18-509: TKW may indicate: Total known weight Teck Whye LRT station (LRT station abbreviation TKW) Tekin Airport ( IATA : TKW ) To Kwa Wan station (MTR station code TKW) Thousand-kernel weight , the weight in grams of a thousand kernels ( grains , seeds ) of a given crop sample. Topics referred to by the same term [REDACTED] This disambiguation page lists articles associated with
36-451: A planet , asteroid , or moon ) known as a parent body . However, with current scientific knowledge, these types of relationships between meteorites are difficult to prove. Meteorites are often divided into three overall categories based on whether they are dominantly composed of rocky material ( stony meteorites ), metallic material ( iron meteorites ), or mixtures ( stony–iron meteorites ). These categories have been in use since at least
54-441: A standardized terminology when discussing them. Meteorites are classified according to a variety of characteristics, especially mineralogical , petrological , chemical , and isotopic properties. There is no single, standardized terminology used in meteorite classification; however, commonly used terms for categories include types , classes , clans , groups , and subgroups . Some researchers hierarchize these terms, but there
72-401: Is a term used mainly by dealers and meteorite collectors to indicate the combined weight of all known pieces from a single named meteorite . The total known mass of a named meteorite is a fraction of the mass of the original meteoroid that entered Earth's atmosphere to produce the meteorite (also called post-atmospheric mass). Meteoroids that produce meteorites ablate as they pass through
90-457: Is also synonymous with the name of a modern group). Below is a representation of how the meteorite groups fit into the more traditional classification hierarchy: A. E. Rubin (2000) classification scheme: Two alternative general classification schemes were recently published, illustrating the lack of consensus on how to classify meteorites beyond the level of groups. In the Krot et al. scheme (2003)
108-431: Is no consensus as to which hierarchy is most appropriate. Meteorites that do not fit any known group (though they may fit somewhere within a higher level of classification) are ungrouped . Meteorite classification may indicate that a "genetic" relationship exists between similar meteorite specimens. Similarly classified meteorites may share a common origin, and therefore may come from the same astronomical object (such as
126-771: The Museum für Naturkunde , Berlin and Maskelyne on the collection of the British Museum , London . Rose was the first to make different categories for meteorites with chondrules (chondrites) and without (nonchondrites). Story-Maskelyne differentiated between siderites, siderolites and aerolites (now called iron meteorites , stony-iron meteorites and stony meteorite , respectively). In 1872 Gustav Tschermak published his first meteorite classification based on Gustav Rose's catalog from 1864: In 1883 Tschermak modified Rose's classification again. Further modifications were made by Aristides Brezina . The first chemical classification
144-406: The "Meteoric Stones" into those that have chondrules (Chondritic Meteoric Stones or Chondrites) and those that don't (Non-chondritic Meteoric Stones or Achondrites). The iron meteorites are subdivided according to their structures as ataxites , hexahedrites and octahedrites . A complete overview of his classification is given in the box below: Brian Harold Mason published a further revision in
162-410: The "total known mass" of the meteorite is fixed at the time of the find, and cannot increase. Low TKW means less materials for scientists and collectors. The total known weight is a key factor in pricing, especially with rare meteorite types . Meteorite types In meteoritics , a meteorite classification system attempts to group similar meteorites and allows scientists to communicate with
180-423: The atmosphere and lose mass. Thus, the total mass of a meteorite fall will always be lower than that of the original meteoroid (neglecting the mass of any terrestrial oxygen added to meteorites during the formation of their fusion crust). The upper limit to the "total known mass" of a meteorite is therefore the mass of the meteorite fall. Several factors can cause the "total known mass" of a meteorite to be less than
198-520: The early 19th century but do not have much genetic significance; they are simply a traditional and convenient way of grouping specimens. In fact, the term "stony iron" is a misnomer as currently used. One group of chondrites (CB) has over 50% metal by volume and contains meteorites that were called stony irons until their affinities with chondrites were recognized. Some iron meteorites also contain many silicate inclusions but are rarely described as stony irons. Nevertheless, these three categories sit at
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#1732923944754216-465: The following hierarchy is used: In the Weisberg et al. (2006) scheme meteorites groups are arranged as follows: where irons and stony–irons are considered to be achondrites or primitive achondrites, depending on the group. Modern meteorite classification was worked out in the 1860s, based on Gustav Rose 's and Nevil Story Maskelyne 's classifications. Gustav Rose worked on the meteorite collection of
234-405: The mass of the fall. Meteorite falls frequently occur as showers of stones (see main article ), produced when the parent meteoroid fragments. Only in cases where 100% of any such fragments are recovered, could the "total known mass" be the same as the mass of the fall. As previously undiscovered fragments are found, the "total known mass" could, in principle, rise. However, this is complicated by
252-420: The method by which meteorites are named. Historically (before the 1970s), every meteorite was given a simple geographical name. The total number of known meteorites was small and it was generally a simple matter to determine when a newly found fragment was "paired" to a previously discovered meteorite. When pairing could be established, the new fragment would not be given a new name, and the "total known mass" of
270-413: The original meteorite would increase. But, recent discoveries of arid regions containing large concentrations of meteorites have resulted in new rules for meteorite nomenclature. In these cases, individual meteorites are numbered, and every newly discovered fragment receives a unique number, even if there is a strong case that the new fragment is paired with an earlier discovered meteorite. In these cases,
288-498: The title TKW . If an internal link led you here, you may wish to change the link to point directly to the intended article. Retrieved from " https://en.wikipedia.org/w/index.php?title=TKW&oldid=1073762695 " Category : Disambiguation pages Hidden categories: Short description is different from Wikidata All article disambiguation pages All disambiguation pages Total known weight Total known weight ( TKW ), also total known mass ,
306-844: The top of the most widely used meteorite classification system. Stony meteorites are then traditionally divided into two other categories: chondrites (groups of meteorites that have undergone little change since their parent bodies originally formed and are characterized by the presence of chondrules ), and achondrites (groups of meteorites that have a complex origin involving asteroidal or planetary differentiation ). The iron meteorites were traditionally divided into objects with similar internal structures ( octahedrites , hexahedrites , and ataxites ), but these terms are now used for purely descriptive purposes and have given way to modern chemical groups. Stony–iron meteorites have always been divided into pallasites (which are now known to comprise several distinct groups) and mesosiderites (a textural term that
324-548: Was published by Oliver C. Farrington , 1907. George Thurland Prior further improved the classification based on mineralogical and chemical data, introducing the terms mesosiderite , lodranite and enstatite chondrite . In 1923 he published a catalogue of the meteorites in the Natural History Museum ( London ). He describes his classification as based on Gustav Tschermak and Aristides Brezina with modifications by himself. His main subdivisions were: He subdivides
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