Though it was once believed that all asteroids are giant pieces of solid rock, later hypotheses have it that some are actually a collection of small gravel-sized rocks, held together by gravity. If one of these "rubble piles" spins fast enough, it's speculated that pieces could separate from it through centrifugal force and form a second collection — in effect, a second asteroid.
Now researchers at Tel Aviv University, in collaboration with an international group of scientists, have proved the existence of these theoretical "separated asteroid" pairs.
Ph.D. student David Polishook of Tel Aviv University's Department of Geophysics and Planetary Sciences and his supervisor Dr. Noah Brosch of the university's School of Physics and Astronomy say the research has not only verified a theory, but could have greater implications if an asteroid passes close to earth. Instead of a solid mountain colliding with earth's surface, says Dr. Brosch, the planet would be pelted with the innumerable pebbles and rocks that comprise it, like a shotgun blast instead of a single cannonball. This knowledge could guide the defensive tactics to be taken if an asteroid were on track to collide with the Earth.
A large part of the research for the study, recently published in the journal Nature, was done at Tel Aviv University's Wise Observatory, located deep in the Negev Desert — the first and only modern astronomical observatory in the Middle East.
via American Friends of Tel Aviv University: Avoiding an Asteroid Collision.
This may explain, without bringing aliens into the picture, how it is possible that I saw two different meteors with snaking green tails about a minute apart headed in the same direction. They were a pair and one got pulled into the atmosphere a minute before the other one.