A. Tsuchiyama
A5050058898- Astro and Planetary Science
- Planetary Science and Exploration
- High-pressure geophysics and materials
- Geological and Geochemical Analysis
- Astrophysics and Star Formation Studies
- Nuclear Physics and Applications
- Isotope Analysis in Ecology
- Spacecraft and Cryogenic Technologies
- Stellar, planetary, and galactic studies
- Glass properties and applications
- Mineralogy and Gemology Studies
- Laser-induced spectroscopy and plasma
- Geology and Paleoclimatology Research
- Hydrocarbon exploration and reservoir analysis
- earthquake and tectonic studies
- Metallurgical Processes and Thermodynamics
- Geomagnetism and Paleomagnetism Studies
- Advanced X-ray Imaging Techniques
- Geochemistry and Geologic Mapping
- Methane Hydrates and Related Phenomena
- Space Science and Extraterrestrial Life
- Paleontology and Stratigraphy of Fossils
- Advanced X-ray and CT Imaging
- Iron and Steelmaking Processes
- X-ray Diffraction in Crystallography
Ritsumeikan University
2019-2025
Guangzhou Institute of Geochemistry
2019-2025
Chinese Academy of Sciences
2019-2025
Kyoto University
2012-2023
Center for Excellence in Education
2022
Planetary Science Institute
1991-2019
Graduate School USA
2014-2019
Osaka University
2005-2014
Osaka Health Science University
2000-2014
Max Planck Institute for Chemistry
2009
The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by Stardust spacecraft appear be weakly constructed mixtures nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, metal, and accessory phases. very wide range olivine low-Ca pyroxene compositions in requires a formation conditions, probably reflecting different locations protoplanetary disk. restricted compositional ranges for absence hydrous phases...
The Hayabusa spacecraft successfully recovered dust particles from the surface of near-Earth asteroid 25143 Itokawa. Synchrotron-radiation x-ray diffraction and transmission scanning electron microscope analyses indicate that mineralogy mineral chemistry Itokawa are identical to those thermally metamorphosed LL chondrites, consistent with spectroscopic observations made Earth by spacecraft. Our results directly demonstrate ordinary most abundant meteorites found on Earth, come S-type...
Laboratory analysis of samples returned from an asteroid establishes a direct link between asteroids and meteorites provides clues to the complex history its surface.
The melting temperature of Earth's mantle provides key constraints on the thermal structures both and core. Through high-pressure experiments three-dimensional x-ray microtomographic imaging, we showed that solidus a primitive (pyrolitic) is as low 3570 ± 200 kelvin at pressures expected near boundary between outer Because lowermost not globally molten, this an upper bound core-mantle (T(CMB)). Such remarkably T(CMB) implies post-perovskite phase present in wide areas mantle. also requires...
Samples of the carbonaceous asteroid Ryugu were brought to Earth by Hayabusa2 spacecraft. We analyzed 17 samples measuring 1 8 millimeters. Carbon dioxide-bearing water inclusions are present within a pyrrhotite crystal, indicating that Ryugu's parent formed in outer Solar System. The contain low abundances materials at high temperatures, such as chondrules and calcium- aluminum-rich inclusions. rich phyllosilicates carbonates, which through aqueous alteration reactions temperature, pH,...
The Hayabusa2 spacecraft investigated the C-type (carbonaceous) asteroid (162173) Ryugu. mission performed two landing operations to collect samples of surface and subsurface material, latter exposed by an artificial impact. We present images second touchdown site, finding that ejecta from impact crater was at sample location. Surface pebbles both sites show morphological variations ranging rugged smooth, similar Ryugu's boulders, shapes quasi-spherical flattened. were returned Earth on 6...
Abstract Volatile and organic-rich C-type asteroids may have been one of the main sources Earth’s water. Our best insight into their chemistry is currently provided by carbonaceous chondritic meteorites, but meteorite record biased: only strongest types survive atmospheric entry are then modified interaction with terrestrial environment. Here we present results a detailed bulk microanalytical study pristine Ryugu particles, brought to Earth Hayabusa2 spacecraft. particles display close...
