研究者業績
基本情報
- 所属
- 国立研究開発法人宇宙航空研究開発機構 宇宙科学研究所 太陽系科学研究系 国際トップヤングフェロー (准教授相当)
- 連絡先
- hyodo
elsi.jp - 研究者番号
- 20814693
- ORCID ID
https://orcid.org/0000-0003-4590-0988- J-GLOBAL ID
- 202001015221817161
- researchmap会員ID
- R000006549
- 外部リンク
About
惑星形成論および惑星探査を専門とし，JAXA 内部から積極的に次世代の惑星探査ミッションの構築を行なっている．ESA・NASA・JAXA の3機関の探査計画に参画．3-4ヶ月/年はパリ大学で活動．
個人ホームページ: https://members.elsi.jp/~hyodo/English/index.html (Here)
google scholar: https://scholar.google.co.jp/citations?user=IjqvVCwAAAAJ&hl=en (Here)
Research Interests
コンピュータシミュレーションと理論的手法を用いて, 多様な惑星系, 小天体, リングの形成と進化過程の理解（惑星形成論）を目指す．また科学的な側面から惑星探査ミッションを積極的に価値最大化・構築すること（惑星探査学）を目的とする．
Mission Involvements
NASA土星探査計画 Cassini / JAXA小惑星探査計画 Hayabusa2 / ESA水星探査計画 BepiColombo / JAXA火星衛星探査計画 MMX / JAXA次世代サンプルリターン計画 (彗星!?) / 深宇宙・超コンステレーション構想 (即応型小天体フライバイ探査構想) / JAXA外惑星探査計画 OPENS (日本初の外惑星探査計画 !?)
主なプレスリリース
『新時代を迎える火星生命探査における火星衛星探査計画「MMX」の役割 (link)』
『後期集積が水星に与える影響 (link)』
『火星衛星、巨大衝突で形成される (link)』
『JAXA火星衛星サンプルリターン(MMX)計画で、火星の全歴史の解明が可能 (link)』
『土星の輪、誕生の謎を解明 (link)』
主な外部インタビュー記事
『日本惑星科学会最優秀研究者賞受賞インタビュー (link)』
『理論研究で月や火星探査の道筋をつける (link)』
『惑星形成論研究者はリュウグウサンプル分析結果のどこに注⽬するのか (link)』
研究分野
1経歴
3-
2019年10月 - 現在
-
2017年4月 - 2019年9月
-
2015年4月 - 2017年3月
受賞
2-
2022年5月
-
2016年9月
論文
48-
Nature Geoscience 2025年1月
-
The Astronomical Journal 2023年4月1日
-
Monthly Notices of the Royal Astronomical Society 2022年12月30日
-
The Astrophysical Journal Letters 2022年10月1日
-
Science 379(6634) 2022年9月22日 査読有りSamples of the carbonaceous asteroid Ryugu were brought to Earth by the Hayabusa2 spacecraft. We analyzed seventeen Ryugu samples measuring 1-8 mm. CO 2 -bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu’s parent asteroid formed in the outer Solar System. The samples contain low abundances of materials that formed at high temperatures, such as chondrules and Ca, Al-rich inclusions. The samples are rich in phyllosilicates and carbonates, which formed by aqueous alteration reactions at low temperature, high pH, and water/rock ratios < 1 (by mass). Less altered fragments contain olivine, pyroxene, amorphous silicates, calcite, and phosphide. Numerical simulations, based on the mineralogical and physical properties of the samples, indicate Ryugu’s parent body formed ~ 2 million years after the beginning of Solar System formation.
