Tomoko Arai - Academia.edu (original) (raw)

Papers by Tomoko Arai

Japan Geoscience Union, Apr 7, 2014

Japan Geoscience Union, 2017

Recent chronological studies [1,2] revealed that reheating of mesosiderites occurred significantl... more Recent chronological studies [1,2] revealed that reheating of mesosiderites occurred significantly later (~30 Ma) than the solidification of the magma ocean (~4563 Ma) on the parent body. At this age, 26-Al cannot be a significant heat source. Also, metal cannot be the heat source because even if it was derived from a core, its composition should have been fractionated by this time. (Mesosiderite metal is not fractionated in siderophile elements.) Therefore, an alternative heat source has to be looked for. Here we report petrography of a mesosiderite which was largely molten by the reheating event, based on which we discuss the heating process.

Japan Geoscience Union, 2018

DESTINY (Demonstration and Experiment of Space Technology for INterplanetary voYage, Phaethon fLy... more DESTINY (Demonstration and Experiment of Space Technology for INterplanetary voYage, Phaethon fLy-by and dUst Science) is a mission proposed for JAXA/ISAS Epsilon class small program, currently in the pre-project phase (Phase-A) with a launch targeted for 2022. DESTINY is a joint mission of technology demonstration and scientific observation. The science mission objectives are (1) to measure physical and chemical properties of cosmic dusts around 1 au and (2) to conduct geological observation of Phaethon upon flyby and analyze dusts nearby Phaethon. Phaethon is known as a parent body of the Geminid meteor shower, the size of which is approximately 6 km in diameter. Phaethon is important as a known source for cosmic dust delivered to the Earth. During the flyby of Phaethon spatially resolved images of Phaethon will be taken by two onboard cameras, the Telescopic CAmera for Phaethon (TCAP) and the Multiband CAmera for Phaethon (MCAP). The relative flyby speed is as high as 33 km/s and...

Astronomy & Astrophysics, 2018

Context. The near-Earth asteroid 3200 Phaethon (1983 TB) is an attractive object not only from a ... more Context. The near-Earth asteroid 3200 Phaethon (1983 TB) is an attractive object not only from a scientific viewpoint but also because of JAXA’s DESTINY+ target. The rotational lightcurve and spin properties were investigated based on the data obtained in the ground-based observation campaign of Phaethon. Aims. We aim to refine the lightcurves and shape model of Phaethon using all available lightcurve datasets obtained via optical observation, as well as our time-series observation data from the 2017 apparition. Methods. Using eight 12-m telescopes and an optical imager, we acquired the optical lightcurves and derived the spin parameters of Phaethon. We applied the lightcurve inversion method and SAGE algorithm to deduce the convex and non-convex shape model and pole orientations. Results. We analysed the optical lightcurve of Phaethon and derived a synodic and a sidereal rotational periods of 3.6039 h, with an axis ratio of a∕b = 1.07. The ecliptic longitude (λp) and latitude (βp) ...

American Mineralogist, May 1, 2015

High-pressure polymorphs recovered in terrestrial craters are evidence of meteoroid impact events... more High-pressure polymorphs recovered in terrestrial craters are evidence of meteoroid impact events on the Earth's surface. Despite countless impact craters on the Moon, high-pressure polymorphs have not been reported to date in returned Apollo samples. On the other hand, recent studies report that the high-pressure polymorphs of silica, coesite, and stishovite occur in shocked lunar meteorites. We investigated regolith breccia 15299, which was returned by the Apollo 15 mission, using the combined techniques of focused ion beam (FIB), synchrotron X-ray diffraction (XRD), and transmission electron of minerals (olivine, pyroxene, plagioclase, silica, and ilmenite) and glass. Several quartz, tridymite, and cristobalite grains of 10-100 veins of less than 200 silica grains are entrained in the melt veins. One of the silica grains entrained in the melt veins consist of stishovite [a = 4.190(1), c = 2.674(1) Å, V = 46.95 Å 3 , space group P4 2 /mnm] along with tridymite TEM images show that the stishovite is needle-like in habit, and up to 400 nm in size. Considering the lithologies and shock features of 15299, it is inferred that the stishovite possibly formed by the Imbrium impact or subsequent local impact event(s) in the Procellarum KREEP Terrane (PKT) of the nearside of the Moon.

Mineralogical study of primitive achondrites and astronomical observation of Phaethon-Geminid-Com... more Mineralogical study of primitive achondrites and astronomical observation of Phaethon-Geminid-Complex showed that an incipient partial melting may have occurred in the active asteroid Phaethon.

SELENE-2 is the next Japanese lunar exploration project that is planned to be launched by the end... more SELENE-2 is the next Japanese lunar exploration project that is planned to be launched by the end of fiscal year 2015. In order to select the landing site candidates which maximize the scientific return from the project, "SELENE-2 Landing Site Research Board" was organized in March, 2010. The board called for scientific proposals with landing site candidates from domestic researchers who are interested in lunar science and members of the Japanese Society for Planetary Sciences, Japan Association of Mineralogical Sciences, the Geochemical Society of Japan, Seismological society of Japan, or the Geodetic society of Japan. At present, we have 35 scientific proposals with over 70 landing site candidates submitted from 21 groups. The proposals were categorized into nine research subjects as follows: 1) Identification of mantle materials, 2) Temporal variation of igneous activity and thermal history of the moon, 3) Lava morphology, 4) Origin of swirl, 5) Crater formation mechani...

Meteoritics & Planetary Science, 2022

The Iron Age was the time when people acquired iron processing technology and is generally though... more The Iron Age was the time when people acquired iron processing technology and is generally thought to have begun after 1200 B.C. Some prehistoric iron artifacts made of iron meteorites are dated from the Bronze Age. A nicely preserved meteoritic iron dagger was found in the tomb of King Tutankhamen (1361–1352 B.C.) of ancient Egypt. Yet, its manufacturing method and origin remain unclear. Here, we report nondestructive two‐dimensional chemical analyses of the Tutankhamen iron dagger, conducted at the Egyptian Museum of Cairo. Elemental mapping of Ni on the dagger blade surface shows discontinuous banded arrangements in places with “cubic” symmetry and a bandwidth of about 1 mm, suggesting a Widmanstätten pattern. The intermediate Ni content (11.8 ± 0.5 wt%) with the presence of the Widmanstätten pattern implies the source meteorite of the dagger blade to be octahedrite. The randomly distributed sulfur‐rich black spots are likely remnants of troilite (FeS) inclusions in iron meteorite. The preserved Widmanstätten pattern and remnant troilite inclusion show that the iron dagger was manufactured by low‐temperature (<950 °C) forging. The gold hilt with a few percent of calcium lacking sulfur suggests the use of lime plaster instead of gypsum plaster as an adhesive material for decorations on the hilt. Since the use of lime plaster in Egypt started during the Ptolemaic period (305–30 B.C.), the Ca‐bearing gold hilt hints at its foreign origin, possibly from Mitanni, Anatolia, as suggested by one of the Amarna letters saying that an iron dagger with gold hilt was gifted from the king of Mitanni to Amenhotep III, the grandfather of Tutankhamen.

Programme and abstracts the Volcanological Society of Japan, 2009

Japan Geoscience Union, 2019