Two Moons for Planet Earth?

A new theory suggests that, after 80 million years of co-existing, a slow collision between our current Moon and a smaller, second Moon occurred. Is this how the mountains on the far side of the Moon formed?

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General Information

Questions for Classroom Discussion

  • How did the Moon form?
  • What is the physical evidence that has led scientists to believe there was a second Moon?
  • Define how the collision took place and the aftermath.
  • How could scientists prove this new idea?
  • What is the significance of this idea of there once being a second Moon?

Compiled August 8, 2011, by L.A. Guertin

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