Did you know that the surface of the moon on the side we do not see is actually different from the side we can see?
When you look up and see the ‘man in the moon’ you are actually looking at the ‘maria’, or seas, that form the flat basins of major impact craters. In 1959 after we got to see the far side (courtesy of the Soviet space program) it was noted that there are far fewer of these ‘seas’ on that side. And no one knew why … and the Lunar Farside Highlands Problem was born.
Well now we think we know the hows and whys.