Violent Volcanoes Knocked the Moon Off Its Axis Three Billion Years Ago

By Bryan Lufkin on at

A bunch of lunar volcanoes heated the Moon up so much, they changed its density, causing it to wander off its original axis aeons ago.

That’s according to a new study published today in the journal Nature. It all started when researchers from Southern Methodist University in Dallas noticed a lack of hydrogen deposits that are found in water-ice on the Moon’s poles—two regions that are permanently cloaked in shadow. So, since there’s no sunlight, shouldn’t there be hydrogen form ice there?

There should be, since the researchers used data from NASA’s Lunar Prospector mission in the late 1990s, which first pinpointed the hydrogen found near the Moon’s poles. That discovery was our first indication that ice exists on the surface in the first place. But what researchers found in this latest study was hydrogen from probable small trails of ice that branch out from each pole in opposite directions, each the same distance.

The team looked into it, and discovered that the cause was an extremely rare event called “total pole wander.” The team predicts that intense heating from lunar volcanoes heated the heavenly body up so much, they changed its density and its moments of inertia, causing it to tilt six degrees off its original axis, and causing those hydrogen deposits to be knocked sideways from the Moon’s original poles.

“It’d be like the Earth’s North Pole going to Greenland,” study author Matt Siegler told The Verge.

At some point in the past, the craters at those poles were exposed to sunlight, deleting all ice found there forever. It was all thanks to the Moon wandering off its original axis. It’s still unclear why those trails of hydrogen exist, since any ice that’s there has clearly been exposed to sunlight. If it’s one thing we do know, however, it’s that there’s always more to learn about our planet’s Moon.

[Nature via]