-
The Planetary Science Journal 2022年8月1日
-
JOURNAL OF GUIDANCE CONTROL AND DYNAMICS 2022年4月
-
2022年2月8日Forming planetesimals from pebbles is a major challenge in our current understanding of planet formation. In a protoplanetary disk, pebbles drift inward near the disk midplane via gas drag and they may enter a dead zone. In this context, we identified that the backreaction of the drag of pebbles onto the gas could lead to a runaway pile-up of pebbles, the so-called no-drift mechanism. We improve upon the previous study of the no-drift mechanism by investigating the nature and characteristics of the resultant planetesimal belt. We performed 1D diffusion-advection simulations of drifting pebbles in the outer region of a dead zone by including the backreaction to the radial drift of pebbles and including planetesimal formation via the streaming instability. We considered the parameters that regulate gas accretion and vertical stirring of pebbles in the disk midplane. In this study, the pebble-to-gas mass flux ($F_{\rm p/g}$) was fixed as a parameter. We find that planetesimals initially form within a narrow ring whose width expands as accumulating pebbles radially diffuse over time. The system finally reaches a steady-state where the width of the planetesimal belt no longer changes. A non-negligible total mass of planetesimals (more than one Earth mass) is formed for a disk having $F_{\rm p/g} \gtrsim 0.1$ for more than $\sim 10-100$ kyr with nominal parameters: a gas mass flux of $\gtrsim10^{-8} {\rm M}_\oplus$/yr, $\tau_{\rm s} \simeq 0.01-0.1$, $\alpha_{\rm mid} \lesssim 10^{-4}$, and $\alpha_{\rm acc} \simeq 10^{-3}-10^{-2}$ at $r \lesssim 10$ au, where $r$, $\tau_{\rm s}$, $\alpha_{\rm mid}$, and $\alpha_{\rm acc}$ are the heliocentric distance, the Stokes number, and the parameters in a dead zone controlling the efficiencies of vertical turbulent diffusion of pebbles (i.e., scale height of pebbles) and gas accretion of the $\alpha$-disk (i.e., gas surface density), respectively.
-
ASTRONOMICAL JOURNAL 162(6) 2021年8月19日
-
Astronomy & Astrophysics 652 2021年8月
-
ASTROPHYSICAL JOURNAL 913(2) 77-77 2021年4月11日
-
Astronomy & Astrophysics 645 L9-L9 2021年1月 査読有り筆頭著者責任著者<italic>Context.</italic> A notable challenge of planet formation is to find a path to directly form planetesimals from small particles. <italic>Aims.</italic> We aim to understand how drifting pebbles pile up in a protoplanetary disk with a nonuniform turbulence structure. <italic>Methods.</italic> We consider a disk structure in which the midplane turbulence viscosity increases with the radius in protoplanetary disks, such as in the outer region of a dead zone. We perform 1D diffusion-advection simulations of pebbles that include back-reaction (the inertia) to the radial drift and the vertical and radial diffusions of pebbles for a given pebble-to-gas mass flux. <italic>Results.</italic> We report a new mechanism, the “no-drift” runaway pile-up, that leads to a runaway accumulation of pebbles in disks, thus favoring the formation of planetesimals by streaming and/or gravitational instabilities. This occurs when pebbles drifting in from the outer disk and entering a dead zone experience a decrease in vertical turbulence. The scale height of the pebble subdisk then decreases, and, for small enough values of the turbulence in the dead zone and high values of the pebble-to-gas flux ratio, the back-reaction of pebbles on gas leads to a significant decrease in their drift velocity and thus their progressive accumulation. This occurs when the ratio of the flux of pebbles to that of the gas is large enough that the effect dominates over any Kelvin-Helmholtz shear instability. This process is independent of the existence of a pressure bump.
