Tomohiro Usui
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View article: Bennu and Ryugu constituents from samples IR analyses and potential source of terrestrial planets’ ingredients
Bennu and Ryugu constituents from samples IR analyses and potential source of terrestrial planets’ ingredients Open
View article: <scp>JAXA</scp> curation for Bennu samples returned by the <scp>NASA</scp> 's <scp>OSIRIS</scp> ‐ <scp>REx</scp> mission
<span>JAXA</span> curation for Bennu samples returned by the <span>NASA</span> 's <span>OSIRIS</span> ‐ <span>REx</span> mission Open
NASA's OSIRIS‐REx mission successfully collected and returned ~121.6 g of bulk samples from the B‐type, near‐Earth asteroid (101955) Bennu to Earth in September 2023. Upon returning to Earth, the samples were transported to the NASA Johnso…
View article: Elastic Properties of Returned Samples From Asteroid (162173) Ryugu
Elastic Properties of Returned Samples From Asteroid (162173) Ryugu Open
The successful sample return from asteroid (162173) Ryugu by Hayabusa2 has contributed to our understanding of the solar system evolution. Over the course of the initial sample analysis, various measurements were conducted, such as mineral…
View article: The nature and formation of silica minerals in eucrite meteorites: Insight into the protoplanetary magma crystallization
The nature and formation of silica minerals in eucrite meteorites: Insight into the protoplanetary magma crystallization Open
Silica polymorphs in meteorites provide critical constraints on crystallization processes associated with thermal activity in the early solar system. A detailed investigation of silica polymorphs in eucrites (the largest group of achondrit…
View article: Long-term and multi-stage ice accumulation in the martian mid-latitudes during the Amazonian
Long-term and multi-stage ice accumulation in the martian mid-latitudes during the Amazonian Open
Subsurface ice in the mid-latitudes of Mars represents one of the largest present-day water ice reservoirs. While atmospheric models predict Late Amazonian (during the past hundreds of millions of years) obliquity-driven ice accumulation, …
View article: A Thermochemical Modeling Perspective of Why Ca/Fe Carbonates Broadly Associate with Felsic Terrains on Mars
A Thermochemical Modeling Perspective of Why Ca/Fe Carbonates Broadly Associate with Felsic Terrains on Mars Open
View article: Longitudinal heterogeneity of Phobos’ crater size-frequency distribution: coevolution of resurfacing and orbital dynamics
Longitudinal heterogeneity of Phobos’ crater size-frequency distribution: coevolution of resurfacing and orbital dynamics Open
Phobos always keeps the same side facing its host planet like Earth’s Moon, making it a key comparative target for studying the coevolution of planet–satellite systems. The heterogeneity of satellite surface evolution under a host planet’s…
View article: Updated estimates of Mercury's global K/Th ratio: An unmixing approach to surface composition analysis
Updated estimates of Mercury's global K/Th ratio: An unmixing approach to surface composition analysis Open
IntroductionObservations by the Mercury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft detected abundant volatiles on Mercury’s surface [1]. The K/Th ratios observed by Gamma-Ray Spectrometer (GRS), 6600 ± 280…
View article: Milankovitch cycles as a driver of climate variation and fluvial erosion on early Mars before 3.8-3.6 Ga
Milankovitch cycles as a driver of climate variation and fluvial erosion on early Mars before 3.8-3.6 Ga Open
Geomorphological evidence suggests that early Mars had oceans and valley networks, which implies that it had a dense atmosphere and an active hydrological cycle. However, the effects of orbital obliquity cycles remain largely unexplored. W…
View article: The Reference Setup for the RAX Raman Spectrometer on the MMX IDEFIX Rover for Phobos in-situ analysis
The Reference Setup for the RAX Raman Spectrometer on the MMX IDEFIX Rover for Phobos in-situ analysis Open
Introduction: In late 2026, JAXA will launch the Martian Moons eXploration mission (MMX) towards the Mars system to gain insights into the origin of the two Martian moons, Phobos and Deimos. After a travel time of about a year and another …
View article: From Asteroids to Martian Moons: Recent Achievements and Future Challenges of JAXA's Small-Body Sample Return Missions
From Asteroids to Martian Moons: Recent Achievements and Future Challenges of JAXA's Small-Body Sample Return Missions Open
Japan Aerospace Exploration Agency (JAXA) has a strategic small-body sample return program to understand the formation, evolution, and migration of planetary building blocks, water, and organics in the early solar system. The JAXA's sample…
View article: MMX mission update and long-term operation plan in the whole mission period
MMX mission update and long-term operation plan in the whole mission period Open
The goal of the MMX mission is to determine the origin and the formation process of the two Martian moons (Kuramoto et al. 2022). Three years remote sensing observation of Phobos and Deimos (Nakamura et al .2021) will provide us mineralogi…
View article: Low-temperature reflectance spectra of meteorites: implications for space missions
Low-temperature reflectance spectra of meteorites: implications for space missions Open
Introduction:The VNIR reflectance spectrum of a surface depends on its composition, physical properties, and the interactions between the surface and the environment. The temperature dependence of spectral properties may complicate the int…
View article: Multi-Stage Ice Accumulation in Martian Mid-Latitude Craters During the Amazonian
Multi-Stage Ice Accumulation in Martian Mid-Latitude Craters During the Amazonian Open
The mid-latitudes of Mars harbor significant subsurface ice, representing one of the largest contemporary reservoirs of Martian water. However, the temporal evolution, extent, and drivers of Amazonian glaciation events remain insufficientl…
