In popular mythology going back ages, the Moon is actually constructed out of green cheese. We know today that this is most certainly not the case, but many people are not exactly sure what the Moon is made of.
When we look at the Moon, we see two primary colorations: a light grayish color and a darker almost bluish grayish color, popularly known as the “seas” of the Moon.
The light gray areas are the crust leftover from the formation of the Moon, about three and a half billion years ago to four billion years ago.
The dark gray areas, on the other hand, are actually volcanic rock. Billions of years ago there were many volcanoes on the Moon, and they changed the surface of the Moon. This rock is much like volcanic rock you would find on Earth today in a place like Hawaii, only much older.
One of the reasons that the green cheese myth was so popular was the appearance of pockmarks and other shapes on the Moon’s surface. These are actually craters caused by meteorites striking the Moon’s face.
Three and half billion years ago, our little corner of the solar system was a much more violent place. Huge meteors and meteorites filled the sky, and a great number of these crashed into the Moon, forever changing its surface. Some of these craters are hundreds of miles wide!
Fortunately for us, the Earth was not nearly as devastated by meteorites as was the Moon. For one thing, the Moon served as somewhat of a buffer, protecting us from many of the meteorites. We also have a much thicker atmosphere than the Moon, so it is much more difficult for meteorites to strike the surface of the Earth, they will most likely burn up or disintegrate in entry.