掲載種別：研究論文（学術雑誌）   出版者・発行元：Astronomy and Astrophysics  

Context. The current period is conducive to exploring our Solar System's origins with recent and future space sample return missions, which provide invaluable information from known Solar System asteroids and comets The Hayabusa2 mission of the Japan Aerospace Exploration Agency (JAXA) recently brought back samples from the surface of the Ryugu carbonaceous asteroid. Aims. We aim to identify the different forms of chemical composition of organic matter and minerals that constitute these Solar System primitive objects, to shed light on the Solar System's origins. Methods. In this work, we recorded infrared (IR) hyper-spectral maps of whole-rock Ryugu asteroid samples at the highest achievable spatial resolution with a synchrotron in the mid-IR (MIR). Additional global far-IR (FIR) spectra of each sample were also acquired. Results. The hyper-spectral maps reveal the variability of the functional groups at small scales and the intimate association of phyl-losilicates with the aliphatic components of the organic matter present in Ryugu. The relative proportion of column densities of the identified IR functional groups (aliphatics, hydroxyl + interlayer and/or physisorbed water, carbonyl, carbonates, and silicates) giving access to the composition of the Ryugu samples is estimated from these IR hyper-spectral maps. Phyllosilicate spectra reveal the presence of mixtures of serpentine and saponite. We do not detect anhydrous silicates in the samples analysed, at the scales probed. The carbonates are dominated by dolomite. Aliphatics organics are distributed over the whole samples at the micron scale probed with the synchrotron, and intimately mixed with the phyllosilicates. The aromatic C=C contribution could not be safely deconvolved from OH in most spectra, due to the ubiquitous presence of hydrated minerals. The peak intensity ratios of the organics methylene to methyl (CH2/CH3) of the Ryugu samples vary between about 1.5 and 2.5, and are compared to the ratios in chondrites from types 1 to 3. Overall, the mineralogical and organic characteristics of the Ryugu samples show similarities with those of CI chondrites, although with a noticeably higher CH2/CH3 in Ryugu than generally measured in C1 chondrites collected on Earth, and possibly a higher carbonate content.

DOI： 10.1051/0004-6361/202244702

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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：Science  

The 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.

DOI： 10.1126/science.abn9033

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PubMed

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

Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by the Hayabusa2 spacecraft. We investigated the macromolecular organic matter in Ryugu samples and found that it contains aromatic and aliphatic carbon, ketone, and carboxyl functional groups. The spectroscopic features of the organic matter are consistent with those in chemically primitive carbonaceous chondrite meteorites that experienced parent-body aqueous alteration (reactions with liquid water). The morphology of the organic carbon includes nanoglobules and diffuse carbon associated with phyllosilicate and carbonate minerals. Deuterium and/or nitrogen-15 enrichments indicate that the organic matter formed in a cold molecular cloud or the presolar nebula. The diversity of the organic matter indicates variable levels of aqueous alteration on Ryugu’s parent body.

DOI： 10.1126/science.abn9057

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PubMed

出版者・発行元：ACS Earth and Space Chemistry  

Sulfur comprises various compound forms in natural environments and could have played important roles in chemical evolution in the universe. Various soluble organosulfur compounds and inorganic sulfur oxides were identified in the methanol extracts of three carbonaceous chondrites (Murchison, Tagish Lake, and Allende) using high-performance liquid chromatography coupled with high-resolution mass spectrometry. The most abundant S-bearing organic compound was hydroxymethane sulfonic acid (HMSA, HOCH2SO3H), which is reported from a meteorite for the first time, at a concentration of 201 nmol/g in the Murchison meteorite. Because HMSA is known to be produced by the reaction of formaldehyde (HCHO) and bisulfite (HSO3-), this result indicates that formaldehyde should be abundant prior to the reaction with HSO3- in the meteorite parent bodies. The bisulfite derivatives of glycolaldehyde and glyceraldehyde were further identified in the methanol extract, suggesting that the formose reaction had proceeded during the aqueous alteration. The finding of these sugar-HSO3- adducts suggests that the formose reaction might have been controlled by the presence of sulfur species in the body. Furthermore, alkylated sulfonic acids (CnH2n+1SO3H) were also present as a series of homologous compounds up to C14 in the Murchison meteorite, even though previous studies found only C1-C4 sulfonic acids. In addition to organosulfur compounds, variable inorganic polysulfur oxides and acids were detected. The abundant S-bearing compounds in the meteorites imply important roles of sulfur in the organic reactions in carbonaceous asteroids.

