Updated on 2025/09/30

写真a

 
Sekine Yasuhito
 
Organization
Institute of Future Science Earth-Life Science Institute Professor
Title
Professor
External link

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News & Media

Degree

  • 博士（理学） ( 東京大学 )

Research Interests

  • planetary science

  • geochemistry

  • astrobiology

  • aquaplanetology

Research Areas

  • Natural Science / Space and planetary sciences

Education

  • The University of Tokyo   Graduate School of Science   Department of Earth and Planetary Science

    2001.4 - 2006.3

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  • The University of Tokyo   Faculty of Science   Department of Earth and Planetary Physics

    1997.4 - 2001.3

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Research History

  • Tokyo Institute of Technology   Earth-Life Science Institute   Director

    2022.4

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  • Tokyo Institute of Technology   Earth-Life Science Institute   Professor

    2018.6

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  • The University of Tokyo   Graduate School of Science   Associate Professor

    2014.10 - 2018.5

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  • The University of Tokyo   Graduate School of Frontier Sciences   Lecturer

    2011.7 - 2014.9

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  • The University of Tokyo   Graduate School of Frontier Sciences   Assistant Professor

    2007.4 - 2011.6

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  • The University of Tokyo   Graduate School of Science

    2006.4 - 2007.3

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Papers

  • Metal Limiting Habitability in Enceladus? Availability of Trace Metals for Methanogenic Life in Hydrothermal Fluids Reviewed

    Shuya Tan, Yasuhito Sekine, Takazo Shibuya

    Journal of Geophysical Research: Planets   2025.3

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    Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2024JE008591

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  • Hydrogen Generation From Ferrous Saponite in Reaction With H2S‐Containing Fluid: Relevance to Early Martian Habitability

    Natsumi Noda, Yasuhito Sekine, Yoshio Takahashi, Keisuke Fukushi, Hiroshi Sakuma, Takahiro Kawai, Mayuko Nakagawa, Norio Kitadai, Kristin Johnson‐Finn, Shawn Erin McGlynn

    Journal of Geophysical Research: Planets   130 ( 1 )   2024.12

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    Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

    Abstract

    Molecular hydrogen is an important gas species for understanding the early Martian climate and redox chemistry. Through ancient aqueous alterations of crustal rocks, ferrous (Fe(II)) saponite formed abundantly on Mars. Subsequent intrusions of hydrothermal fluids may have resulted in a chemical reaction between the dissolved volatiles and the nearby rocks. Here we propose a new H2 generating reaction between ferrous saponite and H2S‐containing fluids, which is possible on early Mars. A series of hydrothermal experiments at a relatively low temperature of 90°C were performed under anoxic conditions using synthesized ferrous saponite to compare the resulting H2 concentration among various gas and fluid compositions. Based on the relationship with the existence of H2S, reaction time, fluid pH, dissolved iron concentration, and amount of minerals, we found that high levels of H2 (∼0.1 mmol/g ferrous saponite) were generated in the presence of H2S most rapidly in moderate pH conditions. Our microscopic chemical analysis of mineral phases suggested that ferrous saponite served as both the iron source of pyrite precipitation and the electron source to form H2. Our results suggest that intrusions of H2S‐containing fluids into the saponite‐containing crust of Mars would generate H2, which could potentially provide locally concentrated chemical energy for chemoautotrophic life.

    DOI： 10.1029/2024je008538

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  • Aqueous alteration in icy planetesimals: The effect of outward transport of gaseous hydrogen

    Takazo Shibuya, Yasuhito Sekine, Sakiko Kikuchi, Hiroyuki Kurokawa, Keisuke Fukushi, Tomoki Nakamura, Sei-ichiro Watanabe

    Geochimica et Cosmochimica Acta   374   264 - 283   2024.6

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    Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.gca.2024.03.022

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  • Comparative study on cavernous weathering features formed by coastal processes and acidic alteration: Implications for rounded pits on Martian rocks

    Mitsuteru Sugiuchi, Yasuhito Sekine, Satoshi Takahashi

    Icarus   410   115889 - 115889   2024.3

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    Authorship：Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.icarus.2023.115889

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  • Aqueous breakdown of aspartate and glutamate to n-ω-amino acids on the parent bodies of carbonaceous chondrites and asteroid Ryugu

    Yamei Li, Hiroyuki Kurokawa, Yasuhito Sekine, Yoko Kebukawa, Yuko Nakano, Norio Kitadai, Naizhong Zhang, Xiaofeng Zang, Yuichiro Ueno, Gen Fujimori, Ryuhei Nakamura, Kosuke Fujishima, Junko Isa

    Science Advances   9 ( 50 )   2023.12

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    Publishing type：Research paper (scientific journal)   Publisher：American Association for the Advancement of Science (AAAS)  

    Amino acids in carbonaceous chondrites may have seeded the origin of life on Earth and possibly elsewhere. Recently, the return samples from a C-type asteroid Ryugu were found to contain amino acids with a similar distribution to Ivuna-type CI chondrites, suggesting the potential of amino acid abundances as molecular descriptors of parent body geochemistry. However, the chemical mechanisms responsible for the amino acid distributions remain to be elucidated particularly at low temperatures (<50°C). Here, we report that two representative proteinogenic amino acids, aspartic acid and glutamic acid, decompose to β-alanine and γ-aminobutyric acid, respectively, under simulated geoelectrochemical conditions at 25°C. This low-temperature conversion provides a plausible explanation for the enrichment of these two n-ω-amino acids compared to their precursors in heavily aqueously altered CI chondrites and Ryugu’s return samples. The results suggest that these heavily aqueously altered samples originated from the water-rich mantle of their water/rock differentiated parent planetesimals where protein α-amino acids were decomposed.

    DOI： 10.1126/sciadv.adh7845

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  • Dark microbiome and extremely low organics in Atacama fossil delta unveil Mars life detection limits

    Armando Azua-Bustos, Alberto G. Fairén, Carlos González-Silva, Olga Prieto-Ballesteros, Daniel Carrizo, Laura Sánchez-García, Victor Parro, Miguel Ángel Fernández-Martínez, Cristina Escudero, Victoria Muñoz-Iglesias, Maite Fernández-Sampedro, Antonio Molina, Miriam García Villadangos, Mercedes Moreno-Paz, Jacek Wierzchos, Carmen Ascaso, Teresa Fornaro, John Robert Brucato, Giovanni Poggiali, Jose Antonio Manrique, Marco Veneranda, Guillermo López-Reyes, Aurelio Sanz-Arranz, Fernando Rull, Ann M. Ollila, Roger C. Wiens, Adriana Reyes-Newell, Samuel M. Clegg, Maëva Millan, Sarah Stewart Johnson, Ophélie McIntosh, Cyril Szopa, Caroline Freissinet, Yasuhito Sekine, Keisuke Fukushi, Koki Morida, Kosuke Inoue, Hiroshi Sakuma, Elizabeth Rampe

    Nature Communications   14 ( 1 )   2023.12

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    Publishing type：Research paper (scientific journal)  

    DOI： 10.1038/s41467-023-36172-1

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  • Comparing the radiolytic oxidation of sulfur and chloride within ice on Europa and Mars

    Shuya Tan, Yasuhito Sekine, Takashi Kikuchi, Hisayuki Suematsu, Tetsuya Hama, Yoshio Takahashi

    Icarus   115873 - 115873   2023.11

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    Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.icarus.2023.115873

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  • Detection of phosphates originating from Enceladus’s ocean

    Frank Postberg, Yasuhito Sekine, Fabian Klenner, Christopher R. Glein, Zenghui Zou, Bernd Abel, Kento Furuya, Jon K. Hillier, Nozair Khawaja, Sascha Kempf, Lenz Noelle, Takuya Saito, Juergen Schmidt, Takazo Shibuya, Ralf Srama, Shuya Tan

    Nature   618 ( 7965 )   489 - 493   2023.6

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    Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    Abstract

    Saturn’s moon Enceladus harbours a global1 ice-covered water ocean2,3. The Cassini spacecraft investigated the composition of the ocean by analysis of material ejected into space by the moon’s cryovolcanic plume4–9. The analysis of salt-rich ice grains by Cassini’s Cosmic Dust Analyzer10 enabled inference of major solutes in the ocean water (Na+, K+, Cl–, HCO3–, CO32–) and its alkaline pH3,11. Phosphorus, the least abundant of the bio-essential elements12–14, has not yet been detected in an ocean beyond Earth. Earlier geochemical modelling studies suggest that phosphate might be scarce in the ocean of Enceladus and other icy ocean worlds15,16. However, more recent modelling of mineral solubilities in Enceladus’s ocean indicates that phosphate could be relatively abundant17. Here we present Cassini’s Cosmic Dust Analyzer mass spectra of ice grains emitted by Enceladus that show the presence of sodium phosphates. Our observational results, together with laboratory analogue experiments, suggest that phosphorus is readily available in Enceladus’s ocean in the form of orthophosphates, with phosphorus concentrations at least 100-fold higher in the moon’s plume-forming ocean waters than in Earth’s oceans. Furthermore, geochemical experiments and modelling demonstrate that such high phosphate abundances could be achieved in Enceladus and possibly in other icy ocean worlds beyond the primordial CO2 snowline, either at the cold seafloor or in hydrothermal environments with moderate temperatures. In both cases the main driver is probably the higher solubility of calcium phosphate minerals compared with calcium carbonate in moderately alkaline solutions rich in carbonate or bicarbonate ions.

    DOI： 10.1038/s41586-023-05987-9

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    Other Link： https://www.nature.com/articles/s41586-023-05987-9

  • Rapid Aggregation and Dissolution of Organic Aerosols in Liquid Methane on Titan

    Eito Hirai, Yasuhito Sekine, Naizhong Zhang, Natsumi Noda, Shuya Tan, Yoshio Takahashi, Hiroyuki Kagi

    Geophysical Research Letters   50 ( 12 )   2023.6

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    Publishing type：Research paper (scientific journal)   Publisher：American Geophysical Union (AGU)  

    DOI： 10.1029/2023gl103015

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  • Solubility of Amorphous Magnesium Carbonate at Low Temperatures: Implications for Carbonate Mineral Formation in Alkaline Lakes

    Takuma Kitajima, Keisuke Fukushi, Gankhurel Baasansuren, Davaasuren Davaadorj, Ganbat Shuukhaaz, Udaanjargal Uyangaa, Gerelmaa Tuvshin, Yasuhito Sekine, Yoshio Takahashi, Masahiro Yoda, Noriko Hasebe

    ACS Earth and Space Chemistry   7 ( 6 )   1227 - 1234   2023.5

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    Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

    DOI： 10.1021/acsearthspacechem.3c00030

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  • Effective formation of surface flow due to salt precipitation within soils upon repeated brine seepages on Mars

    Shoko Imamura, Yasuhito Sekine, Yu Maekawa, Hiroyuki Kurokawa, Takenori Sasaki

    Icarus   396   115500 - 115500   2023.5

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    Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.icarus.2023.115500

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  • Early Water Delivery to Terrestrial Planet Regions during the Stages of Jupiter’s Formation and Migration in the Grand Tack Model

    Masahiro Ogihara, Hidenori Genda, Yasuhito Sekine

    The Planetary Science Journal   4 ( 2 )   32 - 32   2023.2

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    Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

    Abstract

    The formation and subsequent migration of gas giants could significantly affect the material mixing in the solar system. In this study, we use N-body simulations to investigate how much water is transported into the region of the terrestrial planet formation during the growth and migration phases of Jupiter in the Grand Tack model. We found that Jupiter’s growth was accompanied by significant mass transport and that a substantial amount of water (about 10 times Earth’s ocean mass for the initial planetesimal distribution based on the minimum-mass solar nebula) was transported into the terrestrial planet region. The total amount delivered increased further during Jupiter’s migration phase (totaling about 10–40 times Earth’s ocean mass), which was less dependent on simulation parameters. In addition, at these stages, terrestrial planets were not fully grown. Therefore, water supplied during these early stages could interact with metallic iron during the core formation of protoplanets and/or growing Earth. Since hydrogen in water molecules can dissolve into their cores, this could explain the density deficit observed in the current Earth core. Notably, Jupiter could play an important role as a “barrier” in explaining the dichotomy of the isotopic compositions between noncarbonaceous (NC) and carbonaceous (CC) meteorites. This study’s results show that Jupiter’s growth necessitates some mixing of NC and CC materials.

    DOI： 10.3847/psj/acb64b

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    Other Link： https://iopscience.iop.org/article/10.3847/PSJ/acb64b/pdf

  • Characterization of groundwater chemistry beneath Gale Crater on early Mars by hydrothermal experiments

    Natsumi Noda, Yasuhito Sekine, Shuya Tan, Sakiko Kikuchi, Takazo Shibuya, Minako Kurisu, Yoshio Takahashi, Keisuke Fukushi, Elizabeth B. Rampe

    Icarus   386   115149 - 115149   2022.11

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    Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.icarus.2022.115149

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  • Synthesis of ferrian and ferro-saponites: Implications for the structure of (Fe,Mg)-smectites formed under reduced conditions Reviewed

    Hiroshi Sakuma, Koki Morida, Yoshio Takahashi, Keisuke Fukushi, Natsumi Noda, Yasuhito Sekine, Kenji Tamura

    American Mineralogist   107 ( 10 )   1926 - 1935   2022.10

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Mineralogical Society of America  

    Abstract

    Clay minerals are widely distributed on the surface of Earth, Mars, and Ceres in the solar systems. Among numerous clay minerals, smectites can record the history of the environment through the exchange of interlayer cations with those in water or through redox reactions with the atmosphere. Therefore, characterization of chemical compositions and crystal structures of smectites is crucial for revealing the paleoenvironment. For instance, the crystal structure within octahedral sheets of iron-bearing smectites changes to trioctahedral sheets under reduced or dioctahedral sheets under oxidizing conditions. Orbital infrared and X-ray diffraction (XRD) analyses by Mars orbiters/rovers revealed the presence of (Fe,Mg)-smectites on the surface of Mars; however, it has been difficult to characterize the properties of these (Fe,Mg)-smectites, which are rare on the surface of Earth. In this study, we synthesized ferrian (ferric ion-rich) and ferrous (ferrous ion-rich) (Fe,Mg)-saponite and revealed the effect of valence states and iron contents on the crystal structures. These saponites were synthesized using a hydrothermal method under reduced conditions. The crystal structures and valence states of iron were analyzed by XRD, Fourier-transform infrared spectroscopy, transmission electron microscopy, Mössbauer spectroscopy, and X-ray absorption near edge measurements. The synthesized clays were trioctahedral swelling clays and were identified as saponites. The valence state of iron in these synthesized saponites is altered by oxygen and a reducing agent in water; however, the trioctahedral structures are maintained under both oxidizing and reduced conditions, following a reversible reaction. This mechanism can be interpreted by the desorption and adsorption of hydrogen in the hydroxyls of the octahedral sheets of the smectite layers. The maximum basal spacing of the (02l) lattice plane in the octahedral sheets was defined by compiling various smectite data. When the basal spacing of (02l) is larger than the maximum in dioctahedral smectites, smectite can be identified as trioctahedral smectite. The redox state of iron in the octahedral sheet cannot be determined from the basal spacing of (02l). We revealed that the iron content in the trioctahedral sheet has a linear relationship with lattice parameter b. This provides a method to estimate the iron content in saponite from XRD data. The XRD profiles of smectites found at the Yellowknife Bay on Mars can be explained only by trioctahedral smectites, and the iron content in the octahedral sheet is roughly estimated to be 0.5–1.7 in a half-unit cell. These results indicate that the presence of (Fe,Mg)-saponite implies a reduced environment during the formation and that this iron-bearing saponite has both oxidation and reduction capabilities depending on the environment.

