13 results on '"Koyama, Shungo"'
Search Results
2. Strong depletion of $^{13}$C in CO induced by photolysis of CO$_{2}$ in the Martian atmosphere calculated by a photochemical model
- Author
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Yoshida, Tatsuya, Aoki, Shohei, Ueno, Yuichiro, Terada, Naoki, Nakamura, Yuki, Shiobara, Kimie, Yoshida, Nao, Nakagawa, Hiromu, Sakai, Shotaro, and Koyama, Shungo
- Subjects
Astrophysics - Earth and Planetary Astrophysics - Abstract
The isotopic signature of atmospheric carbon offers a unique tracer for the history of the Martian atmosphere and the origin of organic matter on Mars. Photolysis of CO$_{2}$ is known to induce strong isotopic fractionation of carbon between CO$_{2}$ and CO. However, its effect on the carbon isotopic compositions in the Martian atmosphere remains uncertain. Here we develop a 1-D photochemical model considering isotopic fractionation via photolysis of CO$_{2}$ to estimate the vertical profiles of the carbon isotopic compositions of CO and CO$_{2}$ in the Martian atmosphere. We find that CO is depleted in $^{13}$C compared with CO$_{2}$ at each altitude due to the fractionation via CO$_{2}$ photolysis: the minimum value of $\delta ^{13}$C in CO is about $-170$ per mil under the standard eddy diffusion setting. This result supports the hypothesis that fractionated atmospheric CO is responsible for the production of the $^{13}$C-depleted organic carbon in Martian sediments detected by Curiosity Rover through the conversion of CO into organic materials and their deposition on the surface. The photolysis and transport-induced fractionation of CO we report here leads to a $\sim 15$ % decrease in the amount of inferred atmospheric loss when combined with the present-day fractionation of the atmosphere and previous studies of carbon escape to space. The fractionated isotopic composition of CO in the Martian atmosphere may be observed by ExoMars Trace Gas Orbiter (TGO) and ground-based telescopes, and escaping ion species produced by the fractionated carbon-bearing species may be detected by Martian Moons eXploration (MMX) in the future., Comment: 13 pages, 6 figures
- Published
- 2023
3. Photochemical and RadiatiOn Transport model for Extensive USe (PROTEUS)
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Nakamura, Yuki, Terada, Naoki, Koyama, Shungo, Yoshida, Tatsuya, Karyu, Hiroki, Terada, Kaori, Kuroda, Takeshi, Kamada, Arihiro, Murata, Isao, Sakai, Shotaro, Suzuki, Yuhei, Kobayashi, Mirai, and Leblanc, François
- Subjects
Astrophysics - Instrumentation and Methods for Astrophysics ,Astrophysics - Earth and Planetary Astrophysics - Abstract
We introduce a new flexible one-dimensional photochemical model named Photochemical and RadiatiOn Transport model for Extensive USe (PROTEUS), which consists of a Python graphical user interface (GUI) program and Fortran 90 modules. PROTEUS is designed for adaptability to many planetary atmospheres, for flexibility to deal with thousands of or more chemical reactions with high efficiency, and for intuitive operation with GUI. Chemical reactions can be easily implemented into the Python GUI program in a simple string format, and users can intuitively select a planet and chemical reactions on GUI. Chemical reactions selected on GUI are automatically analyzed by string parsing functions in the Python GUI program, then applied to the Fortran 90 modules to simulate with the selected chemical reactions on a selected planet. PROTEUS can significantly save the time for those who need to develop a new photochemical model; users just need to write chemical reactions in the Python GUI program and just select them on GUI to run a new photochemical model.
