Allan Hills A81005

Last updated
Allan Hills A81005 (ALH A81005)
Allan Hills 81005, lunar meteorite.jpg
Type Achondrite
Clan Lunar meteorite
Group Lunar anorthosite [1]
Parent body Moon
CompositionBreccia with plagioclase clasts.
Weathering grade A/B
Country Antarctica
Region Allan Hills
Coordinates 76°49′49″S158°15′32″E / 76.83028°S 158.25889°E / -76.83028; 158.25889 [1]
Observed fall No
Found date17 January 1982 [2]
TKW 31.4 grams (1.11 oz)

Allan Hills A81005 or ALH A81005 (sometimes also named without the "A" in front of the number) was the first meteorite to be recognised as a lunar meteorite. The meteorite Yamato 791197 was discovered in 1979 but its lunar origin was not recognised until 1984. [3] ALH A81005 was found in 1982 in the Allan Hills at the end of the Transantarctic Mountains, during a meteorite gathering expedition (ANSMET). [1]

Contents

Discovery and naming

ALH A81005 was found on 17 January 1982 by John Schutt and Ian Whillans. [2] [4] It is named after the Allan Hills, a mountain chain in Antarctica where many meteorites are gathered by expeditions. [1] The large number of meteorites collected in Antarctica and the lack of geographic terms that could be used for names have led to the adaption of the "Antarctic rules" for meteorite naming. Every meteorite found in Antarctica receives the names of the collection area (Allan Hills) and a number. The number consists of the year the expedition started "81" and a three digit number that is given out consecutively (005). The "A" in front of the number stands for meteorites collected by ANSMET expeditions and can be considered optional. [5] The definition of the year is used because the year changes during the Austral summer season (December to March) and this avoids samples from one expedition having different years. This is the reason ALH A81005 has the year "81" in its name despite being found on 17 January 1982. [5]

Description

ALH A81005 measures 3 × 2.5 × 3 centimetres (1.18 × 0.98 × 1.18 in). It has a dark fusion crust on the outside. The interior is made up of a black to dark grey groundmass (matrix) with larger grey and white angular crystals (clasts). This appearance is typical for breccias, including those originating on Earth. The size of the larger crystals ranges from sub-millimeter to 8 millimetres (0.31 in) in diameter. [1]

Thin section analysis revealed that the crystals are mostly plagioclase, with some pyroxene and olivine. It was also discovered that the meteorite had similarities to terrestrial gabbro or basalt. Microprobe analysis showed that the plagioclase was very calcium-rich. The crystals are a solid solution of 97% anorthite and 3% albite. The pyroxenes have a variable composition lying between enstatite, ferrosilite and wollastonite. The olivine is a solid solution of 11 to 40% fayalite with the rest being forsterite. [1] ALH A81005 is classified as a "lunar anorthosite breccia" and belongs to the group "lunar anorthosite" (abbreviated Lun-A). [1]

History

The determination that ALH A81005 was of lunar origin was made by Robert Clayton and Toshiko Mayeda, researchers at the University of Chicago, [6] following the determination by Smithsonian Institution scientist Brian Harold Mason that the meteorite was similar in chemical and isotopic composition to rocks returned by the Apollo program astronauts from lunar highland areas. [7] Evidence that ALHA 81005 is a lunar sample, was presented at the 18 March 1983 meeting of the Lunar and Planetary Institute. The evidence included fabric data, mineralogical data, compositional data, oxygen isotope data, noble gas data, cosmic ray exposure history, magnetic properties, nuclear particle tracks, and thermoluminescence data. [8]

Related Research Articles

<span class="mw-page-title-main">Gabbro</span> Coarse-grained mafic intrusive rock

Gabbro is a phaneritic (coarse-grained), mafic intrusive igneous rock formed from the slow cooling of magnesium-rich and iron-rich magma into a holocrystalline mass deep beneath the Earth's surface. Slow-cooling, coarse-grained gabbro is chemically equivalent to rapid-cooling, fine-grained basalt. Much of the Earth's oceanic crust is made of gabbro, formed at mid-ocean ridges. Gabbro is also found as plutons associated with continental volcanism. Due to its variant nature, the term gabbro may be applied loosely to a wide range of intrusive rocks, many of which are merely "gabbroic". By rough analogy, gabbro is to basalt as granite is to rhyolite.