    DOI： 10.2138/am-2022-8231

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  • Sulfur mass-independent fractionation during SO2 photolysis in low-temperature/pressure atmospheres Reviewed

    Yoshiaki Endo, Yasuhito Sekine, Yuichiro Ueno

    Chemical Geology   609   121064 - 121064   2022.10

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.chemgeo.2022.121064

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  • Geoelectrochemistry-driven alteration of amino acids to derivative organics in carbonaceous chondrite parent bodies Reviewed

    Yamei Li, Norio Kitadai, Yasuhito Sekine, Hiroyuki Kurokawa, Yuko Nakano, Kristin Johnson-Finn

    Nature Communications   13 ( 1 )   1 - 14   2022.8

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    Abstract

    A long-standing question regarding carbonaceous chondrites (CCs) is how the CCs’ organics were sourced and converted before and after the accretion of their parent bodies. Growing evidence shows that amino acid abundances in CCs decrease with an elongated aqueous alteration. However, the underlying chemical processes are unclear. If CCs’ parent bodies were water-rock differentiated, pH and redox gradients can drive electrochemical reactions by using H2 as an electron source. Here, we simulate such redox conditions and demonstrate that α-amino acids are electrochemically altered to monoamines and α-hydroxy acids on FeS and NiS catalysts at 25 °C. This conversion is consistent with their enrichment compared to amino acid analogs in heavily altered CCs. Our results thus suggest that H2 can be an important driver for organic evolution in water-rock differentiated CC parent bodies as well as the Solar System icy bodies that might possess similar pH and redox gradients.

    DOI： 10.1038/s41467-022-32596-3

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    Other Link： https://www.nature.com/articles/s41467-022-32596-3

  • Recognition and Classification of Martian Chaos Terrains Using Imagery Machine Learning: A Global Distribution of Chaos Linked to Groundwater Circulation, Catastrophic Flooding, and Magmatism on Mars Reviewed

    Hiroki Shozaki, Yasuhito Sekine, Nicholas Guttenberg, Goro Komatsu

    Remote Sensing   14 ( 16 )   3883 - 3883   2022.8

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

    Martian chaos terrains are fractured depressions consisting of block landforms that are often located in source areas of outflow channels. Numerous chaos and chaos-like features have been found on Mars; however, a global-scale classification has not been pursued. Here, we perform recognition and classification of Martian chaos using imagery machine learning. We developed neural network models to classify block landforms commonly found in chaos terrains—which are associated with outflow channels formed by water activity (referred to as Aromatum-Hydraotes-Oxia-like (or AHO) chaos blocks) or with geological features suggesting volcanic activity (Arsinoes-Pyrrhae-like (or AP) chaos blocks)—and also non-chaos surface features, based on >1400 surface images. Our models can recognize chaos and non-chaos features with 93.9% ± 0.3% test accuracy, and they can be used to classify both AHO and AP chaos blocks with >89 ± 4% test accuracy. By applying our models to ~3150 images of block landforms of chaos-like features, we identified 2 types of chaos terrain. These include hybrid chaos terrain, where AHO and AP chaos blocks co-exist in one basin, and AHO-dominant chaos terrain. Hybrid chaos terrains are predominantly found in the circum-Chryse outflow channels region. AHO-dominant chaos terrains are widely distributed across Aeolis, Cydonia, and Nepenthes Mensae along the dichotomy boundary. Their locations coincide with regions suggested to exhibit upwelling groundwater on Hesperian Mars.

    DOI： 10.3390/rs14163883

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  • Spatially Resolved Observations of Europa’s Surface with Subaru/IRCS at 1.0–1.8 μm: Upper Limits to the Abundances of Hydrated Cl-bearing Salts Reviewed

    Shuya Tan, Yasuhito Sekine, Masayuki Kuzuhara

    The Planetary Science Journal   3 ( 3 )   70-1 - 70-18   2022.3

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.3847/psj/ac596c

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    Other Link： https://iopscience.iop.org/article/10.3847/PSJ/ac596c/pdf

  • Concepts for the Future Exploration of Dwarf Planet Ceres’ Habitability Reviewed

    Julie Castillo-Rogez, John Brophy, Kelly Miller, Michael Sori, Jennifer Scully, Lynnae Quick, Robert Grimm, Michael Zolensky, Michael Bland, Debra Buczkowski, Carol Raymond, Amanda Hendrix, Thomas Prettyman, Yasuhito Sekine, Timothy Titus, David Williams, Paul Backes, Laura Barge, Anton Ermakov, Andrew Galassi, Scott Moreland, Kris Zacny

    The Planetary Science Journal   3 ( 2 )   41 - 41   2022.2

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

    Abstract

    Dwarf planet Ceres is a compelling target for future exploration because it hosts at least regional brine reservoirs and potentially ongoing geological activity. As the most water-rich body in the inner solar system, it is a representative of a population of planetesimals that were likely a significant source of volatiles and organics to the inner solar system. Here we describe possible medium-class (around $1 billion) mission concepts that would determine both Ceres’ origin and its current habitability potential. Habitability is addressed through a combination of geological, geophysical, and compositional investigations by (i) searching for evidence from orbit of past and ongoing geological activity near landforms interpreted as brine-driven volcanic structures and (ii) probing the brine distribution below one of these regions with electromagnetic sounding (in situ). Two approaches were considered for compositional measurements, which address both habitability and origins: (1) in situ exploration at two sites and (2) sample return from a single site. Both concepts targeted material at Occator crater, which is one of the youngest features on Ceres (∼20 Ma) and a site rich in evaporites evolved from recently erupted brine sourced from a region >35 km deep. We conclude that a sample return architecture from these young evaporite deposits offers greater science return by enabling high-resolution analysis of organic matter (trapped in salt minerals) and isotopes of refractory elements for a similar cost and less science risk than in situ analyses. This manuscript describes the six science objectives and the two implementation concepts considered to achieve those objectives.

    DOI： 10.3847/psj/ac34ee

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    Other Link： https://iopscience.iop.org/article/10.3847/PSJ/ac34ee/pdf

  • Distant Formation and Differentiation of Outer Main Belt Asteroids and Carbonaceous Chondrite Parent Bodies Reviewed

    H. Kurokawa, T. Shibuya, Y. Sekine, B. L. Ehlmann, F. Usui, S. Kikuchi, M. Yoda

    AGU Advances   3 ( 1 )   2022.2

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2021av000568

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    Other Link： https://onlinelibrary.wiley.com/doi/full-xml/10.1029/2021AV000568

  • Reconstruction of pH, redox condition, and concentrations of major components in ancient liquid water from the Karasburg member, Murray formation, Gale Crater, Mars Reviewed

    Keisuke Fukushi, Yasuhito Sekine, Elizabeth B. Rampe

    Geochimica et Cosmochimica Acta   2022.2

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

    DOI： 10.1016/j.gca.2022.02.005

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  • Arsenic and uranium contamination of Orog Lake in the Valley of Gobi Lakes, Mongolia: Field evidence of conservative accumulation of U in an alkaline, closed-basin lake during evaporation

    Baasansuren Gankhurel, Keisuke Fukushi, Davaadorj Davaasuren, Eigo Imai, Takuma Kitajima, Uyangaa Udaanjargal, Tuvshin Gerelmaa, Yasuhito Sekine, Yoshio Takahashi, Noriko Hasebe

    Journal of Hazardous Materials   46   2022

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  • Doubly substituted isotopologues of methane hydrate ((CH3D)-C-13 and (CH2D2)-C-12): Implications for methane clumped isotope effects, source apportionments and global hydrate reservoirs

    Naizhong Zhang, Glen T. Snyder, Mang Lin, Mayuko Nakagawa, Alexis Gilbert, Naohiro Yoshida, Ryo Matsumoto, Yasuhito Sekine

    GEOCHIMICA ET COSMOCHIMICA ACTA   315   127 - 151   2021.12

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1016/j.gca.2021.08.027

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  • Anaerobic Microscopic Analysis of Ferrous Saponite and Its Sensitivity to Oxidation by Earth’s Air: Lessons Learned for Analysis of Returned Samples from Mars and Carbonaceous Asteroids Reviewed

    Natsumi Noda, Shohei Yamashita, Yoshio Takahashi, Megumi Matsumoto, Yuma Enokido, Kana Amano, Takahiro Kawai, Hiroshi Sakuma, Keisuke Fukushi, Yasuhito Sekine, Tomoki Nakamura

    Minerals   11 ( 11 )   1244 - 1244   2021.11

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：MDPI AG  

    DOI： 10.3390/min11111244

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  • Enceladus as a potential oasis for life: Science goals and investigations for future explorations Reviewed

    Gaël Choblet, Gabriel Tobie, Arnaud Buch, Ondrej Čadek, Laura M. Barge, Marie Bēhounková, Eloi Camprubi, Caroline Freissinet, Matt Hedman, Geraint Jones, Valery Lainey, Alice Le Gall, Alice Lucchetti, Shannon MacKenzie, Giuseppe Mitri, Marc Neveu, Francis Nimmo, Karen Olsson-Francis, Mark Panning, Frank Postberg, Joachim Saur, Jürgen Schmidt, Yasuhito Sekine, Takazo Shibuya, Christophe Sotin, Ondrej Soucek, Cyril Szopa, Tomohiro Usui, Steven Vance, Tim Van Hoolst

    Experimental Astronomy   2021.11

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

    DOI： 10.1007/s10686-021-09808-7

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    Other Link： https://link.springer.com/article/10.1007/s10686-021-09808-7/fulltext.html

  • Field Investigations of Chemical Partitioning and Aqueous Chemistry of Freezing Closed-Basin Lakes in Mongolia as Analogs of Subsurface Brines on Icy Bodies

    Masahiro Yoda, Yasuhito Sekine, Keisuke Fukushi, Takuma Kitajima, Baasansuren Gankhurel, Davaadorj Davaasuren, Tuvshin Gerelmaa, Shuukhaaz Ganbat, Daigo Shoji, Mikhail Y. Zolotov, Yoshio Takahashi

    JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS   126 ( 11 )   2021.11

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    Language：English   Publishing type：Research paper (scientific journal)  

    DOI： 10.1029/2021JE006972

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  • Stability of Atmospheric Redox States of Early Mars Inferred from Time Response of the Regulation of H and O Losses Reviewed

    Shungo Koyama, Naoki Terada, Hiromu Nakagawa, Takeshi Kuroda, Yasuhito Sekine

    The Astrophysical Journal   912 ( 2 )   135 - 135   2021.5

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    Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Astronomical Society  

    Abstract

    The ratio of total losses of H and O from the atmosphere is crucial for determining the Martian atmospheric redox state. The H and O escapes are shown to be regulated in a stoichiometric 2:1 ratio in a converged model of present-day Mars over a timescale of ∼105 yr, which is called self-regulation. Self-regulation timescales under different atmospheric conditions on early Mars are not well understood. Here we use a 1D photochemical model to calculate the timescales of self-regulation for denser CO2 atmospheres with various surface temperatures as benchmark cases for early Mars. Self-regulation is driven by variations in the amount of O2 or CO in the atmosphere, depending on the atmospheric redox state. Self-regulation timescales are likely to be controlled by the net redox balance. A 1 bar CO2 atmosphere with a surface temperature of 240 K has a self-regulation timescale of a few million years. Denser atmospheres of early Mars have a longer regulation timescale and are less redox-stable than the atmosphere of present-day Mars. Obliquity variations cause atmospheric CO2 fluctuations, producing a difference in the self-regulation timescale between high and low obliquity. Because an increase in CO2 suppresses H escape, the net effect of the obliquity cycle could have driven the atmospheric redox states to be more reducing. Our results also suggest the possibility of a CO-dominated atmosphere of 10–100 mbars at 3 Ga. The redox state of ancient Mars might have fluctuated more easily than that of the present.