- Published
- 2023
4. Reduced Water Loss due to Photochemistry on Terrestrial Planets in the Runaway Greenhouse Phase around Pre-main-sequence M Dwarfs
- Author
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Kawamura, Yo, primary, Yoshida, Tatsuya, additional, Terada, Naoki, additional, Nakamura, Yuki, additional, Koyama, Shungo, additional, Karyu, Hiroki, additional, Terada, Kaori, additional, and Sakai, Shotaro, additional
- Published
- 2024
- Full Text
- View/download PDF
5. Photochemical and radiation transport model for extensive use (PROTEUS)
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Nakamura, Yuki, primary, Terada, Naoki, additional, Koyama, Shungo, additional, Yoshida, Tatsuya, additional, Karyu, Hiroki, additional, Terada, Kaori, additional, Kuroda, Takeshi, additional, Kamada, Arihiro, additional, Murata, Isao, additional, Sakai, Shotaro, additional, Suzuki, Yuhei, additional, Kobayashi, Mirai, additional, and Leblanc, François, additional
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- 2023
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6. Strong Depletion of 13C in CO Induced by Photolysis of CO2 in the Martian Atmosphere, Calculated by a Photochemical Model
- Author
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Yoshida, Tatsuya, primary, Aoki, Shohei, additional, Ueno, Yuichiro, additional, Terada, Naoki, additional, Nakamura, Yuki, additional, Shiobara, Kimie, additional, Yoshida, Nao, additional, Nakagawa, Hiromu, additional, Sakai, Shotaro, additional, and Koyama, Shungo, additional
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- 2023
- Full Text
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7. Variations in Vertical CO/CO2 Profiles in the Martian Mesosphere and Lower Thermosphere Measured by the ExoMars TGO/NOMAD: Implications of Variations in Eddy Diffusion Coefficient
- Author
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Yoshida, Nao, Nakagawa, Hiromu, Aoki, Shohei, Erwin, Justin, Vandaele, Ann Carine, Daerden, Frank, Thomas, Ian, Trompet, Loïc, Koyama, Shungo, Terada, Naoki, Neary, Lori, Murata, Isao, Villanueva, Geronimo, Liuzzi, Giuliano, Lopez‐Valverde, Miguel Angel, Brines, Adrian, Modak, Ashimananda, Kasaba, Yasumasa, Ristic, Bojan, Bellucci, Giancarlo, López‐Moreno, José Juan, Patel, Manish, Ministerio de Ciencia e Innovación (España), European Commission, Belgian Science Policy Office, UK Space Agency, and Agenzia Spaziale Italiana
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Geophysics ,Retrieval ,Atmospheric composition ,General Earth and Planetary Sciences ,Mars ,Eddy diffusion coefficient ,Spectroscopy ,Mesosphere - Abstract
This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited., Using the Nadir and Occultation for MArs Discovery instrument aboard Trace Gas Orbiter, we derived the CO/CO2 profiles between 75 and 105 km altitude with the equivalent width technique. The derived CO/CO2 profiles showed significant seasonal variations in the southern hemisphere with decreases near perihelion and increases near aphelion. The estimation of the CO/CO2 profiles with a one-dimensional photochemical model shows that an altitude-dependent eddy diffusion coefficient better reproduces the observed profiles than a vertically uniform one. Our estimation suggests that the eddy diffusion coefficient in Ls = 240–270 is uniformly larger by a factor of ∼2 than that in Ls = 90–120 in the southern hemisphere, while they are comparable in the northern hemisphere. This fact demonstrates that the eddy diffusion coefficient is variable with season and latitude. © 2022. The Authors., The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). This project acknowledges funding by the Belgian Science Policy Office (BELSPO), with the financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493), by Spanish Ministry of Science and Innovation (MCIU) and by European funds under Grants PGC2018-101836-B-I00 and ESP2017-87143-R (MINECO/FEDER), as well as by UK Space Agency through Grants ST/V002295/1, ST/V005332/1, and ST/S00145x/1 and Italian Space Agency through Grant 2018-2-HH.0. This work was supported by the Belgian Fonds de la Recherche Scientifique–FNRS under Grant No. 30442502 (ET_HOME). The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). US investigators were supported by the National Aeronautics and Space Administration. Canadian investigators were supported by the Canadian Space Agency. Y. N. is supported by The international Joint Graduate Program in Earth and Environmental Sciences, Tohoku University (GP-EES), and the Japanese Society for the Promotion of Science (JP21J13710). This work was supported by JSPS KAKENHI Grant Nos. 20H04605 and 19K03943.
- Published
- 2022
8. Variations in Vertical CO/CO 2 Profiles in the Martian Mesosphere and Lower Thermosphere Measured by the ExoMars TGO/NOMAD: Implications of Variations in Eddy Diffusion Coefficient
- Author
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Yoshida, Nao, primary, Nakagawa, Hiromu, additional, Aoki, Shohei, additional, Erwin, Justin, additional, Vandaele, Ann Carine, additional, Daerden, Frank, additional, Thomas, Ian, additional, Trompet, Loïc, additional, Koyama, Shungo, additional, Terada, Naoki, additional, Neary, Lori, additional, Murata, Isao, additional, Villanueva, Geronimo, additional, Liuzzi, Giuliano, additional, Lopez‐Valverde, Miguel Angel, additional, Brines, Adrian, additional, Modak, Ashimananda, additional, Kasaba, Yasumasa, additional, Ristic, Bojan, additional, Bellucci, Giancarlo, additional, López‐Moreno, José Juan, additional, and Patel, Manish, additional
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- 2022
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9. Variation of CO/CO2 profiles in the Marian mesosphere and lower thermosphere retrieved from TGO/NOMAD
- Author
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Yoshida, Nao, primary, Nakagawa, Hiromu, additional, Aoki, Shohei, additional, Erwin, Justin, additional, Vandaele, Ann Carine, additional, Murata, Isao, additional, Thomas, Ian, additional, Daerden, Frank, additional, Neary, Lori, additional, Koyama, Shungo, additional, Terada, Naoki, additional, Yasumasa, Kasaba, additional, Ristic, Bojan, additional, Patel, Manish, additional, Bellucci, Giancarlo, additional, and López Moreno, José Juan, additional
- Published
- 2021
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10. Stability of Atmospheric Redox States of Early Mars Inferred from Time Response of the Regulation of H and O Losses
- Author
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Koyama, Shungo, primary, Terada, Naoki, additional, Nakagawa, Hiromu, additional, Kuroda, Takeshi, additional, and Sekine, Yasuhito, additional
- Published
- 2021
- Full Text
- View/download PDF
11. Variations in Vertical CO/CO2 Profiles in the Martian Mesosphere and Lower Thermosphere Measured by the ExoMars TGO/NOMAD: Implications of Variations in Eddy Diffusion Coefficient.
