Astronomers have discovered intriguing evidence that asteroid break-up has blanketed Earth with dust millions of years ago. The event dramatically cooled the planet and triggered an ice age.
The work, led by Birger Schmitz of Lund University in Sweden, was recently published in Science Advances and provides new insight into the impact of interplanetary events on our planet's evolution. "We know about the 10km asteroid that crashed on Earth 67 million years ago and killed the dinosaurs, but this event is very different," Schmitz told the Observer, "It happened about 470 million years ago when it asteroid 3,000 times bigger than the dinosaur killer was destroyed during a collision with another asteroid beyond the orbit of Mars. It filled the solar system with dust and caused a major dimming of sunlight falling on Earth. "
Reduced radiation caused Earth to cool significantly, setting off a succession of ice. Water froze, ice caps spread and sea levels dropped, isolated on a white background. Cold water therefore has more dissolved oxygen, which would therefore have boosted speciation. Scientists already knew that ice-flocculosis was going on at a great rate in biodiversity, especially in the sea. The first coral reefs began to grow then, and strange tentacled predators called nautiloids appeared. This is known as the great Ordovician biodiversification event, or Gobe.
Scientists have argued over the cause of Gobe, but now Schmitz, after studying dust particles in seabed sediments, said it was triggered by clouds of asteroid dust. "The sediments laid down at this time are rich in the isotope helium-3 – which they could only travel through space," he said. "It is a crucial clue."
Other scientists have backed his idea. "Gobe, but it's certainly a lot of observations," Rebecca Freeman, of the University of Kentucky, Lexington, told the journal Science recently.
However, Schmitz's research also has caused interest for another reason. As the world warms dangerously, some scientists have proposed that they will sit in space above the Earth and reflect on their future. The idea is controversial because it could have many unpleasant side-effects, say critics.
495 million years ago. The result was a major change in our meteorology and the evolution of life here. "It's worth bearing in my mind in coming years," added Schmitz.