    DOI： 10.3847/1538-4357/abf0ac

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    Other Link： https://iopscience.iop.org/article/10.3847/1538-4357/abf0ac/pdf

  • An experimental study of photo-oxidation of Fe(II): Implications for the formation of Fe(III) (hydro)oxides on early Mars and Earth

    Haruhisa Tabata, Yasuhito Sekine, Yoshiki Kanzaki, Seiji Sugita

    GEOCHIMICA ET COSMOCHIMICA ACTA   299   35 - 51   2021.4

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    DOI： 10.1016/j.gca.2021.02.006

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  • Progressive ocean oxygenation at ~2.2 Ga inferred from geochemistry and molybdenum isotopes of the Nsuta Mn deposit, Ghana

    Kosuke T. Goto, Yasuhito Sekine, Takashi Ito, Katsuhiko Suzuki, Ariel D. Anbar, Gwyneth W. Gordon, Yumiko Harigane, Teruyuki Maruoka, Gen Shimoda, Teruhiko Kashiwabara, Yutaro Takaya, Tatsuo Nozaki, James R. Hein, George M. Tetteh, Frank K. Nyame, Shoichi Kiyokawa

    Chemical Geology   567   120116 - 120116   2021.4

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    DOI： 10.1016/j.chemgeo.2021.120116

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  • Deep Trek: Mission Concepts for Exploring Subsurface Habitability & Life on Mars — A Window into Subsurface Life in the Solar System

    Charles Edwards, Vlada Stamenkovic, Penelope Boston, Kennda Lynch, Jesse Tarnas, Barbara Sherwood-Lollar, Sushil Atreya, Alexis Templeton, Anthony Freeman, Woodward Fischer, Tilman Spohn, Chris Webster, Alberto G. Fairén, John (Jack) Mustard, Michael Mischna, Tullis C. Onstott, Magdalena Rose Osburn, Thomas Kieft, Robert E. Grimm, William B. Brinckerhoff, Sarah Johnson, Luther Beegle, James Head, Albert Haldemann, Charles Cockell, John Hernlund, Brian Wilcox, David Paige, Giuseppe Etiope, Daniel Glavin, Maria-Paz Zorzano, Yasuhito Sekine, Stalport Fabien, Joseph Kirschvink, Cara Magnabosco, Roberto Orosei, Matthias Grott, John D. Rummel, Atsuko Kobayashi, Fumio Inagaki, Janice Bishop, Vincent Chevrier, Mary Sue Bell, Beth N. Orcutt, Jennifer McIntosh, Katarina Miljkovic, Doris Breuer, Tomohiro Usui, Kris Zacny, Essam Heggy, Edgard G. Rivera-Valentín, Nathan J. Barba, Ryan Woolley, Oliver Warr, Mike Malaska, Jennifer G. Blank, Donald F. Ruffatto, Haley M. Sapers, Larry H. Matthies, Lewis Ward, Svetlana Shkolyar, Cedric Schmelzbach, Travis S. J. Gabriel, Ceth Parker, Hermes Hernan Bolivar-Torres, Bernadett Pál, Dirk Schulze-Makuch, Jorge Andres Torres Celis, Akos Kereszturi, J. Andy Spry, Kyle Uckert, Marc A. Hesse, Rachel Harris, A.-C. Plesa, Renyu Hu, Ali-akbar Agha-mohammadi, Brian D. Wade, Snehamoy Chatterjee, Patrick McGarey, Heather Valeah Graham, Shino Suzuki, Matt Schrenk, Kristopher Sherrill, Scott Howe, Raju Manthena, Mariko Burgin, Kalind Carpenter, Louis Giersch, Velibor Cormarkovic, Nigel Smith, Jeffrey J. McDonnell, Joseph Michalski, Devanshu Jha, Morgan L. Cable, Elodie Gloesener, Varun Paul, Stewart Gault, Sharon Kedar, Eloise Marteau, Orkun Temel, Seth Krieger, Ryan Timoney

    Bulletin of the AAS   53 ( 4 )   2021.3

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    DOI： 10.3847/25c2cfeb.5f50cebc

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  • The role of hydrothermal sulfate reduction in the sulfur cycles within Europa: Laboratory experiments on sulfate reduction at 100 MPa

    Shuya Tan, Yasuhito Sekine, Takazo Shibuya, Chihiro Miyamoto, Yoshio Takahashi

    Icarus   357   114222 - 114222   2021.3

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    DOI： 10.1016/j.icarus.2020.114222

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  • Distribution of uranium and arsenic between sediment and water of alkaline-hyposaline lake from Valley of Gobi Lakes in Mongolia

    Gankhurel Baasansuren, Fukushi Keisuke, Davaasuren Davaadorj, Imai Eigo, Kitajima Takuma, Gerelmaa Tuvshin, Yasuhito Sekine, Yoshio Takahashi, Noriko Hasebe

    Abstracts of Annual Meeting of the Geochemical Society of Japan   68   15   2021

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    Saline lakes represent 23% of the area of all lakes on Earth and located mostly in arid and semi-arid climates. Olgoi and Orog lakes are located in semi-arid climates of the Valley of the Gobi lakes in Mongolia. It is the desert area that one of the sources of Asian dust (kousa) comes to Japan. Moreover, lake shrinkage has occurred in recent decades if the lake dried up it is possible to be a source of trace elements contamination. It can affect the environment and possible to move to a greater distance beyond the continent by the westerly winds. Then we need to clarify the geochemical behavior (solubility and mobility) of trace elements especially As and U in saline lake water and sediment in this area. Olgoi lake has no inflow and outflow river. Orog lake has one inflow river but no outflow. The depth of both lakes is around 1m. The water samples were collected from both lakes from 2015 to 2020. The major cations and anions of the water sample were analyzed using inductively coupled plasma optical emission spectroscopy and high-performance liquid chromatography. The trace elements were analyzed by using an inductively coupled plasma mass spectrometer. Sediment cores were taken by a gravity corer in August 2018 from Olgoi and Orog lake. Sediment samples were analyzed by using X-ray diffraction (XRD), and synchrotron-based X-ray absorption spectroscopy (XAFS), and 2 step chemical extraction for chemical speciation of As and U using 1M HCl for extractable and using a mixture of 48%HF, 60%HNO3, and 30%HCl, for a residual fraction.Olgoi and Orog lakes exhibited pH >9 and salinity above 1300 mg/kg. The major components of the lake's water are Na+, Cl- and SO42-. The high Na and Cl concentrations are the results of the evaporation of the lake waters. Also, the results showed that high concentrations of As (~3019ppb) and U (~590ppb) in lake water, which exceeded the WHO standards of As (10ppb) and U (30ppb). We found a positive correlation between As and U with Na and Cl. The total As and U concentrations of Olgoi lake sediment was 14.5ppm and 0.9ppm, respectively. The total As and U in Orog lake sediment ranged from 2.4 to 3ppm and 2.2 to 2.7ppm, respectively. The partial extraction results showed that As and U in the sediments are distributed among extractable fraction and residual fraction almost equally. XRD analysis showed the presence of authigenic minerals including calcite and monohydrocalcite. The results of XAFS analysis revealed As in Orog lake sediment was As (V) and primarily coprecipitated with calcite and secondarily adsorbed on ferrihydrite. As in Olgoi lake sediment was mainly As (V) and 20-30% was As (III) and coprecipitated with calcite. As and U possibly are removed by the authigenic carbonates. An extractable fraction of partial extraction is including ferrihydrite and calcium carbonates. This study showed that high concentrations of As and U in saline lake water and low in sediment. Therefore, little amount of As and U were adsorbed into sediments but mostly accumulated in water due to high evaporation. This study suggests that the As and U may be precipitated as salts after drying out of the lake water, which must be highly soluble.

    DOI： 10.14862/geochemproc.68.0_15

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  • Hydrogeochemical Study on Closed-Basin Lakes in Cold and Semi-Arid Climates of the Valley of the Gobi Lakes, Mongolia: Implications for Hydrology and Water Chemistry of Paleolakes on Mars

    Yasuhito Sekine, Takuma Kitajima, Keisuke Fukushi, Baasansuren Gankhurel, Solongo Tsetsgee, Davaadorj Davaasuren, Haruna Matsumiya, Takufumi Chida, Maya Nakamura, Noriko Hasebe

    MINERALS   10 ( 9 )   2020.9

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    DOI： 10.3390/min10090792

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  • In Situ Formation of Monohydrocalcite in Alkaline Saline Lakes of the Valley of Gobi Lakes: Prediction for Mg, Ca, and Total Dissolved Carbonate Concentrations in Enceladus’ Ocean and Alkaline-Carbonate Ocean Worlds Reviewed

    Keisuke Fukushi, Eigo Imai, Yasuhito Sekine, Takuma Kitajima, Baasansuren Gankhurel, Davaadorj Davaasuren, Noriko Hasebe

    Minerals   10 ( 8 )   669 - 669   2020.7

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    The nature of mineral precipitations in terrestrial alkaline soda lakes provides insights into the water chemistry of subsurface oceans on icy bodies in the outer solar system. Saturation analyses of terrestrial alkaline lakes have shown that the solution chemistries of lake waters are generally controlled by the presence of monohydrocalcite (MHC) and amorphous Mg-carbonate (AMC). However, direct observations of the formation of these metastable carbonates in natural alkaline lakes have been limited. This study provides evidence of in situ MHC formation in alkaline lakes, based on the water chemistry and mineralogy of suspended matter in Olgoy, Boon Tsagaan, and Orog Lakes (Valley of Gobi Lakes, Mongolia). The solution chemistries were close to saturation with respect to MHC and AMC, consistent with other alkaline lakes worldwide. Suspended matter was separated by the ultracentrifugation of lake water following freeze-drying. Our results show that MHC is the common mineral phase in the suspended matter. These observations confirm that MHC is the direct authigenic product of evaporation in alkaline lakes. The carbonate fraction in suspended matter from Olgoy Lake has a Mg/Ca ratio of 0.4, suggesting the formation of AMC in association with MHC. Based on the dissolution equilibria of AMC and MHC, we predict the Mg2+, Ca2+, and total dissolved carbonate concentrations in Enceladus’ ocean to be ~1 mmol/kg, ~10 μmol/kg, and 0.06–0.2 mol/kg, respectively, in the presence of AMC and MHC. We propose that the measurements of Mg contents in plumes will be key to constraining the total dissolved carbonate concentrations and chemical affinities of subsurface oceans on Enceladus and other alkaline-carbonate ocean worlds.

    DOI： 10.3390/min10080669

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  • A framework for understanding Mo isotope records of Archean and Paleoproterozoic Fe- and Mn-rich sedimentary rocks: Insights from modern marine hydrothermal Fe-Mn oxides Reviewed

    Kosuke T. Goto, Yasuhito Sekine, Gen Shimoda, James R. Hein, Shogo Aoki, Akira Ishikawa, Katsuhiko Suzuki, Gwyneth W. Gordon, Ariel D. Anbar

    Geochimica et Cosmochimica Acta   280   221 - 236   2020.7

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    DOI： 10.1016/j.gca.2020.04.017

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  • Relict Ocean Worlds: Ceres Reviewed

    Maria Cristina De Sanctis, Giuseppe Mitri, Julie Castillo-Rogez, Christopher H. House, Simome Marchi, Carol A. Raymond, Yasuhito Sekine

    Space Science Reviews   216 ( 4 )   2020.6

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    DOI： 10.1007/s11214-020-00683-w

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  • Experimental and Simulation Efforts in the Astrobiological Exploration of Exooceans Reviewed

    Ruth-Sophie Taubner, Karen Olsson-Francis, Steven D. Vance, Nisha K. Ramkissoon, Frank Postberg, Jean-Pierre de Vera, Andre Antunes, Eloi Camprubi Casas, Yasuhito Sekine, Lena Noack, Laura Barge, Jason Goodman, Mohamed Jebbar, Baptiste Journaux, Ozgur Karatekin, Fabian Klenner, Elke Rabbow, Petra Rettberg, Tina Ruckriemen-Bez, Joachim Saur, Takazo Shibuya, Krista M. Soderlund

    Space Science Review   216 ( 9 )   1 - 41   2020.1

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    DOI： 10.1007/s11214-020-0635-5

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  • Semiarid climate and hyposaline lake on early Mars inferred from reconstructed water chemistry at Gale Reviewed

    Fukushi, K, Y. Sekine, H. Sakuma, K. Morida, R. Wordsworth

    Nature Communications   10 ( 4896 )   1 - 11   2019.10

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  • Pluto’s ocean is capped and insulated by gas hydrates Reviewed

    Shunichi Kamata, Francis Nimmo, Yasuhito Sekine, Kiyoshi Kuramoto, Naoki Noguchi, Jun Kimura, Atsushi Tani

    Nature Geoscience   12 ( 6 )   407 - 410   2019.6

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    DOI： 10.1038/s41561-019-0369-8

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  • Enceladus: Evidence and Unsolved Questions for an Ice-Covered Habitable World Reviewed

    Yasuhito Sekine, Takazo Shibuya, Shunichi Kamata

    Astrobiology   399 - 407   2019

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    DOI： 10.1007/978-981-13-3639-3_25

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  • Salts trapping within ice in frozen saline lakes in Mongolia: Implications for icy bodies in the Solar System.

    Yoda Masahiro, Sekine Yasuhito, Fukushi Keisuke, Takahashi Yoshio, Kitajima Takuma, Gankhurel Baasansuren, Davaasuren Davaadorj, shojo Daigo

    Abstracts of Annual Meeting of the Geochemical Society of Japan   66   221   2019

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    DOI： 10.14862/geochemproc.66.0_221

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  • Highly oxidizing aqueous environments on early Mars inferred fromscavenging pattern of trace metals on manganese oxides Reviewed

    Noda, N, S. Imamura, Y. Sekine, M. Kurisu, K. Fukushi, N. Terada, S. Uesugi, C. Numako, Y. Takahashi, J. Hartmann

    Journal of Geophysical Research - Planets   124 ( 5 )   1 - 14   2019

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    DOI： 10.1029/2018JE005892

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  • 火星における塩水による地形模様の形成に 対する塩析出の役割 Reviewed

    今村 翔子, 関根 康人, 佐々木 猛智, 前川 優

    日本惑星科学会誌 遊星人   27 ( 3 )   163 - 172   2018.7

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  • Experimental study of heterogeneous organic chemistry induced by far ultraviolet light: Implications for growth of organic aerosols by CH3 addition in the atmospheres of Titan and early Earth Reviewed

    Peng Hong, Yasuhito Sekine, Tsutoni Sasamori, Seiji Sugita

    Icarus   307   25 - 39   2018.6

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    DOI： 10.1016/j.icarus.2018.02.019

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  • An experimental study on impact-induced alterations of planetary organic simulants Reviewed

    Yasuhito Sekine, Kenya Kodama, Takamichi Kobayashi, Seiji Obata, Yu Chang, Nanako O. Ogawa, Yoshinori Takano, Naohiko Ohkouchi, Koichiro Saiki, Toshimori Sekine

    Meteoritics & Planetary Science   53 ( 6 )   1267 - 1282   2018.6

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    DOI： 10.1111/maps.13075

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  • Depositional processes of impactites from the YAX-1 drill core in the Chicxulub impact structure inferred from vertical profiles of PDF orientations and grain size distributions of shocked quartz Reviewed

    Chang, Y, K. Goto, Y. Sekine, E. Tajika

    Meteoritics and Planetary Science   53 ( 7 )   1323 - 1340   2018

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    DOI： 10.1111/maps.13082

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  • マンガン酸化物と室内実験から示唆される初期火星の酸化的表層環境 Reviewed

    野田夏実, 今村翔子, 関根 康人, 上杉宗一郎, 栗栖美菜子, 高橋嘉夫, 寺田直樹, 福士圭介

    日本惑星科学会誌   27   138 - 146   2018

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  • An Automated Method for Crater Counting Using Rotational Pixel Swapping Method Reviewed

    Satoru Yamamoto, Tsuneo Matsunaga, Ryosuke Nakamura, Yasuhito Sekine, Naru Hirata, Yasushi Yamaguchi

    IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING   55 ( 8 )   4384 - 4397   2017.8

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    DOI： 10.1109/TGRS.2017.2691758

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  • Frontier of Planetary Science Revealed by Terahertz Wave Observations in Deep-space Explorations Reviewed

    KURODA Takeshi, SAGAWA Hideo, SEKINE Yasuhito, KASAI Yasuko, HARTOGH Paul

    Journal of The Remote Sensing Society of Japan   37 ( 4 )   351 - 361   2017.4

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    Terahertz waves have been utilized for new and/or better understandings of the earth and planetary sciences through observations of atmospheric molecules and the physical properties of surfaces, but applications in the field of planetary science using observations from terahertz instruments on board spacecraft going into deep space are still at the initiation stage. In this review paper, we describe the scientific achievements of Rosetta/MIRO, which was the first terahertz instrument on board a deep-space spacecraft for the observation of the nucleus of comet 67P/Churyumov-Gerasimenko, the expected scientific achievements of JUICE/SWI, which will be launched to observe Jupiter and its icy satellites, and expectations for a future terahertz instrument on a Mars orbiter. Keeping in mind these achievements and expectations, we discuss the expansion of planetary science allowed by the observations made by terahertz instruments on board deep-space spacecraft.

