Curriculum Vitaes
Profile Information
- Affiliation
- Associate Professor, Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency
- J-GLOBAL ID
- 201901015283902873
- researchmap Member ID
- B000362527
Research History
1-
May, 2023 - Present
Papers
64-
Science (New York, N.Y.), 379(6634) eabo0431, Feb 24, 2023The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth's volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measured noble gas and nitrogen isotopes in Ryugu samples and found that they are dominated by presolar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have different abundances among the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating a ~5 million year exposure, and from implanted solar wind record the recent irradiation history of Ryugu after it migrated to its current orbit.
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Science (New York, N.Y.), 379(6634) eabn9033, Feb 24, 2023The Hayabusa2 spacecraft collected samples from the surface of the carbonaceous near-Earth asteroid (162173) Ryugu and brought them to Earth. The samples were expected to contain organic molecules, which record processes that occurred in the early Solar System. We analyzed organic molecules extracted from the Ryugu surface samples. We identified a variety of molecules containing the atoms CHNOS, formed by methylation, hydration, hydroxylation, and sulfurization reactions. Amino acids, aliphatic amines, carboxylic acids, polycyclic aromatic hydrocarbons, and nitrogen-heterocyclic compounds were detected, which had properties consistent with an abiotic origin. These compounds likely arose from an aqueous reaction on Ryugu's parent body and are similar to the organics in Ivuna-type meteorites. These molecules can survive on the surfaces of asteroids and be transported throughout the Solar System.
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Science Advances, 8(46), Nov, 2022The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on 6 December 2020. One day after the recovery, the gas species retained in the sample container were extracted and measured on-site and stored in gas collection bottles. The container gas consists of helium and neon with an extraterrestrial 3He/4He and 20Ne/22Ne ratios, along with some contaminant terrestrial atmospheric gases. A mixture of solar and Earth’s atmospheric gas is the best explanation for the container gas composition. Fragmentation of Ryugu grains within the sample container is discussed on the basis of the estimated amount of indigenous He and the size distribution of the recovered Ryugu grains. This is the first successful return of gas species from a near-Earth asteroid.
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Monthly Notices of the Royal Astronomical Society, 514(4) 6173-6182, Aug 1, 2022The JAXA Hayabusa2 mission accomplished the formation of an artificial crater on the asteroid Ryugu. The aim of this work is to analyse the area surrounding the artificial crater and reveal spectral variability compared to the same region before the crater formation, to mineralogically and physically characterize the subsurface exposed material. The crater's investigation focused on the analysis of two regions corresponding to the inner part of crater (the pit and the crater wall/floor), two areas related to ejecta deposited close to the crater, two areas of ejecta moved far from the crater, and two external areas. Each area was investigated both before and after the crater formation, by the study of the photometrically corrected spectral parameters: the 1.9 μm reflectance, the near-infrared spectral slope, and the depth of the bands at 2.7 and 2.8 μm. The subsurface material of the post-crater areas shows deeper absorption bands, a decrease in reflectance, and a reddening in spectral slope with respect to the surface material of pre-crater areas. The subsurface regolith could have experienced a lower OH devolatilization due to space weathering and/or could be composed of finer dark grains than the surface layer. The ejecta reached distances of ~20 m from the impact point, mainly moving in the northern direction; nevertheless, a few ejecta also reached the south-eastern part of crater.
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Planetary and Space Science, 219 105519-105519, Jun, 2022 Peer-reviewed
Misc.
71-
Planetary people, 19(2) 157-160, Jun 25, 2010
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Planetary People, 18(4) 244-245, Dec 25, 2009
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Abstracts for fall meeting of the Japanese Society for Planetary Science, 2007 107-107, 2007The Hayabusa spacecraft, which was launched in May 2003, arrived at Asteroid Ito-kawa in September 2005, and it made observations of Itokawa and tried touch down in about three months.Hayabusa has four scientific instruments, that is Multi-Spectral Telescopic Imager (AMICA), Laser Altimeter (LIDAR), Near-Infrared Spectrometer (NIRS), and X-ray Fluorescence Spectrometer (XRS). The data obtained by these instruments were firstly analyzed by Hayabusa Science Team and some of the results have been pub-lished as scientific papers. At the same time, the science team was preparing to open them to the public and this work has almost been done. Therefore the science team release the data archives to public from April 24, 2007. All the scientific data that Hayabusa obtained are open to the public.The Hayabusa data archives can be accessed from the following web site:(URL) http://hayabusa.sci.isas.jaxa.jp/
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日本惑星科学会秋季講演会予稿集, 2007 133-133, 2007Analytical procedure and method is under development for the X-Ray Spectrometer onboard SELENE(Kaguya). We present the system in detail. Furterhmore, we investigate the datainterpretation for XRF, including the surface microscopic and macroscopic roughness as well as mineral mixing effects. For a daily automatic analysis for huge amount of data, correction equations for ther effects are necessary to be defined. We also present the currect status of the correction method.
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日本惑星科学会秋季講演会予稿集, 2006 96-76, 2006XRS (x-ray spectrometer) onboard Hayabusa has observed x-ray fluorescence from near-Earth asteroid 25143 Itokawa to determine major elemental composition. Okada et al. (2006) reported average elemental mass ratios of Mg/Si = 0.78 + - 0.09 and Al/Si = 0.07 + - 0.03. In this study, we attempted to estimate upper limits of Ca and Fe. To discussion about abundance of Ca and Fe, we need to integrate data longer time, fallowing the result of numerical simulation. In this poster, we report a result and the method of the analyses.
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Proc ISAS Lunar Planet Symp (CD-ROM), 39th ROMBUNNO.21, 2006
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宇宙科学シンポジウム 平成14年度 第3回, 87-88, 2003
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Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 2001 28-28, Oct 6, 2001We are developing an X-Ray fluorescence Spectrometer (XRS) onboard the asteroid probe MUSES-C. Variation of solar X-rays must be considered to analyze major elements quantitatively. XRS observes solar X-rays indirectly using a standard sample. Therefore X-rays from a planetary surface can be calibrated with those from a standard sample in addition to investigation of the spectra and intensities of solar X-rays. We make a model of solar X-ray flux and simulate X-rays observed from a standard sample under various solar conditions. We estimate inversely solar X-rays with calculated emissions and investigate suitable integration times.
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Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 2001 84-84, Oct 6, 2001We are developing an X-Ray fluorescence Spectrometer (XRS) onboard the asteroid probe MUSES-C. XRS contains 5 CCD chips. XRS will not carry in-flight calibration sources. Therefore we will observe cosmic X-ray objects for the calibration with XRS during the cruise. We performed numerical simulation of observing some known X-ray objects. Those simulations were run with exposure time about 3 hours, based on the best-fit models to the ASCA SIS spectra.
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Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 1999 61-61, Nov 13, 1999
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Abstracts Fall Meeting of the Japanese Society for Planetary Sciences, 1999 62-62, Nov 13, 1999
Research Projects
3-
Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, Apr, 2013 - Mar, 2015
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Grants-in-Aid for Scientific Research, Japan Society for the Promotion of Science, 2011 - 2012
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科学研究費助成事業, 日本学術振興会, 1999 - 2001
