Analyses of carboxylic acids and hydrocarbons in Antarctic carbonaceous chondrites, Yamato-74662 and Yamato-793321.

Analyses of the Yamato-74662 carbonaceous chondrite (C2) showed the presence of carboxylic acids, and aliphatic and aromatic hydrocarbons with various structural isomers, while those of the Yamato-793321 chondrite (C2) did not. The amounts of these compounds in Yamato-74662 are similar to those reported in the Yamato-791198 chondrite (C2) but less than in the Murchison chondrite (C2). The presence of various structural isomers in carboxylic acids and aromatic hydrocarbons indicated an abiotic origin and therefore, that these compounds are indigenous to the chondrite. n-Alkanes and other homologs of aliphatic hydrocarbons were found. However, these aliphatics may not be indigenous, especially under the finding of pristane and phytane. A potential use of the relative amounts of 1-methylnaphthalene and 2-methylnaphthalene was proposed to deduce the extent of thermal alteration. The result was: Yamato-74662<Yamato-791198≤Murchison. Yamato-793321 probably received the alteration too intensely for these organic compounds to survive and is beyond estimation by this method.