THE AMINO ACID COMPOSITION OF CARBONACEOUS CHONDRITES: CLUES TO THEIR PARENT BODIES

摘要

The amino acids found in the CM carbonaceous chondrites Murchison, Murray and LEW90500 are thought to have been formed by the Strecker reaction, a synthetic pathway involving organic precursor molecules (probably of interstellar origin) which assemble and react during aqueous processing on the meteorite parent body. Based on our current knowledge, the question whether the minor differences in the composition of amino acids, observed among those different CM meteorites, are an indication for distinct parent bodies of the same type cannot yet be answered. In contrast, the CI meteorites Orgueil and Ivuna contain a strikingly simpler amino acid mixture. These amino acids were likely formed from a limited set of precursor components such as hydrogen cyanide, ammonia and cyanoacetylene, implying a different type of parent body than for the CMs. A cometary origin would be one possibility since the current inventory of cometary volatiles would favour the formation of these amino acids and would inhibit the formation of a rich variety of others.