Earth endured an ancient ice age 466 million years ago when a giant asteroid broke apart and sent waves of dust toward our planet over the next 2 million years, according to a new study. And surprisingly, while the massive inflow of dust caused global temperatures on Earth to plummet, it also provided a chance for new evolving species to flourish.
The 93-mile-wide asteroid was in the asteroid belt located between Mars and Jupiter when it collided with something else and broke apart, creating a wealth of dust that flooded the inner solar system.
"It is analogous to standing in the middle of your living room and smashing a vacuum cleaner bag, only at a much larger scale," said Birger Schmitz, lead study author and professor of geology at Lund University.
Earth is no stranger to the inflow of space material, like pieces of comets and asteroids.
"Normally, Earth gains about 40,000 tons of extraterrestrial material every year," said Philipp Heck, study author, a curator at the Field Museum and associate professor at the University of Chicago. "Imagine multiplying that by a factor of a thousand or ten thousand."
To put that in perspective, think about semi trucks loaded down with interplanetary dust. Over the course of one year, Earth receives one thousand semis' worth of dust.
But over the 2 million years after the giant asteroid broke apart, Earth was inundated with 10 million semi trucks' worth of dust.
"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," Heck said.
The study published Wednesday in the journal Science Advances.
Dust from the asteroid caused a disruption in the amount of sunlight Earth received, which led to an ice age. This actually set the stage for the conditions we see on Earth now -- arctic conditions at the North and South poles and more tropical conditions around the equator.
Before this ice age, the climate on Earth was more similar across the globe, not divided into climate zones.
But these climate zones also provided a way for Earth's invertebrates to adapt to new conditions and temperatures. Those adaptations led to an evolution boom.
"In the global cooling we studied, we're talking about timescales of millions of years," Heck said. "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."
To understand how this process unfolded, the researchers found evidence of space dust locked in 466-million-year-old rocks that were once on the sea floor. These were compared to micrometeorites that have been recovered in Antarctica. The researchers knew, based on previous studies, that an ice age had occurred at the time.
The space dust was recovered from the rocks by treating them with acid that can dissolve the stone, but not extraterrestrial matter. They also found elements and different forms of atoms that indicate an origin in space, rather than on Earth, in the rocks. They uncovered special helium atoms missing a neutron, which means they originated from the sun, as well as rare metals that are usually located in asteroids.
The rocks also indicate that oceans were more shallow at this time, likely because water was trapped in ice.
Together, the researchers have evidence of an influx of space dust trapped in fossilized rock as well as indications of an ice age both dating to the same time, marrying cause and effect.
"Our results show for the first time that such dust, at times, has cooled Earth dramatically," Schmitz said.
The discovery comes as the Earth is facing climate change again. But could positioning asteroids in orbit around our planet help stop global warming?
"Geoengineering proposals should be evaluated very critically and very carefully, because if something goes wrong, things could become worse than before," Heck said. "We're experiencing global warming, it's undeniable. And we need to think about how we can prevent catastrophic consequences, or minimize them. Any idea that's reasonable should be explored."