Fragments of an exploding short-period comet may have caused destruction of the Paleolithic settlement at Abu Hureyra in northern Syria about 12,800 years ago, according to new research led by Comet Research Group scientists.
Source: Sci News
Abu Hureyra is a mound settlement (commonly known as a ‘tell’) located in northern Syria along the Euphrates River.
The ancient site now lies beneath Lake Assad, created when the Tabqa Dam was completed in 1974.
In 1972 and 1973, before Abu Hureyra was flooded, archaeologists collected enough evidence of houses, food and tools to identify two sites — a Paleolithic settlement and evidence for an early agricultural society.
Found among artifacts and grains were meltglass, nanodiamonds, microspherules, and charcoal.
Some features of the glass from the site suggest it was formed at extremely high temperatures — far higher than what humans could achieve at the time — or that could be attributed to fire, lighting or volcanism.
“To help with perspective, such high temperatures would completely melt an automobile in less than a minute,” said co-author Professor James Kennett, a researcher in the Department of Earth Science and Marine Science Institute at the University of California, Santa Barbara.
“Such intensity could only have resulted from an extremely violent, high-energy, high-velocity phenomenon, something on the order of a cosmic impact.”
“The samples that we collected from this location indicated that enormous pulses of heat energy were delivered to the village,” said co-author Dr. Günther Kletetschka, a researcher from the Czech Institute of Geology, Charles University, and the University of Alaska Fairbanks.
The scientists think a short-period comet exploded in the Earth’s atmosphere around 12,800 years ago. This created airbursts, powerful explosions with destructive shockwaves that can generate numerous smaller fragments.
An impact or an airburst must have occurred close enough to drive massive heat and molten glass over the entire village at Abu Hureyra, likely resulting in its total destruction.
“Because comets fly with speeds of 50 km/sec (31 miles/sec), several tons of porous ice may generate a fireball approaching megaton energy, comparable to the detonation of a nuclear bomb. Such an enormous explosion probably happened over the Syrian village,” Dr. Kletetschka said.
The team analyzed meltglass pieces from Abu Hureyra for geochemical composition, shape, structure, formation temperature, magnetic characteristics and water content.
The results showed that it formed at very high temperatures and included minerals rich in chromium, iron, nickel, sulfides, titanium and even platinum- and iridium-rich melted iron — all of which formed in temperatures higher than 2,200 degrees Celsius (3,992 degrees Fahrenheit).
“Our new discoveries represent much more powerful evidence for very high temperatures that could only be associated with a cosmic impact,” Professor Kennett said.
Abu Hureyra lies at the easternmost sector of what is known as the Younger Dryas Boundary strewnfield, which encompasses about 30 other sites in the Americas, Europe and parts of the Middle East.
These sites hold evidence of massive burning, including a widespread carbon-rich ‘black mat’ layer that contains millions of nanodiamonds, high concentrations of platinum and tiny metallic spherules formed at very high temperatures.
The Younger Dryas comet impact contributed to the extinction of most large animals, including mammoths, horses and camels in the Americas, and the disappearance of the North American Clovis culture, which happened around that time.
It also may be linked to the abrupt onset of the Younger Dryas cooling episode, when Earth’s climate cooled significantly for a 1,200-year period.
“A single major asteroid impact would not have caused such widely scattered materials like those discovered at Abu Hureyra,” Professor Kennett said.
“A large comet entering the atmosphere could potentially cause thousands of airbursts within a span of minutes, enough to cross an entire hemisphere of Earth.”
“The Younger Dryas hypothesis proposed this mechanism to account for the widely dispersed materials across the northern and southern hemispheres.”
The study was published in the journal Scientific Reports.
Source: Sci News