Classification of meteorites is largely based on their mineralogical and petrographic characteristics and their whole-rock chemical and O-isotopic compositions According to the currently used classification scheme, meteorites are divided into chondrites, primitive achondrites, and achondrites There are 15 chondrite groups, including 8 carbonaceous (CI, CM, CO, CV, CK, CR, CH, CB), 3 ordinary (H, L, LL), 2 enstatite (EH, EL), and R and K chondrites Several chondrites cannot be assigned to the existing groups and may represent the first members of new groups Some groups are subdivided into subgroups, which may have resulted from asteroidal processing of a single group of meteorites Each chondrite group is considered to have sampled a separate parent body Some chondrite groups and ungrouped chondrites show chemical and mineralogical similarities and are grouped together into clans The significance of this higher order of classification remains poorly understood The primitive achondrites include ureilites, acapulcoites, lodranites, winonaites, and silicate inclusions in IAB and IIICD irons and probably represent recrystallization or residues from a low-degree partial melting of chondritic materials The genetic relationship between primitive achondrites and the existing groups of chondritic meteorites remains controversial Achondrites resulted from a high degree of melting of chondrites and include asteroidal (angrites, aubrites, howardites-diogenites-eucrites, mesosiderites, 3 groups of pallasites, 15 groups of irons plus many ungrouped irons) and planetary (martian, lunar) meteorites

/pdf/systematics-and-evaluation-of-meteorite-classification-4k05qo1ksk.pdf

Systematics and Evaluation of Meteorite Classification

Stimulated by recent high-profile incidents, concerns about business ethics have increased over the last decade. In response, research has focused on developing theoretical and empirical frameworks to understand ethical decision making. So far, empirical studies have used traditional quantitative tools, such as regression or multiple discriminant analysis (MDA), in ethics research. More advanced tools are needed. In this exploratory research, a new approach to classifying, categorizing and analyzing ethical decision situations is presented. A comparative performance analysis of artificial neural networks, MDA and chance showed that artificial neural networks predict better in both training and testing phases. While some limitations of this approach were noted, in the field of business ethics, such networks are promising as an alternative to traditional analytic tools like MDA.

Comprehensive bibliography

Meteorites are frequently not the pristine record of early solar system processes that we would like them to be. Many unique meteorites, samples that can further our understanding of the environment of the early solar system, are finds, so a knowledge of terrestrial weathering becomes a requirement to accurately interpret their preterrestrial history. This chapter outlines the weathering process in chondrites, the mineralogical changes that occur in response to weathering, the variations in weathering in different environments, the effect of weathering on O isotopes and chemistry, and how weathering varies between different chondrite groups. As the most abundant meteorite group, most studies of meteorite weathering have concentrated on ordinary chondrites, although weathering affects all classes of meteorites. In many cases, these data are relevant to other chondrite groups, as well as irons and achondrites, but there are a number of specific issues related to carbonaceous chondrites (degradation of organic C, mobilization of S, reordering of phyllosilicates) that require a separate discussion. In particular, carbonaceous chondrites appear to be uniquely susceptible to terrestrial weathering, and recent studies have shown a number of alteration effects, even in falls curated in museum collections. The terrestrial alteration of carbonaceous chondrites concludes our chapter.

/pdf/weathering-of-chondritic-meteorites-2vwu8w33k0.pdf

Weathering of Chondritic Meteorites

We examined long-term variations in kelp growth in coincidence with recent (2004– 2006) measurements of underwater photosynthetically active radiation (PAR), light attenuation coeffi cients, chlorophyll concentrations, and total suspended solids (TSS) to determine the impact of sediment resuspension on the productivity of an isolated kelp bed community on the Alaskan Beaufort Sea coast. Attenuation coeffi cients exhibited distinct geographical patterns and interannual variations between 2004 and 2006 that were correlated with temporal and geographical patterns in TSS (range 3.5– 23.8 mg L 1). The low chlorophyll levels ( 3.0 g L 1) in all three years were unlikely to have contributed signifi cantly to periods of low summer water transparency. Blade elongation rates in the arctic kelp, Laminaria solidungula, are excellent integrators of water transparency since their annual growth is completely dependent on PAR received during the summer open-water period. We noted that blade growth at all sites steadily increased between 2004 and 2006, refl ective of increased underwater PAR in each successive year. Mean blade growth at all sites was clearly lowest in 2003 ( 8 cm) compared to 2006 (18– 47 cm). We attribute the low growth in 2003 to reported intense storm activity that likely produced extremely turbid water conditions that resulted in low levels of ambient light. Examination of a 30-year record of annual growth at two sites revealed other periods of low annual growth that were likely related to summers characterized by exceptional strong storm activity. Although kelp growth is expected to be higher at shallower sites, the reverse occurs, since sediment re-suspension is greatest at shallower water depths. The exceptionally low growth of kelp in 2003 indicates that these plants are living near their physiological light limits, but represent excellent indicators of interannual changes in water transparency that result from variations in local climatology.

Smithsonian at the poles : contributions to International Polar Year science

Meteorite Accumulations on Mars

A search of active deflation basins near Jal, Lea County, New Mexico resulted in the discovery of two meteorites, Lea County 001 and 002. Lea County 001 has mean olivine and low-Ca pyroxene compositions of Fa(19) and Fs(17), respectively. These and all other mineralogical and petrological data collected indicate a classification of H5 for this stone. Lea County 002 has mean olivine and low-Ca pyroxene compositions of Fa(2) and Fs(4), and is unequilibrated. Although it is mineralogically most similar to Kakangari and chondritic clasts within Cumberland Falls, the high modal amount of forsterite makes Lea County a unique type 3 chondrite. Oxygen isotope data for Lea County 002 fall on an 0-16-mixing line through those of the enstatite meteorites and IAB irons, a feature shared by Kakangari.

Lea County 001, an H5 chondrite, and Lea County 002, an ungrouped type 3 chondrite

Fission and Spallation Tracks in Merrillite: Their Annealing Behavior and the Recent Thermal History of Meteorites

The Meteorite Concentration at the Lewis Cliff, Antarctia, Ice Tongue

Carbonaceous chondrites of the Vigarano group (CV) are primitive (nearly un‐metamorphosed) meteorites that provide a wealth of information about the early solar system, including constraints on chondrule formation, origin of calcium‐aluminum inclusions, stability of organic compounds, and redox conditions. The US Antarctic meteorite collection contains 119 CV samples from 15 dense collection areas (DCAs) from the TransAntarctic Mountains; these samples have been assigned a preliminary classification as CVs, but not to the subgroups oxidized A, oxidized B, and reduced. Furthermore, variation in petrologic grade can be determined non‐destructively using Raman spectroscopy. To update the classification of both subgroups and petrologic types in the collection, we have acquired magnetic susceptibility, metal and sulfide compositions, and Raman spectra. Overall, there are 55 oxidized A samples, 18 oxidized B samples, and 46 reduced samples. Several of the CVs are quite primitive (Lewis Cliffs Ice Tongue and MacAlpine Hills) but are also very small. Multiple pairing groups have been identified in the Miller Range (MIL), Queen Alexandra Range, and Larkman Nunatak DCAs, including all of the subgroups. In MIL 090981, there is evidence for multiple lithologies. We make suggested updates for all the samples, knowing that this information will help to better guide researchers interested in studying the CV chondrites in the US Antarctic meteorite collection.

Assessment of petrologic subtypes, subgroups, and pairing within CV chondrites in the US Antarctic meteorite collection

Antarctic Search for Meteorites: Preliminary Report of the 1980/81 Field Season in South Victoria Land

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