The oldest rocks on the moon are about the same age as the earth.
The moon, earth's single natural satellite, was a geological mystery until the first moon landing in 1969, where the astronauts picked up rocks and soil samples to bring back and study for their composition and chemical makeup. Although scientists can only speculate about the interior and core materials of the moon, we have learned much more about the surface composition as a result of many missions which gathered rock and soil samples from various locations.
The Moon Core Material
The moon is composed of layers very much like earth. The first or innermost layer composes the core, which tabulates to about 20 percent of the moon's diameter. Scientists believe that metallic iron resides in the core, along with various small amounts of nickel and sulfur. Astronomers surmise that the core of the moon is partly molten, consisting of melted iron.
Mantel
The next layer outside the moon's core consists of the mantle, the largest area of the Moon's solid surface. The lunar mantel is quite shallow at the top, uppermost layer, with roughly a depth of 31 miles below the moon's surface. Scientists believe the mantel consists of rock material containing the minerals clinopyroxene, orhtopyroxene and olivine. It is also believed that the moon's mantel contains more iron than earth's does.
Crust
The moon's outermost or top layer contains the crust, which on average, reaches down to a depth of 31 miles. Samples have shown that several chemicals and minerals are present in the majority of rock samples, such as aluminum, calcium, iron, magnesium, silicon and oxygen. Trace elements have been found containing hydrogen, potassium, uranium, thorium and titanium.
Moon Powder
The moon has rolling layers of fine, powdery soil, scattered among small rocks called regolith. Regolith consists of fine particles that were produced as a result of repeated meteor and asteroid impacts. Every moon crater has a perimeter of ejected material around it called the ejecta blanket.
Geographic Distinctions
The material in the lowest elevations on the moon, like the maria (seas) consist mostly of dark basalts, which occurred during volcanic activity and very rapid cooling. The rocks in the highland areas consist mainly of anorthosite, which is similar to igneous rock after it has cooled more slowly than basaltic rock. Specimens have been found scattered in the maria and highland areas called breccias. Breccias result when meteors strike a surface, then weld or combine with the minerals due to heat and high pressure.
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