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jbWolf writes:

Planetary scientists examined NASA data concerning the moon's north and south poles. Hydrogen ice (hidden from the sun in craters), boils off when exposed to the sun. An odd offset of the ice from the moon's current north and south poles prompted a closer look at the data. Statistical analysis and modeling revealed the ice is offset at each pole by the same distance, but in exactly opposite directions. This precise opposition indicates the moon's axis—the imaginary pole that runs north to south through it's middle, and around which the moon rotates—shifted at least six degrees, likely over the course of 1 billion years starting 3 billion years ago. Ancient volcanic activity some 3.5 billion years ago probably melted a portion of the moon's mantle, causing it to bubble up toward its surface and causing an internal shift of the moon's mass.

The article can be found here.

Lunar true polar wander inferred from polar hydrogen (DOI: 10.1038/nature17166)

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