DOI： 10.1021/acsearthspacechem.2c00157

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記述言語：日本語   掲載種別：研究論文（学術雑誌）   出版者・発行元：Astrophysical Journal Letters  

We have conducted a NanoSIMS-based search for presolar material in samples recently returned from C-type asteroid Ryugu as part of JAXA's Hayabusa2 mission. We report the detection of all major presolar grain types with O- and C-anomalous isotopic compositions typically identified in carbonaceous chondrite meteorites: 1 silicate, 1 oxide, 1 O-anomalous supernova grain of ambiguous phase, 38 SiC, and 16 carbonaceous grains. At least two of the carbonaceous grains are presolar graphites, whereas several grains with moderate C isotopic anomalies are probably organics. The presolar silicate was located in a clast with a less altered lithology than the typical extensively aqueously altered Ryugu matrix. The matrix-normalized presolar grain abundances in Ryugu are 4.8 − 2.6 + 4.7 ppm for O-anomalous grains, 25 − 5 + 6 ppm for SiC grains, and 11 − 3 + 5 ppm for carbonaceous grains. Ryugu is isotopically and petrologically similar to carbonaceous Ivuna-type (CI) chondrites. To compare the in situ presolar grain abundances of Ryugu with CI chondrites, we also mapped Ivuna and Orgueil samples and found a total of 15 SiC grains and 6 carbonaceous grains. No O-anomalous grains were detected. The matrix-normalized presolar grain abundances in the CI chondrites are similar to those in Ryugu: 23 − 6 + 7 ppm SiC and 9.0 − 3.6 + 5.4 ppm carbonaceous grains. Thus, our results provide further evidence in support of the Ryugu-CI connection. They also reveal intriguing hints of small-scale heterogeneities in the Ryugu samples, such as locally distinct degrees of alteration that allowed the preservation of delicate presolar material.

DOI： 10.3847/2041-8213/ac83bd

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記述言語：日本語  

Web of Science

記述言語：日本語  

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出版者・発行元：Research Square Platform LLC  

Abstract

We performed in-situ analysis on a ~1 mm-sized Ryugu grain A0080 returned by the Hayabusa2 spacecraft to investigate the relationship of soluble organic matter (SOM) to minerals. The DESI-HRMS (desorption electrospray ionization-high resolution mass spectrometry) imaging using methanol spray identified more than 200 soluble organic compounds, which were assigned as CHN, CHO, CHO-Na (sodium adducted), and CHNO in molecular composition. Heterogeneous spatial distribution was observed for different compound classes of SOM as well as among the same alkylated homologues on the sample surface. The A0080 sample showed similar mineralogy to that of CI chondrite and contained two different lithologies, which are rich in magnetite, pyrrhotite, and dolomite (lithology 1) and poor in those minerals (lithology 2). CHN compounds were relatively concentrated in lithology 1 than in lithology 2, on the other hand, CHO, CHO-Na, and CHNO compounds were distributed in both lithologies. Such different spatial distribution of SOM is the result of interaction of the SOM with minerals, during precipitation of the SOM via fluid activity, or could be due to difference in transportation efficiencies of SOMs in aqueous fluid. However, organic-related ions measured by ToF-SIMS did not coincide with the spatial distribution revealed by DESI-HRMS imaging, indicating that the ToF-SIMS data would be mainly derived from methanol-insoluble organic matter in A0080. Alkylated homologues of CHN compounds with large C number appeared more abundant in lithology 2 than lithology 1. In contrast, fragments of the Murchison meteorite showed different features to of A0080, implying different formation or growth mechanisms for the alkylated CHN compounds by interaction with fluid and minerals on Murchison parent body and asteroid Ryugu. This difference might be mainly attributed to the carbonate grains, which would have played as a catalyst for CH₂ growth of CHN compounds. Future in-situ analysis of CI chondrite will provide more reliable constraints for the history of soluble organic compounds in asteroid Ryugu.

