Engineering topics

Ebihara, M.

Publications and source records attributed to Ebihara, M..

14 records

NASA NTRS2016

Feldspathic Meteorites MIL 090034 and 090070: Late Additions to the Lunar Crust

Our studies of the Miller Range lunar meteorites MIL 090034, 090036, and 090070 show them to be a diverse suite of rocks from the lunar highlands hereafter referred to as MIL 34, MIL 36, and MIL 70, resp. MIL34 and MIL70, the focus of this work, are crystalline melt breccias. Plagioclase compositions in both peak sharply around An96-97. Mg numbers of olivine vary from 58-65 with a few higher values. MIL36 is a regolith breccia. MIL 34 and MIL 70 have some of the highest Al2O3 abundances of lunar highland meteorites, indicating that they have among the largest modal abundances of plagioclase for lunar meteorites. They have lower Sc and Cr abundances than nearly all lunar highland meteorites except Dho 081, Dho 489 and Dho 733. MIL34 and MIL70 also have similar cosmic ray exposure (CRE) ages of approximately 1-2 Ma indicating they are launch paired. (MIL36 has a larger CRE age approximately greater than 70 Ma). Park et al. found a variation in Ar-Ar ages among subsamples of MIL 34 and MIL70, but preferred ages of 3500+/-110 Ma for the "Dark" phase of MIL 34 anorthite and 3520+/-30 Ma for the "Light" phase of MIL70. Bouvier et al. reported a Pb-Pb age of 3894+/-39 Ma for a feldspathic clast of MIL 34 and a similar age for a melt lithology. Here we reexamine the Rb-Sr and Sm-Nd isotopic data, which show complexities qualitatively consistent with those of the Ar-Ar and Pb-Pb data. The Sm-Nd data in particular suggest that the feldspathic compositions of MIL 34 and MIL 70 formed during initial lunar geochemical differentiation, and REE modeling suggests a relatively late-stage formation.

Nyquist, L. E.↗

NASA NTRS2013

Late Bombardment of the Lunar Highlands Recorded in MIL 090034, MIL 090036 and MIL 090070 Lunar Meteorites

The Kaguya mission detected small but widespread outcrops of nearly pure ferroan anorthosite in and around large impact basins on the Moon. Along with certain lunar rocks, highly feldspathic lunar meteorites such as MIL 090034 (M34), 090036 (M36), and 090070 (M70) may provide samples of this material. We have measured the Ar-40/Ar-39 release patterns and cosmogenic Ar-38 concentrations of several small (<200 microg) samples separated from M34,36, and 70. From petrographic observations concluded that "some of the clasts and grains experienced generations of modifications," a conclusion that we examine in light of our data.

Park, J.↗

NASA NTRS2012

Geochemistry of Lunar Highland Meteorites Mil, 090034, 090036 AND 090070

Apollo and Luna samples were collected from a restricted area on the near side of the Moon, while the source craters of the lunar meteorites are randomly distributed. For example, Takeda et al. [1] and Yamaguchi et al. [2] found a variety of lithic clasts in Dho 489 and Y 86032 which were not represented by Apollo samples, and some of these clasts have lower rare earth elements (REE) and FeO abundances than Apollo anorthosites, respectively. Takeda et al. [1] and Yamaguchi et al. [2] concluded that Dho 489 and Y 86032 originated from the lunar farside. Therefore, lunar meteorites provide an opportunity to study lunar surface rocks from areas not sampled by Apollo and Luna missions. Three lunar anorthitic breccias (MIL 090034, 090036 and 090070) were found on the Miller Range Ice Field in Antarctica during the 2009-2010 ANSMET season [3]. In this study, we determined elemental abudnances for MIL 090034, 090036 and 090070 by using INAA and aimed to characterize these meteorites in chemical compositions in comparison with those for other lunar meteorites and Apollo samples.

Shirai, N.aoki↗

NASA NTRS2011

Three Dimensional Structures of Particles Recovered from the Asteroid Itokawa by the Hayabusa Mission and a Role of X-Ray Microtomography in the Preliminary Examination

Particles of regolith on S-type Asteroid 25143 Itokawa were successfully recovered by the Hayabusa mission of JAXA (Japan Aerospace Exploration Agency). Near-infrared spectral study of Itokawa s surface indicates that these particles are materials similar to LL5 or LL6 chondrites. High-resolution images of Itokawa's surface suggest that they may be breccias and some impact products. At least more than 1500 particles were identified as Itokawa origin at curation facility of JAXA. Preliminary analysis with SEM/EDX at the curation facility shows that they are roughly similar to LL chondrites. Although most of them are less than 10 micron in size, some larger particles of about 100 micron or larger were also identified. A part of the sample (probably several tens particles) will be selected by Hayabusa sample curation team, and sequential examination will start from January 2011 by Hayabusa Asteroidal Sample Preliminary Examination Team (HASPET). In mainstream of the analytical flow, each particle will be examined by microtomography, XRD and XRF first as nondestructive analyses, and then the particle will be cut by an ultra-microtome and examined by TEM, SEM, EPMA, SIMS, PEEM/XANES, and TOF-SIMS sequentially. Three-dimensional structures of Itokawa particles will be obtained by microtomography sub-team of HASPET. The results together with XRD and XRF will be used for design of later destructive analyses, such as determination of cutting direction and depth, to obtain as much information as possible from small particles. Scientific results and a role of the microtomography in the preliminary examination will be presented.

