03 PM | 31 Jul

Scientists discover the moon is shaped like a lemon


Although our visit to its rocky surface confirmed that it’s not covered in vast seas, it’s not home to strange moon-men, and it’s not made of cheese, the moon can still surprise us. It’s only this week that scientists have revealed that, 45 years after Neil Armstrong set foot on the planetoid, our closest celestial neighbor is not actually round.


It’s more of a squashed sphere, with a distinct lump. Ian Garrick-Bethell, who authored the study published in Nature, describes it as “like a lemon with an equatorial bulge,” or like a water balloon that flattens out as it’s spun. But why, given that it spins much slower on its axis than the Earth and has none of our planet’s plate tectonics, is the moon not a perfect sphere? Garrick-Bethell and his team instead ascribed the shape to a process known as tidal heating, in which early orbital forces between the Earth and the moon caused friction in the latter’s interior, causing its crust to expand outward in certain places. As the planetoid moved further away from our planet and slowed down its rotation, one such tidal surge was frozen in place, explaining the modern moon’s strange bulge.

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