Researchers now believe the killer space rock could have been two asteroids orbiting one another. Binary asteroids are actually quote common making up about 15% of those that pass near to the Earth. The craters from such impacts can be found in various places around the world such as those at Clearwater Lakes near Hudson Bay in Canada which formed 290 million years ago. Some binary asteroid impacts are also thought to create only a single crater making it difficult to determine exactly how frequently the Earth is impacted by them.If indeed two large asteroids slammed in to the Earth at the end of the Cretaceous then it is no surprise that the dinosaurs went extinct, it also means that we may have more trouble than expected if we were to be ever faced with deflecting a binary asteroid from impacting the Earth again in modern times.