Lunar meteorites
Rocks from the Moon, found mainly in deserts and Antarctica.
- Classification
- Stony meteorites › Achondrites › Planetary achondrites › Lunar meteorites
- Share of witnessed falls
- none yet seen to fall
- In our catalogue
- 165 meteorites
- Heaviest
- Kalahari 009, 13.5 kg
Lunar meteorites are pieces of the Moon blasted off by impacts. The first to be recognised was Allan Hills A81005, found in Antarctica in January 1982; the Smithsonian's Brian Mason noticed that it resembled the Apollo rocks. Several hundred are now known, totalling over a tonne, though no lunar meteorite has been seen to fall.
Most are feldspar-rich breccias from the bright lunar highlands. Others are dark mare basalts, or mixtures of both. Because they come from random places across the Moon, including the far side, they complement the Apollo and Luna samples, which were collected from a few sites near the equator of the near side.
They are identified by their mineralogy, their chemistry, and isotopes that match Apollo samples. Lunar meteorites usually show little or no magnetic attraction.
Mineralogy and chemistry
The Moon's crust is dominated by anorthosite, a rock made almost entirely of calcium-rich plagioclase, while its dark maria are basalt rich in pyroxene and sometimes titanium. Lunar meteorites reflect both. Compared with asteroidal achondrites they contain almost no water or other volatile elements, their metal is scarce and contains little nickel, and their glasses and breccias record billions of years of impacts. Many carry gases implanted by the solar wind, picked up while their grains lay at the surface.
Types of lunar meteorite
About three-quarters are feldspathic breccias from the highlands. The rest are mare basalts and gabbros, mingled breccias that mix the two, and a few rare rock types such as norites and troctolites from the deeper crust. Some carry KREEP, a distinctive component rich in potassium, rare-earth elements and phosphorus that is concentrated in one region of the near side.
Why they matter
The Apollo and Luna missions sampled nine sites, all on the near side, and the Chang'e 5 and Chang'e 6 missions added two more. Lunar meteorites come from random places, including the far side and the poles. Their compositions show that much of the far-side highlands are poorer in iron and thorium than the Apollo samples suggested, so the Moon's crust is less uniform than the first samples implied. Lunar basalts among the meteorites extend the known range of mare volcanism back to about 4.35 billion years ago.
Most lunar meteorites spent less than a million years in space, and some only a few thousand, far shorter journeys than most asteroidal meteorites.
Famous examples and recognition
Allan Hills A81005 was collected in January 1982; Yamato 791197, found in 1979, was then also recognised as lunar. Kalahari 008 and 009 from Botswana, Dhofar 280 from Oman and Northwest Africa 5000, at about 11.5 kg, are well known. Lunar meteorites often have a thin, greenish or brownish fusion crust that can be glassy and bubbly. Feldspathic ones are pale grey with white clasts in a darker glassy matrix. They are only weakly magnetic. Because of their value, they should be classified by a recognised laboratory.
Groups
Feldspathic lunar meteorites
Pale breccias from the ancient lunar highlands, the most common kind of Moon rock to reach Earth.
96 in the catalogue
Lunar basalts and gabbros
Dark volcanic rock from the lunar maria, the Moon's great lava plains.
24 in the catalogueMingled lunar breccias
Breccias that mix highland and mare rock, from the borders between the two.
3 in the catalogueFamous examples
- Allan Hills A81005 Lunar (anorth), Antarctica, 1981 · 31 g
- Dhofar 280 Lunar (anorth), Oman, 2001 · 251 g
- Northwest Africa 482 Lunar (anorth), 2000 · 1.02 kg
Related groups
- Feldspathic lunar meteorites Pale breccias from the ancient lunar highlands, the most common kind of Moon rock to reach Earth.
- Lunar basalts and gabbros Dark volcanic rock from the lunar maria, the Moon's great lava plains.
- Mingled lunar breccias Breccias that mix highland and mare rock, from the borders between the two.
- Eucrites Volcanic basalt from the crust of Vesta.
- Martian meteorites Rocks from Mars, recognised by gas from the Martian atmosphere trapped inside them.
Photos shared under Creative Commons licences (Wikimedia Commons).