Thomson ReutersFebruary 15, 2013 18:30
* Events are unrelated, scientists say
* Asteroid DA14 was closest known object of its size
* Meteor exploded over Russia, injuring 1,200
By Irene Klotz
BOSTON, Feb 15 (Reuters) - An asteroid half the size of a football field passed closer to Earth than any other known object of its size on Friday, the same day an unrelated and much smaller space rock blazed over central Russia, creating shock waves that shattered windows and injured 1,200 people.