Tsuchiyama, A.↗

NASA NTRS2011

Oxygen and Magnesium Isotopic Compositions of Asteroidal Materials Returned from Itokawa by the Hayabusa Mission

The Hayabusa spacecraft made two touchdowns on the surface of Asteroid 25143 Itokawa on November 20th and 26th, 2005. The Asteroid 25143 Itokawa is classified as an S-type asteroid and inferred to consist of materials similar to ordinary chondrites or primitive achondrites [1]. Near-infrared spectroscopy by the Hayabusa spacecraft proposed that the surface of this body has an olivine-rich mineral assemblage potentially similar to that of LL5 or LL6 chondrites with different degrees of space weathering [2]. The spacecraft made the reentry into the Earth s atmosphere on June 12th, 2010 and the sample capsule was successfully recovered in Australia on June 13th, 2010. Although the sample collection processes on the Itokawa surface had not been made by the designed operations, more than 1,500 grains were identified as rocky particles in the sample curation facility of JAXA, and most of them were judged to be of extraterrestrial origin, and definitely from Asteroid Itokawa on November 17th, 2010 [3]. Although their sizes are mostly less than 10 microns, some larger grains of about 100 microns or larger were also included. The mineral assembly is olivine, pyroxene, plagioclase, iron sulfide and iron metal. The mean mineral compositions are consistent with the results of near-infrared spectroscopy from Hayabusa spacecraft [2], but the variations suggest that the petrologic type may be smaller than the spectroscopic results. Several tens of grains of relatively large sizes among the 1,500 grains will be selected by the Hayabusa sample curation team for preliminary examination [4]. Each grain will be subjected to one set of preliminary examinations, i.e., micro-tomography, XRD, XRF, TEM, SEM, EPMA and SIMS in this sequence. The preliminary examination will start from the last week of January 2011. Therefore, samples for isotope analyses in this study will start from the last week of February 2011. By the time of the LPSC meeting we will have measured the oxygen and magnesium isotopic composition of several grains. We will present the first results from the isotope analyses that will have been performed.

Yurimoto, H↗

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

Basaltic Clasts in Y-86032 Feldspathic Lunar Meteorite: Ancient Volcanism far from the Procellarum Kreep Terrane

Lunar meteorite, Y-86032 is a fragmental or regolith breccia enriched in Al2O3 (28-31 wt%) and having very low concentrations of REEs and Th, U [e.g., 1]. Nyquist et al. [2] suggested that Y- 86032 contains a variety of lithologies not represented by the Apollo samples. They found clasts with old Ar-Ar ages and an ancient Sm-Nd age, and negative Nd indicating a direct link to the primordial magma ocean. Importantly, the final lithification of the Y-86032 breccia was likely >3.8-4.1 Ga ago. Therefore, any lithic components in the breccia formed prior to 3.8 Ga, and lithic components in breccia clasts in the parent breccia formed even earlier. Here we report textures and mineralogy of basaltic and gabbroic clasts in Y- 86032 to better understand the nature of ancient lunar volcanism far from the Procellarum KREEP Terrain (PKT) [3] and the central nearside.

Yamaguchi, A.↗

NASA NTRS2006

Feldspathic Clasts in Yamato 86032: Remnants of the Lunar Crust with Implications for its Formation and Impact History

Yamato (Y)-86032 is a relatively large, feldspathic lunar highlands meteorite composed of a variety of highland lithologies. Low bulk contents of Th and Fe indicated that it came from a region of the moon far distant from the Procellarum KREEP Terrain (PKT) and the Apollo landing sites, perhaps from the farside. A large (5.2 x 3.6 cm) slab was cut from Y-86032 . We report results from coordinated textural, mineralogical-petrological, chemical, and isotopic studies of lithologies identified in the slab, emphasizing the results of Ar-39/Ar-40, Rb-Sr, and Sm-Nd chronological studies as well as Sm-isotopic studies. These studies characterize the history of Y-86032 and its precursors in the farside mega-regolith, leading to inferences about the formation and evolution of the lunar crust. Textural studies establish that the Y-86032 breccia is composed of a variety of highland components including feldspathic breccias, and other components, such as possible VLT mare basalts. Impact melt veins smoothly abut the other lithologies. Thus, Y-86032 experienced at least two impact events. These impacts occurred on a predominantly feldspathic protolith, which formed 4.43+/-0.03 Ga ago as determined from a Sm-Nd isochron for mineral clasts separated from the two dominant lithologies. Initial Nd-143/Nd-144 in the protolith at that time was -0.64+/-0.13 epsilon-units below Nd-143/Nd-144 in reservoirs having chondritic Sm/Nd ratios, consistent with prior fractionation of mafic cumulates from the LMO. Although the mineral chemistry of these clasts differs in detail from that of minerals in Apollo 16 Ferroan Anorthosites (FANs), the Rb-Sr studies establish that the initial Sr-87/Sr-86 in them was the same as in the FANs.

