Yasuhiro Oba
A5060951669- Astrophysics and Star Formation Studies
- Molecular Spectroscopy and Structure
- Atmospheric Ozone and Climate
- Astro and Planetary Science
- Advanced Chemical Physics Studies
- Isotope Analysis in Ecology
- Atmospheric chemistry and aerosols
- Quantum, superfluid, helium dynamics
- Mass Spectrometry Techniques and Applications
- Origins and Evolution of Life
- Chemical Reactions and Isotopes
- Spectroscopy and Laser Applications
- Planetary Science and Exploration
- Material Properties and Processing
- Industrial Vision Systems and Defect Detection
- Textile materials and evaluations
- Groundwater and Isotope Geochemistry
- Methane Hydrates and Related Phenomena
- Groundwater flow and contamination studies
- Photosynthetic Processes and Mechanisms
- Geology and Paleoclimatology Research
- Chemical Analysis and Environmental Impact
- Stellar, planetary, and galactic studies
- Inorganic Fluorides and Related Compounds
- Solar and Space Plasma Dynamics
Hokkaido University
2016-2025
University of Colombo
2023
Hokkaido University of Science
2022
B. Verkin Institute for Low Temperature Physics and Engineering of the National Academy of Sciences of Ukraine
2018-2020
Universitat Autònoma de Barcelona
2020
SpinalCure Australia
2014
Koen Gakuen Women's Junior College
2014
University of Nevada, Reno
2008-2012
Ibaraki University
2010
Okayama University
2006-2009
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...
Abstract The lack of pyrimidine diversity in meteorites remains a mystery since prebiotic chemical models and laboratory experiments have predicted that these compounds can also be produced from precursors found meteorites. Here we report the detection nucleobases three carbonaceous using state-of-the-art analytical techniques optimized for small-scale quantification down to range parts per trillion (ppt). In addition previously detected purine such as guanine adenine, identify various...
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...
Organic matter in meteorites reveals clues about early Solar System chemistry and the origin of molecules important to life, but terrestrial exposure complicates interpretation. Samples returned from B-type asteroid Bennu by Origins, Spectral Interpretation, Resource Identification, Security-Regolith Explorer mission enabled us study pristine carbonaceous astromaterial without uncontrolled Earth's biosphere. Here we show that samples are volatile rich, with more carbon, nitrogen ammonia than...
Formation of H2O molecules through the codeposition oxygen and hydrogen atoms is examined in situ using IR spectroscopy at 10–40 K under various O2 H fluxes. It found that H2O2 are continuously formed by reaction, even 40 K. The ice amorphous, but has a compact (not microporous) structure compared to vapor-deposited amorphous ice, because dangling OH bonds not observed spectrum. This consistent with astronomical observations molecular clouds theoretical predictions, which suggest...
The synthesis of nucleobases in natural environments, especially interstellar molecular clouds, is the focus a long-standing debate regarding prebiotic chemical evolution. Here we report simultaneous detection all three pyrimidine (cytosine, uracil and thymine) purine (adenine, xanthine hypoxanthine) ice analogues composed simple molecules including H2O, CO, NH3 CH3OH after exposure to ultraviolet photons followed by thermal processes, that is, conditions simulate processes accompanying star...
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...
The present study experimentally demonstrated that solid H2O is formed through the surface reaction OH + H2 at 10 K. This first experimental evidence of formation using hydrogen in its molecular form temperatures as low We further found about one order magnitude more effective than HDO D2. significant isotope effect results from differences mass each reaction, indicating reactions proceed quantum tunneling.
Surface reactions between carbon monoxide and non-energetic hydroxyl radicals were carried out at 10 K 20 in order to investigate possible reaction pathways yield dioxide dense molecular clouds. Hydroxyl radicals, produced by dissociating water molecules microwave-induced plasma, cooled down 100 prior the introduction of CO. The abundances species monitored situ using a Fourier transform infrared spectrometer. Formation CO2 was clearly observed, even K, suggesting that CO with OH proceed...
Abstract We report primordial aqueous alteration signatures in water-soluble organic molecules from the carbonaceous asteroid (162173) Ryugu by Hayabusa2 spacecraft of JAXA. Newly identified low-molecular-weight hydroxy acids (HO-R-COOH) and dicarboxylic (HOOC-R-COOH), such as glycolic acid, lactic glyceric oxalic succinic are predominant samples two touchdown locations at Ryugu. The quantitative qualitative profiles for hydrophilic between sampling shows similar trends within order ppb...
