A scattering of rare elements discovered across the Ohio River Valley could indicate that a cosmic cataclysm helped towards the decline of a Native American culture some 1,500 years ago.
Researchers with the University of Cincinnati have found evidence of a cosmic airburst at 11 sites that were once inhabited by the Hopewell culture, an ancient Native American civilization that thrived in settlements along rivers in the northeastern and midwestern Eastern Woodlands around 2,000 years ago.
In their new study, which can be found in the journal Scientific Reports, the researchers detail the detection of rare metals, such as iridium and platinum, as well as stony meteorite fragments called pallasites, at 11 different sites once inhabited by people of the Hopewell culture. They also found a charcoal layer at the sites, indicating the land was exposed to a sudden burst of extreme heat.
"These micrometeorites have a chemical fingerprint. Cosmic events like asteroids and comet airbursts leave behind high quantities of a rare element known as platinum," Tankersley said. "The problem is platinum also occurs in volcanic eruptions. So we also look for another rare element found in nonterrestrial events such as meteorite impact craters -- iridium. And we found a spike in both, iridium and platinum,” Kenneth Tankersley, lead author of the study and a professor of anthropology at the University of Cincinnati, said in a statement.
Altogether, the researchers say this is strong evidence that the area was hit by an airburst. Airbursts are violent explosions that are the result of a large meteor or comet grazing with Earth's atmosphere before bouncing back into space. This latest study indicates that the airburst likely sparked fires across a 23,800 kilometer (~9,200 square mile) area of forest between the years 252 and 383 CE. Neatly tying this story together, this was a time period when Chinese astronomers documented over 60 near-Earth comets.
Perhaps by no coincidence, this catastrophic event also appears to have coincided with a sudden decline of the Hopewell culture. Most people of this ancient civilization likely survived the initial incident, but the resulting fires would have devasted the landscape, likely leading to the collapse of agriculture. Furthermore, various tribes that descended from the Hopewell tribe, such as the Algonquin and Iroquoian, also had tales and legends of a strange catastrophe that befell the Earth from the skies.
“What’s fascinating is that many different tribes have similar stories of the event,” explains Tankersley.
“The Miami tell of a horned serpent that flew across the sky and dropped rocks onto the land before plummeting into the river. When you see a comet going through the air, it would look like a large snake. The Shawnee refer to a ‘sky panther’ that had the power to tear down forest. The Ottawa talk of a day when the sun fell from the sky. And when a comet hits the thermosphere, it would have exploded like a nuclear bomb,” Tankersley continued.
These types of catastrophes are rare, but they have been documented a handful of times. One study last year found evidence of a fiery airburst event at the archeological site of Tall el-Hammam in Jordan around 3,600 years ago. They suspect this catastrophe might have inspired the story of Sodom and Gomorrah, two biblical cities destroyed by God for their wickedness.
In 1908, a vast forest was flattened by a colossal 30 megaton explosion near the Podkamennaya Tunguska River in Siberia. While it's still not certain what caused this freak event, the most likely explanation is an airburst resulting from a meteor skimming past Earth’s atmosphere.