Chemical evolution in the early solar system: amino acids, aliphatic amines, and ammonia in the Murchison meteorite

Abstract

Substantial isotopic enrichments in D, ^(13)C, and ^(15)N in the organic compounds of the Murchison meteorite, a carbonaceous chondrite, have been interpreted as a signature of low-temperature interstellar chemistry. This suggests that interstellar organic molecules survived the collapse of the protosolar cloud and were incorporated into the primitive meteorite parent body(ies). Since meteoritic organic compounds, amino acids, for example, are generally more complex than the known interstellar molecules, the latter probably participated in additional reactions, for example, the Strecker reaction in the case of the amino acid precursors, during aqueous and thermal processing of the parent body. Recent molecular and isotopic analyses of the Murchison volatile bases, which consist mainly of aliphatic amines and ammonia, suggest the possibility that the amines were produced by decarboxylation of amino acids during mild thermal processing of the parent body. A scheme is proposed whereby various other meteoritic compounds can be derived from Strecker reactants, i.e., from simple aldehydes, ketones, HCN, and ammonia, by way of plausible, aqueous phase reactions of the amino acids.

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