The Surface of The Moon

In my view, to understand the moon as it appears today it is necessary to understand that it was once much closer to the earth than it is now.

The same side of the moon always faces the earth, meaning that it's rotation period is the same as it's orbital period around earth. The far side of the moon is more heavily cratered than the side that faces us, but lacks the dark lava "seas" that we can see on the surface of the moon. But this should not be a surprise at all if we consider that the moon was once much closer to us. These lava "seas" were formed by tidal force exerted by the earth.

If the moon, as far away as it is today, can exert tides in the earth's oceans due to the difference in the moon's gravitational effect between the surface of the ocean, because it is closer to the moon, and the bottom of the ocean which is further from the moon, then what tidal effect do you suppose the earth would have exerted on the moon when it was much closer to us? Considering also that the earth is about 81 times the mass of the moon.

There would have been volcanic tides on the moon, which would have formed the "seas" that can be easily seen on the moon. This explains why no such seas are to be seen on the far side of the moon. The close distance of the long-ago time also locked the moon's rotation to that of the earth, so that the same side always faces us. This would not be possible if the moon had not once been much closer to us, because today the gravity of the sun has more than twice the effect on the moon as that of the earth. (To understand why the moon still appears to orbit the earth, see "The Earth, The Moon And, The Sun")

As for the craters, which were formed by meteor impacts on the moon, we see why the far side is more cratered when we consider that the moon was once much closer to the earth. Most meteors would come from the direction in space away from the sun. When the moon was further from the sun than the earth, at full moon, the far side of the moon would be struck with a lot of meteors. But when the moon was between the earth and the sun, at new moon, the side of the moon that faces us would have the earth acting as a shield against meteors.

This is why we see the two sides of the moon as so different. The side facing toward us has the lava "seas", and fewer craters, while the side facing away from us lacks the seas but is more heavily cratered. The craters on the side facing us are also likely newer because this side of the moon would be more exposed as it moved further from earth, while that would not be true for the far side of the moon. The reason that the earth does not have craters like the moon is due to the erosion on earth, but long-ago meteor impacts is why we have deposits of metals in various places.