Lunar meteorites: witnesses of the composition and evolution of the Moon

Abstract Lunar meteorites are fragments of the Moon that escaped the gravity of the Moon following high-energy impacts by asteroids,subsequently fell to Earth.An inventory of 165 lunar meteorites has been developed since the discovery and identification of the first lunar meteorite,ALHA 81005,in 1979.Although the Apollo samples are much heavier in mass than lunar meteorites,the meteorites are still an important sample supplement for scientific research on the composition and history of the Moon.Apart from a small amount of unbrecciated crystalline rocks,the majority of lunar meteorites are breccias that can be classified into three groups:highland feldspathic breccia,mare basaltic breccia,and mingled (including fledspathic and basaltic clasts) breccia.The petrography of lunar rocks suggests that there are a series of rock types of anorthosite,basalt,gabbro, troctolite,norite and KREEP in the Moon.Although KREEP is rare in lunar rocks,KREEP components have been found in the increasing number of lunar meteorites.KREEP provides important information on lunar magmatic evolution,e.g.,the VHK KREEP clasts in SaU 169 may represent the pristine lunar magma (urKREEP).Six launching pairs of lunar meteorites have been proposed now,along with ten possible lunar launching sites.In addition,symplectite is often found in lunar basalts,which is a significant record of shock metamorphism on the lunar surface.Furthermore,isotopic ages and noble gases not only provide information on crystallization processes in lunar rocks and the formation of lunar crust,but also provide insight into shock events on the lunar surface.