Did an Exploding Comet Cause Extinctions 13,000 Years Ago?

Scientists think they might have the solution to a mystery that’s been haunting paleontologists for years: what caused an abrupt period of cooling 13,000 years ago and an extinction of the large mammals. The conventional theory is that when human hunters arrived in North America, they killed off all the tasty large mammals. But there’s evidence that a comet exploded over North America at approximately the same time. This could also cause cooling, and wipe out the animals.

The discovery was made by scientists from the University of California at Santa Barbara. They analyzed more than a dozen archaeological sites across North America, and found they all had high concentrations of iridium. This element is a rare substance on Earth, but known to be in many comets and asteroids. Whenever these objects impact the Earth, they leave a blanket of iridium behind which serves as a marker. As archaeologists dig down through the layers of material, they’re looking back in time, and can accurately date when the object struck.

If this theory is correct, a comet approximately 4 km (2.5 miles) across detonated in the skies above North America, and rained fragments down across the whole region. The extreme temperatures would have ignited wildfires across the continent, destroying the vegetation that the large mammals needed to survive. Their death would then lead to a cascade of deaths by the large predators and the rest of the food chain that relied on them.

The comet might have also destabilized a large portion of the Laurentide ice sheet, causing a high volume of fresh water to flow into the ocean. Climate researchers believe this kind of event can disrupt the normal circulation of the ocean’s flow, and lead to a global cooling event. Ecosystems across the planet would have suffered.

Ancient cultures, such as the Clovis people of North America relied on mammoths and other large mammals for food. They would have been affected by the impact, and this might have caused their culture to die out.

Original Source: NSF News Release