(I)If we could cut the Moon in half, we would find that it's made of three different parts. (II) In the middle is a small ball of hot, heavy, partly melted rocks called the core. (III) To scientists, the Moon is like a world frozen in time. (IV) Around this core is a deep layer of lighter, but still partly melted, rocks called the mantle. (V) Finally, on top of the mantle is the Moon's rocky outer skin, or crust.