Friday, December 19, 2008

Could the Earth once had multiple moons?

An article in the Daily Galaxy has a pretty interesting article that has science fiction story written all over it!

Did multiple moons once orbit Earth? The prevailing theory about the formation of the moon is called the giant impact hypothesis: the theory goes that a Mars-sized object, known as Theia, crashed in to the young Earth. What was left was Earth, and its moon. A new computer model suggests, however, that the Moon may not have been the only reminder of that big collision. The model also suggested that moonlets called Trojans may have been left behind in the collision. These Trojans could well have been caught in the Langrangian points and have persisted in that manner for for up to 100 million years.

The Langrangian points of course are gravity balanced areas in Earth orbit. Over time influences from the other planets would have shifted Earth's orbit ever so slightly, but this would have spelt doom for any moonlets being held in place. They could have been destroyed or pushed out into the solar system. Other models have suggested that much smaller moonlets only a few 10s of kilometers across could have lasted much longer, upwards of a billion years.

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