DOI： 10.21203/rs.3.rs-1812195/v1

その他リンク： https://www.researchsquare.com/article/rs-1812195/v1.html

記述言語：日本語   出版者・発行元：一般社団法人日本地球化学会  

<p>本発表では，その場分析によりリュウグウ粒子表面の可溶性有機物 (SOM)の空間分布と鉱物との関係を調べた結果を報告する．リュウグウ粒子 (A0080)から，CHN, CHO, CHNO, CHO-Na組成のメタノール可溶な同族体化合物を200種以上検出した． CHN, CHO, CHNO, CHO-Na化合物はそれぞれ異なる空間分布を示し，CHO化合物とCHN化合物については変質鉱物，特にCa-Mg炭酸塩との空間的相関が見られた．これは，小惑星リュウグウにおける流体中の有機物と鉱物との相互作用の結果を示唆している．</p>

DOI： 10.14862/geochemproc.69.0_104

CiNii Research

記述言語：日本語  

DOI： 10.35848/1882-0786/abf319

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記述言語：日本語   出版者・発行元：一般社団法人日本地球化学会  

<p>本研究では，DESI-HRMSによるイメージング質量分析を用いてタギッシュレイク隕石から同定した，非常に不均質な空間分布を示す可溶性有機物について報告する。フランボイダル磁鉄鉱の空間分布から，同定した化合物は水質変質の程度の低いリソロジーに集中して存在することが分かった。本研究の結果は，隕石母天体上において，強い水質変質を受けた領域で化合物が流されて消失した結果か，もしくは，鉱物との吸着性の違いによるクロマトグラフィー的効果を示すものである。また，同定した化合物にはアルキル基や水分子の付加によって形成される同族体はほとんど検出されなかったことから，水質変質中に形成・化学進化したのではなく，隕石集積時にもともと存在していた有機化合物である可能性が示唆される。</p>

DOI： 10.14862/geochemproc.68.0_78

CiNii Research

記述言語：日本語   出版者・発行元：一般社団法人日本地球化学会  

<p>近年，高質量分解能質量分析により，始原的隕石の可溶性有機化合物 (SOM)からMgを含む有機化合物 (Mg-OC)が報告され，これらは鉱物由来のMgと有機化合物が反応し形成した物質と考えられている。本研究は，Mg-OCの形成経路を理解するため，始原的隕石の in-situ分析を行い，Mg-OCと鉱物との空間的関係を調査した。脱離エレクトロスプレーイオン化とオービトラップ質量分析装置を利用したイメージング質量分析により，Murchison, Nogoya, Tagish Lake隕石フラグメントからMg-OCのアルキル同族体系列を多数検出した。Mg-OCはマトリックス領域に分布し，Mgを含む粘土鉱物との空間的相関が見られた。Mg-OCの相対イオン強度は，各隕石の水質変質の大小関係と一致した。以上より，Mg-OCは，隕石母天体での水質変質時に形成し，粘土鉱物の表面や層間に保存された物質であると考えられる。</p>

DOI： 10.14862/geochemproc.67.0_80

CiNii Research

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.3390/life9030062

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1111/maps.13211

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記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2343/geochemj.2.0546

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記述言語：日本語  

DOI： 10.14909/yuseijin.27.3_253

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.2138/am-2018-6480

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その他リンク： http://orcid.org/0000-0003-0702-0533

