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Moon rock or lunar rock is rock that is found on the Earth's moon, or lunar material collected during the course of human exploration of the Moon. Moon rocks on Earth come from three sources: those collected by the US Apollo manned lunar landings from 1969 to 1972; samples returned by three Soviet Luna unmanned probes in the 1970s; and rocks that were ejected naturally from the lunar surface by cratering events and subsequently fell to Earth as lunar meteorites. During the six Apollo landing missions, 2,415 samples weighing were collected. Three Luna spacecraft returned with an additional of samples. Since 1980, over 120 lunar meteorites representing about 60 different meteorite fall events (none witnessed) have been collected on Earth, with a total mass of over . About one third of these were discovered by US and Japanese teams searching for Antarctic meteorites (e.g., ANSMET), with most of the remainder having been discovered by collectors in the desert regions of northern Africa and Oman. Rocks from the Moon have been measured by radiometric dating techniques. They range in age from about 3.16 billion years old for the basaltic samples derived from the lunar maria, up to about 4.5 billion years old for rocks derived from the highlands. Based on the age dating technique of "crater counting," the youngest basaltic eruptions are believed to have occurred about 1.2 billion years ago, but scientists do not possess samples of these lavas. In contrast, the oldest ages of rocks from the Earth are between 3.8 and 4.28 billion years old. Almost all lunar rocks are depleted in volatiles and are completely lacking in hydrated minerals common in Earth rocks. In some regards, lunar rocks are closely related to Earth's rocks in their isotopic composition of the element oxygen. The Apollo moon rocks were collected using a variety of tools, including hammers, rakes, scoops, tongs, and core tubes. Most were photographed prior to collection to record the condition in which they were found. They were placed inside sample bags and then a ''Special Environmental Sample Container'' for return to the Earth to protect them from contamination. In contrast to the Earth, large portions of the lunar crust appear to be composed of rocks with high concentrations of the mineral anorthite. The mare basalts have relatively high iron values. Furthermore, some of the mare basalts have very high levels of titanium (in the form of ilmenite). ==Curation and availability== The main repository for the Apollo moon rocks is the Lunar Sample Laboratory Facility at the Lyndon B. Johnson Space Center in Houston, Texas. For safe keeping, there is also a smaller collection stored at White Sands Test Facility in Las Cruces, New Mexico. Most of the rocks are stored in nitrogen to keep them free of moisture. They are only handled indirectly, using special tools. Moon rocks collected during the course of lunar exploration are currently considered priceless. In 1993, three small fragments from Luna 16, weighing 0.2 g, were sold for US$ 442,500. In 2002, a safe, containing minute samples of lunar and Martian material, was stolen from the ''Lunar Sample Building''. The samples were recovered; in 2003, during the court case, NASA estimated the value of these samples at about $1 million for 285 g (10 oz) of material. Naturally transported moon rocks (in the form of lunar meteorites), although expensive, are widely sold and traded among private collectors. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「moon rock」の詳細全文を読む スポンサード リンク
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