Mar 28, 2016 I Paul Seaburn

The Moon is Shifty, Off-Kilter and a Wanderer

If the Moon was a politician, the news that it is shifty, off-kilter and an aimless wanderer would blare from TV news shows and the front pages of tabloids, propelling the Moon to the top of some polls and the bottom of others. Since it instead appeared in the journal Nature under the headline “Lunar true polar wander inferred from polar hydrogen,” it only generated excitement in the science and astronomy communities. Too bad because this is big news.

Researchers studying photographs of the Moon from NASA's Lunar Prospector mission launched in 1998 found proof that water ice exists on the frigid shadowed floors of craters near its poles as expected. However, it was also found in unexpected areas away from the poles in spots that were getting hit by sunlight. Since this is different than most other planetary bodies, the cause was puzzling and worth further investigation.

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How the moon has changed its orientation with respect to the Earth

Planetary scientist Matt Siegler at Southern Methodist University in Texas and a team of astronomers studying the out-of-place ice found that it was located exactly the same distance from the Moon’s north and south poles but in opposite directions. The ice spots were 125 miles or 6 degrees from each pole. What does this mean?

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Maps showing the location of the Moon's poles and the out-of-place ice

Siegler speculates that the Moon’s axis has moved and, based on the age of the ice, the shift occurred over a billion years ago.

Billions of years ago, heating within the Moon's interior caused the face we see to shift upward as the pole physically changed positions," he said. "It would be as if Earth's axis relocated from Antarctica to Australia. As the pole moved, the Man on the Moon turned his nose up at the Earth.

This means the Moon is a "true polar wanderer” and a member of an exclusive group of them consisting of Earth, Mars, Jupiter's moon Europa and Saturn's moon Enceladus. The Moon wins the prize for the “Best of Shifts” because its off-polar ice shows exactly how far it has tilted. The shift was caused by massive magma activity in the Procellarum plain that caused a heavy blob to form big enough to throw the Moon off-kilter.

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A cross section illustration showing how internal magma pushing to the surface in one large blob may have caused the Moon's poles to wander

The age of the ice makes this an even bigger discovery, says Siegler.

We don't know where the Earth's water came from. It appears to have come from the outer solar system well after the Earth and moon formed. Ice on other bodies, like the moon or Mercury, might give us a clue to its origin.

A clue to the origin of Earth’s water from a shifty, off-kilter wanderer. If it was running for office, would you ignore those faults and vote for the Moon?

Paul Seaburn

Paul Seaburn is the editor at Mysterious Universe and its most prolific writer. He’s written for TV shows such as "The Tonight Show", "Politically Incorrect" and an award-winning children’s program. He's been published in “The New York Times" and "Huffington Post” and has co-authored numerous collections of trivia, puzzles and humor. His “What in the World!” podcast is a fun look at the latest weird and paranormal news, strange sports stories and odd trivia. Paul likes to add a bit of humor to each MU post he crafts. After all, the mysterious doesn't always have to be serious.

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