    DOI： 10.11440/rssj.37.351

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    Other Link： https://kaken.nii.ac.jp/grant/KAKENHI-PROJECT-16K05552/

  • The Charon-forming giant impact as a source of Pluto’s dark equatorial regions Reviewed

    Yasuhito Sekine, Hidenori Genda, Shunichi Kamata, Taro Funatsu

    Nature Astronomy   1 ( 2 )   1 - 6   2017.2

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    DOI： 10.1038/s41550-016-0031

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    Other Link： http://www.nature.com/articles/s41550-016-0031

  • Ocean redox conditions during the Paleoproterozoic and Archean: Insights from Mo isotope of modern hydrothermal Fe and Mn oxides

    T. Goto Kosuke, R. Hein James, Sekine Yasuhito, Shimoda Gen, Aoki Shogo, Ishikawa Akira, Suzuki Katsuhiko

    Abstracts of Annual Meeting of the Geochemical Society of Japan   64   2 - 2   2017

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    DOI： 10.14862/geochemproc.64.0_2

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  • Sulfate reduction and hydrothermal environments within Europa

    Tan Shuya, Sekine Yasuhito, Shibuya Takazo, Miyamoto Chiro, Takahashi Yoshio

    Abstracts of Annual Meeting of the Geochemical Society of Japan   64   256 - 256   2017

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    DOI： 10.14862/geochemproc.64.0_256

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  • 還元的な惑星大気における有機物エアロゾルの成長過程に関する実験的研究 Reviewed

    洪 鵬, 関根 康人, 杉田 精司

    日本エアロゾル学会誌 エアロゾル研究   31 ( 3 )   185 - 191   2016.3

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  • High-temperature water-rock interactions and hydrothermal environments in the chondrite-like core of Enceladus Reviewed

    Yasuhito Sekine, Takazo Shibuya, Frank Postberg, Hsiang-Wen Hsu, Katsuhiko Suzuki, Yuka Masaki, Tatsu Kuwatani, Megumi Mori, Peng K. Hong, Motoko Yoshizaki, Shogo Tachibana, Sin-iti Sirono

    NATURE COMMUNICATIONS   6 ( 8604 )   1 - 8   2015.10

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    DOI： 10.1038/ncomms9604

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  • Transition to an oxygen-rich atmosphere with an extensive overshoot triggered by the Paleoproterozoic snowball Earth Reviewed

    Mariko Harada, Eiichi Tajika, Yasuhito Sekine

    EARTH AND PLANETARY SCIENCE LETTERS   419   178 - 186   2015.6

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    DOI： 10.1016/j.eps1.2015.03.005

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  • Ongoing hydrothermal activities within Enceladus Reviewed

    Hsiang-Wen Hsu, Frank Postberg, Yasuhito Sekine, Takazo Shibuya, Sascha Kempf, Mihaly Horanyi, Antal Juhasz, Nicolas Altobelli, Katsuhiko Suzuki, Yuka Masaki, Tatsu Kuwatani, Shogo Tachibana, Sin-iti Sirono, Georg Moragas-Klostermeyer, Ralf Srama

    NATURE   519 ( 7542 )   207 - +   2015.3

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    DOI： 10.1038/nature14262

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  • Rotational Pixel Swapping Method for Detection of Circular Features in Binary Images Reviewed

    Satoru Yamamoto, Tsuneo Matsunaga, Ryosuke Nakamura, Yasuhito Sekine, Naru Hirata, Yasushi Yamaguchi

    IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING   53 ( 2 )   710 - 723   2015.2

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    DOI： 10.1109/TGRS.2014.2327121

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  • Impact chemistry of methanol: Implications for volatile evolution on icy satellites and dwarf planets, and cometary delivery to the Moon Reviewed

    Yasuhito Sekine, Hidenori Genda, Yuta Muto, Seiji Stigita, Toshihiko Kadono, Takafumi Matsui

    ICARUS   243   39 - 47   2014.11

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    DOI： 10.1016/j.icarus.2014.08.034

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  • Rendezvous, Landing and Sample Return Mission to Jupiter Trojans by the Solar Power Sail

    Yano, H, Matsuura, S, Mori, O, Yonetoku, D, Nakamura, R, Sekine, Y, Abe, S

    40th COSPAR Scientific Assembly   B0.4-2   14   2014.8

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  • Formation and geomorphologic history of the Lonar impact crater deduced from in situ cosmogenic Be-10 and Al-26 Reviewed

    Atsunori Nakamura, Yusuke Yokoyama, Yasuhito Sekine, Kazuhisa Goto, Goro Komatsu, P. Senthil Kumar, Hiroyuki Matsuzaki, Ichiro Kaneoka, Takafumi Matsui

    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS   15 ( 8 )   3190 - 3197   2014.8

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    DOI： 10.1002/2014GC005376

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  • Planetary protection on international waters: An onboard protocol for capsule retrieval and biosafety control in sample return mission Reviewed

    Yoshinori Takano, Hajime Yano, Yasuhito Sekine, Ryu Funase, Ken Takai

    ADVANCES IN SPACE RESEARCH   53 ( 7 )   1135 - 1142   2014.4

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    DOI： 10.1016/j.asr.2013.12.041

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  • Organic aerosol on early Earth: its role for climate stability and atmospheric evolution

    Sekine Yasuhito, Kobayashi Jumpei, Hong Peng

    Abstracts of Annual Meeting of the Geochemical Society of Japan   61   62 - 62   2014

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    It is suggested that early Earth's atmosphere contained a substantial amount of methane. In such a reducing atosphere, organic aerosols would have been formed by solar UV and high energy particle irradiations. We investigate the formation rate and optical properties of organic aerosols by performing laboratory experiments. On the basis of the experimental results, we discuss the role of organic aerosol for climate stability and atmospheric evolution of early Earth.

    DOI： 10.14862/geochemproc.61.0_62

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  • Oxygen transition with an overshoot after the Paleoproterozoic snowball Earth: quantification from biogeochemical cycle modeling

    Harada Mariko, Ozaki Kazumi, Tajika Eiichi, Sekine Yasuhito

    Abstracts of Annual Meeting of the Geochemical Society of Japan   61   65 - 65   2014

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  • The drainage systems developing on the hydrologically active impact crater, Lonar, India Reviewed

    Komatsu, G, P. S. Kumar, K. Goto, Y. Sekine, C. Giri, T. Matsui

    Planetary and Space Science   95   45 - 55   2014

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  • Exploration of Enceladus&amp;apos; Water-Rich Plumes toward Understanding of Chemistry and Biology of the Interior Ocean Reviewed

    Sekine, Yasuhito, Takano, Yoshinori, Yano, Hajime, Funase, Ryu, Takai, Ken, Ishihara, Morio, Shibuya, Takazo, Tachibana, Shogo, Kuramoto, Kiyoshi, Yabuta, Hikaru, Kimura, Jun, Furukawa, Yoshihiro

    TRANSACTIONS OF THE JAPAN SOCIETY FOR AERONAUTICAL AND SPACE SCIENCES, AEROSPACE TECHNOLOGY JAPAN   12 ( ists29 )   7 - 11   2014

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    DOI： 10.2322/tastj.12.Tk_7

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  • Drainage systems of Lonar Crater, India: Contributions to Lonar Lake hydrology and crater degradation Reviewed

    Goro Komatsu, P. Senthil Kumar, Kazuhisa Goto, Yasuhito Sekine, Chaitanya Giri, Takafumi Matsui

    Planetary and Space Science   95   45 - 55   2014

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    DOI： 10.1016/j.pss.2013.05.011

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  • Redox conditions in the atmosphere and shallow-marine environments during the first Huronian deglaciation: Insights from Os isotopes and redox-sensitive elements Reviewed

    Kosuke T. Goto, Yasuhito Sekine, Katsuhiko Suzuki, Eiichi Tajika, Ryoko Senda, Tatsuo Nozaki, Ryuji Tada, Kazuhisa Goto, Shinji Yamamoto, Teruyuki Maruoka, Naohiko Ohkouchi, Nanako O. Ogawa

    Earth and Planetary Science Letters   376   145 - 154   2013.8

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    DOI： 10.1016/j.epsl.2013.06.018

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  • Hydrogen Cyanide Production due to Mid-Size Impacts in a Redox-Neutral N-2-Rich Atmosphere Reviewed

    Kosuke Kurosawa, Seiji Sugita, Ko Ishibashi, Sunao Hasegawa, Yasuhito Sekine, Nanako O. Ogawa, Toshihiko Kadono, Sohsuke Ohno, Naohiko Ohkouchi, Yoichi Nagaoka, Takafumi Matsui

    ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES   43 ( 3 )   221 - 245   2013.6

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    DOI： 10.1007/s11084-013-9339-0

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  • LCROSS (Lunar Crater Observation and Sensing Satellite) Observation Campaign: Strategies, Implementation, and Lessons Learned Reviewed

    Jennifer L. Heldmann, Anthony Colaprete, Diane H. Wooden, Robert F. Ackermann, David D. Acton, Peter R. Backus, Vanessa Bailey, Jesse G. Ball, William C. Barott, Samantha K. Blair, Marc W. Buie, Shawn Callahan, Nancy J. Chanover, Young-Jun Choi, Al Conrad, Dolores M. Coulson, Kirk B. Crawford, Russell DeHart, Imke de Pater, Michael Disanti, James R. Forster, Reiko Furusho, Tetsuharu Fuse, Tom Geballe, J. Duane Gibson, David Goldstein, Stephen A. Gregory, David J. Gutierrez, Ryan T. Hamilton, Taiga Hamura, David E. Harker, Gerry R. Harp, Junichi Haruyama, Morag Hastie, Yutaka Hayano, Phillip Hinz, Peng K. Hong, Steven P. James, Toshihiko Kadono, Hideyo Kawakita, Michael S. Kelley, Daryl L. Kim, Kosuke Kurosawa, Duk-Hang Lee, Michael Long, Paul G. Lucey, Keith Marach, Anthony C. Matulonis, Richard M. McDermid, Russet McMillan, Charles Miller, Hong-Kyu Moon, Ryosuke Nakamura, Hirotomo Noda, Natsuko Okamura, Lawrence Ong, Dallan Porter, Jeffery J. Puschell, John T. Rayner, J. Jedadiah Rembold, Katherine C. Roth, Richard J. Rudy, Ray W. Russell, Eileen V. Ryan, William H. Ryan, Tomohiko Sekiguchi, Yasuhito Sekine, Mark A. Skinner, Mitsuru Soma, Andrew W. Stephens, Alex Storrs, Robert M. Suggs, Seiji Sugita, Eon-Chang Sung, Naruhisa Takatoh, Jill C. Tarter, Scott M. Taylor, Hiroshi Terada, Chadwick J. Trujillo, Vidhya Vaitheeswaran, Faith Vilas, Brian D. Walls, Jun-ihi Watanabe, William J. Welch, Charles E. Woodward, Hong-Suh Yim, Eliot F. Young

    SPACE SCIENCE REVIEWS   167 ( 1-4 )   93 - 140   2012.5

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  • Giant impacts in the Saturnian system: A possible origin of diversity in the inner mid-sized satellites Reviewed

    Yasuhito Sekine, Hidenori Genda

    PLANETARY AND SPACE SCIENCE   63-64   133 - 138   2012.4

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    DOI： 10.1016/j.pss.2011.05.015

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  • Analyses of Planar Deformation Features (PDFs) of Shocked Quartz Grains derived from K/Pg Boundary Deposit within the Chicxulub Crater.

    Chang Yu, Tajika Eiichi, Goto Kazuhisa, Sekine Y

    Annual Meeting of the Geological Society of Japan   2012   52 - 52   2012

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    DOI： 10.14863/geosocabst.2012.0_52

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  • Beppu Hotspring, Japan, as a Terrestrial Analog for Ancient Hydrothermal Systems on Mars

    Komatsu, G, Takemura, K, Goto, K, Shibuya, H, Yamagishi, A, Sekine, Y, Ishimaru, R

    LPS XXXXIII, Abstract   1659   2012

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  • Aqueous environmental history of Mars revealed by mineralogy and geochemistry of outcrop exposures of sedimentary rocks

    Sekine Yasuhito

    The Journal of the Geological Society of Japan   118 ( 10 )   650 - 663   2012

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    Recent high-resolution spectral images and in-situ observations have revealed more than 1000 outcrops of diverse aqueous mineral deposits on Mars. Layered deposits of phyllosilicates (and carbonates) have been found in the oldest terrains, suggesting active interactions between liquid water and basalts in the subsurface and/or on the surface of Mars at around 4.3–4.0 billion years ago. Hydrated sulfates and silica deposits formed by evaporation of acidic and oxidizing surface water under arid conditions have been found in the second period (∼4.0–3.2 billion years ago). After this period, liquid water does not seem to have played a major role for the formation of sediments on Mars. Here, we describe characteristics and possible origins of these aqueous sediments, review hypothesis for the causative mechanisms for Martian environmental change, and discuss new questions posed by the measurements.

