A huge collision in the Solar System’s asteroid belt may have triggered an ice age on Earth that froze our planet... some 466 million years ago.
Eggheads believe a 93-mile wide space rock floating between Mars and Jupiter was smashed to pieces as it crashed into something else, perhaps another cosmic boulder. The prang showered our home world with dust, which blocked out the Sun’s rays and chilled global temperatures.
Particles from space enter the Earth’s atmosphere all the time. However, the abundance of debris coming our way after that particular collision was particularly high. "Normally, Earth gains about 40,000 tons of extraterrestrial material every year,” said Phillip Heck, coauthor of a study into the super-smash, published in Science Advances and an associate professor at the University of Chicago, this week.
“Imagine multiplying that by a factor of a thousand or ten thousand.To contextualize that, in a typical year, one thousand semi trucks' worth of interplanetary dust fall to Earth. In the couple million years following the collision, it'd be more like ten million semis.”
After about two million years, the dust levels accrued enough to clog up Earth's atmosphere and prevent sunlight and heat from getting through. “Our results show for the first time that such dust, at times, has cooled Earth dramatically," said Birger Schmitz, lead author of the paper and a geology professor at Lund University, Sweden.
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For this research, the team of scientists studied ancient rocks found on Earth from nearly 470 million years ago for signs of extraterrestrial material, clues that would suggest the chunks were formed from bits of rock from outer space – such as an asteroid prang. The rocks were compared to micrometeorites from Antarctica.
"We studied extraterrestrial matter, meteorites and micrometeorites, in the sedimentary record of Earth, meaning rocks that were once seafloor. And then we extracted the extraterrestrial matter to discover what it was and where it came from," said Heck. The presence of strange isotopes and rare metals signaled the dust came from the depths of the galaxy.
It’s been well established that the Earth was experiencing an ice age around that time. The terrestrial rocks from seabed also signaled that the oceans were shallower at that time, something the researchers took as a sign that some of that water was trapped in sea ice and glaciers. Together with the presence of elevated levels of space dust, the team have pieced together evidence of how the ice age started. "The timing appears to be perfect," said Schmitz.
Since the ice age took hold gradually over millions of years, it was a more gentle deep freeze unlike the one that led to the extinction of the dinosaurs. “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,” said Heck.
Sending up massive plumes of dust isn’t a quick fix to counter global warming, however, he warned. "Geoengineering proposals should be evaluated very critically and very carefully, because if something goes wrong, things could become worse than before." ®