The big dark spots on the surface of our moon that give it the appearance of having a face were caused by massive pools of moon lava that cooled billions of years ago. When we first started sending satellites up there to take pictures of the “darkside,” we expected to find similar dark blotches. There were none. It was a uniform shade of white, pocked with regular old craters. There was no face – no Mare in the Moon.
Current data suggests that the “darkside” of the moon has a crust that is 40 miles thicker than the side that we can see, so very little moon lava ever made it to the surface, thus the “darkside’s” lack of a “face.” After decades of mystery, recent computer simulations doing intensely complex moon math have figured out the most likely reason for this major difference between the two sides of the moon.
Once upon a time, there was not one moon, but two – a big moon, and a little moon – both born of the same collision with Earth. Over the course of billions of years, the two moons fused, creating the wonder we see today.
So when you look up at the night sky, and see those dark patches (that really do look like the Mare in the Moon), remember: that imprint is only there because a long, long time ago, a big sibling imprisoned a little sibling there.
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