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Volume 50 (2016)
- Issue 4 Pages 04_v-
- Issue 3 Pages 117-
- Issue 2 Pages 29-
- Issue 1 Pages 01_i-
Volume 50, Issue 2
Displaying 1-6 of 6 articles from this issue
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Special issue “Astrochemistry”
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Yoshihiro Furukawa, Yoshinori Takano2016 Volume 50 Issue 2 Pages 29-31
Published: June 20, 2016
Released on J-STAGE: June 20, 2016
JOURNAL FREE ACCESSRecent advances in telescope based observation and onsite analysis of extraterrestrial organic compounds provided valuable information and hence significantly expanded our knowledge in astrochemistry. This information is primarily on the present space and constrained our technological limitations in space. Laboratory-based simulation experiments and high-precision analysis of extraterrestrial materials provide more comprehensive understanding of organic matters in space, early stage of planetary system, and the evolution history. This special issue “Astrochemistry” brings four review articles, in which the authors introduced unique organic chemical aspects and recent progresses from the view of individual expertise. We hope that you enjoy those overview contents and that this issue works to spread this research framework. This special issue is followed by a consecutive special issue, “Early Earth Chemistry.”View full abstractDownload PDF (274K)
Reviews (Special issue)
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Tetsuya Hama, Hirokazu Ueta, Naoki Watanabe, Akira Kouchi2016 Volume 50 Issue 2 Pages 33-50
Published: June 20, 2016
Released on J-STAGE: June 20, 2016
JOURNAL FREE ACCESSAromatic hydrocarbon is abundant constituent of interstellar and circumstellar dust. The hydrogenation and deuteration of interstellar aromatic hydrocarbons are of particular interest for the formation of aliphatic hydrocarbons and their deuterated isotopologues. Here, we investigated the hydrogenation/deuteration reactions of amorphous solid benzene (C6H6) at low temperatures of 10–50 K. In situ infrared spectroscopy revealed that cyclohexane or deuterated cyclohexane are efficiently formed by H or D atom addition. Given the activation barriers and low temperatures, these reactions proceeded via tunneling. However, the ratio of the hydrogenation and deuteration rates (H/D) was 1–1.5 at 15–25 K, whereas deuteration by tunneling typically occurs at a rate more than two orders of magnitude smaller than that of the comparable hydrogenation. This indicates that the isotopically insensitive surface processes (e.g., adsorption and diffusion) of the atoms physisorbed on solid C6H6 masked the tunneling kinetic isotope effect. The present results suggest that interstellar aromatic hydrocarbons can be hydrogenated or deuterated by the tunneling of H or D atoms at low temperatures, and that the tunneling kinetic isotope effect would not strongly inhibit the deuteration of interstellar aromatic hydrocarbons.View full abstractDownload PDF (3554K) -
Minako Hashiguchi2016 Volume 50 Issue 2 Pages 51-66
Published: June 20, 2016
Released on J-STAGE: June 20, 2016
JOURNAL FREE ACCESSPrimitive meteorites and planetary dusts contain organic materials extremely enriched in deuterium (D) and/or 15N compared with solar materials, which have been identified as micro-sized “hotspots” in insoluble organic matter (IOM) and matrices. They are believed to have been formed in cold environment of molecular clouds and outer region of early solar nebula. The hotspots tell us important information of formation and chemical evolution of extraterrestrial organic materials and physical/chemical conditions in molecular clouds and outer region of early solar nebula. Here, current results of “hotspots” studies are reviewed.View full abstractDownload PDF (1040K) -
Yoko Kebukawa2016 Volume 50 Issue 2 Pages 67-76
Published: June 20, 2016
Released on J-STAGE: June 20, 2016
JOURNAL FREE ACCESSInsoluble organic matter (IOM) in meteorites shows large variations in molecular structures. At least some of the variations attribute to the differences of parent asteroidal processes including aqueous alteration and thermal metamorphism. In general, alteration/metamorphism reduces the hydrogen, nitrogen and oxygen contents of the organic matter through decompositions of the aliphatic and oxygen-containing moieties. However, alteration effects are not only destructive but can also be constructive. For example, macromolecular organic residues can be condensed from simple molecules such as formaldehyde and ammonia with the presence of liquid water. This review covers the results from recent works on analyses and experimental studies of organic matter (mostly IOM) in meteorites, and discusses the chemistry plausibly occurred at the early stage of planetesimal formations.View full abstractDownload PDF (2081K) -
Haruna Sugahara2016 Volume 50 Issue 2 Pages 77-96
Published: June 20, 2016
Released on J-STAGE: June 20, 2016
JOURNAL FREE ACCESSComets are most pristine materials in the solar system, which were formed by accumulation of icy dusts from the solar nebula or molecular clouds. Comets mainly consist of water ice, silicates, and organic refractory materials, and also contain abundant organic molecules. The astronomical observation revealed that more than 27 different organic molecules exist in comets. It also revealed the isotopic compositions of some organic molecules. In addition, in situ analyses of comets by cometary explorers and the analyses of returned cometary samples have provided further information about cometary organic molecules. These findings showed that comets contain important biomolecules and their precursors such as amino acid, amine, and hydrogen cyanide. On the other hand, the new knowledge raised new questions about the distinct isotopic compositions of comets. In this review, I summarize the latest knowledge about cometary organic molecules from astronomical observation and two recent successful space missions: Stardust mission and Rosetta mission. Then, I discuss the role of comets in molecular evolution of organic molecules that lead to the origins of life on the early Earth, with special emphasis on the effect of impact shock on organic molecules at comet impacts.View full abstractDownload PDF (2995K)
Original paper
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Shoko Koji, Kohei Sasaki, Akira Ueda, Toshimasa Nakamoto2016 Volume 50 Issue 2 Pages 97-114
Published: June 20, 2016
Released on J-STAGE: June 20, 2016
JOURNAL FREE ACCESSChemical and isotopic (δD and δ18O) compositions of 30 hot spring waters and 5 river waters in Okuhida Hot Springs, Gifu, were investigated to examine the geochemical characteristics and geothermal resources. Most hot springs were of meteoric origin and of Na+–Cl-・HCO3- and Na+–HCO3- types with low salinity (less than 30 meq/L). In the study area, meteoric water infiltrates into ground and is heated by magmatic source and enriched in Ca2+and HCO3- during interaction with underlying carbonate rocks. A part of the hot spring is enriched in CO2 due to contribution of CO2-rich volcanic fluid. The estimated underground temperatures by several geothermometers are 150 to 200℃ at the depth of ca. 1 km. The total geothermal resources in the study area are estimated to be ca. 400 MWe for producing the electricity. In the study area, most hot springs have been provided for bathing in hotels and a part of them (60℃, 3,000 L/min) has not been used. We provide this unused geothermal energy to apply for snow melting on road and room heating. For the safety use of geothermal resources in the study area, scaling problem was considered. On the basis of the saturation index of several minerals from the observed chemical compositions of hot spring waters, calcite scale is expected to be precipitated in the reservoir and in the production wells and should be considered to prohibit the precipitation.View full abstractDownload PDF (1847K)
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