Minako HASHIGUCHI^1* and Hiroshi NARAOKA^1,2
Meteoritics & Planetary Science (in Press) Link to Article [https://doi.org/10.1111/maps.13211]
¹Research Center for Planetary Trace Organic Compounds, Kyushu University, Motooka 744, Nishi-ku,Fukuoka 819-0395, Japan
²Department of Earth and Planetary Sciences, Kyushu University, Motooka 744, Nishi-ku, Fukuoka 819-0395, Japan
*Corresponding author. E-mail: hashiguchi.minako.123@m.kyushu-u.ac.jp
Published by arrangement with John Wiley & Sons

High‐resolution mass spectrometry (HRMS) imaging by desorption electrospray ionization (DESI) coupled with Orbitrap MS using methanol (MeOH) spray was performed on a fragment of the Murchison (CM2) meteorite in this study. Homologues of C_nH_2n–1N₂⁺(n = 7–9) and C_nH_2nNO⁺ (n = 9–14) were detected on the sample surface by the imaging. A high‐performance liquid chromatography (HPLC)/HRMS analysis of MeOH extracts from the sample surface after DESI/HRMS imaging indicated that the C_nH_2n–1N₂⁺ homologues corresponds to alkylimidazole, and that a few isomers of the C_nH_2nNO⁺ homologues present in the sample. The alkylimidazoles and C_nH_2nNO⁺ homologues displayed different spatial distributions on the surface of the Murchison fragment, indicating chromatographic separation effects during aqueous alteration. Moreover, the distribution pattern of compounds is also different among homologues. This is probably also resulting from the separation of isomers by similar chromatographic effects, or different synthetic pathways. Alkylimidazoles and the C_nH_2nNO⁺ homologues are mainly distributed in the matrix region of the Murchison by mineralogical observations, which is consistent with previous reports. Altered minerals (e.g., Fe‐oxide, Fe‐sulfide, and carbonates) occurred in this region. However, no clear relationship was found between these minerals and the organic compounds detected by DESI/HRMS imaging. Although this result might be due to scale differences between the spatial resolution of DESI/HRMS imaging and the grain size in the matrix of the Murchison, our results would indicate that alkylimidazoles and the C_nH_2nNO⁺ homologues in the Murchison fragment were mainly synthesized by different processes from hydrothermal alteration on the parent body.

Tao Chen^1,2
Astrophysical Journal 866, 113 Link to Article [DOI: 10.3847/1538-4357/aae38f]
¹Leiden University, Leiden Observatory, Niels Bohrweg 2, NL-2333 CA Leiden, Netherlands
²School of Engineering Sciences in Chemistry, Biotechnology and Health, Department of Theoretical Chemistry & Biology, Royal Institute of Technology, SE-10691, Stockholm, Sweden

Photo-/ion-induced ionization and dissociation processes are commonly observed for polycyclic aromatic hydrocarbon (PAH) molecules. This work performs theoretical studies of PAHs and their fragments. Molecular dynamics simulations in combination with static quantum chemical calculations reveal that following a single hydrogen atom loss, the fragments, PAH-H, are extremely reactive. They catch a neighbor molecule within picoseconds to form a covalently bonded large molecule regardless of orientations/angles and temperatures. We calculate the infrared spectra of the covalently bonded molecules, which indicate that such species could be the carrier of unidentified infrared emission bands. It also implies that regular PAHs might be less abundant in space than what is expected.

¹Cavosie, A.J., ¹Timms, N.E., ²Ferrière, L., ³Rochette, P.
Geology 46, 891-894 Link to Article [DOI: 10.1130/G45079.1]
¹Space Science Technology Centre and The Institute for Geoscience Research (TIGeR), School of Earth and Planetary Science, Curtin University, Perth, WA 6102, Australia
²Natural History Museum, Burgring 7, Vienna, A-1010, Austria
³Aix-Marseille Univ, CNRS, INRA, IRD, Coll. France, CEREGE, Aix-en-Provence, 13545, France

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