Dinosaur-killing space rock was a terrible twosome

摘要

Asteroids 2, dinosaurs o. The infamous space rock that slammed into Earth and helped wipe out the dinosaurs may have been a binary - two asteroids orbiting each other. This surprise conclusion emerges from a new look at the likelihood of binary craters forming on Earth, and could spell bad news for those hoping to protect our world from future catastrophic collisions. Earth bears the scars of a few twin-asteroid impacts: the Clearwater Lakes near Hudson Bay in Canada, for instance, are craters that formed together about 290 million years ago. But just one in 50 craters on Earth comes in a pair. That is a puzzle because counts of the rocks zooming around near Earth suggest binary asteroids are far more common than that.