What are lunar meteorites made of?
Most lunar meteorites are breccias of pale highland rock rich in feldspar, while others are dark basalts from the maria or mixtures of both.
Lunar meteorites are rocks blasted off the Moon by impacts that then landed on Earth. Several hundred have been found, mostly in hot deserts and Antarctica, and many are paired fragments of the same fall.
They fall into a few main kinds:
Feldspathic breccias. The majority are breccias made of fragments of anorthosite and other highland rocks, rich in calcium plagioclase feldspar. They are pale grey to white inside, often with dark glassy veins and clasts. They come from the bright lunar highlands, which cover most of the Moon, including much of the far side. ALH A81005, found in 1982, was the first meteorite recognised as lunar and is of this type.
Mare basalts. Some lunar meteorites are basalts, dark volcanic rocks from the maria, made of pyroxene, plagioclase and sometimes olivine and ilmenite. They can be compared with basalts collected by Apollo and Luna missions.
Mixed breccias. Others are regolith or fragmental breccias containing both highland and mare material, along with impact glass and melt.
KREEP-rich rocks. A few, such as some from Oman, are rich in potassium, rare earth elements and phosphorus, characteristic of a region on the Moon's near side.
Lunar meteorites are identified by their oxygen isotopes, which match Earth and the Moon, their mineral chemistry, such as the iron-to-manganese ratio of pyroxene, and their resemblance to Apollo samples. Because they come from random locations, they help scientists understand the whole Moon, not just the landing sites.