Ken‐ichi Bajo
A5058167394- Astro and Planetary Science
- Planetary Science and Exploration
- Isotope Analysis in Ecology
- Nuclear Physics and Applications
- Geological and Geochemical Analysis
- Geology and Paleoclimatology Research
- Mass Spectrometry Techniques and Applications
- Ion-surface interactions and analysis
- Solar and Space Plasma Dynamics
- High-pressure geophysics and materials
- Spacecraft and Cryogenic Technologies
- Quantum, superfluid, helium dynamics
- Space Science and Extraterrestrial Life
- Space Exploration and Technology
- Radioactivity and Radon Measurements
- Atomic and Subatomic Physics Research
- Diamond and Carbon-based Materials Research
- Stellar, planetary, and galactic studies
- Analytical Chemistry and Chromatography
- Geomagnetism and Paleomagnetism Studies
- Astrophysics and Star Formation Studies
- Nuclear reactor physics and engineering
- Solar Thermal and Photovoltaic Systems
- Methane Hydrates and Related Phenomena
- Spaceflight effects on biology
Hokkaido University
2015-2025
Hokkaido University of Science
2020
Planetary Systems (United States)
2016
The University of Tokyo
2008-2012
Tokyo University of Science
2011-2012
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...
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...
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...
Little is known about the origin of spectral diversity asteroids and what it says conditions in protoplanetary disk. Here, we show that samples returned from Cb-type asteroid Ryugu have Fe isotopic anomalies indistinguishable Ivuna-type (CI) chondrites, which are distinct all other carbonaceous chondrites. Iron isotopes, therefore, demonstrate CI chondrites formed a reservoir was different source regions asteroids. Growth migration giant planets destabilized nearby planetesimals ejected some...
The extraterrestrial materials returned from asteroid (162173) Ryugu consist predominantly of low-temperature aqueously formed secondary minerals and are chemically mineralogically similar to CI (Ivuna-type) carbonaceous chondrites. Here, we show that high-temperature anhydrous primary in chondrites exhibit a bimodal distribution oxygen isotopic compositions: 16O-rich (associated with refractory inclusions) 16O-poor chondrules). Both the probably inner solar protoplanetary disk were...
Abstract Phobos and Deimos occupy unique positions both scientifically programmatically on the road to exploration of solar system. Japan Aerospace Exploration Agency (JAXA) plans a sample return mission (MMX: Martian Moons eXploration). The MMX spacecraft is scheduled be launched in 2024, orbit (multiple flybys), retrieve >10 g regolith back Earth 2029. represents mixture endogenous building blocks exogenous materials that contain system projectiles (e.g., interplanetary dust particles...
Preliminary analyses of asteroid Ryugu samples show kinship to aqueously altered CI (Ivuna-type) chondrites, suggesting similar origins. We report identification C-rich, particularly primitive clasts in that contain preserved presolar silicate grains and exceptional abundances SiC isotopically anomalous organic matter. The high abundance (104 ppm) indicates the clast escaped extensive alteration. 5 10 times higher (~235 ppm), N-rich matter, organics with N isotopic anomalies (1.2%), C (0.2%)...
Abstract 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. report the detection all major grain types with O- and C-anomalous isotopic compositions typically identified carbonaceous chondrite meteorites: 1 silicate, oxide, O-anomalous supernova ambiguous phase, 38 SiC, 16 grains. At least two grains are graphites, whereas several moderate C anomalies probably organics. The silicate was...
Studies of material returned from Cb asteroid Ryugu have revealed considerable mineralogical and chemical heterogeneity, stemming primarily brecciation aqueous alteration. Isotopic anomalies could also been affected by delivery exogenous clasts mobilization soluble elements. Here, we show that isotopic for mildly Cr are highly variable in CI chondrites, whereas those Ti relatively uniform. This variation isotope ratios is most likely due to physicochemical fractionation between 54Cr-rich...
The isotopic compositions of samples returned from Cb-type asteroid Ryugu and Ivuna-type (CI) chondrites are distinct other carbonaceous chondrites, which has led to the suggestion that Ryugu/CI formed in a different region accretion disk, possibly around orbits Uranus Neptune. We show that, like for Fe, CI also have indistinguishable Ni isotope anomalies, differ those chondrites. propose this unique Fe composition reflects efficiencies small FeNi metal grains among chondrite parent bodies....
Ryugu C A CI CM CV CO 44/40 Ca SRM915a (age corrected)The Hayabusa2 spacecraft has returned samples from the Cb-type asteroid (162173) to Earth.Previous petrological and chemical analyses support a close link between chondrites that are presumed be chemically most primitive meteorites with solar-like composition.However, highly enriched in compared typical chondrites.To identify cause of this discrepancy, here we report stable isotopic data (expressed as δ ) for collected two sites.We found...