    DOI： 10.5575/geosoc.2012.0001

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  • OXIDIZING PROTO-ATMOSPHERE ON TITAN: CONSTRAINT FROM N-2 FORMATION BY IMPACT SHOCK Reviewed

    Ryo Ishimaru, Yasuhito Sekine, Takafumi Matsui, Olivier Mousis

    ASTROPHYSICAL JOURNAL LETTERS   741 ( 1 )   1 - 6   2011.11

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    DOI： 10.1088/2041-8205/741/1/L10

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  • Osmium evidence for synchronicity between a rise in atmospheric oxygen and Palaeoproterozoic deglaciation Reviewed

    Yasuhito Sekine, Katsuhiko Suzuki, Ryoko Senda, Kosuke T. Goto, Eiichi Tajika, Ryuji Tada, Kazuhisa Goto, Shinji Yamamoto, Naohiko Ohkouchi, Nanako O. Ogawa, Teruyuki Maruoka

    NATURE COMMUNICATIONS   2 ( 502 )   1 - 6   2011.10

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    DOI： 10.1038/ncomms1507

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  • Manganese enrichment in the Gowganda Formation of the Huronian Supergroup: A highly oxidizing shallow-marine environment after the last Huronian glaciation Reviewed

    Yasuhito Sekine, Eiichi Tajika, Ryuji Tada, Takemaru Hirai, Kosuke T. Goto, Tatsu Kuwatani, Kazuhisa Goto, Shinji Yamamoto, Shogo Tachibana, Yukio Isozaki, Joseph L. Kirschvink

    EARTH AND PLANETARY SCIENCE LETTERS   307 ( 1-2 )   201 - 210   2011.7

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    DOI： 10.1016/j.epsl.2011.05.001

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  • A ground-based observation of the LCROSS impact events using the Subaru Telescope Reviewed

    Peng K. Hong, Seiji Sugita, Natsuko Okamura, Yasuhito Sekine, Hiroshi Terada, Naruhisa Takatoh, Yutaka Hayano, Tetsuharu Fuse, Tae-Soo Pyo, Hideyo Kawakita, Diane H. Wooden, Eliot F. Young, Paul G. Lucey, Kosuke Kurosawa, Hidenori Genda, Junichi Haruyama, Reiko Furusho, Toshihiko Kadono, Ryosuke Nakamura, Shunichi Kamata, Taiga Hamura, Tomohiko Sekiguchi, Mitsuru Soma, Hirotomo Noda, Jun-ichi Watanabe

    ICARUS   214 ( 1 )   21 - 29   2011.7

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    DOI： 10.1016/j.icarus.2011.05.008

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  • Replacement and late formation of atmospheric N-2 on undifferentiated Titan by impacts Reviewed

    Yasuhito Sekine, Hidenori Genda, Seiji Sugita, Toshihiko Kadono, Takafumi Matsui

    NATURE GEOSCIENCE   4 ( 6 )   359 - 362   2011.6

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    DOI： 10.1038/NGEO1147

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  • Oxidizing Proto-Titan: Constraint from the Impact Origin of Its N2 Atmosphere

    Ishimaru, R, Sekine, Y, Matsui, T, Mousis, O

    LPS XXXXII, Abstract   1608   1358   2011

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  • In-situ spectroscopic observations of silicate vaporization due to &gt; 10 km/s impacts using laser driven projectiles Reviewed

    Kosuke Kurosawa, Seiji Sugita, Toshihiko Kadono, Keisuke Shigemori, Yoichiro Hironaka, Kazuto Otani, Takayoshi Sano, Akiyuki Shiroshita, Norimasa Ozaki, Kohei Miyanishi, Tatsuhiro Sakaiya, Yasuhito Sekine, Shogo Tachibana, Keisuke Nakamura, Sho Fukuzaki, Sohsuke Ohno, Ryosuke Kodama, Takafumi Matsui

    GEOPHYSICAL RESEARCH LETTERS   37 ( L23203 )   1 - 5   2010.12

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    DOI： 10.1029/2010GL045330

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  • Impact-induced N-2 production from ammonium sulfate: Implications for the origin and evolution of N-2 in Titan's atmosphere Reviewed

    Sho Fukuzaki, Yasuhito Sekine, Hidenori Genda, Seiji Sugita, Toshihiko Kadono, Takafumi Matsui

    ICARUS   209 ( 2 )   715 - 722   2010.10

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    DOI： 10.1016/j.icarus.2010.04.015

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  • Anomalous negative excursion of carbon isotope in organic carbon after the last Paleoproterozoic glaciation in North America Reviewed

    Yasuhito Sekine, Eiichi Tajika, Naohiko Ohkouchi, Nanako O. Ogawa, Kazuhisa Goto, Ryuji Tada, Shinji Yamamoto, Joseph L. Kirschvink

    GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS   11 ( Q08019 )   1 - 10   2010.8

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    DOI： 10.1029/2010GC003210

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  • A ground-based observation of LCROSS impact using the Subaru Telescope Reviewed

    HONG Peng K, OKAMURA Natsuko, SUGITA Seiji, SEKINE Yasuhito, TERADA Hiroshi, TAKATOH Naruhisa, HAYANO Yutaka, FUSE Tetsuji

    Planetary people   19 ( 2 )   96 - 104   2010.6

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    LCROSS探査とは,月極域の永久影における氷の有無を,人工衝突によって表層を掘削して直接的に観測する探査である.我々はLCROSSの羊飼い探査衛星とは独立に月面上の水の有無を確認することと,羊飼い探査衛星の観測からは得られない放出物の鉛直分布に関する制約条件を得ることを目的として,すばる望遠鏡を用いて近赤外波長域での放出物の高分散分光および撮像観測を行った.事前の数値計算による予想では,かなりの量の水やダストの放出物が観測される見込みであったが,実際の観測データからはそれらは検出されなかった.そのため,水の分布などに対する情報は得られなかったが,本観測の結果はLCROSSの衝突が従来の標準的なクレーター形成モデルの予測とは大きくかけ離れたものであったことを示唆している.

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  • Impact experiments with a new technique for acceleration of projectiles to velocities higher than Earth&apos;s escape velocity of 11.2 km/s Reviewed

    T. Kadono, T. Sakaiya, Y. Hironaka, K. Otani, T. Sano, T. Fujiwara, T. Mochiyama, K. Kurosawa, S. Sugita, Y. Sekine, W. Nishikanbara, T. Matsui, S. Ohno, A. Shiroshita, K. Miyanishi, N. Ozaki, R. Kodama, A. M. Nakamura, M. Arakawa, S. Fujioka, K. Shigemori

    JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS   115 ( E04003 )   1 - 9   2010.4

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    DOI： 10.1029/2009JE003385

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  • Hydrocarbon lakes and watery matrices/habitats for life on Titan Reviewed

    Naganuma, T, Y. Sekine

    Journal of Cosmology   5   905 - 911   2010

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  • Direct measurements of chemical composition of shock-induced gases from calcite: an intense global warming after the Chicxulub impact due to the indirect greenhouse effect of carbon monoxide Reviewed

    Ko Kawaragi, Yasuhito Sekine, Toshihiko Kadono, Seiji Sugita, Sohsuke Ohno, Ko Ishibashi, Kosuke Kurosawa, Takafumi Matsui, Susumu Ikeda

    EARTH AND PLANETARY SCIENCE LETTERS   282 ( 1-4 )   56 - 64   2009.5

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    DOI： 10.1016/j.epsl.2009.02.037

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  • Origin, Evolution, and Diversities of Habitable Planets

    KURAMATO Kiyoshi, ABE Yutaka, HASHIMOTO George, HAYASHI Yoshi-Yuki, SEKINE Yasuhito, SATO Mitsuteru

    The astronomical herald   102 ( 3 )   184 - 189   2009.2

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  • IMPACT EXPERIMENTS WITH PROJECTILES AT VELOCITIES HIGHER THAN 10 KM/S Reviewed

    T. Kadono, T. Sakaiya, Y. Hironaka, K. Otani, T. Sano, T. Fujiwara, T. Mochiyama, K. Kurosawa, S. Sugita, Y. Sekine, T. Matsui, S. Ohno, A. Shiroshita, K. Miyanishi, N. Ozaki, R. Kodama, A. M. Nakamura, M. Arakawa, S. Fujioka, K. Shigemori

    SHOCK COMPRESSION OF CONDENSED MATTER - 2009, PTS 1 AND 2   1195   875 - +   2009

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    DOI： 10.1063/1.3295282

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    Other Link： http://orcid.org/0000-0002-3978-8427

  • A New View of Impact Degassing Based on Laser Gun Experiments Reviewed

    OHNO Sohsuke, KADONO Toshihiko, KAWARAGI Ko, ISHIBASHI Ko, KUROSAWA Kosuke, SEKINE Yasuhito, SUGITA Seiji, NAKAMURA Eizo, MATSUI Takafumi

    Planetary people   17 ( 2 )   98 - 104   2008.6

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    衝突脱ガス現象は大気の形成やその後の表層環境の進化に大きな影響を与えたと考えられている.我々は,反射衝撃波や封圧の影響を受けずに衝突脱ガス生成気体を回収できる,レーザー銃を用いた衝突脱ガス実験の新しい手法を開発した.炭酸塩岩,硫酸塩岩へ適用した結果,多くの先行研究よりも弱い衝撃波,特に圧縮状態での脱ガスに必要な衝撃圧と比べると数分の一程度と非京に低い衝撃圧で衝突脱ガスが開始することがわかった.これは,比較的低い衝撃圧の条件では圧力解放過程での脱ガス反応が重要であること,天然の衝突でも衝撃圧縮された後圧力が低圧まで開放される領域ではこれまで考えられてきたよりも衝突脱ガスが起こりやすいことを示唆する.

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  • The role of organic haze in Titan's atmospheric chemistry II. Effect of heterogeneous reaction to the hydrogen budget and chemical composition of the atmosphere Reviewed

    Yasuhito Sekine, Sebastien Lebonnois, Hiroshi Imanaka, Takafumi Matsui, Emma L. O. Bakes, Christopher P. Mckay, Bishun N. Khare, Seiji Sugita

    ICARUS   194 ( 1 )   201 - 211   2008.3

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    DOI： 10.1016/j.icarus.2007.08.030

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  • The role of organic haze in Titan's atmospheric chemistry I. Laboratory investigation on heterogeneous reaction of atomic hydrogen with Titan tholin Reviewed

    Yasuhito Sekine, Hiroshi Imanaka, Takafumi Matsui, Bishun N. Khare, Emma L. O. Bakes, Christopher P. Mckay, Seiji Sugita

    ICARUS   194 ( 1 )   186 - 200   2008.3

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    DOI： 10.1016/j.icarus.2007.08.031

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  • カナダ・原生代初期ヒューロニアン累層群における氷河性堆積物層のオスミウム同位体変動：酸素増大イベントと気候変動の因果関係に与える示唆

    関根 康人, 鈴木 勝彦, 仙田 量子, 田近 英一, 多田 隆治, 後藤 和久, 山本 信治, 大河内 直彦, 小川 奈々子

    日本地球化学会年会要旨集   55   389 - 389   2008

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    Language：Japanese   Publisher：日本地球化学会  

    原生代初期には、地球進化における最大の表層環境変動があったことが知られる。大気進化に関しては、この時代を境に、大気中の酸素濃度が著しく上昇したと考えられ、またこの時代には、複数回の氷河期があり、全球凍結が生じたことも示唆されている。このような大気進化と気候変動は、互いに関連していた可能性があるが、これまでその因果関係を示す具体的な証拠はほとんどない。本研究では、カナダ・ヒューロニアン累層群において、約２３億年前の氷河期に由来した氷河性堆積物（ブルース層）とそのキャップカーボネイト（エスパノーラ層）に関して、高解像度オスミウム同位体分析を行った。その結果、ブルース層とエスパノーラ層の境界付近で大陸性オスミウムの海洋への供給の開始を示す同位体異常を発見した。このことは、大陸性オスミウムの酸素大気下での風化が退氷期に開始したことを示し、酸素濃度の上昇が氷河期直後から始まったことを示唆する。

    DOI： 10.14862/geochemproc.55.0.389.0

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  • Optical and chemical properties of tholins Reviewed

    Bishun N. Khare, Christopher P. McKay, Dale P. Cruikshank, Yasuhito Sekine, Patrick Wilhite, Tomoko Ishihara

    IAU: ORGANIC MATTER IN SPACE   ( 251 )   441 - 442   2008

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    DOI： 10.1017/S1743921308022114

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  • Molecular species of impact-induced gas from carbonate mineral

    Kawaragi Kou, Kadono Toshihiko, Ohno Sohsuke, Sekine Yasuhito, Ishibashi Ko, Kurosawa Kosuke, Ishimaru Ryo, Sugita Seiji, Matsui Takafumi

    Abstracts for fall meeting of the Japanese Society for Planetary Science   2007f   48 - 48   2007

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    Meteorite impacts on the Earth induce the release of a huge amount of climatically active gases from the impacting body and crustal material under very high temperature and pressure condition. Here, we focused on the impact-induced degassing from carbonate minerals which is abundant on the Earth. Previous researches have assumed that impact-induced gas from carbonate is wholly CO2 [e.g. O'Keefe and Ahrens, 1989]. However, there is a prospect that the gas from carbonate contains CO which is stable under high temperature. The release of CO and its atmospheric chemical reactions may cause the increase of tropospheric ozone which has intensive greenhouse effect. Hence, when we consider the climatic effects caused by impact-induced gases from carbonate, it is very crucial problem whether the gas is CO or CO2. Now we conducted the impact-degassing experiments using a laser gun and specified the molecular species of impact-induced gas from carbonate.

