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In meteoritics, a meteorite classification system attempts to group similar meteorites and allows scientists to communicate with a standardized terminology when discussing them. Meteorites are classified according to a variety of characteristics, especially mineralogical, petrological, chemical, and isotopic properties.
A chondrule is a round grain found in a chondrite. Chondrules form as molten or partially molten droplets in space before being accreted to their parent asteroids. Because chondrites represent one of the oldest solid materials within the Solar System and are believed to be the building blocks of the planetary system, it follows that an understanding of the formation of chondrules is important to understand the initial development of the planetary system.
A chondrite is a stony (non-metallic) meteorite that has not been modified, by either melting or differentiation of the parent body. They are formed when various types of dust and small grains in the early Solar System accreted to form primitive asteroids. Some such bodies that are captured in the planet's gravity well become the most common type of meteorite by arriving on a trajectory toward the planet's surface. Estimates for their contribution to the total meteorite population vary between 85.7% and 86.2%.
The pallasites are a class of stony–iron meteorite. They are relatively rare, and can be distinguished by the presence of large olivine crystal inclusions in the ferro-nickel matrix.
Iron meteorites, also called siderites or ferrous meteorites, are a type of meteorite that consist overwhelmingly of an iron–nickel alloy known as meteoric iron that usually consists of two mineral phases: kamacite and taenite. Most iron meteorites originate from cores of planetesimals, with the exception of the IIE iron meteorite group
Mbozi is an ungrouped iron meteorite found in Tanzania. It is one of the world's largest meteorites, variously estimated as the fourth-largest to the eighth-largest, it is located near the city of Mbeya in Tanzania's southern highlands. The meteorite is 3 metres (9.8 ft) long, 1 metre high, and weighs an estimated 16 metric tons.
CI chondrites, also called C1 chondrites or Ivuna-type carbonaceous chondrites, are a group of rare carbonaceous chondrite, a type of stony meteorite. They are named after the Ivuna meteorite, the type specimen. CI chondrites have been recovered in France, Canada, India, and Tanzania. Their overall chemical composition closely resembles the elemental composition of the Sun, more so than any other type of meteorite.
Lodranites are a small group of primitive achondrite meteorites that consists of meteoric iron and silicate minerals. Olivine and pyroxene make up most of the silicate minerals. Like all primitive achondrites lodranites share similarities with chondrites and achondrites.
Winonaites are a group of primitive achondrite meteorites. Like all primitive achondrites, winonaites share similarities with chondrites and achondrites. They show signs of metamorphism, partial melting, brecciation and relic chondrules. Their chemical and mineralogical composition lies between H and E chondrites.
IAB meteorites are a group of iron meteorites according to their overall composition and a group of primitive achondrites because of silicate inclusions that show a strong affinity to winonaites and chondrites.
IIICD meteorites are a group of primitive achondrites. They are classified in a clan together with the IAB meteorites and the winonaites.
Brachinites are a group of meteorites that are classified either as primitive achondrites or as asteroidal achondrites. Like all primitive achondrites, they have similarities with chondrites and achondrites. Brachinites contain 74 to 98% (volume) olivine.
The Eagle Station group is a set of pallasite meteorite specimen that do not fit into any of the other defined pallasite groups. In meteorite classification five meteorites have to be found, so they can be defined as their own group. Currently only five Eagle Station type meteorites have been found, which is just enough for a separate group.
The pyroxene pallasite grouplet is a subdivision of the pallasite meteorites (stony-irons).
Stony-iron meteorites or siderolites are meteorites that consist of nearly equal parts of meteoric iron and silicates. This distinguishes them from the stony meteorites, that are mostly silicates, and the iron meteorites, that are mostly meteoric iron.
The Winona meteorite is a primitive achondrite meteorite. It is the type specimen and by far the largest meteorite of the winonaite group.
Nonmagmatic meteorite is a deprecated term formerly used in meteoritics to describe iron meteorites that were originally thought to have not formed by igneous processes, to differentiate them from the magmatic meteorites, produced by the crystallization of a metal melt. The concept behind this was developed in the 1970s, but it was quickly realized that igneous processes actually play a vital role in the formation of the so-called "nonmagmatic" meteorites. Today, the terms are still sometimes used, but usage is discouraged because of the ambiguous meanings of the terms magmatic and nonmagmatic. The meteorites that were described to be nonmagmatic are now understood to be the product of partial melting and impact events and are grouped with the primitive achondrites and the achondrites.
This is a glossary of terms used in meteoritics, the science of meteorites.
Robert Norman Clayton was a Canadian-American chemist and academic. He was the Enrico Fermi Distinguished Service Professor Emeritus of Chemistry at the University of Chicago. Clayton studied cosmochemistry and held a joint appointment in the university's geophysical sciences department. He was a member of the National Academy of Sciences and was named a fellow of several academic societies, including the Royal Society.
Toshiko K. Mayeda was a Japanese American chemist who worked at the Enrico Fermi Institute in the University of Chicago. She worked on climate science and meteorites from 1958 to 2004.
References
- 1 2 3 M. K. Weisberg; T. J. McCoy; A. N. Krot (2006). "Systematics and Evaluation of Meteorite Classification". In D.S. Lauretta; H.Y. McSween Jr. (eds.). Meteorites and the early solar system II (PDF). Tucson: University of Arizona Press. pp. 19–52, 942. ISBN 978-0816525621 . Retrieved 17 October 2013.
foreword by Richard P. Binze
- ↑ "Vermillion". Meteoritical Society.
- ↑ Boesenberg, J. S.; M. Prinz; M. K. Weisberg; A. M. Davis; R. N. Clyton; T. K. Mayeda (1995). "Pyroxene Pallasites: A New Pallasite Grouplet". Meteoritics. 30: 488–489. Bibcode:1995Metic..30R.488B . Retrieved 29 December 2012.
- 1 2 Boesenberg, Joseph S.; Davis, Andrew M.; Prinz, Martin; Weisberg, Michael K.; Clayton, Robert N.; Mayeda, Toshiko K. (1 July 2000). "The pyroxene pallasites, Vermillion and Yamato 8451: Not quite a couple". Meteoritics & Planetary Science. 35 (4): 757–769. Bibcode:2000M&PS...35..757B. doi:10.1111/j.1945-5100.2000.tb01460.x.