1) How was it formed, 2) what is it made of, and 3) how far away is it are some of the questions that we can begin to answer.
1) How was the Moon formed?
There were at least five major ideas that were proposed as to the formation of the Moon.
Fission – The Moon split off from the Earth.
Capture – The Moon was captured by the gravity of the Earth.
Condensation – The Moon coalesced out of the same “stuff” the Earth did.
Colliding Planetesimals – Formed from colliding Planetesimals during the early formation of the solar system.
Collision – A body collided with the Earth causing a piece of the Earth’s crust to form the Moon from a resultant ring produced by that collision
The evidence points to the collision theory. First, the Moon does not have an iron core. This pretty much rules out that it coalesced from the same cloud of debris that the Earth did. Second, throughout the solar system, the oxygen isotopes have been found to be different. If the Moon were captured, it too would not match the Earth’s oxygen isotope ratio (which it does). Fourth, by looking at the angular momentum and energy required, the theory that the Moon spun off the Earth after the Earth formed does not hold up.
This leaves us with the Collision theory as the best model we have for the formation of the Moon. The resultant collision caused a ring of debris from the Earths crust to form outside the Roche limit. If it had not, tidal forces would have not allowed for the Moon we see today.
A more in depth discussion of tidal locking since the Moon is tidal locked to the Earth. The reason the Moon keeps one face to the Earth (Its rotation on its axis matches the period of its orbit) is it is tidally locked to the Earth. Here is a more in depth explanation. The total angular momentum of the earth moon system, which is spin angular momentum plus the orbital angular momentum, is constant. (The Sun plays apart also) Friction of the oceans caused by the tides is causing the Earth to slow down a tiny bit each year. This is approximately two milliseconds per century causing the moon to recede by about 3.7 centimeters per year. As the Earth slows down, the Moon must recede to keep the total angular momentum a constant. In other words as the spin angular momentum of the earth decreases, the lunar orbital angular momentum must increase. Here is an interesting side note. The velocity of the moon will slow down as the orbit increases.
Another example of tidal locking is the orbit period and rotation of the planet Mercury. What is interesting about this one is that instead of a 1:1 synchronization where Mercury would keep one face to the Sun at all times, it is actually in a 2/3:1 synchronization. This is due to the High eccentricity of its orbit.
There also can be more than one body “locked” to each other. Lets take a look at the moon Io. Io is very nearly the same size as the Earth’s moon. It is approximately 1.04 times the size of the moon. There is a resonance between Io, Ganymede, and Europa. Io completes four revolutions for every one of Ganymede and two of Europa. This is due to a Laplace Resonance phenomenon. A Laplace Resonance is when more than two bodies are forced into a minimum energy configuration.
2) What is the Moon made of?
From here:
http://lunar.arc.nasa.gov/science/geochem.htm
“Primary elements: The lunar crust is composed of a variety of primary elements, including uranium, thorium, potassium, oxygen, silicon, magnesium, iron, titanium, calcium, aluminum and hydrogen. When bombarded by cosmic rays, each element bounces back into space its own radiation, in the form of gamma rays. Some elements, such as uranium, thorium and potassium, are radioactive and emit gamma rays on their own. However, regardless of what causes them, gamma rays for each element are all different from one another -- each produces a unique spectral "signature," detectable by an instrument called a spectrometer. A complete global mapping of the Moon for the abundance of these elements has never been performed.
Hydrogen and helium: Because its surface is not protected by an atmosphere, the Moon is constantly exposed to the solar wind, which carries both hydrogen and helium -- each potentially very valuable resources. One natural variant of helium, [3]helium, is the ideal material to fuel fusion reactions. When scientists develop a more thorough understanding of fusion, and can practically implement such reactions, the Moon will be a priceless resource, since it is by far the best source of [3]helium anywhere in the Solar System.”
This pretty much answers the question; are there valuable materials up there?
3) What is the distance to the Moon?
The mean distance to the Moon is approximately 238,800 miles. From past experience, we can design spacecraft to get there in about three days. This is far shorter than the months the early voyages took to the new world.
Final thoughts on the Moon.
So here we have this tremendous resource at our fingertips. Unfortunately (not unlike the early explorers), the initial cost is staggering. However, in the long run it would end up being an invaluable resource for both material and scientific study. One of the big advantages is that the Moon keeps one side facing the Earth. This minimizes communication problems between the two bodies. Also since the backside of the Moon is shielded from the Earth, it would be an ideal spot to place a radio telescope array.
First, the Moon does not have an iron core. This pretty much rules out that it coalesced from the same cloud of debris that the Earth did.:') That is evidence in support of capture. The apparent lack of an iron core -- the Earth's is 90 per cent iron, with about 10 per cent other stuff -- also suggests it wasn't born of the Earth, but obviously, either through an impact or an overspin one could suppose it would be made of core material. It would indicate a formation further out in the solar system.
If the Moon were captured, it too would not match the Earth’s oxygen isotope ratio...There's no reason to expect it wouldn't -- the supposed impactor would contribute some (http://www.lpi.usra.edu/meetings/lpsc2000/pdf/1669.pdf assumes 50 per cent) of the lunar material, which means the supposed impactor must have had oxygen isotopes essentially identical to those of the Earth. It's simpler to say, there were two, not three. In addition, the lunar surface has been under bombardment continually for billions of years, and the oxygen isotope ratios of the incoming material must have had no contaminating effect at all.
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