    DOI： 10.14909/jsps.2007f.0.48.0

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  • The role of Fischer-Tropsch catalysis in Jovian subnebular chemistry Reviewed

    O. Mousis, Y. Alibert, Y. Sekine, S. Sugita, T. Matsui

    ASTRONOMY & ASTROPHYSICS   459 ( 3 )   965 - 968   2006.12

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    DOI： 10.1051/0004-6361:20064947

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  • An experimental study on Fischer-Tropsch catalysis: Implications for impact phenomena and nebular chemistry Reviewed

    Yasuhito Sekine, Seiji Sugita, Takafumi Shido, Takashi Yamamoto, Yasuhiro Iwasawa, Toshihiko Kadono, Takafumi Matsui

    METEORITICS & PLANETARY SCIENCE   41 ( 5 )   715 - 729   2006.5

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    DOI： 10.1111/j.1945-5100.2006.tb00987.x

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  • An experimental study on Fischer-Tropsch catalysis Implications for impact phenomena and nebular chemistry Reviewed

    Yasuhito Sekine, Seiji Sugita, Takafumi Shido, Takashi Yamamoto, Yasuhiro Iwasawa, Toshihiko Kadono, Takafumi Matsui

    Meteoritics & Planetary Science   Vol.41 ( No.5 )   715 - 729   2006.5

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    DOI： 10.1111/j.1945-5100.2006.tb00987.x

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  • The role of Fischer-Tropsch catalysis in the origin of methane-rich Titan Reviewed

    Y Sekine, S Sugita, T Shido, T Yamamoto, Y Iwasawa, T Kadono, T Matsui

    ICARUS   178 ( 1 )   154 - 164   2005.11

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    DOI： 10.1016/j.icarus.2005.03.016

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  • Evaluation of mineralogical alteration of micrometeoroid analog materials captured in aerogel Reviewed

    K Okudaira, T Noguchi, T Nakamura, S Sugita, Y Sekine, H Yano

    SCIENTIFIC EXPLORATION, PLANETARY PROTECTION, ACTIVE EXPERIMENTS AND DUSTY PLASMAS   34 ( 11 )   2299 - 2304   2004

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    DOI： 10.1016/j.asr.2004.06.003

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  • Methane production by large iron meteorite impacts on early Earth Reviewed

    Y Sekine, S Sugita, T Kadono, T Matsui

    JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS   108 ( E7 )   6-1 - 6-11   2003.7

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    DOI： 10.1029/2002JE002034

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  • Vapor clouds generated by laser ablation and hypervelocity impact Reviewed

    T Kadono, S Sugita, NK Mitani, M Fuyuki, S Ohno, Y Sekine, T Matsui

    GEOPHYSICAL RESEARCH LETTERS   29 ( 20 )   40-1 - 40-4   2002.10

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    DOI： 10.1029/2002GL015694

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  • Establishment and application of STXM system for the development of aquaplanetology research

    高橋嘉夫, 高橋嘉夫, 河合敬宏, 中村智樹, 榎戸祐馬, 井上皓介, 野田夏実, 山下翔平, 武市泰男, 木村正雄, 伊規須素子, 若林大祐, 薮田ひかる, 癸生川陽子, 諸野祐樹, 浦本豪一郎, 白石史人, 浅野眞希, 奥村大河, 宮原正明, 福士圭介, 関根康人

    量子ビームサイエンスフェスタ(Web)   2021   2022

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  • JUpiter ICy moons Explorer JUICE: Science goals of JUICE-Japan and cooperation with Japanese geochemists and cosmochemists

    Sekine Yasuhito, Saito Yoshifumi, Asamura Kazushi, Enya Keigo, Kasai Yasko, Kasaba Yasumasa, Haruyama Jun'ichi, Matsuoka Ayako

    Abstracts of Annual Meeting of the Geochemical Society of Japan   68   80   2021

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    DOI： 10.14862/geochemproc.68.0_80

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  • Solubility of Amorphous Magnesium Carbonate at Low Temperature

    北島卓磨, 福士圭介, 関根康人, 依田優大, GANKHUREL Baasansuren, DAVAASUREN Davaadorj, 高橋嘉夫

    日本鉱物科学会年会講演要旨(Web)   2021   2021

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  • Solubility of amorphous magnesium carbonate: rarity of Mg-carbonate on surface of closed-basin lakes that existed on early Mars

    北島卓磨, 福士圭介, 関根康人, 関根康人, 依田優大, 依田優大, GANKHUREL Baasansuren, DAVAASUREN Davaadorj

    日本地球惑星科学連合大会予稿集(Web)   2021   2021

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  • Verification of ice-mineralization process: formation of authigenic carbonates in alkaline lakes during freezing condition in south Mongolia.

    北島卓磨, 福士圭介, 福士圭介, GANKHUREL Baasansuren, 関根康人, 依田優大, 依田優大, DAVAASUREN Davaadorj

    日本地球惑星科学連合大会予稿集(Web)   2020   2020

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  • AQUAPLANETOLOGY-A PROJECT THAT QUESTS FOR PLANETARY HABITABILITY IN THE SOLAR SYSTEM AND BEYOND

    Yasuhito Sekine, Takazo Shibuya, Hidenori Genda, Keisuke Fukushi, Tomohiro Usui

    ELEMENTS   15 ( 2 )   122 - 122   2019.4

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  • モンゴル塩湖の凍結時における氷への塩取り込みと太陽系氷天体への応用

    依田優大, 依田優大, 関根康人, 関根康人, 福士圭介, 高橋嘉夫, 北島卓磨, GANKHUREL Baasansuren, DAVAASUREN Davaadorj, 庄司大悟

    日本地球化学会年会要旨集(Web)   66th   2019

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  • モンゴル塩湖の凍結時における氷への塩取り込みと太陽系氷天体への応用

    依田優大, 依田優大, 関根康人, 関根康人, 福士圭介, 高橋嘉夫, 北島卓磨, GANKHUREL Baasansuren, DAVAASUREN Davaador j, 庄司大悟

    日本惑星科学会秋季講演会予稿集(Web)   2019   2019

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  • Meeting on master plan proposals

    Nakamoto T, Kuramoto K, Sekine Y

    Planetary People - The Japanese Society for Planetary Sciences   27 ( 4 )   341 - 343   2018

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    DOI： 10.14909/yuseijin.27.4_341

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  • 水惑星学の創成

    関根康人, 渋谷岳造, 玄田英典, 福士圭介, 臼井寛裕, 高橋嘉夫, 倉本圭, 鍵裕之, 渡邊誠一郎

    日本惑星科学会秋季講演会予稿集(Web)   2017   2017

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  • aqua planetology

    Sekine Yasuhito, Shibuya Takazo, Genda Hidenori, Fukushi Keisuke, Usui Tomohiro, Takahashi Yoshio, Kuramoto Kiyoshi, Kagi Hiroyuki, Watanabe Sei―ichiro

    Abstracts of Annual Meeting of the Geochemical Society of Japan   64 ( 0 )   139 - 139   2017

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    DOI： 10.14862/geochemproc.64.0_139

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  • Report of the 5th Workshop on Satellite Systems

    Tanigawa Takayuki, Kimura Jun, Okuzumi Satoshi, Sekine Yasuhito, Kuramoto Kiyoshi, Ohtsuki Keiji, Tanaka Hidekazu

    Planetary People - The Japanese Society for Planetary Sciences   26 ( 4 )   190 - 191   2017

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    DOI： 10.14909/yuseijin.26.4_190

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  • 「宇宙科学の今後20年の構想を検討する委員会」活動報告

    今村剛, 矢野創, 関根康人, 三好由純, 清水敏文

    日本惑星科学会秋季講演会予稿集(Web)   2017   2017

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  • 生体高分子試料を含む氷衛星プリューム模擬微粒子の超高速衝突捕集と分析(1)：ペプチド回収と検出の成功

    矢野 創, 藤島 晧介, 田端 誠, 河口 優子, 高野 淑識, 渋谷 岳造, 高井 研, 平井 隆之, 関根 康人, Carbonnier Benjamin, Guerrouache Mohamed, Rothschild Lynn J., Yano Hajime, Fujishima Kosuke, Tabata Makoto, Kawaguchi Yuko, Takano Yoshinori, Shibuya Takazo, Takai Ken, Hirai Takayuki, Sekine Yasuhito, Carbonnier Benjamin, Guerrouache Mohamed, Rothschild Lynn J.

    平成27年度宇宙科学に関する室内実験シンポジウム 講演集 = Proceedings of 2016 Symposium on Laboratory Experiment for Space Science   2016.2

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    平成27年度宇宙科学に関する室内実験シンポジウム (2016年2月23日-24日. 宇宙航空研究開発機構宇宙科学研究所(JAXA)(ISAS)相模原キャンパス), 相模原市, 神奈川県著者人数: 12名資料番号: SA6000055004

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  • Subsurface Oceans of Icy Bodies in The Solar System and Its Habitability

    35 ( 2 )   140 - 144   2016

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  • Report of Workshop on Satellite Systems 2015

    Tanigawa T, Kimura J, Sekine Y, Kuramoto K, Ohtsuki K

    Planetary People   24 ( 4 )   343 - 345   2015.12

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  • SHOCK-INDUCED EFFECT ON CHATHODO-LUMINESENCE OF EXPERIMENTALLY SHOCKED QUARTZ

    Y. Chang, M. Kayama, E. Tajika, Y. Sekine, T. Sekine, H. Nishido, T. Kobayashi

    METEORITICS & PLANETARY SCIENCE   50   2015.8

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  • Cratering age using Rotational Pixel Swapping Method

    Yamamoto S, Matsunaga T, Nakamura R, Sekine Y

    Planetary People   24 ( 1 )   20 - 32   2015.3

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    本論文では,かぐや地形カメラで取得されたデジタル地形モデル(DTM)を使った,回転ピクセルスワッピング法を基にした衝突クレーター自動検出手法の開発を行った.この手法は,DTMから斜面勾配と斜面方位を計算し,それらの空間分布の回転対称性に着目して,クレーター形状を自動検出するものである.大きな特徴としては(1)欠損クレーターや複数個重なったクレーター集団であっても高い精度で検出できること,(2)ノイズ除去等の前処理が不要であること,(3)従来のクレーター自動識別法と比べて100倍以上の高速処理が可能であることが挙げられる.また,本手法を月面上の海・高他領域に対して適用し,実際にモデル年代を算出したところ,クレーター手動カウンティングによるモデル年代結果と調和的な結果が得られた.

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  • 紫外線望遠鏡による系外惑星観測計画の検討状況

    亀田真吾, 池澤祥太, 村上豪, 成田憲保, 生駒大洋, 関根康人, 吉川一朗, 杉田精司

    日本地球惑星科学連合大会予稿集(Web)   2015   ROMBUNNO.PCG32‐13 (WEB ONLY)   2015

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  • O13-06 木星圏探査機(JUICE)搭載サブミリ波分光計の開発と科学目標(口頭発表セッション13 ダスト・探査I,口頭発表)

    笠井 康子, 佐川 英夫, 関根 康人, 黒田 剛史, 碓井 英雄, 菊池 健一, 西堀 俊幸, 真鍋 武嗣, Hartogh Paul, JUICE-SWIチーム

    日本惑星科学会秋期講演会予稿集   2014   "O13 - 06"   2014.9

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  • O6-06 氷衛星および小惑星における有機化合物の生成と衝撃変成に関する実験的研究(口頭発表セッション6 表層進化・物質I,口頭発表)

    兒玉 賢哉, 関根 康人, 高野 淑識, 小川 奈々子, 大河内 直彦, 小林 敬道, 関根 利守

    日本惑星科学会秋期講演会予稿集   2014   "O6 - 06"   2014.9

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  • O9-03 観測衛星による分光画像および数値地形モデルを用いた衝突クレーター自動判別手法の開発(口頭発表セッション9 月・内部構造,口頭発表)

    山本 聡, 松永 恒雄, 中村 良介, 関根 康人, 平田 成, 山口 靖

    日本惑星科学会秋期講演会予稿集   2014   "O9 - 03"   2014.9

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  • Let's go to Jupiter again, and further to icy satellites(2)Challenges of the JUICE-SWI (Sub-millimetre Wave Instrument)

    Kasai Y., Sagawa H., Sekine Y., Kuroda T., Kikuchi K.

    Planetary People   23 ( 2 )   140 - 148   2014.6

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  • DESTINY応用:紫外線望遠鏡による太陽系外惑星観測ミッション

    亀田真吾, 村上豪, 成田憲保, 生駒大洋, 関根康人, 杉田精司

    宇宙科学技術連合講演会講演集(CD-ROM)   58th   ROMBUNNO.2B06   2014

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  • 地球と宇宙の化学事典, 日本地球化学会【編集】, 朝倉書店, 2012年9月刊行, 全479ページ, 定価12,000円, ISBN978-4-254-16057-4

    関根 康人

    遊・星・人 : 日本惑星科学会誌   22 ( 4 )   286 - 287   2013.12

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  • Evolution of surface environments of the Earth and terrestrial planets(2)

    Kadoya S., Watanabe Y., Sekine Y., Tajika E.

    Planetary People   22 ( 4 )   234 - 241   2013.12

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  • O6-06 土星衛星エンセラダスにおける熱水活動(口頭発表セッション6(衛星系・リング),口頭発表)

    関根 康人, 渋谷 岳造, 鈴木 勝彦, 桑谷 立, 橘 省吾

    日本惑星科学会秋期講演会予稿集   2013   "O6 - 06"   2013.11

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  • P2-10 熱水実験と反応理論モデルに基づくセレスの表面鉱物の解釈 : 形成・熱進化への示唆(ポスターセッション2,ポスター発表)

    森 愛美, 関根 康人, 桑谷 立, 橘 省吾, 澁谷 岳造, 鈴木 勝彦, 正木 裕香

    日本惑星科学会秋期講演会予稿集   2013   "P2 - 10"   2013.11

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  • Age and geomorphology of the Lonar impact crater using in-situ cosmogenic ^<10>Be and ^<26>Al

    NAKAMURA A., YOKOYAMA Y., SEKINE Y., GOTO K., KOMATSU G., KUMAR P. Senthil, MATUZAKI H., MATSUI T.

    2013   245 - 245   2013.9

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  • Hydrothermal activity in Enceladus inferred from silica formation

    SEKINE Y., SHIBUYA T., SUZUKI K., KUWATANI T., MASAKI Y., TACHIBANA S.

    2013   244 - 244   2013.9

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  • 16 A theoretical study of hydrothermal reactions on icy moons : Constraints on the temperature and habitability of Enceladu's' ocean(Space Science,General Contributions,The 38^<th> Annual Meeting of the SSOEL-Japan)

    Mishima S., Sekine Y., Sugita S.

    Viva origino   41   16 - 16   2013

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  • O5-07 ASTERによるマルチスペクトルデータを用いた地球衝突クレータ捜索(口頭発表セッション5(衝突科学II,室内実験I),口頭発表)

    山本 聡, 松永 恒雄, 中村 良介, 関根 康人, 平田 成, 山口 靖

    日本惑星科学会秋期講演会予稿集   2012   51 - 51   2012.10

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  • Evolution of surface environments of the Earth and terrestrial planets : I

    KADOYA S., WATANABE Y., SEKINE Y., TAJIKA E.

    Planetary People   21 ( 3 )   294 - 306   2012.9

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  • Report : The third symposium on deep space exploration : a letter from asteroids and small bodies

    SEKINE Y.

    Planetary People   21 ( 3 )   320 - 323   2012.9

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  • Estimates for Peak Shock Pressure Based on Analyses of Planar Deformation Features (PDFs) of Shocked Quartz Grains Derived from K/Pg Boundary Deposit within the Chicxulub Crater

    CHANG Yu, TAJIKA Eiichi, GOTO Kazuhisa, SEKINE Yasuhito

    2012   200 - 200   2012.9

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  • 衛星エンセラダスのプルーム探査に関わる国際連携及び科学立案のFS調査

    高野淑識, 高井研, 渋谷岳造, 矢野創, 船瀬龍, 関根康人, 吉村義隆, 山岸明彦, 木下大輔, TSOU Peter, TSOU Peter, TSOU Peter

    宇宙利用シンポジウム   28th   230 - 232   2012.3

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  • Exploration of Enceladus' water-rich plumes toward understanding chemistry and biology of the interior ocean (Special issue: Planetary exploration in a coming decade activity: Reports of 2nd stage)

    Sekine Y., Yabuta H., Kimura J., Furukawa Y., Takano Y., Yano H., Funase R., Takai K., Ishihara M., Shibuya T., Tachibana S., Kuramoto K.

