Tatsuhiro Michikami
A5069037196- Astro and Planetary Science
- Planetary Science and Exploration
- Geology and Paleoclimatology Research
- Isotope Analysis in Ecology
- Geological and Geochemical Analysis
- earthquake and tectonic studies
- Landslides and related hazards
- Space Exploration and Technology
- Space Satellite Systems and Control
- Space Science and Extraterrestrial Life
- High-pressure geophysics and materials
- Earthquake and Tsunami Effects
- Marine and environmental studies
- Methane Hydrates and Related Phenomena
- Maritime and Coastal Archaeology
- Urban and spatial planning
- Rock Mechanics and Modeling
- Stellar, planetary, and galactic studies
- Image Processing and 3D Reconstruction
- Seismology and Earthquake Studies
- Flood Risk Assessment and Management
- Geological Modeling and Analysis
- Computer Graphics and Visualization Techniques
- Geomagnetism and Paleomagnetism Studies
- Earthquake and Disaster Impact Studies
Kindai University
2015-2024
Instituto de Astrofísica de Canarias
2023
Universidad de La Laguna
2023
Hiroshima University
2023
Fukushima National College of Technology
2004-2011
The Open University
2009
Japan Aerospace Exploration Agency
2006-2007
Institute of Space and Astronautical Science
2006-2007
The University of Tokyo
2006-2007
Planetary Science Institute
2006-2007
High-resolution images of the surface asteroid Itokawa from Hayabusa mission reveal it to be covered with unconsolidated millimeter-sized and larger gravels. Locations morphologic characteristics this gravel indicate that has experienced considerable vibrations, which have triggered global-scale granular processes in its dry, vacuum, microgravity environment. These likely include convection, landslide-like migrations, particle sorting, resulting segregation fine gravels into areas potential...
Laboratory analysis of samples returned from an asteroid establishes a direct link between asteroids and meteorites provides clues to the complex history its surface.
Abstract C-type asteroids 1 are considered to be primitive small Solar System bodies enriched in water and organics, providing clues the origin evolution of building blocks life. asteroid 162173 Ryugu has been characterized by remote sensing 2–7 on-asteroid measurements 8,9 with Hayabusa2 (ref. 10 ). However, ground truth provided laboratory analysis returned samples is invaluable determine fine properties other planetary bodies. We report preliminary results analyses on from particle size...
Carbonaceous meteorites are thought to be fragments of C-type (carbonaceous) asteroids. Samples the asteroid (162173) Ryugu were retrieved by Hayabusa2 spacecraft. We measured mineralogy and bulk chemical isotopic compositions samples. The samples mainly composed materials similar those carbonaceous chondrite meteorites, particularly CI (Ivuna-type) group. consist predominantly minerals formed in aqueous fluid on a parent planetesimal. primary altered fluids at temperature 37° ± 10°C, about...
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 collected samples from the surface of carbonaceous near-Earth asteroid (162173) Ryugu and brought them to Earth. were expected contain organic molecules, which record processes that occurred in early Solar System. We analyzed molecules extracted samples. identified a variety containing atoms CHNOS, formed by methylation, hydration, hydroxylation, sulfurization reactions. Amino acids, aliphatic amines, carboxylic polycyclic aromatic hydrocarbons, nitrogen-heterocyclic...
Presented here are the observations and interpretations from a comprehensive analysis of 16 representative particles returned C-type asteroid Ryugu by Hayabusa2 mission. On average consist 50% phyllosilicate matrix, 41% porosity 9% minor phases, including organic matter. The abundances 70 elements in close agreement with those CI chondrites. Bulk show higher δ18O, Δ17O, ε54Cr values than As such, sampled most primitive least-thermally processed protosolar nebula reservoirs. Such finding is...
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...
Samples of the carbonaceous asteroid (162173) Ryugu were collected and brought to Earth by Hayabusa2 spacecraft. We investigated macromolecular organic matter in samples found that it contains aromatic aliphatic carbon, ketone, carboxyl functional groups. The spectroscopic features are consistent with those chemically primitive chondrite meteorites experienced parent-body aqueous alteration (reactions liquid water). morphology carbon includes nanoglobules diffuse associated phyllosilicate...
Rendezvous of the Japanese spacecraft Hayabusa with near-Earth asteroid 25143 Itokawa took place during interval September through November 2005. The onboard camera imaged solid surface this tiny (535 meters by 294 209 meters) a spatial resolution 70 centimeters per pixel, revealing diverse morphologies. Unlike previously explored asteroids, reveals both rough and smooth terrains. Craters generally show unclear Numerous boulders on Itokawa's suggest rubble-pile structure.
In 2018, the Japanese spacecraft Hayabusa2, arrived at small asteroid Ryugu. The surface of this C-type is covered with numerous boulders whose size and shape distributions are investigated in study. Using a few hundred Optical Navigation Camera (ONC) images pixel scale approximately 0.65 m, we focus on greater than 5 m diameter. Smaller also considered using five arbitrarily chosen ONC close-up scales ranging from 0.7 to 6 cm. Across entire area (~2.7 km2) Ryugu, nearly 4400 larger were...
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...
The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth's volatiles. Samples were retrieved by Hayabusa2 spacecraft. We measured noble gas and nitrogen isotopes in samples found they are dominated presolar primordial components, incorporated during Solar System formation. Noble concentrations higher than those Ivuna-type (CI) chondrite meteorites. Several host phases isotopically distinct have...
Abstract The surface of asteroid 25143 Itokawa is covered with numerous boulders although gravity very small compared that other asteroids previously observed from spacecraft. Here we report the size-frequency statistics on entire based high-resolution images (1 pixel ≈0.4 m) obtained by Hayabusa There are 373 larger than 5 m in mean horizontal dimension surface—0.393 km 2 —and number density nearly 10 3 /km . cumulative boulder size distribution has a power-index −3.1 ± 0.1. For east and...
Abstract Intact lunar lava tubes offer a pristine environment to conduct scientific examination of the Moon's composition and potentially serve as secure shelters for humans instruments. We investigated SELENE Lunar Radar Sounder (LRS) data at locations close Marius Hills Hole (MHH), skylight leading an intact tube, found distinctive echo pattern exhibiting precipitous decrease in power, subsequently followed by large second peak that may be evidence existence tube. The search area was...
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...
Asteroid (162173) Ryugu is the target object of Hayabusa2, an asteroid exploration and sample return mission led by Japan Aerospace Exploration Agency (JAXA). Ground-based observations indicate that a C-type near-Earth with diameter less than 1 km, but knowledge its detailed properties very limited prior to Hayabusa2 observation. This paper summarizes our best understanding physical dynamical based on ground-based remote sensing theoretical modeling before Hayabusa2's arrival at asteroid....
Laboratory impact experiments have found that fragments tend to be elongated. Their shapes, as defined by axes a, b and c, these being the maximum dimensions of fragment in three mutually orthogonal planes (a ⩾ c), are distributed around mean values axial ratios b/a ∼ 0.7 c/a 0.5. This corresponds a:b:c simple proportion 2:√2:1. The shape distributions some boulders on Asteroid Eros, small- fast-rotating asteroids (diameter <200 m rotation period <1 h), young families, similar those...
The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on 6 December 2020. One day after recovery, gas species retained in sample container were extracted and measured on-site stored collection bottles. consists of helium neon with an extraterrestrial 3 He/ 4 He 20 Ne/ 22 Ne ratios, along some contaminant terrestrial atmospheric gases. A mixture solar Earth’s is best explanation for composition. Fragmentation grains within discussed basis estimated amount indigenous size...