The Lunar Interior

A few hints:

The Moon has no magnetic field
The average density of the Moon is similar to that of ordinary rock (rho ~ 3.4 g/cm³)

What does this tell us about the Moon's interior?

Where does the rest of our information on the interior come from? Moonquakes!

How do we monitor moonquakes?
Where do moonquakes come from?

The Moon has a thick, solid lithosphere (unlike the Earth), and therefore has no plate tectonics -- no surface activity.

Many silicates are found in the Moon's crust -- composition similar to that in the Earth's mantle.

In the crust, many refractory elements (high melting points) and few volatile elements (low melting points) are found, suggesting the Moon's surface was originally very hot. The volatile elements ``boiled off.''

The inner portions of the Moon are somewhat denser then the crust, but any iron-rich core must be very small.

Why is the moon solid, while the Earth has a molten interior?

Cooling Time of a planet:

Rough consideration: The amount of heat production in a planet is proportional to its volume (ie more radioactive material, or more mass, etc):

The rate at which it looses heat is proportional to its surface area:

So the cooling rate is proportional to the planets radius:

Larger planets cool more slowly. Small planets or moons cool quickly.

Why are all the maria on the near side?

The center of mass of the moon is not at the moon's geometric center! The center of mass is actually about 2 km closer to the Earth than the geometric center.Why might that be?

So the near side crust is thinner; molten material (in the early history of the Moon) could more easily reach the surface to form lava basins.