Why the moon hits your eye like a big … lemon?

BY Justin Scuiletti  July 31, 2014 at 4:42 PM EST
That's not Amore, that's a lemon. Photo by Flickr user Paolo Nespoli

That’s not amore, that’s a lemon. Photo by Flickr user Paolo Nespoli

Scientists have finally made lemonade out of the origins of our lemon-shaped moon.

While the moon may look, to quote crooner Dean Martin, like a big pizza pie — the real shape is a bit more similar to a lemon. To explain, a study published in the journal Nature says, one needs to go back to when the satellite first formed.

“This happened a long time ago, when the moon was not completely solid,” said Ian Garrick-Bethell, lead author of the study. “This was in the first 100 to 200 million years of lunar thermal evolution.”

The moon consisted initially of liquid, molten rock. As the rock began to cool and solidify, the process was not even; the thin outer crust hardened first and continued to float on the molten core. The moon, at that time, was spinning rapidly, its shape bulging at the equator similar to the same effect you see in a spinning water balloon. All the while, its close proximity to earth allowed tidal and gravitational forces to pull at the thin crust, further distorting it. As it began to move away from Earth and cool more completely, the odd shape “froze” in place.

Garrick-Bethell told Space.com that solving the lunar mystery can aid in future studies of gravitational effects on celestial objects. “Chipping away at this problem of the shape of the moon can give us insight into those types of fundamental geology problems,” he said.