-
Icarus 354 114064-114064 2021年1月 査読有り
-
ASTRONOMY & ASTROPHYSICS 646 2020年12月12日 査読有り筆頭著者責任著者
-
ASTRONOMY & ASTROPHYSICS 646 2020年11月26日
-
The Astrophysical Journal 2020年7月1日 査読有り
-
Space Science Reviews 216(4) 2020年6月 査読有り
-
Scientific Reports 9(1) 2019年12月 査読有り筆頭著者責任著者
-
Life Sciences in Space Research 23 85-100 2019年11月 査読有りThis paper presents a case study of microbe transportation in the Mars-satellites system. We examined the spatial distribution of potential impact-transported microbes on the Martian moons using impact physics by following a companion study (Fujita et al., in this issue). We used sterilization data from the precede studies (Patel et al., 2018; Summers, 2017). We considered that the microbes came mainly from the Zunil crater on Mars, which was formed during 1.0-0.1 Ma. We found that 70-80% of the microbes are likely to be dispersed all over the moon surface and are rapidly sterilized due to solar and galactic cosmic radiation except for those microbes within a thick ejecta deposit produced by natural meteoroids. The other 20-30% might be shielded from radiation by thick regolith layers that formed at collapsed layers in craters produced by Mars rock impacts. The total number of potentially surviving microbes at the thick ejecta deposits is estimated to be 3-4 orders of magnitude lower than at the Mars rock craters. The microbe concentration is irregular in the horizontal direction due to Mars rock bombardment and is largely depth-dependent due to the radiation sterilization. The surviving fraction of transported microbes would be only ∼1 ppm on Phobos and ∼100 ppm on Deimos, suggesting that the transport processes and radiation severely affect microbe survival. The microbe sampling probability from the Martian moons was also investigatesd. We suggest that sample return missions from the Martian moons are classified into Unrestricted Earth-Return missions for 30 g samples and 10 cm depth sampling, even in our conservative scenario. We also conducted a full statistical analysis pertaining to sampling the regolith of Phobos to include the effects of uncertainties in input parameters on the sampling probability. The most likely probability of microbial contamination for return samples is estimated to be two orders of magnitude lower than the 10-6 criterion defined by the planetary protection policy of the Committee on Space Research (COSPAR).
-
Life Sciences in Space Research 23 73-84 2019年11月 査読有りPotential microbial contamination of Martian moons, Phobos and Deimos, which can be brought about by transportation of Mars ejecta produced by meteoroid impacts on the Martian surface, has been comprehensively assessed in a statistical approach, based on the most probable history of recent major gigantic meteoroid collisions on the Martian surface. This article is the first part of our study to assess potential microbial density in Mars ejecta departing from the Martian atmosphere, as a source of the second part (Kurosawa et al., 2019) where statistical analysis of microbial contamination probability is conducted. Potential microbial density on the Martian surface as the source of microorganisms was estimated by analogy to the terrestrial areas having the similar arid and cold environments, from which a probabilistic function was deduced as the asymptotic limit. Microbial survival rate during hypervelocity meteoroid collisions was estimated by numerical analysis of impact phenomena with and without taking internal friction and plastic deformation of the colliding meteoroid and the target ground into consideration. Trajectory calculations of departing ejecta through the Martian atmosphere were conducted with taking account of aerodynamic deceleration and heating by the aid of computational fluid dynamic analysis. It is found that Mars ejecta smaller than 0.03 m in diameter hardly reach the Phobos orbit due to aerodynamic deceleration, or mostly sterilized due to significant aerodynamic heating even though they can reach the Phobos orbit and beyond. Finally, the baseline dataset of microbial density in Mars ejecta departing for Martian moons has been presented for the second part of our study.