<span class="mw-page-title-main">Martian meteorite</span> Meteorite made of rock originating from Mars

A Martian meteorite is a rock that formed on Mars, was ejected from the planet by an impact event, and traversed interplanetary space before landing on Earth as a meteorite. As of September 2020, 277 meteorites had been classified as Martian, less than half a percent of the 72,000 meteorites that have been classified. The largest complete, uncut Martian meteorite, Taoudenni 002, was recovered in Mali in early 2021. It weighs 14.5 kilograms and is on display at the Maine Mineral and Gem Museum.

<span class="mw-page-title-main">Bytownite</span> Mineral: intermediate member of a solid solution series (70 to 90 % anorthite and albite)

Bytownite is a calcium rich member of the plagioclase solid solution series of feldspar minerals with composition between anorthite and labradorite. It is usually defined as having between 70 and 90%An. Like others of the series, bytownite forms grey to white triclinic crystals commonly exhibiting the typical plagioclase twinning and associated fine striations.

<span class="mw-page-title-main">Allan Hills 84001</span> Martian meteorite discovered in Antarctica in 1984

Allan Hills 84001 (ALH84001) is a fragment of a Martian meteorite that was found in the Allan Hills in Antarctica on December 27, 1984, by a team of American meteorite hunters from the ANSMET project. Like other members of the shergottite–nakhlite–chassignite (SNC) group of meteorites, ALH84001 is thought to have originated on Mars. However, it does not fit into any of the previously discovered SNC groups. Its mass upon discovery was 1.93 kilograms (4.3 lb).

<span class="mw-page-title-main">Lunar meteorite</span> Meteorite that originated from the Moon

A lunar meteorite is a meteorite that is known to have originated on the Moon. A meteorite hitting the Moon is normally classified as a transient lunar phenomenon.

<span class="mw-page-title-main">Anorthosite</span> Mafic intrusive igneous rock composed predominantly of plagioclase

Anorthosite is a phaneritic, intrusive igneous rock characterized by its composition: mostly plagioclase feldspar (90–100%), with a minimal mafic component (0–10%). Pyroxene, ilmenite, magnetite, and olivine are the mafic minerals most commonly present.

<span class="mw-page-title-main">Genesis Rock</span> Rock retrieved from the Moon in 1971

The Genesis Rock is a sample of Moon rock retrieved by Apollo 15 astronauts James Irwin and David Scott in 1971 during the second lunar EVA, at Spur crater on Earth's Moon. With a mass of c. 270 grams, it is currently stored at the Lunar Sample Laboratory Facility in Houston, Texas.

<span class="mw-page-title-main">ANSMET</span> Program funded by the National Science Foundation

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 throughout Antarctica. Such meteorites are quickly covered by subsequent snowfall and begin a centuries-long journey traveling "downhill" across the Antarctic continent while embedded in a vast sheet of flowing ice. Portions of such flowing ice can be halted by natural barriers such as the Transantarctic Mountains. Subsequent wind erosion of the motionless ice brings trapped meteorites back to the surface once more where they may be collected. This process concentrates meteorites in a few specific areas to much higher concentrations than they are normally found everywhere else. The contrast of the dark meteorites against the white snow, and lack of terrestrial rocks on the ice, makes such meteorites relatively easy to find. However, the vast majority of such ice-embedded meteorites eventually slide undiscovered into the ocean.

<span class="mw-page-title-main">Moon rock</span> Rocks on or from the Moon

Moon rock or lunar rock is rock originating from Earth's Moon. This includes lunar material collected during the course of human exploration of the Moon, and rock that has been ejected naturally from the Moon's surface and landed on Earth as meteorites.

Yamato 791197, official abbreviation Y-791197, is a meteorite that was found in Antarctica on November 20, 1979.