    Planetary People - The Japanese Society for Planetary Sciences   21 ( 3 )   229 - 238   2012

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    DOI： 10.14909/yuseijin.21.3_229

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  • S34-10 衛星リモートセンシングによるスペクトルデータを用いた地球衝突クレータ判別の研究(口頭セッション34:太陽系における衝突科学,口頭発表)

    山本 聡, 松永 恒雄, 中村 良介, 関根 康人, 平田 成

    日本惑星科学会秋期講演会予稿集   2011   93 - 93   2011.10

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  • SP2-08P CPS衝突実験実習の取り組み(特別セッション2<実習会,アウトリーチ>,ポスター発表)

    荒川 政彦, 門野 敏彦, 杉田 精司, 中村 昭子, 鈴木 絢子, 関根 康人, 山下 靖幸, 長谷川 直, 大野 宗祐

    日本惑星科学会秋期講演会予稿集   2011   106 - 106   2011.10

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  • S21-03P 土星系中型質量衛星における多様性の起源 : SPH流体コードを用いたジャイアントインパクトのシミュレーション(一般ポスターセッション1,ポスター発表)

    藤田 航, 玄田 英典, 関根 康人, 杉田 精司

    日本惑星科学会秋期講演会予稿集   2011   120 - 120   2011.10

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  • S35-03P 氷衛星エンセラダスの熱水環境に対する実験的制約(一般ポスターセッション3,ポスター発表)

    関根 康人, 澁谷 岳造, 桑谷 立, 鈴木 勝彦

    日本惑星科学会秋期講演会予稿集   2011   151 - 151   2011.10

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  • S33-03P 光化学大気モデルの構築と地球型系外惑星への応用(一般ポスターセッション3,ポスター発表)

    洪 鵬, 関根 康人, 杉田 精司

    日本惑星科学会秋期講演会予稿集   2011   139 - 139   2011.10

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  • S32-08 初期地球大気における有機物ヘイズの生成実験と表層環境の安定性への応用(口頭セッション32:惑星環境進化,口頭発表)

    笹森 務仁, 関根 康人, Larson Erik J, 杉田 精司

    日本惑星科学会秋期講演会予稿集   2011   78 - 78   2011.10

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  • Report of Frontier Seminar on Planetary Sciences 2011

    SEKINE Y.

    Planetary people   20 ( 3 )   225 - 227   2011.9

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  • Planetary chemistry : Toward understanding the origin and variety of planetary environments

    SEKINE Yasuhito

    Planetary people   19 ( 4 )   305 - 315   2010.12

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  • E ects of Laser Energy on LIBS Spectra

    Cho, Y, Sugita, S, Ishibashi, K, Ohno, S, Kamata, S, Kurosawa, K, Sekine, Y, Arai, T, Kobayashi, M, Senshu, H, Wada, K, Namiki, N, n, Matsui, T

    Proc. Lunar Planet. Sci. Conf.   41st   # (CD-ROM)   2010

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  • 313 タイタン大気の窒素の起源と進化 : 氷地殻からの衝突脱ガスの役割(オーラルセッション10 惑星気象・惑星大気)

    福崎 翔, 関根 康人, 玄田 英典, 杉田 精司, 門野 敏彦, 松井 孝典

    日本惑星科学会秋期講演会予稿集   2009   64 - 64   2009.9

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  • Prebiotic Molecules Derived from Tholins

    Bishun N. Khare, Christopher P. McKay, Dale P. Cruikshank, Yasuhito Sekine, Patrick Wilhite, Tomoko Ishihara, Lauren Tracy, Katherine Lanier, Delphine Nna-Mvondo

    ORIGINS OF LIFE AND EVOLUTION OF BIOSPHERES   39 ( 3-4 )   242 - 243   2009.8

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  • Osmium evidence for relationship between atmospheric oxygenation and Paleoproterozoic glaciation

    Y. Sekine, K. Suzuki, R. Senda, E. Tajika, R. Tada, K. Goto, S. Yamamoto, N. Ohkouchi, N. O. Ogawa

    GEOCHIMICA ET COSMOCHIMICA ACTA   73 ( 13 )   A1193 - A1193   2009.6

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  • Projectile acceleration and impact experiments using a high-power laser : Impacts with a velocity higher than 10km/s

    Kadono T, Shigemori K, Sakaiya T, Hironaka Y, Sano T, Ohtani K, Fujiwara T, Mochiyama T, Fujioka S, Kurosawa K, Shiroshita A, Miyanishi K, Ozaki N, Kodama R, Sekine Y, Sugita S, Matsui T, Tachibana S, Ohno S, Arakawa M, Takeuchi T, Nakamura A.M

    Planetary People   18 ( 1 )   4 - 9   2009.3

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    大阪大学レーザーエネルギー学研究センターの高出力レーザーを使ってマクロサイズ(0.1mm以上)の弾丸飛翔体を加速する実験を行っている.これまでに直径0.1〜0.3mmの弾丸飛翔体が秒速10〜60kmに加速されている.この高速度に加速された弾丸飛翔体を使って金属どうしの衝突実験を行い,クレーター,放出破片による二次クレーター,衝突により発生したガスからの輝線,などを観測した.惑星科学への応用を念頭に置いた,珪酸塩物質の衝突発光観測,岩石ターゲットを使ったクレーター形成実験,エアロジェルによる岩石放出破片の捕獲,などの実験も並行して進行中である.

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  • 216 高速度衝突蒸発現象の発光分光観測 : シリケイト蒸気の発生(衝突現象および関連室内実験,オーラルセッション6)

    黒澤 耕介, 杉田 精司, 門野 敏彦, 関根 康人, 弘中 陽一郎, 大谷 一人, 佐野 孝好, 境家 達弘, 藤原 隆史, 寶田 圭司, 城下 明之, 宮西 宏併, 尾崎 典雅, 藤岡 慎介, 重森 啓介, 大野 宗祐, 橘 省吾

    日本惑星科学会秋期講演会予稿集   2008   50 - 50   2008.11

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    Language：Japanese   Publisher：日本惑星科学会  

    秒速10km/sを超える速度の天体衝突が起きた場合,惑星及び衝突天体物質を構成するケイ酸塩も蒸発すると言われている[e.g., Ahrens &amp; O&#039;keefe, 1972]。ケイ酸塩蒸気の発生は月形成過程や衝突蒸気雲内での化学反応を議論する上で極めて重要な問題である[e.g., Pahleven &amp; Stevenson, 2007]。しかし実験の困難さのため,今まで秒速10km/sを超える高速度衝突実験は行われていない。宇宙速度での衝突が起こると,衝突直下点のケイ酸塩は&gt;100GPa,&gt;10^4Kという超高温高圧の熱力学状態に達すると予想される。しかし,そのような高温高圧のケイ酸塩の物性データは揃っておらず,実際にどのような熱力学に達するかは未解明である。従って実際にケイ酸塩試料への宇宙速度衝突実験を行い,ケイ酸塩の蒸発を確認し,衝撃加熱温度を実測する必要がある。我々は阪大レーザー研にある高出力レーザー,激光12号を用いて,金属箔(Ta,厚さ:50μm,密度:16.6g/cc)を〜10km/sまで加速し,代表的なケイ酸塩鉱物(Forsterite, Diopside, Quartz)への高速度衝突実験を行っている。弾丸に密度の大きいTaを用いているのでケイ酸塩同士が衝突した場合よりも高い衝撃圧を達成することができる(ケイ酸塩同士の衝突では〜15km/sの衝突に対応)。今回は第一ステップとして超強力な閃光を捉え,発光スペクトルを取得する光学系の構築とケイ酸塩蒸気の発生を確認することを目的とした。長時間露光分光器(露光時間:1秒)を用いて標的背面から発光分光観測を行った。透明な鉱物試料を用いているため,標的背面からでも,衝突直下点からの発光を捉えることができる。その結果Diopsideへの衝突の場合,Caの輝線が確認された。このことはDiopsideが衝突によって蒸発したことを強く示唆している。今後,より高時間,高波長分解能を持つ分光器で発光スペクトルを取得し,宇宙速度衝突の際のケイ酸塩の熱力学状態を推定する予定である。

    CiNii Books

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  • Heterogeneous Reactions on the Surface of Titan's Organic Aerosol

    SEKINE Yasuhito, IMANAKA Hiroshi, SUGITA Seiji, LEBONNOIS Sebastien, BAKES Emma, KHARE Bishun, MCKAY Chris, MATSUI Takafumi

    Planetary people   17 ( 2 )   105 - 116   2008.6

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    Language：Japanese   Publisher：The Japanese Society for Planetary Sciences  

    CiNii Books

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  • New Face

    SEKINE Yasuhito

    Planetary People   16 ( 4 )   342 - 343   2007.12

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    Language：Japanese   Publisher：The Japanese Society for Planetary Sciences  

    CiNii Books

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  • Do tholins act in maintaining the mixing ratio of methane in the atmosphere of titan?

    Bishun N. Khare, Christopher P. McKay, Yasuhito Sekine, Patrick Wilhite, Dale P. Cruikshank, Tomoko Ishihara

    ASTROBIOLOGY   7 ( 3 )   486 - 486   2007.6

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    Language：English   Publishing type：Research paper, summary (international conference)  

    Web of Science

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  • An experimental study on Fischer-Tropsch catalysis: Implications for planetary science

    Y Sekine, T Shido, S Sugita, T Matsui, T Yamamoto, Y Iwasawa

    GEOCHIMICA ET COSMOCHIMICA ACTA   67 ( 18 )   A422 - A422   2003.9

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    Language：English   Publishing type：Research paper, summary (international conference)  

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Awards

  • Inoue Prize for Science

    2023.12   Inoue Foundation for Science  

    Yasuhito Sekine

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  • JSPS Prize

    2022.12   JSPS  

    Yasuhito Sekine

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  • 文部科学大臣表彰若手科学者賞

    2016   文部科学省  

    関根康人

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  • 奨励賞

    2012   地球化学研究協会  

    関根康人

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  • 最優秀研究者賞

    2009   日本惑星科学会  

    関根康人

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Research Projects

  • Understanding of subsurface ocean via dust analysis in the international Europa Clipper mission

    Grant number：24KK0075  2024.9 - 2029.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Fund for the Promotion of Joint International Research (International Collaborative Research)

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    Grant amount：\20800000 （ Direct Cost: \16000000 、 Indirect Cost：\4800000 ）

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  • K-Na-Clの格子欠陥をセンサーとしたエウロパ氷下の温度計開発

    Grant number：24K21747  2024.6 - 2027.3

    日本学術振興会  科学研究費助成事業  挑戦的研究(萌芽)

    末松 久幸, 菊池 崇志, 今田 剛, 関根 康人, Do T.M.Dung

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    Grant amount：\6240000 （ Direct Cost: \4800000 、 Indirect Cost：\1440000 ）

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  • Experimental and theoretical predictions of ocean chemistry and organic chemical evolution of icy bodies in the Solar System

    Grant number：23H00144  2023.4 - 2027.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (A)

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    Grant amount：\46670000 （ Direct Cost: \35900000 、 Indirect Cost：\10770000 ）

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  • Exploration of periglacial landforms and subsurface structures of terrestrial analog sites for estimation of subsurface ice distribution on Mars

    Grant number：23H01232  2023.4 - 2026.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Grant amount：\18850000 （ Direct Cost: \14500000 、 Indirect Cost：\4350000 ）

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  • Exploration of periglacial landforms and subsurface structures of terrestrial analog sites for estimation of subsurface ice distribution on Mars

    Grant number：23K25928  2023.4 - 2026.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

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    Grant amount：\18850000 （ Direct Cost: \14500000 、 Indirect Cost：\4350000 ）

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  • Understanding of the diversity of prebiotic chemistries and emergence of molecular systems in various planetary environments in the Solar System

    Grant number：22K21344  2022.12 - 2029.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Fund for the Promotion of Joint International Research (International Leading Research )

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    Grant amount：\689000000 （ Direct Cost: \530000000 、 Indirect Cost：\159000000 ）

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  • Aquaplanetology

    Grant number：22H04900  2022.4 - 2023.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

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    Grant amount：\3900000 （ Direct Cost: \3000000 、 Indirect Cost：\900000 ）

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  • Exploring habitability on Early Mars from Environmental Science Approaches

    Grant number：21H04515  2021.4 - 2024.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (A)

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    Grant amount：\43680000 （ Direct Cost: \33600000 、 Indirect Cost：\10080000 ）

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  • 地下凍土融解地域の地質・微生物調査及び機械学習に基づく火星水環境の理解

    Grant number：20H00195  2020.4 - 2023.3

    日本学術振興会  科学研究費助成事業  基盤研究(A)

    関根 康人, McGlynn Shawn・E., 庄司 大悟, 福士 圭介, 石上 玄也, GUTTENBERG NICHOLAS・RYAN

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    Grant amount：\45630000 （ Direct Cost: \35100000 、 Indirect Cost：\10530000 ）

    火星における液体の水の存否、生命生存可能性は長年の謎である。本研究では、これに答える鍵が、火星斜面上に出現・消失を繰り返す暗い筋模様（Recurring Slope Lineae: RSL）にあると考える。RSLは地下凍土層の季節的融解によって形成されている可能性があるが、周回観測のみではその成因を特定できない。本研究では、乾燥寒冷なモンゴル国ゴビ・アルタイ地域に見つかるRSLの地球アナログに着目し、調査・観測を行う。地球RSLの地質調査と現地無人観測ステーションによる長期観測、機械学習による地形パターン認識により、１）RSL形成メカニズムの解明、２）RSL付近の生態系推定、３）水の活動を伴う火星RSLの判定・探索を行う。
    初年度は、新型コロナウィルスによる海外調査の制限から、当初の野外調査に関する計画を変更し、研究活動を行った。調査地域の国際共同研究者に依頼し、調査地域の調査、サンプリングを行ってもらったため、計画に致命的な影響はでていない。
    １）RSL形成メカニズムの解明については、無人観測ステーションのシステム設計と開発を行った。日本国内の類似野外環境でステーションを設置し、実地テストをくり返すことでノウハウを蓄積した。また、土壌試料や地下水の化学組成から、水の供給プロセスを明らかにすることを目的とし、土壌中での地下水からの鉱物沈殿実験を行った。国際共同研究者が得た乾燥域の湖の水質季節変化データを再現するモデルを構築し、この知見を氷衛星や初期火星の水質復元へと適応し、高精度の水質復元を可能にした。
    ２）RSL付近の生態系推定については、国際共同研究者の調査により採取・輸送された土壌サンプルからDNA抽出およびシーケンス解析を行った。
    ３）水の活動を伴う火星RSLの判定・探索については、リモートセンシングデータの収集・解析を進め、機械学習に用いるためのカテゴライズを完了した。

