Geochemical Journal | 2019
Preface: Evolution of molecules in space: From interstellar clouds to protoplanetary nebulae
Abstract
Copyright © 2019 by The Geochemical Society of Japan. acids showed that negligible isotopic fractionation of nitrogen occurred during UV-irradiation of the amorphous ice in relation to the starting gas (NH3) composition, implying that the 15N-enrichment in extraterrestrial organic matter was caused by other processes and/or represents the initial nitrogen isotopic composition of gas. Orthous-Daunay et al. (2019) conducted UV-irradiation experiments of chondritic SOMs extracted from Murchison (CM2) chondrite to examine UV irradiation effect on the SOM chemisty. The analysis of photo-irradiated Murchison SOMs with Orbitrap high resolution mass spectrometry showed that UV irradiation causes selective photo-induced alteration of SOMs by removing hydrogen and small carbon bearing volatile species. This results in shifting the mass distribution of remaining molecules to lower masses and increasing the fractions of aromatic cycles and double bonds in molecular structures. This study suggests that the chondritic SOMs never experienced severe photo-irradiation in the Sun’s parent molecular cloud and/or the protosolar disk before incorporation into planetesimals. Solvent soluble organic molecules in different chemical groups of carbonaceous chondrites may represent different chemical environments of parent planetesimals. Naraoka and Hashiguchi (2019) analyzed soluble CHN organic molecules extracted from CM and CR carbonaceous chondrites. They found that hydrogenated alkylpiperidines (CnH2n+1N) are more abundant in the CR chondrite (Yamato 002540) while alkylpyridines (CnH2n– 5N) are more abundant in the CM chondrites (Murray and Murchison). This difference in the relative abundance of hydrogenated alkylpiperidines and alkylpyridines within the CHN molecules could be attributed to the difference in redox condition between CR and CM chondrite parent bodies. Isono et al. (2019) investigated the bulk chemical characteristics of soluble polar organic molecules synthesized from formaldehyde and ammonia under hydrothermal Preface: Evolution of molecules in space: From interstellar clouds to protoplanetary nebulae