Abstract Despite extensive studies on the formation of organic molecules in various extraterrestrial environments, it still remains under debate when, where, and how such were abiotically formed. A key molecule to solve problem, hexamethylenetetramine (HMT) has not been confirmed materials despite laboratory experimental evidence that can be produced interstellar or cometary environments. Here we report first detection HMT functionalized species carbonaceous chondrites Murchison, Murray,...
We present the experimental results of carbonic acid (H2CO3) formation through surface reactions CO molecules with non-energetic hydroxyl (OH) radicals at 10–40 K. The H2CO3 was clearly identified both in IR spectra and thermally programmed desorption mass spectra. yield rather high, amounting to approximately 40%–70% relative that CO2 formed by reaction OH. structure OH may differ from energetic processes such as UV irradiation, ion electron irradiation H2O/CO2 binary ices. In this paper,...
ABSTRACT The study of hot corinos in solar-like protostars has been so far mostly limited to the Class 0 phase, hampering our understanding their origin and evolution. In addition, recent evidence suggests that planet formation starts already during I which therefore represents a crucial step future planetary system chemical composition. Hence, become paramount importance. Here, we report discovery corino towards prototypical protostar L1551 IRS5, obtained within ALMA (Atacama Large...
It has been implicitly assumed that ices on grains in molecular clouds and proto planetary disks are formed by homogeneous layers regardless of their composition or crystallinity. To verify this assumption, we observed the H2O deposition onto refractory substrates crystallization amorphous (H2O, CO2, CO) using an ultra-high-vacuum transmission electron microscope. In H2O-deposition experiments, found three-dimensional islands crystalline ice (Ic) were at temperatures above 130 K. The...
Abstract We have observed the very low-mass Class 0 protostar IRAS 15398−3359 at scales ranging from 50 to 1800 au, as part of Atacama Large Millimeter/Submillimeter Array Program FAUST. uncover a linear feature, visible in H 2 CO, SO, and C 18 O line emission, which extends source direction almost perpendicular known active outflow. Molecular emission SiO, CH 3 OH further reveals an arc-like structure connected outer end feature separated protostar, 15398−3359, by 1200 au. The is...
The activation energy for desorption (Edes) and that surface diffusion (Esd) of adsorbed molecules on dust grains are two the most important parameters chemistry in interstellar medium. Although Edes is often measured by laboratory experiments, measurement Esd sparse. Due to lack data, astrochemical models usually assume a simple scaling relation, = fEdes, where f constant, irrespective species. Here, we experimentally measure CH4, H2S, OCS, CH3OH, CH3CN water-ice surfaces using an...
The samples returned from near-Earth asteroid (162173) Ryugu provide a pristine record of the 4.6 billion years since birth Solar System. Hayabusa2 initial analysis team has integrated range analytical techniques to investigate Ryugu's organic chemistry. Here, we highlight their latest findings, potential questions which may be answered, and an overview new prospects in decade come.
Abstract We performed in-situ analysis on a ~ 1 mm-sized grain A0080 returned by the Hayabusa2 spacecraft from near-Earth asteroid (162173) Ryugu to investigate relationship of soluble organic matter (SOM) minerals. Desorption electrospray ionization-high resolution mass spectrometry (DESI-HRMS) imaging mapped more than 200 CHN, CHO, CHO–Na (sodium adducted), and CHNO compounds. A heterogeneous spatial distribution was observed for different compound classes SOM as well among alkylated...
Abstract The sample from the near-Earth carbonaceous asteroid (162173) Ryugu is analyzed in context of meteorites soluble organic matter. analysis molecules samples collected by Hayabusa2 spacecraft shines light on an extremely high molecular diversity C-type asteroid. Sequential solvent extracts increasing polarity are using mass spectrometry with complementary ionization methods and structural information confirmed nuclear magnetic resonance spectroscopy. Here we show a continuum size...
We investigated the OH-related formation routes of two astrophysically important molecules, H(2)O and CO(2), under relatively warm astrophysical conditions. OH radicals, together with other neutral species such as H, O, H(2), O(2), were produced in microwave-discharge plasma cooled to 100 K before being deposited on an Al substrate at 40-60 K. formed 40 50 K, but not 60 Taking experimental conditions into account, a possible route is via reactions involving + OH, which yield H(2)O(2) main...
Interstellar ice is believed to be a cradle of complex organic compounds, commonly found within icy comets and interstellar clouds, in association with ultraviolet (UV) irradiation subsequent warming. We that UV-irradiated amorphous ices composed H2O, CH3OH, NH3 pure H2O behave like liquids over the temperature ranges 65 150 kelvin 50 140 kelvin, respectively. This low-viscosity liquid-like may enhance formation compounds including prebiotic molecules accretion dust form planetesimals under...