Aiko Nakato
A5034787603- Astro and Planetary Science
- Planetary Science and Exploration
- Isotope Analysis in Ecology
- Geological and Geochemical Analysis
- High-pressure geophysics and materials
- Geology and Paleoclimatology Research
- Nuclear Physics and Applications
- Spacecraft and Cryogenic Technologies
- Geomagnetism and Paleomagnetism Studies
- Mass Spectrometry Techniques and Applications
- Crystallization and Solubility Studies
- X-ray Diffraction in Crystallography
- Astrophysics and Star Formation Studies
- Stellar, planetary, and galactic studies
- Radioactive element chemistry and processing
- X-ray Spectroscopy and Fluorescence Analysis
- Geochemistry and Geologic Mapping
- Radioactive contamination and transfer
- Space Exploration and Technology
- Laser-induced spectroscopy and plasma
- Nuclear and radioactivity studies
- Scientific Research and Discoveries
- Methane Hydrates and Related Phenomena
- Hydrocarbon exploration and reservoir analysis
- Space Science and Extraterrestrial Life
Institute of Space and Astronautical Science
2015-2024
National Institute of Polar Research
2023-2024
Japan Aerospace Exploration Agency
2007-2024
Chiba University
2024
National Sagamihara Hospital
2022-2024
Korea Polar Research Institute
2024
University of Aizu
2022
Kyoto University
2017-2019
Graduate School USA
2018-2019
Tohoku University
2011-2014
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...
Hayabusa2 at the asteroid Ryugu Asteroids fall to Earth in form of meteorites, but these provide little information about their origins. The Japanese mission is designed collect samples directly from surface an and return them for laboratory analysis. Three papers this issue describe team's study near-Earth carbonaceous 162173 Ryugu, which spacecraft arrived June 2018 (see Perspective by Wurm). Watanabe et al. measured asteroid's mass, shape, density, showing that it a “rubble pile” loose...
The reflectance spectra of the most abundant meteorites, ordinary chondrites, are different from those S-type (mnemonic for siliceous) asteroids. This discrepancy has been thought to be due space weathering, which is an alteration surfaces airless bodies exposed environment. Here we report evidence weathering on particles returned asteroid 25143 Itokawa by Hayabusa spacecraft. Surface modification was found in 5 out 10 particles, varies depending mineral species. Sulfur-bearing Fe-rich...
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...
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...
The pristine sample from the near-Earth carbonaceous asteroid (162173) Ryugu collected by Hayabusa2 spacecraft enabled us to analyze extraterrestrial material without uncontrolled exposure Earth's atmosphere and biosphere. initial analysis team for soluble organic matter reported detection of wide variety molecules including racemic amino acids in samples. Here we report uracil, one four nucleobases ribonucleic acid, aqueous extracts In addition, nicotinic acid (niacin, a B3 vitamer), its...
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...
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...
All life on Earth contains amino acids and carbonaceous chondrite meteorites have been suggested as their source at the origin of Earth. While many meteoritic are considered indigenous, deciphering extent terrestrial contamination remains an issue. The Ryugu asteroid fragments (JAXA Hayabusa2 mission), represent most uncontaminated primitive extraterrestrial material available. Here, concentrations from two particles different touchdown sites (TD1 TD2) reported. show that N,N-dimethylglycine...
Chondrule-like objects and Ca-Al-rich inclusions (CAIs) are discovered in the retuned samples from asteroid Ryugu. Here we report results of oxygen isotope, mineralogical, compositional analysis chondrule-like CAIs. Three dominated by Mg-rich olivine 16O-rich -poor with Δ17O (=δ17O - 0.52 × δ18O) values ~ -23‰ -3‰, resembling what has been proposed as early generations chondrules. The likely to be melted amoeboid aggregates that escaped incorporation into 16O-poor chondrule precursor dust....
Samples from the carbonaceous asteroid (162173) Ryugu provide information on chemical evolution of organic molecules in early solar system. Here we show element partitioning major component ions by sequential extractions salts, carbonates, and phyllosilicate-bearing fractions to reveal primordial brine composition primitive asteroid. Sodium is dominant electrolyte salt fraction extract. Anions NH4+ are more abundant than carbonate phyllosilicate fractions, with molar concentrations order...
Polycyclic aromatic hydrocarbons (PAHs) contain ≲20% of the carbon in interstellar medium. They are potentially produced circumstellar environments (at temperatures ≳1000 kelvin), by reactions within cold (~10 kelvin) clouds, or processing carbon-rich dust grains. We report isotopic properties PAHs extracted from samples asteroid Ryugu and meteorite Murchison. The doubly-13C substituted compositions (Δ2×13C values) naphthalene, fluoranthene, pyrene 9 to 51‰ higher than values expected for a...
Abundant organic compounds were detected in brine-bearing halite crystals from a hydrovolcanically active asteroid.