August 3, 2011

Early Earth, Two Moons Into One

clipped from www.nature.com

Early Earth may have had two moons

Collision with lost second satellite would explain Moon's asymmetry.

Earth once had two moons, which merged in a slow-motion collision that took several hours to complete, researchers propose in Nature today.

colliding moons
A previous collision with a smaller companion could explain why the Moon's two sides look so different.Martin Jutzi and Erik Asphaug
Both satellites would have formed from debris that was ejected when a Mars-size protoplanet smacked into Earth late in its formation period. Whereas traditional theory states that the infant Moon rapidly swept up any rivals or gravitationally ejected them into interstellar space, the new theory suggests that one body survived, parked in a gravitationally stable point in the Earth–Moon system.
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This is a different theory than the one about a Mars size body striking the Earth early in its development which gave rise to the Moon. These researchers posit that our planet once had 2 moons and they joined to form one. Interesting indeed.

Filed under General Astronomy by admin

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