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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.
[2] [3] After the classes were devised, a more rigorous definition was found: C-chondrites contain proportionally higher magnesium than ordinary chondrites. [4] [5] [6] The C-chondrites subdivide into CI, CM, CO, CV, CK, CR, and lesser groups (CH, CB, and ungrouped C-meteorites). Specimens are formed into groups by their petrological and ...
A chondrite / ˈ k ɒ n d r aɪ t / is a stony (non-metallic) meteorite that has not been modified by either melting or differentiation of the parent body. [a] [1] They are formed when various types of dust and small grains in the early Solar System accreted to form primitive asteroids.
[3] In 2006 a classification was published that assigned 7 groups to the primitive achondrites, but the classification remains controversial. The authors define primitive achondrites as meteorites "that exceeded their solidus temperature on the parent body" and thus would partially melt. Meteorites that have been fully melted are included if ...
[1] [2] They yield a weighted mean age of 4567.30 ± 0.16 Myr, which is often interpreted as representing the beginning of the formation of the planetary system (so-called ‘CAI time-zero). It is of note that all four Pb-Pb dated CAIs come from the same group of meteorite ( CV chondrites ).
The LL group includes many of the most primitive ordinary chondrites, including the well-studied Semarkona (type 3.0) chondrite. However, most LL chondrites have been thermally metamorphosed to petrologic types 5 and 6, meaning that their minerals are homogeneous in composition and chondrule borders are difficult to discern.
[1] [2] They are believed to be a common feature of the evolution of planetary nebulae, but can only be resolved in the nearest examples. [2] They are generally larger than the size of the Solar System (i.e. the orbit of Pluto ), with masses of around 0.00001 times the mass of the Sun , which is comparable to the mass of the Earth .
Ordinary chondrite NWA 3189 sliced. Field of view c. 2.2 cm across. NWA 3189 has been classified as an LL3.2–3.4 ordinary chondrite ("LL" means very low total iron content; "3" refers to well-preserved chondrules – the rock has not been subjected to metamorphism intense enough to disrupt the chondritic texture).