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Chicxulub crater may be result of binary impact

The dino-killing asteroid is usually thought of as a single rock with a diameter of 7 to 10 kilometres, but it may really have been two widely separated rocks with that combined diameter.

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.
"It's been known for 15 years that about 15 per cent of near-Earth asteroids are binary," says Katarina Miljkovic' 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?

Miljkovic' and her colleagues have found an explanation. They ran computer simulations of binary asteroids hitting Earth and found that they often form a single crater.
The simulations also suggest that it is possible to identify which of Earth's single craters had binary origins. These craters should be subtly asymmetrical, and that makes the crater near Chicxulub in Mexico thought to be the result of an asteroid impact 65.5 million years ago that wiped out the dinosaurs a strong candidate.

"The Chicxulub crater shows some important asymmetries," says Miljkovic'. "It is worth considering that it was formed by a binary asteroid."

Morphology and population of binary asteroid impact craters