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01/23/14 David Stevenson SO/NOAO Joint Colloquium Series


David Stevenson, CalTech
Origin of the Moon

This is a puzzle and the problem has only grown bigger as we study it more closely. It is as if one grabbed a piece of Earth, dusted it off (i.e., got rid of some volatiles) and put that in Earth orbit. A Darwinian story (George Darwin, that is) but getting the dynamics to work and satisfy all the isotopic and other evidence has proved increasingly challenging. There seems little prospect of any explanation for the moon that does not involve a giant impact on Earth but the projectile should have left some of its distinctive signature in the resulting moon. I will discuss the current dynamical and impact modeling efforts to resolve this problem and put this story in the broader context of why Venus has no moon and whether there should be binary planets elsewhere in the universe.

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