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Noguchi, T.

Publications and source records attributed to Noguchi, T..

26 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2011

Neutron Activation Analysis of Single Grains Recovered by the Hayabusa Spacecraft

The Hayabusa spacecraft was launched on May 9, 2003 and reached an asteroid Itokawa (25143 Itokawa) in September 2005. After accomplishing several scientific observations, the spacecraft tried to collect the surface material of Itokawa by touching down to the asteroid in November. The spacecraft was then navigated for the earth. In encountering several difficulties, Hayabusa finally returned to the earth on June 12, 2010 and the entry capsule was successfully recovered. Initially, a g-scale of solid material was aimed to be captured into the entry capsule. Although the sample collection was not perfectly performed, it was hoped that some extraterrestrial material was stored into the capsule. After careful and extensive examination, more than 1500 particles were recognized visibly by microscopes, most of which were eventually judged to be extraterrestrial, highly probably originated from Itokawa [1]. Several years before the launching of the Hayabusa spacecraft, the initial analysis team was officially formed under the selection panel at ISAS. As a member of this team, we have been preparing for the initial inspection of the returned material from many scientific viewpoints [2]. Once the recovered material had been confirmed to be much less than 1 g, a scheme for the initial analysis was updated accordingly [3]. In this study, we aim to analyze tiny single grains by instrumental neutron activation analysis (INAA). As the initial analysis is to be started in mid-January, 2011, some progress for the initial analysis using INAA is described here. Analytical procedure

Ebihara, M.↗
NASA NTRS2011

Preliminary Examination of Particles Recovered from the Surface of the Asteroid Itokawa by the Hayabusa Mission

The Hayabusa spacecraft arrived at S-type Asteroid 25143 Itokawa in November 2006, and reveal astounding features of the small asteroid (535 x 294 x 209 m). Near-infrared spectral shape indicates that the surface of this body has an olivinerich mineral assemblage potentially similar to that of LL5 or LL6 chondrites with different degrees of space weathering. Based on the surface morphological features observed in high-resolution images of Itokawa s surface, two major types of boulders were distinguished: rounded and angular boulders. Rounded boulders seem to be breccias, while angular boulders seem to have severe impact origin. Although the sample collection did not be made by normal operations, it was considered that some amount of samples, probably small particles of regolith, was collected from MUSES-C regio on the Itokawa s surface. The sample capsule was successfully recovered on the earth on June 13, 2010, and was opened at curation facility of JAXA (Japan Aerospace Exploration Agency), Sagamihara, Japan. A large number of small particles were found in the sample container. Preliminary analysis with SEM/EDX at the curation facility showed that at least more than 1500 grains were identified as rocky particles, and most of them were judged to be of extraterrestrial origin, and definitely from Asteroid Itokawa. Minerals (olivine, low-Ca pyroxene, high-Ca pyroxene, plagioclase, Fe sulfide, Fe-Ni metal, chromite, Ca phosphate), roughly estimated mode the minerals and rough measurement of the chemical compositions of the silicates show that these particles are roughly similar to LL chondrites. Although their size are mostly less than 10 m, some larger particles of about 100 m or larger were also identified. A part of the sample (probably several tens particles) will be selected by Hayabusa sample curation team and examined preliminary in Japan within one year after the sample recovery in prior to detailed analysis phase. Hayabusa Asteroidal Sample Preliminary Examination Team (HASPET) has been preparing for the preliminary examination with close cooperation with the curation team.

Tsuchiyama, A.↗
NASA NTRS2008

Mineralogy, Three Dimensional Structure, and Oxygen Isotope Ratios of Four Crystalline Particles from Comet 81P/Wild 2

Preliminary examinations of small dust particles from comet 82P/Wild 2 revealed many expected and unexpected features. Among them the most striking feature is the presence of abundant crystalline material in the comet. Synchrotron radiation X-ray diffraction and microtomography are the most efficient methods to detect and describe bulk mineralogical features of crystalline cometary particles. In the present study, in addition to these two non-destructive techniques, electron microscopy and ion-probe mass spectrometry were carried out on the four crystalline particles.

