Roughly 466 million years ago, a cataclysmic asteroid collision sent debris hurtling toward Earth. For the next 2 million years, our planet was shrouded in a patina of dust—the shrapnel of a destructive event that, paradoxically, ushered in a new era of life.
By shielding Earth from sunlight, this massive influx of asteroid dust drove global temperatures down, triggering an ice age that boosted biodiversity on a global scale, new research suggests. The study, published today in the journal Science Advances, underscores the vulnerability of life on Earth to extraterrestrial events—and hints at the myriad ways in which our planet’s climate can be put into flux.
Melinda Hutson, curator of the Cascadia Meteorite Laboratory at Portland State University, and who wasn’t involved in the study, praised the link the paper’s authors drew between dust and cooling. “The authors had to have a good combination of background specialties to put this all together,” she told Richard A. Lovett at Cosmos.
Earth is no stranger to space schmutz: Some 40,000 tons of extraterrestrial dust accumulates on our planet each year. That’s enough to fill about 1,000 semi-trucks—but spread across the globe, the particles don’t have much of an effect. The amount of space dust that cloaked our planet’s atmosphere 466 million years ago, however, was at least 1,000 to 10,000 times that.
Some of the dust is still around today, embedded in rock formations that were once a part of Earth’s sea floor, study author Philipp Heck of the University of Chicago said in a statement. A chemical analysis of these sediments hinted at a cosmic origin, leading Heck and his team to conclude that the disintegration of a 93-mile-wide asteroid was probably the source of the debris.
The cause of the asteroid’s demise is still a mystery. But the researchers have come up with a likely scenario: This space rock was probably hanging out in the asteroid belt located between Mars and Jupiter when it collided with another big body. The encounter ended very badly for at least one of the two—and for the next 2 million years, bits of annihilated asteroid flooded the inner solar system, wreathing Earth and other planets with debris.
Over time, the dust accumulated into a sparse umbrella, blocking a good deal of the sunlight that would have otherwise reached Earth. This drove global temperatures downward—as much as 50 degrees Fahrenheit—coinciding neatly with a known ice age that began around the same time. “The timing appears to be perfect,” study author Birger Schmitz of Lund University in Sweden said in a statement.
As the land and ocean cooled, ice built up, causing sea levels to drop. Eventually, a gradient of climatic zones appeared, from the chilly climes at the poles to the tropical conditions at the equator.
This worldwide shift happened gradually enough that species had time to adapt and diversify in a multitude of new habitats, Heck told Emma Goldberg at The New York Times.. “We’re talking about gentle changes that happened over 2 million years,” he said. “If we could travel back in time, it wouldn’t appear as a catastrophe to us. It would be more like a gentle nudge that led to global change.”
Nowadays, however, human-driven climate change is proceeding at a far faster and more dangerous pace, Heck said in the statement. But he and his colleagues suggest that there’s more than a cautionary tale in Earth’s ancient dust bath: Perhaps a modern asteroid could be artificially blitzed to smithereens to help our planet cool off.
That’s an idea that’s been proposed before—and it’s risky, to say the least, Heck told Goldberg. Still, it’s at least worth considering: “We're experiencing global warming, it's undeniable,” he said in the statement. “We need to think about how we can prevent catastrophic consequences, or minimize them. Any idea that's reasonable should be explored.”