<span class="mw-page-title-main">Lunar magma ocean</span> Theorized historical geological layer on the Moon

The Lunar Magma Ocean (LMO) is the layer of molten rock that is theorized to have been present on the surface of the Moon. The Lunar Magma Ocean was likely present on the Moon from the time of the Moon's formation to tens or hundreds of millions of years after that time. It is a thermodynamic consequence of the Moon's relatively rapid formation in the aftermath of a giant impact between the proto-Earth and another planetary body. As the Moon accreted from the debris from the giant impact, gravitational potential energy was converted to thermal energy. Due to the rapid accretion of the Moon, thermal energy was trapped since it did not have sufficient time to thermally radiate away energy through the lunar surface. The subsequent thermochemical evolution of the Lunar Magma Ocean explains the Moon's largely anorthositic crust, europium anomaly, and KREEP material.

The Yamato 691 is a 4.5 billion year old chondrite meteorite discovered by members of the Japanese Antarctic Research Expedition on the blue ice field of the Queen Fabiola Mountains in Antarctica, on December 21, 1969.

This is a glossary of terms used in meteoritics, the science of meteorites.

<span class="mw-page-title-main">Northwest Africa 7034</span> Martian meteorite

Northwest Africa 7034 is a Martian meteorite believed to be the second oldest yet discovered. It is estimated to be two billion years old and contains the most water of any Martian meteorite found on Earth. Although it is from Mars it does not fit into any of the three SNC meteorite categories, and forms a new Martian meteorite group named "Martian ". Nicknamed "Black Beauty", it was purchased in Morocco and a slice of it was donated to the University of New Mexico by its American owner. The image of the original NWA 7034 was photographed in 2012 by Carl Agee, University of New Mexico.

<span class="mw-page-title-main">Ursula Marvin</span> American geologist, mineralogist and historian of science

Ursula Bailey Marvin was an American planetary geologist and author who worked for the Smithsonian Astrophysical Observatory.

<span class="mw-page-title-main">Yamato 000593</span> Meteorite found in Antarctica

Yamato 000593 is the second largest meteorite from Mars found on Earth. Studies suggest the Martian meteorite was formed about 1.3 billion years ago from a lava flow on Mars. An impact occurred on Mars about 11 million years ago and ejected the meteorite from the Martian surface into space. The meteorite landed on Earth in Antarctica about 50,000 years ago. The mass of the meteorite is 13.7 kg (30 lb) and has been found to contain evidence of past water alteration.

Catherine Margaret Corrigan, often known as Cari Corrigan, is an American scientist best known as a curator of the meteorite collection at the Smithsonian Institution. She is a scientist in the Department of Mineral Science at the National Museum of Natural History.

<span class="mw-page-title-main">Allan Hills 77005</span> Martian meteorite found in Antarctica

Allan Hills 77005 is a Martian meteorite that was found in the Allan Hills of Antarctica in 1977 by a Japanese National Institute of Polar Research mission team and ANSMET. Like other members of the group of SNCs, ALH-77005 is thought to be from Mars.

References

  1. 1 2 3 4 5 6 7 "Allan Hills A81005". Meteoritical Society. Retrieved 11 January 2013.
  2. 1 2 Kevin Righter; John Gruener. "Lunar Meteorite Compendium ALH A81005" (PDF). NASA . Retrieved 11 January 2013.
  3. "Lunar Meteorite: Yamato 791197 | Some Meteorite Information | Washington University in St. Louis". sites.wustl.edu. Retrieved 2024-08-04.
  4. Kevin Righter; John Gruener. "The Lunar Meteorite Compendium". NASA. Retrieved 11 January 2013.
  5. 1 2 "Antarctic Rules". Meteoritical Society. Retrieved 26 February 2013.
  6. "Meteorite came from moon". The Leader-Post . Regina, Saskatchewan. March 16, 1983. p. A5. Retrieved 27 February 2013.
  7. "Scientists say meteorite is likely piece of the moon". Spokane Chronicle . Spokane, Washington. March 16, 1983. p. A9. Retrieved 27 February 2013.
  8. Cassidy, William (2003). Meteorites, Ice, and Antarctica: A personal account . Cambridge: Cambridge University Press. pp.  144-185, 320. ISBN   9780521258722.