Nakamura, T.↗
NASA NTRS2004

Mineralogical Study of Hydrated IDPs: X-Ray Diffraction and Transmission Electron Microscopy

Chondritic hydrated interplanetary dust particles (IDPs) comprise up to 50% of all IDPs collected in the stratosphere [1]. Hydrated IDPs are generally believed to be derived from asteroidal sources that have undergone aqueous alteration. However, the high C contents of hydrated IDPs (by 2 to 6X CI levels [2,3]) indicate that they are probably not derived from the same parent bodies sampled by the known chondritic meteorites. Some hydrated IDPs exhibit large deuterium enrichments [4] similar to those observed in anhydrous IDPs. Both anhydrous and hydrated IDPs contain a variety of anhydrous minerals such as silicates, sulfides, oxides, and carbonates. Controversies on hydrated IDPs still exist regarding their formation, history, and relationship to other primitive solar system materials, because of the lack of a systematic series of analysis on individual hydrated IDPs. In this study, we combine our observations of the bulk mineralogy, mineral/ organic chemistry in order to derive a more complete picture of hydrated IDPs.

Nakamura, K.↗
NASA NTRS2004

Glass Veins in the Unequilibrated Eucrite Yamato 82202

The unequilibrated eucrite Yamato 82202 (Y82202) contains a network of glass veins, which are relatively thick (up to 1 mm in width) and are not devitrified. The host of the meteorite represents volcanic rock that crystallized >4.3 Gyr ago, probably as a lava flow on the surface of 4 Vesta. The impact event that formed the glass veins occurred at approx. 3.9 Gyr under conditions of low effective fo2 and very rapid cooling. A S-rich vapor probably was generated by impact vaporization of sulfides. The impact melt was not superheated and it retains some disordered structural characteristics of the original pyroxene and feldspar of the eucritic target lithology. The unequilibrated pyroxenes of this eucrite and the pristine character of the glass indicate that the meteorite experienced no significant metamorphism after initial crystallization. Hence, it was not buried to a significant depth or covered by a lava flow or hot layer of impact ejecta. The meteorite resided at a shallow level (though not at the surface) on 4 Vesta or on one of the vestoids until it was ejected and traveled to Earth, probably with other HED materials that have Ar-36 exposure ages of approx. 13 Myr.

Bogard, Donald↗
NASA NTRS2003

Comprehensive Study of Hydrated IDPs: X-Ray Diffraction, IR Spectroscopy and Electron Microscopic Analysis

Chondritic hydrated interplanetary dust particles (IDPs) comprise up to 50% of all IDPs collected in the stratosphere(1). Although much is known about the mineralogy, chemistry and carbon abundance of hydrated IDPs (2-4) controversies still exist regarding their formation, history, and relationship to other primitive solar system materials. Hydrated IDPs are generally believed to be derived from asteroidal sources that have undergone some degree of aqueous alteration. However, the high C contents of hydrated IDPs (by 2 to 6X CI levels (3,4) indicate that they are probably not derived from the same parent bodies sampled by the known chondritic meteorites. We report the comprehensive study of individual hydrated IDPs. The strong depletion in Ca (I) has been used as a diagnostic feature of hydrated IDPs. The particles are embedded in elemental sulfur or low viscosity epoxy and ultramicrotomed thin sections are observed using a transmission electron microscope (TEM) equipped with an energy-dispersive X-ray detector (EDX) followed by other measurements including: 1) FTIR microspectroscopy to understand the significant constraints on the organic functionality and the nature of the C-bearing phases and 2) powder X-ray difiaction using a synchrotron X-ray source to understand the bulk mineralogy of the particles.

Nakamura, K.↗
NASA NTRS2001

Sayama CM2 Chondrite: Fresh but Heavily Altered

Noble gas composition and mineralogy of Sayama meteorite, that fell in Japan and recently identified as a CM2 chondrite, revealed many unique features, indicating that it experienced extensive aqueous alteration under highly oxidized condition compared with typical CMs. Additional information is contained in the original extended abstract.

Takaoka, N.↗