- Author
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Yoshida, Nao, Nakagawa, Hiromu, Aoki, Shohei, Erwin, Justin, Vandaele, Ann Carine, Daerden, Frank, Thomas, Ian, Trompet, Loïc, Koyama, Shungo, Terada, Naoki, Neary, Lori, Murata, Isao, Villanueva, Geronimo, Liuzzi, Giuliano, Lopez‐Valverde, Miguel Angel, Brines, Adrian, Modak, Ashimananda, Kasaba, Yasumasa, Ristic, Bojan, and Bellucci, Giancarlo
- Subjects
DIFFUSION coefficients ,MESOSPHERE ,TRACE gases ,THERMOSPHERE ,MIDDLE atmosphere ,EDDIES - Abstract
Using the Nadir and Occultation for MArs Discovery instrument aboard Trace Gas Orbiter, we derived the CO/CO2 profiles between 75 and 105 km altitude with the equivalent width technique. The derived CO/CO2 profiles showed significant seasonal variations in the southern hemisphere with decreases near perihelion and increases near aphelion. The estimation of the CO/CO2 profiles with a one‐dimensional photochemical model shows that an altitude‐dependent eddy diffusion coefficient better reproduces the observed profiles than a vertically uniform one. Our estimation suggests that the eddy diffusion coefficient in Ls = 240–270 is uniformly larger by a factor of ∼2 than that in Ls = 90–120 in the southern hemisphere, while they are comparable in the northern hemisphere. This fact demonstrates that the eddy diffusion coefficient is variable with season and latitude. Plain Language Summary: The eddy diffusion coefficient is widely used to parameterize the efficiency of vertical diffusion in the planetary atmosphere, whose variation characterizes the transportation of trace gas species. Additionally, it could vary their vertical distributions in the middle and upper atmosphere, which might cause an impact on the species escaping to space. However, the variability of the eddy diffusion coefficient in those altitude regions have been poorly understood. In this study, we focus on the estimation of variation in the eddy diffusion coefficient by analyzing the CO and CO2 measurements made by the ExoMars Trace Gas Orbiter. The observed CO/CO2 ratio between altitudes of 75 and 105 km shows a significant seasonal variation in the southern hemisphere. The observed CO/CO2 profiles are compared with the simulated profiles obtained with a one‐dimensional photochemical model assigning several shapes and intensity of eddy diffusion coefficient. The comparison shows that the eddy diffusion coefficient is not constant but variable depending on altitude, season, and latitude, which suggests that the efficiency of the vertical diffusion varies with season and latitude. This fact is useful to other 1D photochemical models to reproduce the seasonal and latitudinal variation of atmospheric composition. Key Points: The CO/CO2 profiles from 75 to 105 km measured by NOMAD aboard TGO are used to investigate variations in the eddy diffusion coefficientThe estimated CO/CO2 profiles agree well with the observed profiles if altitude‐dependent eddy diffusion coefficients are consideredOur results demonstrate a substantial seasonal variation in the eddy diffusion coefficient in the southern hemisphere [ABSTRACT FROM AUTHOR]
- Published
- 2022
- Full Text
- View/download PDF
12. Variations in Vertical CO/CO2Profiles in the Martian Mesosphere and Lower Thermosphere Measured by the ExoMars TGO/NOMAD: Implications of Variations in Eddy Diffusion Coefficient
- Author
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Yoshida, Nao, Nakagawa, Hiromu, Aoki, Shohei, Erwin, Justin, Vandaele, Ann Carine, Daerden, Frank, Thomas, Ian, Trompet, Loïc, Koyama, Shungo, Terada, Naoki, Neary, Lori, Murata, Isao, Villanueva, Geronimo, Liuzzi, Giuliano, Lopez‐Valverde, Miguel Angel, Brines, Adrian, Modak, Ashimananda, Kasaba, Yasumasa, Ristic, Bojan, Bellucci, Giancarlo, López‐Moreno, José Juan, and Patel, Manish
- Abstract
Using the Nadir and Occultation for MArs Discovery instrument aboard Trace Gas Orbiter, we derived the CO/CO2profiles between 75 and 105 km altitude with the equivalent width technique. The derived CO/CO2profiles showed significant seasonal variations in the southern hemisphere with decreases near perihelion and increases near aphelion. The estimation of the CO/CO2profiles with a one‐dimensional photochemical model shows that an altitude‐dependent eddy diffusion coefficient better reproduces the observed profiles than a vertically uniform one. Our estimation suggests that the eddy diffusion coefficient in Ls= 240–270 is uniformly larger by a factor of ∼2 than that in Ls= 90–120 in the southern hemisphere, while they are