New Scientist
Image: Calsidyrose
Asteroids 2, dinosaurs 0. The infamous space rock that slammed into Earth and helped wipe it clean of large dinosaurs may have been a binary – two asteroids orbiting each other. The surprise conclusion comes from a re-evaluation of the proportion of asteroid craters on Earth that were formed from binary impacts. It could also spell bad news for those hoping to protect our world from catastrophic collisions in future.
Earth bears the scars of twin-asteroid impacts: the Clearwater Lakes near Hudson Bay in Canada, for instance, are really twin craters that formed about 290 million years ago. Examples like Clearwater are rare, though. Just 1 in 50 of craters on Earth come in such pairs.
That is a puzzle because counts of the rocks zooming around in the vicinity of Earth suggest binaries are far more common. “It’s been known for 15 years that about 15 per cent of near-Earth asteroids are binary,” says Katarina Miljkovi? at the Institute of Earth Physics in Paris, France. All else being equal, 15 per cent of Earth’s impact craters should be the result of twin impacts. Why does the real figure appear so much lower? Read more on newscientist.com