Nyquist, L.↗

NASA NTRS2004

The Origin and Impact History of Lunar Meteorite Yamato 86032

Yamato (Y) 86032 is a feldspathic lunar highland breccia having some characteristics of regolith breccia. The absence of KREEP components in the matrix in Y86032 indicates that these meteorites came from a long distance from Mare Imbrium, perhaps from the far-side of the moon. One ferroan anorthosite (FAN) clast in Y86032 has a very old Ar-Ar age of approximately 4.35-4.4 Ga. The negative Nd of this clast may suggest a direct link with the primordial magma ocean. The facts indicate that Y86032 contains components derived from a protolith of the original lunar crust. Detailed petrologic characterization of each component in this breccia is essential to understand the early impact history and origin of the lunar highland crust. We made a large slab (5.2 x 3.6 cm x 3-5 mm) of Y86032 to better understand the relationship of various lithologies and their petrologic origin.

Yamaguchi, A.↗

NASA NTRS1986

Core formation in the earth and shergottite parent body (SPB) - Chemical evidence from basalts

Abundances of siderophile and chalcophile elements in the shergottite parental body (SPB) have been compared with those of the earth. To this end, new INAA and RNAA analyses of non-Antarctic meteorites have been performed, and the composition of the shergottite SPB mantle has been inferred from the compositions of the SNC meteorites. The composition of the earth's mantle has been inferred from the compositions of terrestrial basalt. Finally, the effects of volatile depletion, core formation, and mineral/melt fractionation on the abundances of siderophile and chalcophile elements in the SPB and the earth have been taken into consideration. Compared to the earth, the SPB mantle is richer in moderately siderophile elements and more depleted with respect to chalcophile elements. The observed relative abundances of siderophile and chalcophile elements in the SPB and the earth mantles indicate that the SPB underwent accretion and/or differentiation processes which differ from those in the earth.

Treiman, A. H.↗

NASA NTRS1983

Aubrites and diogenites - Trace element clues to their origin

A typically igneous siderophile element pattern emerges from an RNAA analysis of 25 aubrite and nine diogenite samples for 13-29 siderophile, volatile, and lithophile trace elements, although it is noted that abundances are about 10 times higher in the case of aubrites. Se is also surprisingly abundant in aubrites. Factor analysis shows several parallel groupings for aubrites and diogenites. Several element pairs that differ greatly in volatility correlate closely in aubrites, in approximately C1-chondrite proportions, suggesting that aubrites originated by igneous processes in their parent body.

Wolf, R.↗

NASA NTRS1982

Solar-system abundances of the elements

Elemental analyses of the Ogueil Cl meteorite and all previous Cl chondrite analyses were employed to develop a new solar system abundance table, including the standard deviation and number of analyses for each element. The table also comprises the abundances of radioactive and radiogenic nuclides at the present and 4.55 AE ago, as well as abundances by weight in a typical Cl chondrite. The new abundances were within 20% of those determined by Cameron (1982), except for 14 cases in the range 20-50%, and 5 over 50%. The solar abundances were compared with the Cl abundances, showing a total of only 7 disagreements. No significant discrepancies were detected in the major cosmochemical groups, and a smooth trend was found in the abundances of odd-A nuclides. The new set is interpreted as accurate to 10%, with the Cl chondrites matching the primordial solar system abundances to at most 10% deviation.

Anders, E.↗

NASA NTRS1982

Are C1 chondrites chemically fractionated - A trace element study

Six C1 chondrite samples and a C2 xenolith from the Plainview H5 chondrite were analyzed by radiochemical neutron activation for a large variety of elements, including rare earths. The sample processing is described, including the irradiation, chemical procedure, rare earths separation, counting techniques, radiochemical purity check, and chemical yields. The results of consistency checks on a number of elements are discussed. Abundances for siderophiles, volatiles, and rare earths are presented and discussed. Tests are presented for fractionation of rare earths and other refractories, compositional uniformity of C1's, and interelement correlations. There is no conclusive evidence for nebular fractionation affecting C1's. Three fractionation-prone rare earths have essentially the same relative abundances in C1's and all other chondrite classes, and hence are apparently not fractionated in C1's.

Ebihara, M.↗