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Chondrules in the chondrite classification Grassland. A millimeter scale is shown. Chondrules in the Carbonaceous Chondrite NWA 13887. A chondrule (from Ancient Greek χόνδρος chondros, grain) 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.
The chondrules have distinct texture, composition and mineralogy, and their origin continues to be the object of some debate. [11] The scientific community generally accepts that these spheres were formed by the action of a shock wave that passed through the Solar System, although there is little agreement as to the cause of this shock wave. [12]
Primitive achondrites are a subdivision of meteorites.They are classified on the same rank (historically called "Class") and lying between chondrites and achondrites.They are called primitive because they are achondrites that have retained much of their original chondritic properties.
Aqueous alteration promotes a composition of hydrous phyllosilicates, magnetite, and olivine crystals occurring in a black matrix, and a possible lack of chondrules. It is thought they have not been heated above 50 °C (122 °F), indicating that they condensed in the cooler outer portion of the solar nebula.
The term 'chondrite' indicates that these contain (or may have contained) chondrules in a matrix. Chondrules are cooled droplets of minerals, predating the meteorites themselves. The term 'carbonaceous' was assigned relative to the ordinary chondrites; some Enstatite and Ureilite meteorites may have more carbon than C-chondrites. [1]
The RCW Catalogue (from Rodgers, Campbell & Whiteoak) is an astronomical catalogue of Hα-emission regions in the southern Milky Way, described in (Rodgers et al. 1960).It contains 182 objects, including many of the earlier Gum catalogue (84 items) objects.
The 1 in C1 stands for the type 1 meteorites in the older classification scheme of Van Schmus-Wood, [4] still used for petrography. Petrographic type-1 meteorites, by definition, have no fully-visible chondrules .
[1] [4] Entries in the catalogue are designated with a "C" and the catalogue number (1 to 109). Unlike objects in the Messier catalogue, which are listed roughly in the order of discovery by Messier and his colleagues, [ 5 ] the Caldwell catalogue is ordered by declination , with C1 being the most northerly and C109 being the most southerly ...