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  • 太陽系天体における水-氷相互作用

    Grant number：17H06456  2017.6 - 2022.3

    日本学術振興会  科学研究費助成事業  新学術領域研究(研究領域提案型)

    関根 康人, 谷 篤史, 荒川 雅, 野口 直樹

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    Grant amount：\221260000 （ Direct Cost: \170200000 、 Indirect Cost：\51060000 ）

    本研究では、火星や氷衛星の表面で起きることが予想される、光に駆動された化学反応や氷の変形流動といった物理化学過程を室内実験により定量化することを目的とする。令和２年度では、上記の環境を再現する実験装置群を使った研究の実施が主となる。(1)～(4)の実験についての実験・研究実施を行った。
    (1) 光化学／液相反応実験：嫌気状態の氷・水溶液への紫外線・電子線照射実験装置を用いて、光酸化反応の反応率を得た。特に、水溶液の酸素濃度を制御し、中性pHまでの量子収率を得ることに初めて成功し、これを使った火星表層水での酸化鉄沈殿速度を明らかにした。
    (2) クラスター反応実験：酸化鉄クラスターと気相メタンとの化学反応により、メタンが効率的に気相から除去されることを明らかにした。これは火星でのメタンの噴出とその後の急激な減少を説明する化学過程である可能性もあり、現在は定量的な消費率を求めてメタン除去に必要となるクラスター量を求めている。
    (3) 氷変形流動実験：低温高圧条件におけるメタンクラスレートのケージ内の状態を実験的に明らかにした。ケージの構造を推定し、高圧下における流動性への示唆を得た。特に、巨大氷衛星タイタンの高圧氷層の流動に対して重要な制約となる。
    (4) 氷結晶・クラスレート：実験で得られたクラスレートの熱物性を用いて、氷天体の熱進化への影響を系統的に評価した。また、実験によりセミクラスレートハイドレート系の分解エンタルピーといった基礎熱力学データを取得した。

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  • Aqua planetology

    Grant number：2901  2017.6 - 2022.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

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  • Aqua planetology

    Grant number：17H06454  2017.6 - 2022.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

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    Grant amount：\103090000 （ Direct Cost: \79300000 、 Indirect Cost：\23790000 ）

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  • Investigation of organic chemical evolution on extraterrestrial planetary bodies

    Grant number：16K13873  2016.4 - 2018.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Challenging Exploratory Research

    Sekine Yasuhito

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    Grant amount：\3510000 （ Direct Cost: \2700000 、 Indirect Cost：\810000 ）

    The present study performed exploratory research to investigate organic syntheses occurred within exo-oceans of icy bodies in the Solar system toward understanding of the mechanisms and variety of chemical evolution beyond Earth. By comparing the reflectance spectra of organic matter on Pluto obtained by the spacecraft with our laboratory experimental data, we show the occurrence of a giant impact and subsequent organic synthesis onto this icy dwarf planet in the early stage of its evolution. We also investigate shock-induced alterations of organic matter through hyper-velocity impact experiments, which is necessary for future sample-return missions to icy bodies in the Solar system.

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  • Environmental change elucidated from seawater Os isotope in Phanerozoic

    Grant number：15H02142  2015.4 - 2019.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (A)

    SUZUKI Katsuhiko

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    Grant amount：\37830000 （ Direct Cost: \29100000 、 Indirect Cost：\8730000 ）

    Based on the project, the following results have been obtained. 1. Analyses of microfossils in the well-preserved sedimentary rocks in the Phanerozoic have been conducted, leading to reliable stratigraphy and age constraints. 2. Isotope analyses of each layer of chert leads to high age-resolution. One of the results based on this technique is that the Sr and Os isotope ratios increase in the sediments in late-Triassic suggested that orogeny after closing of Palaeo-Tethys Ocean. 3. Combinig the above techniques, we can strongly imply the processes of mass extinction and environmental change.

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  • Hydrothermal experiments and chemical evolution model for icy bodies in the Solar system: Implications for formation of the Solar system and habitability

    Grant number：26707024  2014.4 - 2017.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists (A)

    Sekine Yasuhito

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    Grant amount：\24830000 （ Direct Cost: \19100000 、 Indirect Cost：\5730000 ）

    The present study aims at understanding water environments (redox, pH, temperature) and habitability within interior oceans of geologically-active icy bodies in the Solar system, based on laboratory experiments and spacecraft observations. We have constrained chemical conditions and rock compositions of hydrothermal environments within Enceladus. We further suggest the occurence of large-scale planetary migrations at the early stage of the Solar system from the interpretations of surface materials on Ceres and Pluto.

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  • Investigating the Nature of Super-Earths via High-Precision Near-Infrared 3-color Simultaneous Transit Photometry

    Grant number：25247026  2013.5 - 2017.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (A)

    Narita Norio, FUKUI Akihiko, SATO Bun' ei, TAMURA Motohide, YANAGISAWA Kenshi, NAGAYAMA Takahiro, ENYA Keigo, SEKINE Yasuhito, GENDA Hidenori, KURITA Mikio

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    Grant amount：\42900000 （ Direct Cost: \33000000 、 Indirect Cost：\9900000 ）

    In this study, we aimed to investigate the nature of super-Earths, which are emerging population of extrasolar planets. To do so, we have worked on development of a new astronomical instrument named MuSCAT (Multi-color Simultaneous Camera for studying Atmospheres of Transiting exoplanets), which is a 3-color simultaneous camera, for the 188cm telescope at Okayama Astrophysical Observatory. Using the instrument and other facilities, we conducted observations and theoretical modeling to reveal properties of super-Earths.
    Consequently, we succeeded in developing MuSCAT faster than we expected, and discovered 2 new super-Earths based on our observations using MuSCAT. We also succeeded in detecting a planetary transit of the habitable super-Earth K2-3d using MuSCAT for the first time from the ground, and improved the knowledge about properties of this planet.
    Based on the above and other publication results, we have made better-than-expected achievements from this study.

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  • Modelling and theoretical study for exoplanet atmospheres

    Grant number：23103003  2011.4 - 2016.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research on Innovative Areas (Research in a proposed research area)

    Kuramoto Kiyoshi, ISHIWATARI Masaki, GENDA Hidenori, TAKEHIRO Shinichi, SASAKI Yohei, NAKAJIMA Kensuke, HAMANO Keiko, ONISHI Masanori

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    Grant amount：\143000000 （ Direct Cost: \110000000 、 Indirect Cost：\33000000 ）

    Evolution of steam atmospheres on earth-like planets after each final giant impact event is theoretically solved with an analysis of its observability. Two types of evolutionary tracks are found: one is the rapid formation of a water ocean and another is the long-term persistence of the magma ocean state. The secular loss of surface water due to atmospheric escape driven by stellar UV irradiation may rather stabilize surface liquid water than merely produce an arid surface environment. General circulation experiments provided with various boundary conditions reveal that a synchronously rotating planet and a land planet may have wider habitable zones than previously thought. Numerical models to solve cloud convection and radiative transfer in gas giant planets are also developed, revealing the mechanisms for the intermittencies observed for cloud convection in the solar system gas planets as well as roles of cloud layers on controlling the thermal emission from gas giant atmospheres.

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  • Investigation on lake sediments of Lonar impact crater, India: applications for Asian climate change and Mars paleoenvironments

    Grant number：23403015  2011.4 - 2014.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    MATSUI Takafumi, KOMATSU Goro, GOTO Kazuhisa, SEKINE Yasuhito, NASU Hiroo

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    Grant amount：\19500000 （ Direct Cost: \15000000 、 Indirect Cost：\4500000 ）

    Based on geological survey of Lonar crater, India, we revealed hydrological cycles surrounding the crater, especially responses to Asian monsonn. We also discussed formation processes of lake sediments on ancient Mars, based on the knowledge of formation and modification processes occurring on the Lonar crater. In addition, we investigated the surface ages from the cosmogenic species contained in the rocks surrounding the crater. We discussed the erosion rate and its timescales on the Earth and ancient Mars.

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  • Estimation of the molecular composition and hydrogen escape rate of impact-induced steam atmospheres

    Grant number：23340168  2011.4 - 2014.3

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    SUGITA Seiji, TACHIBANA Shogo, SEKINE Yasuhito, ABE Yutaka

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    Grant amount：\20540000 （ Direct Cost: \15800000 、 Indirect Cost：\4740000 ）

    We obtained three main results in this project. First is on the molecular compositions of impact-induced planetary atmospheres. Calculation results revealed that Venus and super Earth's around M-type stars would have CO-H2-rich atmosphere and Mars and Earth would have CH4-rich atmosphere.Second is on hydrogen escape rate from terrestrial planets. Calculation results indicate that hydrogen escape rate depends greatly on whether or not a steam atmosphere would condense to an ocean after accretion and determines whether an Earth-like wet planet or Venus-like dry planet, including its interior, would form. Third is impact experiments and mass spectroscopic measurements of impact-degassed volatiles. Experimental results show that the K/Pg impact would generate acid rain sufficient to acidify the ocean surface layer, which may lead to the K/Pg mass extinction.

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  • Laboratory experiments of hydrothermal reactions in Enceladus : Toward understanding chemistry in the interior ocean

    Grant number：22740352  2010 - 2011

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Young Scientists (B)

    SEKINE Yasuhito

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    Grant amount：\4290000 （ Direct Cost: \3300000 、 Indirect Cost：\990000 ）

    We have investigated chemical reactions between primordial volatiles(such as ammonia and carbon dioxide) and primitive minerals(such as olivine) in Enceladus' interior ocean by conducting laboratory experiments of hydrothermal reactions. By comparing the results with the observations of Enceladus' plume by the Cassini spacecraft, we have discussed the temperature conditions of possible hydrothermal systems and habitability in Enceladus' ocean.

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  • Reconstruction and system analyses of the global events of the Earth during the Paleoproterozoic

    Grant number：18340128  2006 - 2008

    Japan Society for the Promotion of Science  Grants-in-Aid for Scientific Research  Grant-in-Aid for Scientific Research (B)

    TAJIKA Eiichi, TADA Ryuji, TACHIBANA Shogo, SEKINE Yasuhito, GOTO Kazuhisa, OHKOUCHI Naohiko, SUZUKI Katsuhiko, HAMANO Yozo, NAGAHARA Hiroko, ISOZAKI Yukio, MURAKAMI Takashi

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    Grant amount：\9760000 （ Direct Cost: \8200000 、 Indirect Cost：\1560000 ）

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  • 太古代及び原生代初期における大気化学と地球環境進化に関する基礎研究

    Grant number：18840015  2006 - 2007

    日本学術振興会  科学研究費助成事業  若手研究(スタートアップ)

    関根 康人

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    Grant amount：\2760000 （ Direct Cost: \2760000 ）

    太古代と原生代の境界にあたる25-20億年前には、地球進化における最大規模の表層環境の変動があったことが知られている。この時代には、太古代のメタンを含む還元的な大気組成が、原生代以後の酸素を含む酸化的な組成へと変わり、また同時期に、大規模氷河期が繰り返し生じたことが示されている。しかしながら、このような大気組成の進化と気候変動の間にどのような因果関係があったのか、還元的大気をもつ天体の地表環境や物資循環はどのように成り立っているのか、といった詳細に関しては、ほとんどわかっていない。
    本研究では、室内実験と野外採取試料の分析を行い、原生代初期及び太古代の地表環境や大気進化を明らかにすることを目的とする。本年度は、カナダ・オンタリオ州で採取した約23億年前の氷河性堆積物に対して、氷河期直後のオスミウムと炭素の同位体比の高解像度分析を行った。その結果、氷河の退氷に伴い、オスミウムの酸化的風化が開始していることを明らかにした。このことは、氷河期後の温暖化への環境変動が引き金となり、その結果として大気酸素濃度の増大が引き起こされていることを示唆する。
    さらに室内実験においては、土星の衛星タイタンを例に、大気中にメタンを含む還元大気をもつ天体の地峡環境の安定性を調べた。具体的には、光化学反応により、大気中でメタンから生成される有機物エアロゾルの表面反応や成長率を実験的に求め、大気-表層間の物質循環やタイタンの大気組成に果たした役割を議論した。特に、最新のカッシーニ探査機による詳細な大気組成の観測結果と、我々の実験により予想される大気組成を比較し、有機物エアロゾルの表面反応が現在の大気組成を維持する役割を果たしていることを示した。

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  • 隕石重爆撃期における大気、海洋及び生命の起源・進化に関する基礎研究

    Grant number：03J52241  2003 - 2005

    日本学術振興会  科学研究費助成事業  特別研究員奨励費

    関根 康人

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    Grant amount：\2600000 （ Direct Cost: \2600000 ）

    タイタンは土星系最大の衛星であり、窒素とメタンに富む厚い大気を持っている。この大気組成は、原始地球大気の組成に近いと考えられ、タイタン大気の起源・進化を調べることは、原始地球の大気や生命の起源を考える上でも重要と考えられる。本研究では、固体微粒子の触媒反応に注目し、タイタン大気の起源と進化を明らかにすることを目的に研究を行った。
    タイタン大気のメタンの起源を考える上では、原始ガス惑星円盤における主成分である一酸化炭素からメタンが生成する反応が重要になる。Fischer-Tropsch触媒反応は、金属表面で一酸化炭素と水素からメタンが生成される反応である。本研究では、ダストとガスからなるガス円盤を模擬した条件において実験を行い、触媒反応によるメタンの生成率を測定した。その結果、温度が600K以上では、触媒表面の炭素がグラファイト化し、生成率が低下することが分かった。そのため、ガス円盤におけるメタン生成は、温度が550K付近の領域において進行することが分かった。この結果は、触媒反応によってガス円盤にメタンに富む領域ができ、そこで生成した微衛星が、タイタン大気におけるメタンの供給源として重要であったことを示唆する。
    現在のタイタン大気には、有機物エアロゾルが存在していることが知られている。このエアロゾルは大気中の水素原子と何らかの化学反応を起こすことが予想されるが、これを実験的に確かめた例はない。本研究では、エアロゾル模擬物質に水素原子を照射する実験を行った。その結果、この表面反応は、エアロゾルの水素化反応と水素分子生成反応から成り立っていることが分かった。また、それらの反応率を実験的に求めた。これらの反応率をタイタン大気モデルに組み込んだ結果、エアロゾルとの表面反応によって、大気中の水素原子が効率的に除去され、メタンから複雑な有機分子への化学進化が促進されることが分かった。

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