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1002/rcm.8121

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PubMed

記述言語：英語   掲載種別：研究論文（学術雑誌）  

DOI： 10.1016/j.epsl.2017.12.020

Scopus

記述言語：英語   掲載種別：研究論文（学術雑誌）   出版者・発行元：PERGAMON-ELSEVIER SCIENCE LTD  

A comprehensive study of the organic chemistry and mineralogy of an ultracarbonaceous micrometeorite (UCAMM D05IB80) collected from near the Dome Fuji Station, Antarctica, was carried out to understand the genetic relationship among organic materials, silicates, and water. The micrometeorite is composed of a dense aggregate of similar to 5 mm-sized hollow ellipsoidal organic material containing submicrometer-sized phases such as glass with embedded metal and sulfides (GEMS) and mineral grains. There is a wide area of organic material (similar to 15 x 15 mu m) in its interior. Low-Ca pyroxene is much more abundant than olivine and shows various Mg/(Mg + Fe) ratios ranging from similar to 1.0 to 0.78, which is common to previous works on UCAMMs. By contrast, GEMS grains in this UCAMM have unusual chemical compositions. They are depleted in both Mg and S, which suggests that these elements were leached out from the GEMS grains during very weak aqueous alteration, without the formation of phyllosilicates.
The organic materials have two textures-smooth and globular with an irregular outline- and these are composed of imine, nitrile and/or aromatic nitrogen heterocycles, and amide. The ratio of nitrogen to carbon (N/C) in the smooth region of the organics is similar to 0.15, which is five times higher than that of insoluble organic macromolecules in types 1 and 2 carbonaceous chondritic meteorites. In addition, the UCAMM organic materials are soluble in epoxy and are thus hydrophilic; this polar nature indicates that they are very primitive. The surface of the material is coated with an inorganic layer, a few nanometers thick, that consists of C, O, Si, S, and Fe. Sulfur is also contained in the interior, implying the presence of organosulfur moieties. There are no isotopic anomalies of D, C-13, or N-15 in the organic material.
Interstellar photochemistry alone would not be sufficient to explain the N/C ratio of the UCAMM organics; therefore, we suggest that a very small amount of fluid on a comet must have been necessary for the formation of the UCAMM. The GEMS grains depleted in Mg and S in the UCAMM prove a very weak degree of aqueous alteration; weaker than that of carbonaceous chondrites. Short-duration weak alteration probably caused by planetesimal shock locally melted cometary ice grains and released water that dissolved the organics; the fluid would likely have not mobilized because of the very low thermal conductivity of the porous icy body. This event allowed the formation of the large organic puddle of the UCAMM, as well as organic matter sulfurization, formation of thin membrane-like layers of minerals, and deformation of organic nanoglobules. (C) 2017 Elsevier Ltd. All rights reserved.

DOI： 10.1016/j.gca.2017.06.047

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記述言語：日本語   出版者・発行元：一般社団法人日本地球化学会  

<p>本研究では，始原的隕石の可溶性有機化合物の空間分布を明らかにするため，脱離エレクトロスプレーイオン化技術と高質量分解能・高精度で分析可能なオービトラップ質量分析装置を用いて，Murchison隕石表面の質量イメージングを行った。Murchison隕石表面から，CnH2n-2N2 (アルキルイミダゾール)およびCnH2n-1ONの精密質量に相当するシグナルを，質量精度5 ppm以内で検出した。これらの有機物は，炭素数の異なる複数の同族体が検出されており，隕石試料表面の分布は一様では無かった。本発表では，検出した有機化合物の空間分布と，岩石学的観察の結果を比較し，議論を行う。</p>

DOI： 10.14862/geochemproc.64.0_134

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

Many studies in the past decade have sought to explore the origin and evolution of water in planetary bodies based on the hydrogen isotopic compositions of apatite. However, no investigation has studied hydrogen diffusivity in apatite. This work reports hydrogen diffusion experiments using a natural Durango fluorapatite carried out under a saturated (H2O)-H-2/O-2 vapor flow at temperatures of 500-700(omicron)C. Diffusion depth profiles for H-1 and H-2 were measured using secondary ion mass spectrometry (SIMS), indicating that H-2 diffusion occurred by an exchange reaction between the original H-1 and H-2 during annealing. Hydrogen diffusion coefficients were obtained by the fitting of diffusion profiles of H-2 using Fick's second law; they followed an Arrhenius-type relationship. The temperature dependence of hydrogen diffusion parallel to the c-axis at 500-700(omicron)C can be expressed as D = 6.71X10(-13) exp(- 80.5 +/- 3.3) / RT) [m(2) / s]. Hydrogen diffusion coefficients in apatite are several orders of magnitude greater than those of other elements. Hydrogen diffusion in apatite occurs at relatively low temperatures (below 700(omicron)C). This study indicates that the hydrogen isotopic compositions of apatite are readily affected by the presence of water vapor through the H-1-H-2 exchange reaction without changing the total water content in the crystal.

DOI： 10.2343/geochemj.2.0460

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開催年月日： 2022年3月

記述言語：英語   会議種別：ポスター発表  

開催地：The Woodlands, Texas/Online   国名：アメリカ合衆国