View article: Characteristics of natural remanence records in fine-grained particles returned from asteroid Ryugu
Characteristics of natural remanence records in fine-grained particles returned from asteroid Ryugu Open
View article: Microgravity penetrometry flight campaign in support of MMX sampler science exploitation
Microgravity penetrometry flight campaign in support of MMX sampler science exploitation Open
Characterising the mechanical properties of minor bodies is essential for understanding their origin and evolution. Past missions such as Hayabusa2 have landed on asteroids to sample and discover what these bodies are made of. However, the…
View article: Near-infrared spectral variation in Ryugu particles and implication for rapid space weathering by solar UV radiation
Near-infrared spectral variation in Ryugu particles and implication for rapid space weathering by solar UV radiation Open
View article: Fractional Crystallization Scenario for Magma Evolution on Mercury Inferred From Geochemical Variation Around the Caloris Basin
Fractional Crystallization Scenario for Magma Evolution on Mercury Inferred From Geochemical Variation Around the Caloris Basin Open
The observed geochemical heterogeneity on the surface of Mercury is key to understanding the planet's volcanic activity and mantle conditions. The Caloris basin shows a diversity in elemental composition, spectral properties, and geomorpho…
View article: Iron and copper sulfides in asteroid (162173) Ryugu: Formation conditions and a comparison to the <scp>CI</scp> and <scp>CY</scp> chondrites
Iron and copper sulfides in asteroid (162173) Ryugu: Formation conditions and a comparison to the <span>CI</span> and <span>CY</span> chondrites Open
JAXA's Hayabusa2 sample return mission visited the volatile‐rich carbonaceous (C‐type) asteroid (162173) Ryugu with the aim of ground‐truthing remote observations, returning a pristine sample from a C‐type asteroid, and strengthening links…
View article: The elemental abundances of Ryugu: Assessment of chemical heterogeneities and the nugget effect
The elemental abundances of Ryugu: Assessment of chemical heterogeneities and the nugget effect Open
View article: Experimental evidence of phase transition of silica polymorphs in basaltic eucrites: implications for thermal history of protoplanetary crust
Experimental evidence of phase transition of silica polymorphs in basaltic eucrites: implications for thermal history of protoplanetary crust Open
View article: The Ni isotopic composition of Ryugu reveals a common accretion region for carbonaceous chondrites
The Ni isotopic composition of Ryugu reveals a common accretion region for carbonaceous chondrites Open
The isotopic compositions of samples returned from Cb-type asteroid Ryugu and Ivuna-type (CI) chondrites are distinct from other carbonaceous chondrites, which has led to the suggestion that Ryugu/CI chondrites formed in a different region…
View article: Phosphorus-rich grains in Ryugu samples with major biochemical potential
Phosphorus-rich grains in Ryugu samples with major biochemical potential Open
View article: A primordial noble gas component discovered in the Ryugu asteroid and its implications
A primordial noble gas component discovered in the Ryugu asteroid and its implications Open
Ryugu is the C-type asteroid from which material was brought to Earth by the Hayabusa2 mission. A number of individual grains and fine-grained samples analysed so far for noble gases have indicated that solar wind and planetary (known as P…
View article: Breunnerite grain and magnesium isotope chemistry reveal cation partitioning during aqueous alteration of asteroid Ryugu
Breunnerite grain and magnesium isotope chemistry reveal cation partitioning during aqueous alteration of asteroid Ryugu Open
Returned samples from the carbonaceous asteroid (162173) Ryugu provide pristine information on the original aqueous alteration history of the Solar System. Secondary precipitates, such as carbonates and phyllosilicates, reveal elemental pa…
View article: Variations of organic functional chemistry in carbonaceous matter from the asteroid 162173 Ryugu
Variations of organic functional chemistry in carbonaceous matter from the asteroid 162173 Ryugu Open
View article: A Technique for Retrieving the Exospheric Number Density Distribution from Pickup Ion Ring Distributions
A Technique for Retrieving the Exospheric Number Density Distribution from Pickup Ion Ring Distributions Open
Ion pickup by the solar wind is ubiquitous in space plasma. Because pickup ions are originally produced by ionization of an exospheric neutral atmosphere, their measurements contain information on the exospheric neutral abundance. Here we …
View article: Primordial aqueous alteration recorded in water-soluble organic molecules from the carbonaceous asteroid (162173) Ryugu
Primordial aqueous alteration recorded in water-soluble organic molecules from the carbonaceous asteroid (162173) Ryugu Open
View article: Spectral variations of the 2.7 &#181;m feature at sub-mm scales in Ryugu samples, within the ISAS Curation Facility
Spectral variations of the 2.7 µm feature at sub-mm scales in Ryugu samples, within the ISAS Curation Facility Open
In December 2020, the Hayabusa2/JAXA mission returned to Earth ~5.4g of primitive material from the carbonaceous asteroid (162173) Ryugu. Since their return, the samples are stored and analysed in the ISAS (Institute of Space and Astronaut…
View article: A glimpse of the start of the Earth: international exhibits of the asteroid Ryugu grains collected by the Hayabusa2 mission&#160;
A glimpse of the start of the Earth: international exhibits of the asteroid Ryugu grains collected by the Hayabusa2 mission  Open
On 6th December 2020, a capsule parachuted down into the Australian desert. Inside the sealed chamber were grains collected from asteroid Ryugu: a type of carbonaceous asteroid whose minerals might offer clues as to how the Earth became ha…