Lunar meteorite - AbsoluteAstronomy.com

A Lunar meteorite is a meteorite

Meteorite

A meteorite is a natural object originating in outer space that survives impact with the Earth's surface. Meteorites can be big or small. Most meteorites derive from small astronomical objects called meteoroids, but they are also sometimes produced by impacts of asteroids...

that is known to have originated on the Moon

Moon

The Moon is Earth's only known natural satellite,There are a number of near-Earth asteroids including 3753 Cruithne that are co-orbital with Earth: their orbits bring them close to Earth for periods of time but then alter in the long term . These are quasi-satellites and not true moons. For more...

Discovery

In January 1982, John Schutt

John Schutt

John Schutt is an American mountaineer and a member of the yearly Antarctic search for meteorites program. John has probably recovered more meteorites than any single person in history and has personally recovered more samples of Mars...

, leading an expedition in Antarctica for the ANSMET

ANSMET

ANSMET is a program funded by the Office of Polar Programs of the National Science Foundation that looks for meteorites in the Transantarctic Mountains. This geographical area serves as a collection point for meteorites that have originally fallen on the extensive high-altitude ice fields...

program, found a meteorite that he recognized to be unusual. Shortly thereafter, the meteorite now called Allan Hills 81005 was sent to Washington, DC, where Smithsonian Institution

Smithsonian Institution

The Smithsonian Institution is an educational and research institute and associated museum complex, administered and funded by the government of the United States and by funds from its endowment, contributions, and profits from its retail operations, concessions, licensing activities, and magazines...

geochemist Brian Mason

Brian Harold Mason

Brian Harold Mason was a New Zealand born geochemist and mineralogist who was one of the pioneers in the study of meteorites.Mason has played a leading part in understanding the nature of the solar system through his studies of meteorites and lunar rocks.Mason has also examined and classified...

recognized that the sample was unlike any other known meteorite and resembled some rocks brought back from the Moon

Moon

by the Apollo program. Several years later, Japanese scientists recognized that they had also collected a lunar meteorite, Yamato 791197

Yamato 791197

Yamato 791197, official abbreviation Y-791197, is a meteorite that was found in Antarctica on November 20, 1979.It is the first rock to be found on Earth identified as a lunar meteorite...

, during the 1979 field season in Antarctica. About 134 lunar meteorites have been discovered so far (as of October, 2010), perhaps representing more than 50 separate meteorite falls (i.e., many of the stones are "paired" fragments of the same meteoroid

Meteoroid

A meteoroid is a sand- to boulder-sized particle of debris in the Solar System. The visible path of a meteoroid that enters Earth's atmosphere is called a meteor, or colloquially a shooting star or falling star. If a meteoroid reaches the ground and survives impact, then it is called a meteorite...

). The total mass is more than 46 kg. All lunar meteorites have been found in deserts; most have been found in Antarctica, northern Africa

Africa

Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...

, and the Sultanate of Oman. None have yet been found in North America, South America, or Europe.

Lunar origin is established by comparing the mineralogy, the chemical composition, and the isotopic composition between meteorites and samples from the Moon collected by Apollo missions.

Transfer to Earth

Most lunar meteorites are launched from the Moon by impacts making lunar craters of a few kilometers in diameter or less. No source crater of lunar meteorites has been positively identified, although there is speculation that the highly anomalous lunar meteorite Sayh al Uhaymir 169

Sayh al Uhaymir 169

Sayh al Uhaymir 169 is a 206g lunar meteorite found in the Sayh al Uhaymir region of the Sultanate of Oman in January 2002.This stone is an impact-melt breccia with exceedingly high concentrations of thorium and other incompatible elements; phosphorus, rare earth elements, and the three most...

derives from the Lalande

Lalande (crater)

Lalande is a small lunar impact crater that lies in the central part of the visible Moon, on the eastern edge of Mare Insularum. The crater is surrounded by a high-albedo area of ejecta that extends into a ray system with a maximum radius of over 300 kilometers. The interior wall has a terrace...

impact crater on the Lunar nearside.

Cosmic ray exposure history established with noble gas measurements have shown that all lunar meteorites were ejected from the Moon in the past 20 million years. Most left the Moon in the past 100,000 years. After leaving the Moon, most lunar meteoroids go into orbit around Earth and eventually succumb to Earth's gravity. Some meteoroids ejected from the Moon get launched into orbits around the sun. These meteoroids remain in space longer but eventually intersect the Earth's orbit and land.

Scientific relevance

All six of the Apollo missions on which samples were collected landed in the central nearside of the Moon, an area that has subsequently been shown to be geochemically anomalous by the Lunar Prospector

Lunar Prospector

The Lunar Prospector mission was the third selected by NASA for full development and construction as part of the Discovery Program. At a cost of $62.8 million, the 19-month mission was designed for a low polar orbit investigation of the Moon, including mapping of surface composition and possible...

mission. In contrast, the numerous lunar meteorites are random samples of the Moon and consequently provide a more representative sampling of the lunar surface than the Apollo samples. Half the lunar meteorites, for example, likely sample material from the farside of the Moon.

At the time the first meteorite from the Moon was discovered in 1982, there was speculation that some other unusual meteorites that had been found previously originated from Mars. The positive identification of lunar meteorites on Earth supported the hypothesis that meteoroid impacts on Mars could eject rocks from that planet. There are also speculations about the possibility of finding "Earth meteorites" on the surface of the Moon. This would be very interesting because in this case stones from Earth older than 3.9 billion years, which are destroyed on Earth by various geological processes, may have survived on the Moon. Thus some scientists propose new missions to the Moon to search for ancient rocks from Earth

Earth

Earth is the third planet from the Sun, and the densest and fifth-largest of the eight planets in the Solar System. It is also the largest of the Solar System's four terrestrial planets...

History

Today, about one in every thousand newly discovered meteorites is a lunar meteorite, whereas the vast majority of meteorites are from the asteroid belt. In the early 19th century most scientists believed that all meteorites were from the Moon. Although today supported only by a minority of researchers, there are also theories that tektite

Tektite

Tektites are natural glass rocks up to a few centimeters in size, which most scientists argue were formed by the impact of large meteorites on Earth's surface. Tektites are typically black or olive-green, and their shape varies from rounded to irregular.Tektites are among the "driest" rocks, with...

s are from the Moon and should therefore also be regarded as lunar meteorites. However, most scientists regard such theories as outdated.

Private ownership

Lunar meteorites collected in Africa and Oman are, for all practical purposes, the only source of moon rocks available for private ownership. This is because all rocks collected during the Apollo moon-landing program are property of the United States government or of other nations to which the U.S. conveyed them as gifts. Similarly, all lunar meteorites collected by the U.S. and Japanese Antarctic programs are, by treaty, held by those governments for research and education purposes only. Although there is no U.S. law specifically against the ownership of Apollo moonrocks, none has ever been (or is likely to ever be) given or sold by the U.S. government to private citizens. Even in the cases of plaques containing genuine Apollo moonrocks given in 2004 to astronauts and Walter Cronkite

Walter Cronkite

Walter Leland Cronkite, Jr. was an American broadcast journalist, best known as anchorman for the CBS Evening News for 19 years . During the heyday of CBS News in the 1960s and 1970s, he was often cited as "the most trusted man in America" after being so named in an opinion poll...

, NASA retained ownership of the rocks themselves. Most of the moonrocks collected by the Luna 16

Luna 16

-External links:*...

probe are also unavailable for private ownership, although three tiny samples were sold at auction for $442,500 in 1993.

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