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...
Carbonaceous chondrites are considered to have originated from C-type asteroids and represent some of the most primitive material in our solar system. Furthermore, since carbonaceous can contain significant quantities volatile elements, they may played a crucial role supplying volatiles organic Earth other inner system bodies. However, major challenge unravelling composition chondritic meteorites is distinguishing between which features were inherited parent body, what be secondary feature...
Abstract Unusual explosive activity occasionally occurs from the Sun, releasing large amounts of solar energetic particles. Extreme particle ejection events in past 11,000 yr have been detected by sharp increases cosmogenic isotopes annual tree rings and ice cores. However, quantitative estimation event magnitudes is not straightforward, as are indirect records Similar may also accumulate surface materials airless bodies such Moon asteroids. Samples asteroid 25143 Itokawa irradiated winds...
Abstract Solar wind (SW) is preserved in meteorites as abundant solar noble gases. We performed situ 4 He isotope imaging of mineral grains the CR2 chondrite matrix Northwest Africa 801 using time‐of‐flight secondary neutral mass spectrometry with strong‐field post ionization. + signals were detected along surfaces individual Fe‐Ni metal, ferrihydrite, olivine, pyroxene, and troilite. The high concentrations indicate implantation SW into grains. determined SW‐ fluence eight from line...
Solar wind noble gases in extraterrestrial materials provide important insights into past solar activity and space weathering processes. These are concentrated within the uppermost 100 nm of material...
Abstract Oxygen 3‐isotope ratios of magnetite and carbonates in aqueously altered carbonaceous chondrites provide important clues to understanding the evolution fluid asteroidal parent bodies. We conducted oxygen analyses magnetite, dolomite, breunnerite two sections asteroid Ryugu returned samples, A0058 C0002, using a secondary ion mass spectrometer (SIMS). Magnetite was analyzed by lower primary energy that reduced instrumental biases due crystal orientation effect. found groups data...
Abstract Rock fragments of the Cb-type asteroid Ryugu returned to Earth by JAXA Hayabusa2 mission share mineralogical, chemical, and isotopic properties with Ivuna-type (CI) carbonaceous chondrites. Similar CI chondrites, these underwent extensive aqueous alteration consist predominantly hydrous minerals likely formed in presence liquid water on parent asteroid. Here we present an situ analytical survey performed secondary ion mass spectrometry from which have estimated D/H ratio Ryugu’s...
Isotope imaging is commonly used to investigate the localization of trace elements and their isotopes. In situ noble gas analysis meteorites revealed distribution primordial gases that were trapped in building blocks asteroids planets during early stage solar system evolution. Solar wind are among present through exposure wind. Micrometer-resolution has not been achieved due lack sensitivity spatial resolution. The microscale technique crucial for identifying carrier phase gases. We have...
We have developed a new nano‐beam time‐of‐flight secondary neutral mass spectrometry system: laser ionization nanoscope or LIMAS. The primary ion beam column was equipped with Ga liquid metal source and aberration correction optics. down to 40 nm in diameter under current of 100 pA an energy 20 keV. sputtered particles were post‐ionized non‐resonance mode by femtosecond laser. ions introduced into multi‐turn spectrometer. A resolution up 000 achieved. vacuum the sample chamber maintained...
The distribution of solar-wind ions in Genesis mission collectors, as determined by depth profiling analysis, constrains the physics ion-solid interactions involving solar wind. Thus, they provide an experimental basis for revealing ancient activities represented implants natural samples. We measured first profile 4He a collector; shallow implantation (peaking at <20 nm) required us to use sputtered neutral mass spectrometry with post-photoionization strong field. wind He fluence calculated...
Laser ionization mass nanoscope is a time‐of‐flight sputtered neutral spectrometer associated with laser post‐ionization by tunneling effect. A spherical and chromatic aberration corrector installed in the primary ion column. The lateral spatial resolving power of He imaging solid surface has been evaluated scanning image using probe diameter 90 nm from crater edge slope ion‐implanted Si substrate. Helium distribution quantitatively equivalent depth profiling analysis same substrate,...
We have evaluated the performance of a multi‐turn time‐of‐flight mass spectrometer (MULTUM II) equipped with ion injection optics laser ionization nanoscope (LIMAS). surveyed optimal parameters for optics, which consist extraction from sample surface and introduction into MULTUM II. developed calibration methods correcting modulation load voltage II timing optics. As result, mass‐resolving power LIMAS increased linearly increasing flight path length, reached 6.2 × 10 5 (full width at half...