Titanium carbide particles as pre-solar grains     

Y. Kimura  C. Kaito 《Monthly notices of the Royal Astronomical Society》2003,343(2):385-389

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Sylvite and halite on particles recovered from 25143 Itokawa: A preliminary report     

T. Noguchi  M. Kimura  T. Hashimoto  M. Konno  T. Nakamura  M. E. Zolensky  A. Tsuchiyama  T. Matsumoto  J. Matsuno  R. Okazaki  M. Uesugi  Y. Karouji  T. Yada  Y. Ishibashi  K. Shirai  M. Abe  T. Okada 《Meteoritics & planetary science》2014,49(7):1305-1314

We observed cross sectional ultra‐thin sections near the surface of 12 particles recovered from the S‐type asteroid Itokawa by the Hayabusa spacecraft in 2010, using spherical aberration–corrected STEM and conventional TEM. Although their mineralogy is almost identical to the equilibrated LL chondrites and therefore basically anhydrous, micrometer‐to‐submicrometer‐sized sylvite was identified on the surface of Itokawa particle RA‐QD02‐0034. Separately, micrometer‐sized halite was also identified on the surface of Itokawa particle RA‐QD02‐0129. Detailed inspection of the sample processing procedures at the JAXA's Planetary Materials Sample Curation Facility and textural observation of the sylvite and halite indicate that they were clearly present on two Itokawa particles before they were removed from Clean Chamber #2 at JAXA. However, there is no direct evidence for their extraterrestrial origin at present. If the sylvite and halite are extraterrestrial, their presence suggests that they may be more abundant on the surface of S‐type asteroids than previously thought.  相似文献   

Dust in the solar system and in extra-solar planetary systems     

Ingrid Mann  Melanie Köhler  Hiroshi Kimura  Andrzej Cechowski  Tetsunori Minato 《Astronomy and Astrophysics Review》2006,13(3):159-228

Among the observed circumstellar dust envelopes a certain population, planetary debris disks, is ascribed to systems with optically thin dust disks and low gas content. These systems contain planetesimals and possibly planets and are believed to be systems that are most similar to our solar system in an early evolutionary stage. Planetary debris disks have been identified in large numbers by a brightness excess in the near-infrared, mid-infrared and/or submillimetre range of their stellar spectral energy distributions. In some cases, spatially resolved observations are possible and reveal complex spatial structures. Acting forces and physical processes are similar to those in the solar system dust cloud, but the observational approach is obviously quite different: overall spatial distributions for systems of different ages for the planetary debris disks, as opposed to detailed local information in the case of the solar system. Comparison with the processes of dust formation and evolution observed in the solar system therefore helps understand the planetary debris disks. In this paper, we review our present knowledge of observations, acting forces, and major physical interactions of the dust in the solar system and in similar extra-solar planetary systems.  相似文献   

Laboratory production of monophase pyrrhotite grains using solid-solid reaction and their characteristic infrared spectra     

Y. Kimura  K. Tamura  H. Chihara  C. Kaito 《Icarus》2005,177(1):280-285

A new method of producing pyrrhotite grains, which are most commonly found in cometary material and interplanetary dust particles, was developed. Pyrrhotite grains in the monophase having a 7C structure were predominately produced using a solid-solid reaction between iron and sulfur grains at room temperature. The characteristic infrared peaks were observed at 602, 563, and 397 cm⁻¹ (16.6, 17.8, and 25.2 μm).  相似文献   

Yamato 792947, 793408 and 82038: The most primitive H chondrites,with abundant refractory inclusions     

M. Kimura  H. Hiyagon  H. Palme  B. Spettel  D. Wolf  R. N. Clayton  T. K. Mayeda  T. Sato  A. Suzuki  H. Kojima 《Meteoritics & planetary science》2002,37(10):1417-1434

Abstract— In this paper we report petrological and chemical data of the unusual chondritic meteorites Yamato (Y)‐792947, Y‐93408 and Y‐82038. The three meteorites are very similar in texture and chemical composition, suggesting that they are pieces of a single fall. The whole‐rock oxygen isotopes and the chemical compositions are indicative of H chondrites. In addition, the mineralogy, and the abundances of chondrule types, opaque minerals and matrices suggest that these meteorites are H3 chondrites. They were hardly affected by thermal and shock metamorphism. The degree of weathering is very low. We conclude that these are the most primitive H chondrites, H3.2–3.4 (S1), known to date. On the other hand, these chondrites contain extraordinarily high amounts of refractory inclusions, intermediate between those of ordinary and carbonaceous chondrites. The distribution of the inclusions may have been highly heterogeneous in the primitive solar nebula. The mineralogy, chemistry and oxygen isotopic compositions of inclusions studied here are similar to those in CO and E chondrites.  相似文献   

Erratum to “Dust grains in the comae and tails of sungrazing comets: modeling of their mineralogical and morphological properties”: [Icarus 159, 529-541 (2002)]     

Hiroshi Kimura  Ingrid Mann  Elmar K. Jessberger 《Icarus》2004,169(2):505-506

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Formation of stars by implosion of a gas cloud     

Toshiya Kimura  Makoto Tosa 《Astrophysics and Space Science》1987,135(2):261-269

In the standard Friedmann cosmology the black-body radiation spectrum is usually taken (without explicit proof as far as we know) to have the same familiarT ⁴-form that it has in a flat space. With explicit use of the equation of motion of a quantized massless field propagating in a curved background Robertson-Walker metric we show (for the readily tractable scalar field case) that the assumption is in fact true for an open Universe. For a closed Universe, we find that there is an in principle modification to theT ⁴-law. Unfortunately, the correction turns out to be too small to be experimentally detectable. In passing, we also obtain a simple derivation for the cosmological red shift of frequencies.  相似文献   

