When was the first lunar meteorite identified?
In 1982, a small meteorite found in Antarctica, ALH A81005, was recognised in 1983 as coming from the Moon, the first meteorite proven to be lunar.
Before the 1980s, many scientists doubted that impacts on the Moon could launch rocks fast enough to reach Earth without melting them.
The discovery. In January 1982, an American field team searching the Allan Hills in Antarctica found a small greenish-brown meteorite weighing about 31 grams. It was catalogued as ALH A81005, meaning it was collected in the 1981 to 1982 season.
Recognition. When scientists examined it, they noticed it looked remarkably like lunar highland breccias collected by Apollo astronauts. It was a breccia rich in calcium plagioclase feldspar, with chemistry and mineral compositions matching lunar rocks. Its oxygen isotopes were like those of Earth and the Moon. In 1983, after studies by many laboratories, scientists concluded that it came from the Moon.
Japanese meteorites. Japanese scientists then realised that a meteorite found by their team in Antarctica in 1979, Yamato 791197, was also lunar. It had been found earlier but was recognised slightly later.
Significance. The discovery proved that rocks could be ejected from the Moon by impacts and reach Earth. This made the idea of Martian meteorites much more plausible, and the identification of Martian meteorites followed.
Today. Hundreds of lunar meteorites are known, found mostly in hot deserts and Antarctica. Many are paired fragments. They come from many places on the Moon, including areas never sampled by spacecraft.
ALH A81005 is held in the American Antarctic meteorite collection and remains a landmark specimen.