Mathematics – Logic
Scientific paper
Jul 1973
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1973ssrv...14..832v&link_type=abstract
Space Science Reviews, Volume 14, Issue 6, pp.832-879
Mathematics
Logic
Scientific paper
The Mighei meteorite is generally considered to be unique amongst the group of stony meteorites known as the carbonaceous chondrites in a number of scientifically interesting aspects. The meteorite, which is related to the type II carbonaceous chondrites of Wiik's classification (or type C2 according to van Schmus and Wood), contains extraterrestrial organic compounds (general C content = 2.6%), and extraterrestrial water associated with iron-magnesium silicate crystals (general H2O content=12%). The meteorite fall occurred in 1889, over a region in the Ukraine. In structure it was found to be a chondritic meteorite, having chondrules of order 0.5 mm in size. The composition of the meteorite is inhomogeneous. In mineralogical terms the meteorite is composed of two paragenetic associations, described as ‘high’ and ‘low temperature’, which are generally distributed in equal proportions. The ‘low temperature’ associations are a characteristic only of carbonaceous chondrites: the minerals involved are chlorites or the serpentine group, carbonates, free sulphur, sulphates and ‘low temperature’ glass. In chemical terms the Mighei meteorite is somewhat enriched in the volatile elements S, C, H, N, O in comparison to the usual chondrites. These elements are found in different forms and the isotopic composition of the elements S, C, O, is different for different phases. The meteorite is also rich in a number of other fairly volatile element admixtures such as: B, F, Cl, Cu, Zn, Ga, Ge, Br, In, Te, I, Hg, Tl, Pb, Bi, and contains somewhat enhanced initial quantities of rare gases. The organic compounds are of an abiological nature in the meteorite and are located in finely dispersed distributions between the chondrules. They are present in the main, as polymerized organic compounds. Among these polymers there are gaseous hydrocarbons (saturated and non-saturated) and extractable organic compounds. In the latter condition the following organic compounds have been identified: aliphatic hydrocarbons, aromatic hydrocarbons, amino acids and others. The meteorite contains free organic radicals (1017 centres g-1), uncoupled π-electrons which are delocalized in the aromatic structure of the polymeric matter. The radiogenic age of the meteorite has been determined as from 2.4 to 3.2 × 109 yr (by the K-Ar method) and up to 4.54 × 109 yr (by the Rb-Sr method), while the radiation age is put at 0.5 to 2.4 × 106 yr. Details of the meteorite structure give evidence of at least two processes in its formation; the accretion of the meteoritic matter, together with the simultaneous formation of organic compounds could have taken place at temperatures between 450 and 300 K.
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