Creatures of the seafloor in the late OrdovicianAstronomers in Sweden have discovered new evidence that an exploding asteroid blanketed Earth's atmosphere with dust about 470 millions of years ago, causing the planet to cool dramatically. The ice ages that followed led to a rapid increase in the number of new animal species, a stage in the evolution of life on Earth which scientists call the Great Ordovician Biodiversification Event (or GOBE).
Asteroid destroyed following a collisionAccording to the team led by Birger Schmitz of Lund University, Sweden, the asteroid measured 150 kilometres (nearly 100 miles) across. That's 3000 times bigger than the one that crashed to Earth 66 million years ago, wiping out the dinosaurs and many other species. The asteroid was destroyed during a collision with another asteroid beyond the orbit of Mars. Vast clouds of dust from the collision would have swirled around the inner Solar System. About 1000 times the current levels of dust gathered in Earth's atmosphere, causing a major dimming of sunlight falling on Earth. This caused the planet to cool significantly, setting off a series of ice ages. As water froze and became "locked up" in the expanding ice caps, sea levels dropped.
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