More than 1,500 years ago, a vast culture known as the Hopewell tradition (or Hopewell culture) spread across what is now the eastern United States.
The cause of the decline of culture has long been debated, with war and climate change two of the possibilities, but now a new avenue of investigation has opened up: the remains of a near-Earth comet.
Researchers working at 11 different Hopewell archaeological sites covering three states have found unusual concentrations of iridium and platinum in their excavations, telltale signs of meteorite fragments. Meanwhile, a layer of charcoal in the sediment suggests an intense period of high heat.
The hypothesis is that debris from a passing comet may have struck near Ohio Hopewell communities, causing an airborne outburst that would have profound and potentially devastating effects on the local environment.
Signs that people collected meteorite fragments and incorporated them into their jewelry and instruments, along with hints of a calamity in local folklore, suggest there was certainly some significant event, one that researchers suggest may have contributed to an upheaval. significant in the social sphere. .
There are other clues, too: Hopewell built a kite-shaped mound near the epicenter of the meteor shower region, now called the Milford Earthworks. Furthermore, even today there is talk of a calamitous event in history among the descending tribes.
“The Miamis tell of a horned serpent that flew through the sky and dropped rocks on the ground before plummeting into the river,” says anthropologist Kenneth Tankersley of the University of Cincinnati in Ohio. “When you see a comet going through the air, it would look like a big snake.”
“The Shawnee refer to a ‘sky panther’ that had the power to fell forests. The Ottawa speak 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. “
Micrometeorites left over from such events can reveal a chemical fingerprint, the researchers say.
“Cosmic events like asteroid and cometary outbursts leave behind large amounts of a rare element known as platinum,” says Tankersley.
“The problem is that platinum also occurs in volcanic eruptions. So we also looked for another rare element found in non-terrestrial events, such as meteorite impact craters: iridium. And we found a peak in both iridium and platinum.”
The team used techniques including scanning electron microscopy and energy dispersive spectrometry to identify the elements in the sediment they collected. The meteorite fragments were unusually concentrated compared to other places and times.
At the same time, the material was also dated using radiocarbon and typological dating. The researchers estimate that the event took place between 252 CE and 383 CE. Historical records show that 69 near-Earth comets were documented during the same time period.
The explosion from space would have caused fires that would cover some 9,200 square miles (about 23,828 square kilometers), this latest study suggests.
More studies are now planned to get a better idea of how the meteor shower might have impacted such a large area. The botanical landscape of the time can be analyzed through careful observation of pollen trapped in sediments, for example.
However, scientists admit that there are still many unanswered questions: looking back through 1,500 years of history is not particularly easy. There is still much to be explored in these particular places during this particular time period.