-
Astronomy & Astrophysics 629 2019年9月 査読有り
-
Astronomy & Astrophysics 627 A50-A50 2019年7月 査読有り<italic>Context.</italic> When and where planetesimals form in a protoplanetary disk are highly debated questions. Streaming instability is considered the most promising mechanism, but the conditions for its onset are stringent. Disk studies show that the planet forming region is not turbulent because of the lack of ionization forming possibly dead zones (DZs). <italic>Aims.</italic> We investigate planetesimal formation in an evolving disk, including the DZ and thermal evolution. <italic>Methods.</italic> We used a 1D time-evolving stratified disk model with composite chemistry grains, gas and dust transport, and dust growth. <italic>Results.</italic> Accretion of planetesimals always develops in the DZ around the snow line, due to a combination of water recondensation and creation of dust traps caused by viscosity variations close to the DZ. The width of the planetesimal forming region depends on the disk metallicity. For <italic>Z</italic> = <italic>Z</italic>⊙, planetesimals form in a ring of about 1 au width, while for <italic>Z</italic> > 1.2 <italic>Z</italic>⊙ planetesimals form from the snow line up to the outer edge of the DZ ≃ 20 au. The efficiency of planetesimal formation in a disk with a DZ is due to the very low effective turbulence in the DZ and to the efficient piling up of material coming from farther away; this material accumulates in region of positive pressure gradients forming a dust trap due to viscosity variations. For <italic>Z</italic> = <italic>Z</italic>⊙ the disk is always dominated in terms of mass by pebbles, while for <italic>Z</italic> > 1.2 <italic>Z</italic>⊙ planetesimals are always more abundant than pebbles. If it is assumed that silicate dust is sticky and grows up to impact velocities ~10 m s−1, then planetesimals can form down to 0.1 au (close to the inner edge of the DZ). In conclusion the DZ seems to be a sweet spot for the formation of planetesimals: wide scale planetesimal formation is possible for <italic>Z</italic> > 1.2 <italic>Z</italic>⊙. If hot silicate dust is as sticky as ice, then it is also possible to form planetesimals well inside the snow line.
-
Nature Astronomy 3(9) 802-807 2019年6月24日 査読有り
-
The Astrophysical Journal 2018年6月20日 査読有り
-
Astrophysical Journal Letters 856(2) 2018年4月1日 査読有り
-
Astrophysical Journal 853(2) 118-118 2018年2月1日 査読有り
-
Astrophysical Journal 851(2) 122-122 2017年12月20日 査読有り
-
Astrophysical Journal 845(2) 125-125 2017年8月20日 査読有り筆頭著者責任著者
-
Astronomical Journal 154(1) 2017年7月1日 査読有り
-
Ring formation around giant planets by tidal disruption of a single passing large Kuiper belt objectIcarus 282 195-213 2017年1月15日 査読有り
-
日本惑星科学会誌遊星人 26(3) 82-91 2017年<p>本研究では, 約38 億年前に起こったと考えられている後期重爆撃期に, 冥王星サイズの巨大な微惑星が巨大惑星と少なくとも数回の近接遭遇を経験しうることに着目し, SPH計算とN体計算を用いて, 分化した微惑星の近接遭遇時の潮汐破壊過程，および，惑星に捕獲された破片の長期進化を詳細に調べることで, リングの形成可能性について議論する.</p>
-
Astrophysical Journal Letters 828(1) 2016年9月1日 査読有り
-
Nature Geoscience 9(8) 581-583 2016年8月1日 査読有り
-
Nature Geoscience 8(9) 686-689 2015年10月1日 査読有り筆頭著者責任著者
-
Astrophysical Journal 799(1) 40-40 2015年1月20日 査読有り
-
Astrophysical Journal 787(1) 56-56 2014年5月20日 査読有り
MISC
9担当経験のある科目(授業)
1-
2020年4月 - 現在全学共通科目「地球の理解」 (立教大学)
共同研究・競争的資金等の研究課題
9-
日本学術振興会 科学研究費助成事業 2022年4月 - 2026年3月
-
日本学術振興会 科学研究費助成事業 基盤研究(A) 2021年4月 - 2026年3月
-
日本学術振興会 科学研究費助成事業 基盤研究(A) 2021年4月 - 2026年3月
-
日本学術振興会 科学研究費助成事業 国際共同研究加速基金(国際共同研究強化(B)) 2020年10月 - 2026年3月
-
日本学術振興会 科学研究費助成事業 若手研究 2018年4月 - 2022年3月
