Scientists say a comet exploded over North America 12,800 years ago

Scientists have found evidence for the so-called Younger Dryas impact hypothesis, which holds that a comet exploded in Earth's atmosphere about 12,800 years ago, causing a drop in the Earth's temperature.

A paper published in the journal Airburst and cratering Signs of an ancient cosmic airburst have been found at three different sites in New Jersey, Maryland and South Carolina. The evidence includes platinum, meltglass and shock-fractured quartz, all of which suggest the types of forces and high temperatures associated with “airburst” comets.

This is similar to what happens during a nuclear explosion near the Earth's surface.

'Touchdown' Airburst

Although large asteroids and comets do hit Earth, creating craters, most of them explode in the air as fireballs or air blasts. “We found that the pressures and temperatures were not characteristic of large crater-forming impacts, but were consistent with so-called “touchdown” air blasts, which don't create much in the way of craters,” said James Kennett, emeritus professor at the University of California, Santa Barbara.

It is believed that the burning effect of the comet's explosion may have also wiped out giant creatures in North America, such as mammoths and giant ground sloths.

thousands of pieces

During this event, a comet about 62 miles (100 kilometers) wide was likely shattered into thousands of pieces. This could explain the sediment layer over much of the northern hemisphere that contains impact-related materials such as iridium, platinum, molten glass and nano-diamonds.

Similarly, fragmented quartz particles and molten glass have been found at the Trinity atomic bomb test site in New Mexico, where a 20-kiloton bomb was detonated atop a 100-foot (30.5 m) tall tower in July 1945.

Tunguska event

One of the most famous cosmic airbursts was the so-called “Tunguska event” of 1908, when the shockwave from a 130-foot (40-meter) asteroid or comet fragment exploded about six miles (120 kilometers) over Siberia. It destroyed 830 square miles (2,150 square kilometers) of forest.

This is not the only comet strike that has significantly affected Earth's climate and biodiversity. It is known that an asteroid or comet hit Earth near Mexico's Yucatan Peninsula 66 million years ago, creating the 110-mile (180 kilometer) wide Chicxulub crater. This strike is believed to have caused the decades-long winter that killed the dinosaurs.

Cosmic companion

In 2022, scientists announced they had found a suspected second asteroid impact crater of the same age, five miles (nine kilometers) wide, beneath the North Atlantic Ocean off the coast of Guinea in western Africa. This suggests the space rock that killed the dinosaurs may have had a smaller cosmic companion or may be part of a cluster.

Only about 200 impact craters have ever been discovered on Earth's surface – about a tenth of them on the ocean floor – while asteroids have been hitting it throughout its existence.

Wishing you clear skies and big eyes.

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