More than a dozen meteorites found on Earth are currently assumed to come from the Moon. The first was designated ALH 81005, found near th> Basalt is a volcanic rock, composed chiefly of plagioclase/feldspar and pyroxene.. Breccias are fragments of rock cemented together under heat and pressure.
The outer layer of the moon's surface is the regolith, which can be up to about 10 meters deep (shallower in the maria, 2-8 meters). It is composed mostly of fine particles..
The highlands are the brighter and older parts of the surface. They are composed of light-colored igneous rocks and cover 80% of the surface (but only 65% of the visible face). These highlands are the result of meteorite impact - material that has 'flowed away' from major impact points.
The maria are expanses of volcanic basalt laid down about 3 - 4 billion years ago, filling giant impact craters about 1 billion years after these impact craters were formed. The older impact craters had lost their shape a bit due to later impacts (e.g. Sea of Tranquility and Sea of Fertility), but the younger ones retain a more circular shape (e.hg. Mare Crisium, Sea of Serenity and Mare Nectaris). The Mare Imbrium (Sea of Showers) covers one one of the most recent impact basins - this was a multi-ringed basin. The first ring has been mostly, but not totally covered. The second ring appears in the North-East as the Alps. The third ring has produced the Apennines and the Caucasus. The usual explanation for maria only really occuring on the visible side of the Moon is that the crust is thinner on that side. 'Mare' areas are actually given various designations - thus (in decreasing order of size
- Lacus (kake)
- Palus (swamp)
- Sinus (bay)
Rilles are long, thin channels.
The entire surface is covered with regolith, a powdery soil which has been produced by the shattering of the surface by prolonged meteorite bombardment.
There is an aluminium crust about 60 km thick, covering a mantle rich in iron and magnesium.
Micrometorites travel at up to 115.000 kilometers per hour. They remove about 1 mm. of lunar surface in a million years. e Allan Hills in Antartica.