15:00 〜 15:15
[MIS14-12] Parent body processes reproduce soluble organics in carbonaceous chondrites via geo-electrochemistry
★Invited Papers
キーワード：炭素質コンドライト、可溶性有機物、地球電気化学、氷の微惑星
Organics in carbonaceous chondrites (CCs) and other extraterrestrial bodies recorded the history of solar system chemistry and/or parent body processes. Biologically relevant organics, particularly amino acids, have been intensively investigated owing to their ubiquitous presence and plausible contribution to the prebiotic chemical evolution towards the origin of life on the Earth. Organics in CCs showed substantial heterogeneity in molecular abundance, isomer/homolog, and isotopic features, providing unique chemical signatures. To account for such chemical heterogeneity, the nature of the underlying driving force needs to be clarified in the context of interstellar and/or parent body processes. This will be also important for constraining the geochemical parameters including redox and energetic conditions.
In solvent-extractable fractions of CCs, amino acids typically coexist with a complex suite of other soluble, low molecular weight organics, including α-hydroxy acids, monocarboxylic acids, and monoamines. These organics show associated structures and similar isomer distributions with amino acids, which suggests a strong mechanistic relation in their genesis or conversion. Notably, these soluble organics are biologically significant, because of their participation in various organic syntheses for the chemical evolution or roles as essential nutrients for the primordial life.
Here we attempted to test whether geo-electrochemical processes in icy planetesimals can facilitate the decomposition of amino acids to generate meteoritic organics (e.g., amines, carboxylic and hydroxy acids). Four types of amino acids with aliphatic side chains, including glycine, alanine, valine, and 2-aminobutyric acid (ABA) were tested, which are among the most common and pervasive amino acids in CCs. Our results show that geo-electrochemical decomposition of these amino acids simultaneously generates monoamines, monocarboxylic and α-hydroxy acids under a wide range of redox conditions. The generated amines exhibited a similar homolog tendency as reported in CM2 Murchison meteorites, showing the validity of this model. Based on the quantitative results obtained, the water-rock interaction conditions were constrained for the parent icy planetesimals of Murchison meteorite. The implications on the geochemistry of icy bodies were addressed.
In solvent-extractable fractions of CCs, amino acids typically coexist with a complex suite of other soluble, low molecular weight organics, including α-hydroxy acids, monocarboxylic acids, and monoamines. These organics show associated structures and similar isomer distributions with amino acids, which suggests a strong mechanistic relation in their genesis or conversion. Notably, these soluble organics are biologically significant, because of their participation in various organic syntheses for the chemical evolution or roles as essential nutrients for the primordial life.
Here we attempted to test whether geo-electrochemical processes in icy planetesimals can facilitate the decomposition of amino acids to generate meteoritic organics (e.g., amines, carboxylic and hydroxy acids). Four types of amino acids with aliphatic side chains, including glycine, alanine, valine, and 2-aminobutyric acid (ABA) were tested, which are among the most common and pervasive amino acids in CCs. Our results show that geo-electrochemical decomposition of these amino acids simultaneously generates monoamines, monocarboxylic and α-hydroxy acids under a wide range of redox conditions. The generated amines exhibited a similar homolog tendency as reported in CM2 Murchison meteorites, showing the validity of this model. Based on the quantitative results obtained, the water-rock interaction conditions were constrained for the parent icy planetesimals of Murchison meteorite. The implications on the geochemistry of icy bodies were addressed.