A team of researchers led by an archaeologist from Aiken has found widespread evidence that a large object from outer space, such as a comet or an asteroid, hit the Earth about 12,800 years ago.
That collision might explain why the climate in the Northern Hemisphere, which had been warming up in the wake of an ice age, abruptly returned to near glacial conditions during a period known as the Younger Dryas.
It also might be the reason why mastodons, saber-toothed cats, ground sloths and other big beasts known as megafauna disappeared from South Carolina and other areas.
In addition, the discoveries by Dr. Chris Moore and his colleagues could provide support for some scientists’ claims that a large number of Paleo-Indians from the Clovis culture also died off around that time because of a comet strike.
“It may have been an impact without any impact, but my suspicion is that it probably did have an effect because it is coincident with a major ecological calamity,” said Moore, outreach coordinator for the Savannah River Archeological Research Program, which is based at the Savannah River Site.
Overhunting of megafauna by humans and natural changes in the climate and the environment also could have been factors, he added.
“As things usually are, it probably was a combination of events,” Moore said. “The debate has raged in paleoanthropology and archaeology. The comet thing is sort of a new twist on it, and some scientists absolutely do not buy it.”
Moore’s team wrote a paper about its work that was published by Scientific Reports earlier this year.
In 2013, researchers from Harvard University revealed that they had detected higher-than-normal concentrations of platinum in ice core samples from Greenland that coincided with the start of Younger Dryas.
The scientists said the likely source of the precious metal was a “sub-kilometer iron meteorite.”
Moore and his colleagues wanted to see if they could find the same platinum anomalies in sediment samples from other places.
“Platinum is rare in the Earth’s crust, but it’s common in asteroids and comets,” Moore said. “The only way it could have gotten into the ice was through atmospheric input, which means it fell out of the atmosphere.”
Moore’s team analyzed sediment samples that were about the same age as the Greenland ice core samples from 11 different sites in the United States.
One of the locations was on Santa Rosa Island off the coast of California. Five were in South Carolina, two were in North Carolina and there was one each in Arizona, New Mexico and Ohio.
Nearly all of the sediment samples contained abnormally high levels of platinum.
“At one of the sites in North Carolina, there was some weird stuff going on,” Moore said. “It had multiple platinum anomalies, and some of them were in sediments that postdated Younger Dryas. It was the only one like that, and we think we can explain it by water and wind moving the sediments around and ‘redepositing’ them.”
Scientists haven’t identified a crater yet that can be traced back to the onset of Younger Dryas, but Moore still believes one might exist.
“There are some candidate craters, and one, in the Gulf of Saint Lawrence, is going to be investigated very soon,” he said.
There also are explanations for why an extraterrestrial object wouldn’t leave behind a huge hole.
“It might have hit an ice sheet up where Canada is today,” Moore said. “In some places, the ice was 2 miles thick. Impact studies have shown that ice absorbs energy, so there wouldn’t have been any crater. It also might have come in at a low angle, hit the Earth’s atmosphere and exploded, sending out shock waves” that caused more damage than the small pieces that fell to the ground.
Moore is exploring platinum anomalies further, and that effort includes examining a sediment core from the bottom of a pond near Columbia. He also is looking for spores that were present in the dung of large herbivores.
“If there are a lot of spores, a lot of spores and then no more spores, that would indicate an extinction event,” he said.