The Stardust spacecraft returned cometary samples that contain crystalline material, but the origin of material is not yet well understood. We found four particles from comet 81P/Wild 2 were apparently formed by flash-melting at a high temperature and are texturally, mineralogically, compositionally similar to chondrules. Chondrules submillimeter dominate chondrites believed have in inner solar nebula. show oxygen isotope compositions chondrules carbonaceous compose middle-to-outer asteroid...
We measured the elemental compositions of material from 23 particles in aerogel and residue seven craters aluminum foil that was collected during passage Stardust spacecraft through coma comet 81P/Wild 2. These are chemically heterogeneous at largest size scale analyzed (â¼180 ng). The mean composition this Wild 2 is consistent with CI meteorite composition, which thought to represent bulk solar system, for elements Mg, Si, Mn, Fe, Ni 35%, Ca Ti 60%. Cu, Zn, Ga appear enriched material,...
Meteorite studies suggest that each solar system object has a unique oxygen isotopic composition. Chondrites, the most primitive of meteorites, have been believed to be derived from asteroids, but compositions asteroids themselves not established. We measured, using secondary ion mass spectrometry, rock particles asteroid 25143 Itokawa returned by Hayabusa spacecraft. Compositions are depleted in (16)O relative terrestrial materials and indicate Itokawa, an S-type asteroid, is one sources LL...
This paper describes a procedure used to characterize the three-dimensional (3D) grain shape of lunar soil and undertake simulations by image-based discrete element method (DEM). Given that detailed 3D grain-shape information is unavailable for real soil, simulant material, FJS-1, in this study. We use high-resolution micro X-ray CT system at SPring-8, synchrotron radiation facility Japan, visualize precise images granular assembly FJS-1. A newly developed image-analysis then applied...
Noble gas isotopes were measured in three rocky grains from asteroid Itokawa to elucidate a history of irradiation cosmic rays and solar wind on its surface. Large amounts helium (He), neon (Ne), argon (Ar) trapped various depths the observed, which can be explained by multiple implantations particles into grains, combined with preferential He loss caused frictional wear space-weathered rims grains. Short residence time less than 8 million years was implied for an estimate...
Abstract On the basis of observations using Cs‐corrected STEM , we identified three types surface modification probably formed by space weathering on surfaces Itokawa particles. They are (1) redeposition rims (2–3 nm), (2) composite (30–60 and (3) vesicular (60–80 nm). These characterized a combination zones. Zone I occupies outermost part modification, which contains elements that not included in unchanged substrate minerals, suggesting this zone is composed sputter deposits and/or impact...
Without a protective atmosphere, space-exposed surfaces of airless Solar System bodies gradually experience an alteration in composition, structure and optical properties through collective process called space weathering. The return samples from near-Earth asteroid (162173) Ryugu by Hayabusa2 provides the first opportunity for laboratory study space-weathering signatures on most abundant type inner solar system body: C-type asteroid, composed materials largely unchanged since formation...
Abstract Transmission electron microscopy analyses of Hayabusa2 samples show that Ryugu organic matter exhibits a range morphologies, elemental compositions, and carbon functional chemistries consistent with those carbonaceous chondrites have experienced low‐temperature aqueous alteration. Both nanoglobules diffuse are abundant. Non‐globular particles also present, including some contain nanodiamond clusters. Diffuse is finely distributed in around phyllosilicates, forms coatings on other...
The mass absorption spectra of crystalline olivine particles with different ratios, between forsterite (, Fo) and fayalite Fa), were measured for synthetic natural samples in the mid- far-infrared regions. main strong peaks show a systematic shift to longer wavelengths as ratio decreases. In 10–17 μm region, these trends are very clear, peak positions good indicator composition dust grains. 20–100 also rather though they slightly complicated; intensity width various bands become weak broad,...
The microstructure of bubbles in magma controls the dynamics flow a volcanic conduit. To investigate shear‐induced evolution bubble microstructures, we performed series deformation experiments on vesiculated rhyolitic melts by twisting columnar obsidians at temperature 975°C and rotation rates 0.3–0.5 rpm for up to 10 rotations. Three‐dimensional shapes run products were analyzed using X ray–computed tomography. experimental results demonstrate that shear strain rate control degree...