Did comet's fiery destruction lead to downfall of ancient Hopewell?


Date:
February 1, 2022
Source:
University of Cincinnati
Summary:
The rapid decline of the Hopewell culture about 1,500 years ago
might be explained by falling debris from a near-Earth comet that
created a devastating explosion over North America, laying waste
to forests and Native American villages alike. Researchers found
evidence of a cosmic airburst at 11 Hopewell archaeological sites
in three states stretching across the Ohio River Valley.



FULL STORY ==========================================================================
The rapid decline of the Hopewell culture about 1,500 years ago might
be explained by falling debris from a near-Earth comet that created a devastating explosion over North America, laying waste to forests and
Native American villages alike.


========================================================================== Researchers with the University of Cincinnati found evidence of a cosmic airburst at 11 Hopewell archaeological sites in three states stretching
across the Ohio River Valley. This was home to the Ohio Hopewell, part of
a notable Native American culture found across much of the American East.

The comet's glancing pass rained debris down into the Earth's atmosphere, creating a fiery explosion. UC archaeologists used radiocarbon and
typological dating to determine the age of the event.

The airburst affected an area bigger than New Jersey, setting fires across 9,200 square miles between the years A.D. 252 and 383. This coincides
with a period when 69 near-Earth comets were observed and documented by
Chinese astronomers and witnessed by Native Americans as told through
their oral histories.

The study was published in the Nature journal Scientific Reports.

UC archaeologists found an unusually high concentration and diversity
of meteorites at Hopewell sites compared to other time periods. The
meteorite fragments were identified from the telltale concentrations of
iridium and platinum they contained. They also found a charcoal layer
that suggests the area was exposed to fire and extreme heat.



==========================================================================
In his lab, lead author Kenneth Tankersley, a professor of anthropology
in UC's College of Arts and Sciences, held up a container of tiny micrometeorites collected at the sites. A variety of meteorites, including stony meteorites called pallasites, were found at Hopewell sites.

"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."
The Hopewell people collected the meteorites and forged malleable metal
from them into flat sheets used in jewelry and musical instruments called
pan flutes.

Beyond the physical evidence are cultural clues left behind in the
masterworks and oral histories of the Hopewell. A comet-shaped mound
was constructed near the epicenter of the airburst at a Hopewell site
called the Milford Earthworks.

Various Algonquin and Iroquoian tribes, descendants of the Hopewell,
spoke of a calamity that befell the Earth, said Tankersley, who is
Native American.



========================================================================== "What's fascinating is that many different tribes have similar stories
of the event," he said.

"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," he said.

"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."
And the Wyandot recount a dark cloud that rolled across the sky and was destroyed by a fiery dart, Tankersley said.

"That's a lot like the description the Russians gave for Tunguska," he
said of a comet airburst documented over Siberia in 1908 that leveled
830 square miles of forest and shattered windows hundreds of miles away.

"Witnesses reported seeing a fireball, a bluish light nearly as bright as
the sun, moving across the sky. A flash and sound similar to artillery
fire was said to follow it. A powerful shockwave broke windows hundreds
of miles away and knocked people off their feet," according to a story
in EarthSky.

UC biology professor and co-author David Lentz said people who survived
the airburst and its fires would have gazed upon a devastated landscape.

"It looks like this event was very injurious to agriculture. People
didn't have good ways to store corn for a long period of time. Losing
a crop or two would have caused widespread suffering," Lentz said.

And if the airburst leveled forests like the one in Russia, native people
would have lost nut trees such as walnut and hickory that provided a
good winter source of food.

"When your corn crop fails, you can usually rely on a tree crop. But
if they're all destroyed, it would have been incredibly disruptive,"
Lentz said.

UC's Advanced Materials Characterization Center conducted scanning
electron microscopy and energy dispersive spectrometry of the sediment
samples.

Inductively coupled plasma mass spectrometry was employed at the
University of Georgia's Center for Applied Isotope Studies. The
U.S. Geological Survey provided stable carbon isotope analysis.

Despite what scientists know, there is still much they do not, Lentz said.

"It's hard to know exactly what happened. We only have a few points of
light in the darkness," he said. "But we have this area of high heat
that would have been catastrophic for people in that area and beyond."
Now researchers are studying pollen trapped in layers of sediment to
see how the comet airburst might have changed the botanical landscape
of the Ohio River Valley.

Co-author Steven Meyers, a UC geology alumnus, said their discovery
might lead to more interest in how cosmic events affected prehistoric
people around the world.

"Science is just a progress report," Meyers
said. "It's not the end. We're always somewhere in
the middle. As time goes on, more things will be found." ========================================================================== Story Source: Materials provided by University_of_Cincinnati. Original
written by Michael Miller. Note: Content may be edited for style and
length.


========================================================================== Related Multimedia:
* Studying_micrometeorites ========================================================================== Journal Reference:
1. Kenneth Barnett Tankersley, Stephen D. Meyers, Stephanie A. Meyers,
James
A. Jordan, Louis Herzner, David L. Lentz, Dylan
Zedaker. The Hopewell airburst event, 1699-1567 years
ago (252-383 CE). Scientific Reports, 2022; 12 (1) DOI:
10.1038/s41598-022-05758-y ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2022/02/220201143951.htm

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