A Comet That Exploded Over Earth 12,800 Years Ago May Have Triggered Centuries of Bitter Cold

In 2024, scientists studying ancient sediments in the eastern United States reported signs of a comet exploding in Earth’s skies 12,800 years ago. That event, they suggested, might have plunged the planet into a thousand-year cold spell known as the Younger Dryas. 

Now, a new study has taken the search deep beneath the ocean, and the results strengthen the case. Researchers from the University of South Carolina analyzed seafloor mud from Baffin Bay, near Greenland, and found tiny traces of comet dust and metallic debris consistent with a cosmic airburst. 

For years, scientists have argued over what triggered the abrupt global cooling that interrupted the warming at the end of the last Ice Age. Many linked it to meltwater flooding the Atlantic and disrupting ocean currents. Others believed something from space was to blame, but until now, the lack of a crater or solid proof made the comet idea easy to dismiss. This new line of evidence may change that.

“Our new findings further support the hypothesis that the Earth collided with a large comet about 12,800 years ago. The amount of comet dust in the atmosphere was enough to cause a short-term ‘impact winter,’ followed by a 1,400-year cooling period,” Vladimir Tselmovich, one of the study authors, told The Debrief.

Digging for answers in the ocean floor

The researchers wanted to test whether hints of a comet impact found on land also appeared in the ocean. For this purpose, they turned to sediment cores—long, cylindrical samples drilled vertically into the seabed. 

These cores preserve layers of mud and minerals laid down year after year, much like pages in Earth’s diary. From Baffin Bay, close to Greenland and far from human contamination, the researchers retrieved four cores whose layers matched the Younger Dryas period by radiocarbon dating.

“Having studied in detail the microscopic traces of this disaster in Baffin Bay, we were able to find multiple traces of cometary matter, which was identified by the morphology and composition of the microparticles found,” Tselmovich said.

To hunt for extraterrestrial fingerprints, the scientists used several advanced techniques. For instance, electron microscopes revealed the shapes of microscopic particles. Whereas spectroscopy and mass spectrometry measured their chemical makeup with high precision. The results were striking.

They found metallic grains containing unusually high levels of nickel, cobalt, platinum, and iridium, elements often linked to material from space. Some iron particles showed very little oxygen but a lot of nickel, a chemical signature common in comets and meteorites. They also discovered tiny spheres of melted rock, or microspherules, that appeared to have formed when Earth materials fused with a small amount of alien dust during an airburst explosion. 

“Microspherules are geochemically most similar to terrestrial sediments with traces of extraterrestrial material,” the study authors note.

Other nanoparticles resembled twisted, deformed metallic droplets, again hinting at the extreme heat and pressure of a cosmic blast in the atmosphere. This discovery mirrors what other studies have found on land across several continents—a distinct layer from around 12,800 years ago, rich in platinum, iridium, meltglass, nanodiamonds, and fractured quartz. 

This much consistency between land and ocean sites strengthens the case that the Younger Dryas cooling was not only sudden but also global, and potentially caused by a fragmented comet that shattered in the skies.

That haze of comet dust swirled into the upper atmosphere, scattering sunlight back into space. For humans and animals below, it would have been like the sun suddenly dimmed. Temperatures plunged, plants withered, and the delicate balance of warming at the end of the Ice Age stalled almost overnight.

“The results of this study support the Younger Dryas impact hypothesis (YDIH), suggesting that Earth’s encounter and interaction with a large comet and its debris trail at the YD onset led to major climatic and environmental changes,” the study author concluded.

We need more evidence

If correct, this research reframes one of the biggest climate mysteries of the past. The Younger Dryas wasn’t just a minor blip; it lasted about 1,400 years, dropped global temperatures by around 10°C, and transformed entire ecosystems. 

It coincided with the disappearance of mammoths and other giant animals in North America, and the decline of the ancient Paleo-Indian culture. Linking such changes to a comet airburst would place it alongside other major cosmic disasters in Earth’s history, though on a smaller scale than the dinosaur-killing asteroid. 

However, the evidence of the comet explosion is not complete. The researchers acknowledge the absence of a crater and suggest that more studies are needed. Their next step is to examine cores from other ocean sites to see if the signs of comet dust appear there as well. 

The study is published in the journal PLOS One.