Experts have discovered that around 470 million years ago, two major asteroids, one of which was at least 93 miles wide, collided in the asteroid belt, located between Jupiter and Mars. Over the course of two million years, the debris from the collision headed Earth’s way and seeped into the atmosphere, according to the international team of researchers from Sweden and the US. The researchers reached this conclusion by searching for helium isotopes – chemical elements often found in asteroids – on the ocean floor.
Philipp Heck, a curator at the Field Museum, associate professor at the University of Chicago, and one of the paper’s authors, said: “We studied extraterrestrial matter, meteorites and micrometeorites, in the sedimentary record of Earth, meaning rocks that were once sea floor.
“And then we extracted the extraterrestrial matter to discover what it was and where it came from.”
At the same time, 470 million years ago, Earth was heading into an ice age, and the researchers now know the debris from the asteroid collision blocked out the Sun, causing temperatures to drop on the planet.
Prof Heck said: “Normally, Earth gains about 40,000 tons of extraterrestrial material every year.
“Imagine multiplying that by a factor of a thousand or ten thousand.
“Our hypothesis is that the large amounts of extraterrestrial dust over a timeframe of at least two million years played an important role in changing the climate on Earth, contributing to cooling.”
This has led to theories that Earth, which is warming due to climate change and putting many species’, including humans, existence at risk, could be cooled again by blocking out the Sun.
Birger Schmitz of Sweden’s Lund University, the study’s lead author and a research associate at the Field Museum, said: “Our results show for the first time that such dust, at times, has cooled Earth dramatically.
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“It’s very different from the climate change caused by the meteorite 65 million years ago that killed the dinosaurs, and it’s different from the global warming today – this global cooling was a gentle nudge. There was less stress.
“We’re experiencing global warming, it’s undeniable.
“And we need to think about how we can prevent catastrophic consequences, or minimise them. Any idea that’s reasonable should be explored.”