Scientists find 'rubble pile' asteroids

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TEL AVIV, Israel, Sept. 13 (UPI) -- Asteroids made of gravel-sized rocks held together by gravity could hit the Earth like a shotgun blast rather than a single cannonball, Israeli researchers say.

It was long theorized that these "rubble pile" asteroids, if they spun fast enough, could throw off material through centrifugal force to create a second collection of rocks -- a "separated" twin -- that would spin around the sun in the exact same orbit.

Now researchers at Tel Aviv University, using the school's Wise Observatory deep in the Negev Desert, have proved the existence of these theoretical "separated asteroid" pairs, a university release said Monday.

David Polishook and Noah Brosh of the school's Department of Geophysics and Planetary Sciences say the research has not only verified a theory, but could have implications if such an asteroid passes close to Earth.

Instead of a giant solid rock colliding with the Earth's surface, Brosch says, the planet would be pelted with the innumerable pebbles and rocks that make up one of these asteroids.

This knowledge could make a difference in the defensive tactics to be considered if an asteroid were on a collision course with Earth, the researchers say.