in some cases for centuries.

The researchers said that at White Pond, and elsewhere, some of the large animals may have gone extinct at the beginning of the Younger Dryas likely due to the environmental disruption caused by impact-related wildfires and climate change.

According to Moore and his team, the discovery of microscopic spherical particles and nanodiamonds in other studies pertaining to this time period indicated that enough heat and pressure were present to fuse materials on the Earth's surface.

"These kinds of things in science sometimes take a really long time to gain widespread acceptance. That was true for the dinosaur extinction when the idea was proposed that an impact had killed them. It was the same thing with plate tectonics. But now those ideas are completely established science," Moore said.