Astronomers believe thousands of large undiscovered asteroids, that could cause regional damage, may be in space.

"This has been a decade-long detective story, with each recorded meteorite fall providing a new clue," said one astronomer.

NASA was recently tracking a large asteroid, known as the "city killer," after finding a small chance of it hitting Earth in 2032. NASA says it "no longer poses a significant threat" in an analysis, ...