Cathodoluminescence microscopy and spectroscopy of forsterite from Kaba meteorite: An application to the study of hydrothermal alteration of parent body     

Arnold Gucsik  Taro Endo  Hirotsugu Nishido  Kiyotaka Ninagawa  Masahiro Kayama  Szaniszló Bérczi  Szabolcs Nagy  Péter Ábrahám  Yuki Kimura  Hitoshi Miura  Ildikó Gyollai  Irakli Simonia  Péter Rózsa  József Posta  Dániel Apai  Krisztián Mihályi  Mihály Nagy  Ulrich Ott 《Meteoritics & planetary science》2013,48(12):2577-2596

Highly forsteritic olivine (Fo: 99.2–99.7) in the Kaba meteorite emits bright cathodoluminescence (CL). CL spectra of red luminescent forsterite grains have two broad emission bands at approximately 630 nm (impurity center of divalent Mn ions) in the red region and above 700 nm (trivalent Cr ions) in the red–IR region. The cores of the grains show CL blue luminescence giving a characteristic broad band emission at 400 nm, also associated with minor red emissions related to Mn and Cr ions. CL color variation of Kaba forsterite is attributed to structural defects. Electron probe microanalyzer (EPMA) analysis shows concentrations of Ca, Al, and Ti in the center of the forsterite grain. The migration of diffusible ions of Mn, Cr, and Fe to the rim of the Kaba meteoritic forsterite was controlled by the hydrothermal alteration at relatively low temperature (estimated at about 250 °C), while Ca and Al ions might still lie in the core. A very unusual phase of FeO (wüstite) was also observed, which may be a terrestrial alteration product of FeNi‐metal.  相似文献   

Primordial,thermal, and shock features of ordinary chondrites: Emulating bulk X‐ray diffraction using in‐plane rotation of polished thin sections     

Naoya Imae  Makoto Kimura  Akira Yamaguchi  Hideyasu Kojima 《Meteoritics & planetary science》2019,54(4):919-937

Using an X‐ray diffractometer, powder‐like diffraction patterns were acquired from in‐plane rotation of polished thin sections (PTSs) of 60 ordinary chondrites (23 H, 21 L, and 16 LL), in order to explore the thermal and shock metamorphism and its modifications of primordial features. The olivine (Ol) 130 peak position shown as Bragg indices clearly correlates with the chemical group for equilibrated ordinary chondrites (EOCs), while the peak is split or broad for unequilibrated ordinary chondrites (UOCs). The intensity ratio of kamacite may be useful for distinguishing the chemical group between H and L‐LL, but it is not definite because of heterogeneous terrestrial weathering of kamacite, especially in H chondrites. The summed intensities of the orthoenstatite (Oen) 511 and 421 peaks positively correlates with the metamorphic sequence from 3 to 6, while that of clinoenstatite (Cen) 22 is inversely correlated. The shock stage positively correlates with the summed full width of half maximum values of the Oen 511 and 421 peaks and the FWHM of Ol 130 peak for each class. Significant amount of Oen (Pbca) transformed through Cen (C2/c) finally to Cen (P2₁/c) is stable at high pressure for shock stage S6 (Tenham and NWA 4719). The shock melted LL chondrite is characterized by the occurrence of Cen and abundant homogeneous olivine. The effects of both thermal and shock metamorphism are thus incorporated into the bulk X‐ray diffraction (XRD) data. The bulk XRD method is useful for determining the bulk mineralogy, resulting in the classification of ordinary chondrites. The method is also applicable to samples other than PTS.  相似文献   

Oxygen isotope systematics of chondrule olivine,pyroxene, and plagioclase in one of the most pristine CV3Red chondrites (Northwest Africa 8613)     

Andreas T. Hertwig  Makoto Kimura  Cline Defouilloy  Noriko T. Kita 《Meteoritics & planetary science》2019,54(11):2666-2685

We performed in situ oxygen three‐isotope measurements of chondrule olivine, pyroxenes, and plagioclase from the newly described CV_Red chondrite NWA 8613. Additionally, oxygen isotope ratios of plagioclase in chondrules from the Kaba CV3_OxB chondrite were determined to enable comparisons of isotope ratios and degree of alteration of chondrules in both CV lithologies. NWA 8613 was affected by only mild thermal metamorphism. The majority of oxygen isotope ratios of olivine and pyroxenes plot along a slope‐1 line in the oxygen three‐isotope diagram, except for a type II and a remolten barred olivine chondrule. When isotopic relict olivine is excluded, olivine, and low‐ and high‐Ca pyroxenes are indistinguishable regarding Δ¹⁷O values. Conversely, plagioclase in chondrules from NWA 8613 and Kaba plot along mass‐dependent fractionation lines. Oxygen isotopic disequilibrium between phenocrysts and plagioclase was caused probably by exchange of plagioclase with ¹⁶O‐poor fluids on the CV parent body. Based on an existing oxygen isotope mass balance model, possible dust enrichment and ice enhancement factors were estimated. Type I chondrules from NWA 8613 possibly formed at moderately high dust enrichment factors (50× to 150× CI dust relative to solar abundances); estimates for water ice in the chondrule precursors range from 0.2× to 0.6× the nominal amount of ice in dust of CI composition. Findings agree with results from an earlier study on oxygen isotopes in chondrules of the Kaba CV chondrite, providing further evidence for a relatively dry and only moderately high dust‐enriched disk in the CV chondrule‐forming region.  相似文献