Astronomers have discovered intriguing evidence that an asteroid destroyed the Earth with dust millions of years ago. The event has greatly cooled the planet and triggered an ice age that was followed by major increases in the number of new animal species.
The work, led by Birger Schmitz of Lund University in Sweden, was recently published in Science advances and provides new information on the impact of interplanetary events on the evolution of our planet. "We know of the 10 km asteroid that crashed on Earth 67 million years ago and killed the dinosaurs, but this event was very different," Schmitz told Observer. "It happened about 470 million years ago when an asteroid 3000 times larger than the dinosaur killer was destroyed during a collision with another asteroid beyond the Mars orbit. He filled the solar system with dust and caused a strong blackout of the sunlight falling on the Earth. "
The reduced radiation caused a considerable cooling of the Earth, triggering a series of ice ages. The water froze, the ice sheet spread and the sea level dropped, creating shallow and isolated seas ideal for the generation of new species. Cold water also contains more dissolved oxygen, which would also have increased speciation. Scientists already knew that the ice ages appeared at that time and that life went through a spectacular increase in biodiversity, particularly in the sea. The first coral reefs began to grow then and strange tentacled predators called nautiloids appeared. This is known as the great biodiversity event of Ordovician, or Gobe.
Scientists discussed the cause of Gobe, but now Schmitz, after studying the dust particles in the sediments of the seabed deposited at this time, states that it was triggered by clouds of dust from asteroids. "The sediments deposited at this time are rich in the helium-3 isotope – which they could have collected only by traveling in space," he said. "It's a crucial clue."
Other scientists supported his idea. "It is not necessarily the answer to all the questions we have about Gobe, but it certainly links many observations," he told the magazine Rebecca Freeman, of the University of Kentucky, Lexington Science recently.
However, Schmitz's research also aroused interest in another reason. As the world heats up dangerously, some scientists have proposed to spread a veil of dust that should stay in the space above the Earth and reflect sunlight away from our overheated planet. The idea is controversial because it could have many unpleasant side effects, critics say.
Now the evidence shows that such an experiment occurred naturally 470 million years ago. The result was a great change in our meteorology and the evolution of life here. "It is certainly worth remembering in the coming years," added Schmitz.