掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/s41561-024-01598-9

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DOI： 10.5194/epsc2021-161

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DOI： 10.5194/epsc2020-487

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.icarus.2023.115891

Scopus

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掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-3881/acbf53

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.icarus.2022.115335

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掲載種別：研究論文（学術雑誌）  

DOI： 10.1093/mnras/stac3522

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掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/2041-8213/ac922d

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掲載種別：研究論文（学術雑誌）   出版者・発行元：American Association for the Advancement of Science (AAAS)  

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.

DOI： 10.1126/science.abn8671

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掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/PSJ/ac88d2

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2514/1.G006487

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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.

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その他リンク： http://arxiv.org/pdf/2202.04143v2

掲載種別：研究論文（学術雑誌）  

DOI： 10.1186/s40623-021-01423-2

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-3881/ac1f91

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その他リンク： http://arxiv.org/pdf/2108.08553v1

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1051/0004-6361/202038797

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.icarus.2021.114451

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担当区分：筆頭著者,　責任著者   記述言語：英語  

DOI： 10.1126/science.abj1512

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.icarus.2021.114505

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その他リンク： http://arxiv.org/pdf/2104.13516v1

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/abf6d8

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その他リンク： http://arxiv.org/pdf/2104.04981v1

担当区分：筆頭著者,　責任著者   掲載種別：研究論文（学術雑誌）   出版者・発行元：{EDP} Sciences  

<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.

DOI： 10.1051/0004-6361/202040031

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

DOI： 10.1016/j.icarus.2020.114064

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1051/0004-6361/202039894

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その他リンク： http://arxiv.org/pdf/2012.06700v2

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1051/0004-6361/202039705

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その他リンク： http://arxiv.org/pdf/2011.13164v1

掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/ab9897

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media LLC  

DOI： 10.1007/s11214-020-00694-7

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その他リンク： http://link.springer.com/article/10.1007/s11214-020-00694-7/fulltext.html

DOI： 10.1093/acrefore/9780190647926.013.24

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掲載種別：研究論文（学術雑誌）  

DOI： 10.14909/yuseijin.29.3_104

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1038/s41598-019-56139-x

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

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).

DOI： 10.1016/j.lssr.2019.07.006

PubMed

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Elsevier BV  

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.

DOI： 10.1016/j.lssr.2019.07.009

PubMed

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掲載種別：研究論文（学術雑誌）   出版者・発行元：{EDP} Sciences  

DOI： 10.1051/0004-6361/201935935

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掲載種別：研究論文（学術雑誌）   出版者・発行元：EDP Sciences  

<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> &gt; 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> &gt; 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> &gt; 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.

DOI： 10.1051/0004-6361/201833216

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掲載種別：研究論文（学術雑誌）   出版者・発行元：Springer Science and Business Media {LLC}  

DOI： 10.1038/s41550-019-0797-9

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掲載種別：研究論文（学術雑誌）  

DOI： 10.3847/1538-4357/aac024

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Institute of Physics Publishing  

DOI： 10.3847/2041-8213/aab7f0

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Institute of Physics Publishing  

DOI： 10.3847/1538-4357/aaa23e

Scopus

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その他リンク： http://stacks.iop.org/0004-637X/853/i=2/a=118?key=crossref.cb970045f0430f3036683fcd1d26dbbd

掲載種別：論文集(書籍)内論文   出版者・発行元：Springer International Publishing  

DOI： 10.1007/978-3-319-30648-3_54-1

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Institute of Physics Publishing  

DOI： 10.3847/1538-4357/aa9984

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その他リンク： http://stacks.iop.org/0004-637X/851/i=2/a=122?key=crossref.fb2416c7cbdbe3a1342cbb1dc80164e5

担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Institute of Physics Publishing  

DOI： 10.3847/1538-4357/aa81c4

Scopus

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その他リンク： http://stacks.iop.org/0004-637X/845/i=2/a=125?key=crossref.e80c30944b7d1ac839b33fc466042090

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Institute of Physics Publishing  

DOI： 10.3847/1538-3881/aa74c9

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Academic Press Inc.  

DOI： 10.1016/j.icarus.2016.09.012

Scopus

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記述言語：日本語   出版者・発行元：日本惑星科学会  

<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>

DOI： 10.14909/yuseijin.26.3_82

CiNii Article

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Institute of Physics Publishing  

DOI： 10.3847/2041-8205/828/1/L8

Scopus

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Nature Publishing Group  

DOI： 10.1038/ngeo2742

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担当区分：筆頭著者,　責任著者   記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Nature Publishing Group  

DOI： 10.1038/ngeo2508

Scopus

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その他リンク： http://www.nature.com/articles/ngeo2508

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Institute of Physics Publishing  

DOI： 10.1088/0004-637X/799/1/40

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記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Institute of Physics Publishing  

DOI： 10.1088/0004-637X/787/1/56

Scopus

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その他リンク： http://stacks.iop.org/0004-637X/787/i=1/a=56?key=crossref.7167fd82c5dcd3677116b9e82afa7f80

J-GLOBAL

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記述言語：日本語   出版者・発行元：日本惑星科学会  

CiNii Article

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記述言語：日本語   出版者・発行元：日本惑星科学会  

CiNii Article

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記述言語：日本語   出版者・発行元：日本惑星科学会  

CiNii Article

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