Some 466 million years ago, long before the Age of Dinosaurs came, the Earth froze.The seas began to freeze at Earth’s poles, and the new range of terrestrial temperatures set the stage for an explosive emergence of new, evolving species. The cause of this ice age was a mystery, until now: a new study published in the journalScience Advances argues that the ice age was caused by global cooling, triggered by additional dust in the atmosphereafter a collision of giant asteroids in outer space.
Thus, scientists say that a huge dust cloud that swept across the ancient solar system sent Earth into a small ice age that caused an explosion in the planet’s early life.
Space dust was created when a large asteroid shattered in a violent collision somewhere between Mars and Jupiter nearly half a billion years ago.
The destruction of the 150-kilometer-wide space rock scattered so much dust in the inner solar system that it blocked some of the sunlight reaching Earth,the researchers say. As a result, temperatures dropped for at least 2 million years. Because the cooling lasted so long,life on Earth had time to adapt.And while many species remained unaffected in the warmer places near the equator, others evolved to take full advantage of the newly formed cooler regions of the world.
“This is the first time that dust from a ruptured asteroid has been shown to lead to cooling that triggers an ice age on Earth,” said Birger Schmitz, professor of nuclear physics at Lund University, Sweden. and co-author of the work.
Clearing up a mystery
The drop in temperature encased the water in ice that covered much of the planet, causing the sea level to drop globally. The period coincided with an apparent increase in the diversity of life on the planet, where most of it was still in the oceans.
Hoping to shed light on the mysterious ice age, scientists went looking for clues in ancient limestone rocks exposed at sites in southern Sweden and near St. Petersburg in Russia. In particular, they searched for remains of the huge asteroid, which geologists call the “body of the chondrite L parents.”
The researchers used acid to dissolve more than a ton of limestone rocks of different ages from the sites. Then they picked up what was left behind. They found that after the destruction of the asteroid, the abundance of grains matching its chemical composition increased between 1,000 and 10,000 times. The levels remained high for 2-4 million years. “The grains come with the dust, so when you see an increase in these, you know that there has been an increase in the dust,” Schmitz clarified.
Additional tests on the ancient limestone revealed a similar spike in the levels of a helium isotope flowing from the sun in the wave of particles known as the solar wind. Researchers believe that helium was brought to Earth when it became embedded in the finest dust particles from space as they traveled through the solar system.
The researchers describe how dust and coarse-grained particles from the asteroid’s destruction rained down onto Earth and embedded themselves in sedimentary rocks. “We can say that this ice age began to form when the dust from the rupture fell to Earth,” said Schmitz.
Scientists call the apparent explosion in marine life at the time of the Great Ordovician Biodiversification Event, or GOBE. David Harper, a paleontologist at Durham University who worked on the study, said it was “the most spectacular walk of marine diversity in the history of life.”
“Ice ages have been associated with large volcanic eruptions, but for the first time the team has implicated asteroid-derived dust in the onset of global cooling and a huge leap in biodiversity that changed marine ecosystems forever,” concluded the expert.
This discovery comes as the Earth faces climate change again. But could the positioning of asteroids in orbit around our planet help stop global warming?
Referencia: B. Schmitz el al., “An extraterrestrial trigger for the Mid-Ordovician ice age: Dust from the breakup of the L-chondrite parent body,” Science Advances (2019). advances.sciencemag.org/content/5/9/eaax4184
