Why is there no maria on the far side of the moon?

Question

Explain tidal locking as simple as you can as well.

Answer 1

Actually, there's a few areas where Maria exists, but they're very small. And, this is most likely due to the fact that most in-bound asteroids heading toward the moon are intercepted by the Earth. The far side has no such protection, and is always exposed to deep space (and rocks barrelling in...)

the moon's center of gravity is *not* at the center of the moon - it's a couple of hundred miles away from it's core, facing the Earth. The moon at one time rotated, but because of this lopsided mass, and Earth's gravity acting on it, it's rotation grew slower & slower, until finally the side with the most mass contnually faced Earth.

Answer 2

Lopsided mass is probably a poor description. Tidal influences caused by the earth gravity caused small shape changes in the moon during it rotation and orbit and these small non sysmetrical tugs are what slowed it's axial rotation. The same effect applies to most moons (and planets - ie see Mercury now tidally locked to the sun).

In Minor Planet (asteroid) work we seen many synchronous moons orbiting them (there are of course still a lot of asynchronous binaries as well)

Answer 3

The moon's crust facing the earth is thinner than on the far side of the moon. Therefore magma on the near side had less distance to travel before it hit the surface. It took less time for the magma to move up and break out, than on the far side where it had further to travel. Magmas may have formed on the far side also, but hardened before they reached the surface.

Answer 4

because of the earth's gravity, the underground lava was pulled closer to the surface on the near side than the far side. In other words, the crust is thinner on the near side, and so it was more easily punctured by impacts.