{"id":785272,"date":"2024-07-05T06:58:56","date_gmt":"2024-07-05T11:58:56","guid":{"rendered":"http:\/\/spaceweekly.com\/?p=785272"},"modified":"2024-07-05T06:58:56","modified_gmt":"2024-07-05T11:58:56","slug":"did-a-comet-burst-crash-earths-climate-12800-years-ago","status":"publish","type":"post","link":"https:\/\/spaceweekly.com\/?p=785272","title":{"rendered":"Did a comet burst crash Earth\u2019s climate 12,800 years ago?"},"content":{"rendered":"


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View at EarthSky Community Photos. | John Ashley shared this composite image of Comet Pons-Brooks setting behind Kitt Peak Observatory in Arizona in April, 2024. Thank you, John! A new study adds to the evidence that a comet exploded in Earth\u2019s atmosphere about 12,800 years ago. The comet burst could have triggered the Younger Dryas cooling period, which lasted around 1,200 years.<\/figcaption><\/figure>\n

Comet burst almost killed humanity 12,800 years ago<\/h3>\n

About 12,800 years ago \u2013 a geological blink of the eye \u2013 global temperatures suddenly and dramatically plummeted. The icy conditions of the Younger Dryas cooling period lasted more than 1,200 years. But it shouldn\u2019t have happened. Earth was warming when the cooling began. On June 25, 2024, scientists said they\u2019ve found more evidence that a comet impact might have been responsible for Earth\u2019s sudden cooling.<\/p>\n

The researchers published their peer-reviewed paper on May 8, 2024, in the ScienceOpen journal Airbursts and Cratering Impacts<\/em>. They said physical evidence shows a 62-mile-wide (100-km-wide) comet exploded just about the same time humanity invented agriculture.<\/p>\n

Previously published studies show human populations dropped dramatically at the same moment. The resulting bottleneck almost ended the human race. It took us more than three centuries to begin our recovery.<\/p>\n

Exotic materials and microscopic metals litter Earth<\/h3>\n

Because the hypothetical comet never hit the ground, evidence for it comes from an abundance of tiny particles in the geological record. These micro-size bits of material \u2013 the metals iridium and platinum, exotic magnetic micro-spherules, melt glass and miniscule nanodiamonds \u2013 cover the entire globe. Scientists have found these particles in the layer of sediment that matches the start of the Younger Dryas.<\/p>\n

Emeritus Professor James Kennett of the University of California, Santa Barbara\u2019s earth science department said the team found strong evidence supporting a cometary airburst:<\/p>\n

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There\u2019s a whole range of different shocked quartz, so we have to make a well-documented case that they are indeed significant for interpreting cosmic impact, even though they\u2019re not reflecting a traditional major crater-forming event. These are from very-low-altitude \u201ctouchdown\u201d airbursts almost certainly associated with cometary impact.<\/p>\n<\/blockquote>\n

Kennett is one of several authors of the new paper. The latest publication is part of a series of scholarly works providing mounting evidence a cosmic impactor altered humanity\u2019s destiny. Kennett\u2019s research even hints the comet strike sparked widespread adoption of agriculture.<\/p>\n

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This image shows microscopic shocked quartz grains with fissures filled with melt glass. Such particles are evidence for a cometary burst in Earth\u2019s atmosphere. Researchers believe such an event could have triggered the Younger Dryas cooling period 12,800 years ago. Image via UCSB.<\/figcaption><\/figure>\n

Comet burst came from a comet at least 60 miles wide<\/h3>\n

While there\u2019s evidence of fallout from the comet\u2019s atmospheric explosion all over the Earth \u2013 even in Australia \u2013 the latest paper focuses on three locations in the eastern United States. All were on the East Coast: Flamingo Bay, South Carolina; Parsons Island, Maryland; and Newtonville, New Jersey. A distance of 620 miles (1,000 km) separates the survey sites.<\/p>\n

Of special interest to the researchers are lamellae, tiny laminated layers of alternating materials in the micro-size particles. Their abundance in the geologic record at 12,800 years ago provides strong evidence for a Younger Dryas comet impact. Kennett explained their importance:<\/p>\n

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In the extreme form, such as when an asteroid hammers into the Earth\u2019s surface, all the fractures are very parallel. When you think about it, the pressures and temperatures that produce these fractures will vary depending on the density, entry angle, altitude of the impact and the impactor\u2019s size.<\/p>\n<\/blockquote>\n

With that in mind, the evidence suggests the Younger Dryas comet was about 62 miles (100 km) wide. That\u2019s much larger than the object that killed the dinosaurs. The Chicxulub impactor \u2013 suspected of wiping out much of life on Earth \u2013 was likely an asteroid. The asteroid that took out the dinos was only 6 miles (10 km) across. Yet because it was so much more dense and actually hit Earth, it was far more destructive.<\/p>\n

The Younger Dryas comet burst was more like the atmospheric explosion of a meteor over Tunguska in Russia in 1908. That object was likely just 130 feet (40 meters) wide. But, it took out 830 square miles (2,150 square km) of forest. It also left no impact crater.<\/p>\n