Murchison meteorite macromolecular material

The Murchison meteorite shown in Figure 6.7, like all meteorites, is named after the place from which it was recovered and in this case it is the town of Murchison, Victoria in Australia about 100 km north of Melbourne. The fall occurred in 1969 and was followed by an analysis of the chemical composition in some considerable detail. The Murchison meteorite is a carbonaceous chondrite containing about 2 per cent carbon, some as inorganic carbonates, and some as soluble compounds such as amino acids but the bulk as a macromolecular heterogeneous material referred to as kerogen. 

The kerogen-like material from the Murchison meteorite is shown in Figure 6.8 and consists of a rich macromolecular carbonaceous material made from aromatic and aliphatic compounds observed in fluorescence following excitation at 280 nm. 

The majority of the carbon in the Murchison macromolecular material is present within aromatic ring systems. This aromatic nature has been revealed by a series of pyrolysis studies of meteorites such as OrgueU (CIl), Murchison (CM2), Murray (CM2), and Allende (CV3) in which the macromolecular material was thermally fragmented to produce benzene, toluene, alkyl-benzenes, naphthalene, alkylnaphthalenes, and PAHs with molecular weights up to around 200-300 amu (Simmonds et al, 1969 Studier et al, 1972 Levy et al, 1973 Bandurski and Nagy, 1976 Holtzer and Oro, 1977 Murae, 1995 Kitajima et al, 2002). Further identification of the aromatic units in the Murchison macromolecular material was achieved by Hayatsu et al (1977),... 

The GC-MS analyses of Murchison, Orgueil and Cold Bokkeveld macromolecular material indicate that the macromolecular materials in different meteorites are qualitatively veiy similar (e.g. made up of the same units) 11), In addition, oxygen-, sulfur- and nitrogen-containing moieties such as phenols, thiophenes and benzonitrile have also been detected in the pyrolysates. The H2-pyrolysis further demonstrated that the refractory component probably consists of a network dominated by at least five- or six-ring PAH units that are crosslinked together 13). 

Although the macromolecular material has been found to be qualitatively very similar between the Murchison, Cold Bokkeveld and Orgueil meteorites variations in the ratios between one-ring aromatic hydrocarbons (benzene and alkylated derivaties), two-ring aromatic hydrocarbons and phenols exist between these meteorites (//). Phenol abundances increase in the order Orgueil < Cold Bokkeveld < Murchison, while the one-ring aromatic compounds show the opposite trend. These characteristics may be explained by the effect of aqueous... 

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