By Donna Lu
A meteor caused a massive explosion over Earth last year, but nobody noticed until now. It is the second-largest recorded impact in the past century, after the meteor that exploded over the Russian region of Chelyabinsk in 2013.
The giant fireball hit at 2350 GMT on 18 December over the Bering Sea, a part of the Pacific Ocean between Russia and Alaska.
Peter Brown at the University of Western Ontario, Canada, …