comparable in the northern hemisphere. This fact demonstrates that the eddy diffusion coefficient is variable with season and latitude. The eddy diffusion coefficient is widely used to parameterize the efficiency of vertical diffusion in the planetary atmosphere, whose variation characterizes the transportation of trace gas species. Additionally, it could vary their vertical distributions in the middle and upper atmosphere, which might cause an impact on the species escaping to space. However, the variability of the eddy diffusion coefficient in those altitude regions have been poorly understood. In this study, we focus on the estimation of variation in the eddy diffusion coefficient by analyzing the CO and CO2measurements made by the ExoMars Trace Gas Orbiter. The observed CO/CO2ratio between altitudes of 75 and 105 km shows a significant seasonal variation in the southern hemisphere. The observed CO/CO2profiles are compared with the simulated profiles obtained with a one‐dimensional photochemical model assigning several shapes and intensity of eddy diffusion coefficient. The comparison shows that the eddy diffusion coefficient is not constant but variable depending on altitude, season, and latitude, which suggests that the efficiency of the vertical diffusion varies with season and latitude. This fact is useful to other 1D photochemical models to reproduce the seasonal and latitudinal variation of atmospheric composition. The CO/CO2profiles from 75 to 105 km measured by NOMAD aboard TGO are used to investigate variations in the eddy diffusion coefficientThe estimated CO/CO2profiles agree well with the observed profiles if altitude‐dependent eddy diffusion coefficients are consideredOur results demonstrate a substantial seasonal variation in the eddy diffusion coefficient in the southern hemisphere The CO/CO2profiles from 75 to 105 km measured by NOMAD aboard TGO are used to investigate variations in the eddy diffusion coefficient The estimated CO/CO2profiles agree well with the observed profiles if altitude‐dependent eddy diffusion coefficients are considered Our results demonstrate a substantial seasonal variation in the eddy diffusion coefficient in the southern hemisphere
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- 2022
- Full Text
- View/download PDF
13. Unexpected increase of the deuterium to hydrogen ratio in the Venus mesosphere.
- Author
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Mahieux A, Viscardy S, Yelle RV, Karyu H, Chamberlain S, Robert S, Piccialli A, Trompet L, Erwin JT, Ubukata S, Nakagawa H, Koyama S, Maggiolo R, Pereira N, Cessateur G, Willame Y, and Vandaele AC
- Abstract
This study analyzes H
2 O and HDO vertical profiles in the Venus mesosphere using Venus Express/Solar Occultation in the InfraRed data. The findings show increasing H2 O and HDO volume mixing ratios with altitude, with the D/H ratio rising significantly from 0.025 at ~70 km to 0.24 at ~108 km. This indicates an increase from 162 to 1,519 times the Earth's ratio within 40 km. The study explores two hypotheses for these results: isotopic fractionation from photolysis of H2 O over HDO or from phase change processes. The latter, involving condensation and evaporation of sulfuric acid aerosols, as suggested by previous authors [X. Zhang et al. , Nat. Geosci. 3, 834-837 (2010)], aligns more closely with the rapid changes observed. Vertical transport computations for H2 O, HDO, and aerosols show water vapor downwelling and aerosols upwelling. We propose a mechanism where aerosols form in the lower mesosphere due to temperatures below the water condensation threshold, leading to deuterium-enriched aerosols. These aerosols ascend, evaporate at higher temperatures, and release more HDO than H2 O, which are then transported downward. Moreover, this cycle may explain the SO2 increase in the upper mesosphere observed above 80 km. The study highlights two crucial implications. First, altitude variation is critical to determining the Venus deuterium and hydrogen reservoirs. Second, the altitude-dependent increase of the D/H ratio affects H and D escape rates. The photolysis of H2 O and HDO at higher altitudes releases more D, influencing long-term D/H evolution. These findings suggest that evolutionary models should incorporate altitude-dependent processes for accurate D/H fractionation predictions., Competing Interests: Competing interests statement:The authors declare no competing interest.- Published
- 2024
- Full Text
- View/download PDF
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