One such meteorite, named NWA ("Northwest Africa") 2200, was discovered in the Atlas Mountains of Morocco in August 2004. It was a 552 gram stone, dark grey and crystalline with whitish splotches of mineral grain all oriented in one direction. It likely originated from the highlands of the Moon. Its chemical composition was presented in an article in Polar Science published this month. Unlike the Apollo 16 Moon rocks, this meteorite found in Morocco had fewer rare earth elements, but more ferrous iron and feldspar minerals.
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Meteorites from the moon or Mars are extremely rare, and proposed samples are compared against rock samples collected by the Apollo missions to confirm their origins. The rocks are then legitimized by The Meteorological Society, and the collector must provide a 20 gram chunk of it to a museum or another academic institute for scientists to study.
The samples are needed because our knowledge is curtailed by the limited extent of our previous lunar missions. The six Apollo missions that returned with rocks all landed in the same region, on the central nearside hemisphere of the Moon. To make matters worse, the region was geo-chemically anomalous, and as such the samples did not reveal very much about the composition and origins of the lunar crust.
Chunks of lunar rock that split off from the surface of the moon (due to various unknown impacts) and hurtle into Earth are ideal samples since they are completely random. Scientists and professional collectors have so far found around 100 lunar meteorites - give or take a few dozen depending on whether one counts meteorites that may have been found as separate rocks, but are suspected to have originated from the same meteor event.
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The rocks are used to confirm the observations of sophisticated spectrometers that remotely sense the mineral and elemental composition of the lunar surface.
Image: A composite image from an overnight photography adventure at the Needle's Eye in South Dakota during the Geminids Meteor Shower where we light painted the Needle formations while meteors streaked across the sky above. (Mike Berenson / Colorado Captures / Getty Images)