Moon Is Lemon-Shaped

While we often picture the Moon as a perfect, silvery orb, its actual shape is a bit more peculiar. It is slightly squashed, with subtle bulges on both the side facing Earth and the one directly opposite. This makes its true form closer to that of a lemon or a water balloon that has been gently squeezed at its top and bottom. This unique distortion is a permanent relic from the Moon's fiery, formative youth more than four billion years ago.

This shape was forged by the powerful gravitational relationship between our planet and its satellite. When the Moon's crust was still molten and pliable, Earth's gravity exerted a constant tidal force on it. This force pulled more strongly on the side of the Moon closest to us, stretching it outward. As the Moon cooled and solidified, this elongated shape became locked in place. The bulge on the far side is a result of the same tidal forces, as Earth pulled the main body of the Moon away from the crust on the far side. Today, this "fossil bulge" is a frozen (Review) testament to the intense gravitational dance that shaped our nearest celestial neighbor.