Researchers from the Pennsylvania State University in the US, may have solved a 55-year-old moon mystery.
Though everyone can make out the ‘man in the moon’ – in the Earth-facing side – no ‘face’ exists on its far side. It is believed the man in the moon appeared when meteoroids struck the near side, creating large flat seas of basalt that we see as dark areas called maria.
It was called the dark side because it was unknown, not because sunlight does not reach it. Researchers immediately noticed that fewer ‘seas’ or maria existed on this portion of the moon that always faces away from the Earth.
Arpita Roy, a graduate student in astronomy and astrophysics at Penn State, realized that the absence of maria, which is due to a difference in crustal thickness between the side of the moon we see and the hidden side, is a consequence of how the moon originally formed.
Earlier in its history, large meteoroids struck the nearside of the moon and punched through the crust, releasing the vast lakes of basaltic lava that formed the nearside maria that make up the man in the moon. When meteoroids struck the far side of the moon, in most cases the crust was too thick and no magmatic basalt welled up, creating the dark side of the moon with valleys, craters and highlands, but almost no maria.
