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Early Earth May Have Had Two Moons

Full Moon

Once upon a time the Earth may have had two moons, which merged together in a slow-motion collision over the course of several hours. According to scientists, this could be why our current lunar orb is lumpier on one side than the other.

The shape of the moon has always baffled scientists. The side facing the Earth is low and flat, while the side facing away from the earth has a thicker crust and a high, mountainous look. A new computer model explains the differences in each side of the moon with a collision early in the Earth’s history. The collision would have left the far side rocky and hard, creating what scientists refer to as the lunar highlands. Who knew the moon’s surface was so complex?

In order for the collision to have taken place, scientists say one moon would have had to run into the other at about 4,400 miles an hour. This is the slowest possible speed for the orbs to go if they were to fall into the gravity of one another. It’s too slow to actually carve a crater, but fast enough to plaster materials from one moon to the other, molding them into one lump of rock.

The two could have moons existed harmoniously for about 80 million years, each with its own stable orbit and one at about three times the size of the other. Natural gravity interactions caused them to drift further away from the planet, while the gravitational pull of the sun desensitized the orbit of the smaller moon, causing it to fall right into place with the bigger one.

Sounds like things went down pretty smoothly, but trillions of tons of debris would have been sent into space, hiding both moons for a few days, then sending meteor showers to Earth for the next MILLION years after the single moon showed back up. Not just any meteor shower, either. Some of the pieces could have been 62 miles wide. That’s big enough to wipe out Los Angeles, and then some.

Scientists are still trying to figure out why there is a higher level of aluminum on the lumpier side of the moon, but if anything, this discovery opens up new doors to discover more about what went down before we all showed up on Earth.

Via National Geographic
Image credit: NASA

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