Mineralogy of Y-981971 LL Chondrite and Brecciation Processes of the LL Parent Body

第3回極域科学シンポジウム/第35回南極隕石シンポジウム 11月30日（金） 国立国語研究所 2階講

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

Mineral Chemistry and Reflectance Spectra for the Anorthosite Clast in Lunar Meteorite Dhofar 489 with Reference to Lunar Farside Crust.

第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月18日（金） 国立国語研究所 2階講

Comparisons of Mineralogy Between Cumulate Eucrites and Lunar Meteorites Possibly from the Farside Anorsothitic Crust

Anorthosites composed of nearly pure anorthite (PAN) at many locations in the farside highlands have been observed by the Kaguya multiband imager and spectral profiler [1]. Mineralogical studies of lunar meteorites of the Dhofar 489 group [2,3] and Yamato (Y-) 86032 [4], all possibly from the farside highlands, showed some aspects of the farside crust. Nyquist et al. [5] performed Sm-Nd and Ar-Ar studies of pristine ferroan anorthosites (FANs) of the returned Apollo samples and of Dhofar 908 and 489, and discussed implications for lunar crustal history. Nyquist et al. [6] reported initial results of a combined mineralogical/chronological study of the Yamato (Y-) 980318 cumulate eucrite with a conventional Sm-Nd age of 4567 24 Ma and suggested that all eucrites, including cumulate eucrites, crystallized from parental magmas within a short interval following differentiation of their parent body, and most eucrites participated in an event or events in the time interval ~4400- 4560 Ma in which many isotopic systems were partially reset. During the foregoing studies, we recognized that variations in mineralogy and chronology of lunar anorthosites are more complex than those of the crustal materials of the HED parent body. In this study, we compared the mineralogies and reflectance spectra of the cumulate eucrites, Y-980433 and 980318, to those of the Dhofar 307 lunar meteorite of the Dhofar 489 group [2]. Here we consider information from these samples to gain a better understanding of the feldspathic farside highlands and the Vesta-like body

The characteristics of Hayabusa returned samples and their distributions for NASA and international announcement of opportunity (AO).

第3回極域科学シンポジウム/第35回南極隕石シンポジウム 11月30日（金） 国立国語研究所 2階講

Petrology of Two Itokawa Particles: Comparison with Equilibrated LL Chondrites

A strong link between Itokawa particles and LL chondrites was confirmed by preliminary examinations of Hayabusa particles [e.g., 1, 2]. Both poorly equilibrated and highly equilibrated particles have been found among the grains returned from Itokawa [1], and it is suggested that they correspond to LL4 and LL5-6, respectively. Here we report the petrography of two Itokawa particles and TEM study of one, and compare them to Antarctic LL chondrites with variable petrologic types (LL4-LL7) in order to understand the metamorphic history of asteroid Itokawa

Asteroid Itokawa sample curation and distribution in the Planetary Material Sample Curation Facility of JAXA.

第2回極域科学シンポジウム/第34回南極隕石シンポジウム 11月17日（木） 国立国語研究所 2階講

Minerology and Crystallography of Some Itokawa Particles Returned by the Hayabusa Mission

JAXA Hayabusa mission success-fully returned particles of the asteroid Itokawa to the earth in 2010. The recovered particles were carefully studied by the preliminary examination (PE) team and the obtained results are providing significant and unique information about the formation and evolution of meteorite parent bodies [1-6]. These particles further revealed that their mineral compositions and oxygen isotopes are close to those of equilibrated LL chon-drites [1,2], which matches with the observation at the orbit [7]. After the PE, JAXA distributed the samples as international AO study and we received 4 new and 3 PE particles. The new samples may contain some exot-ic components that have not been found by the PE study, and are of special interest. We have performed a detailed mineralogical and crystallographic study on these particles and here report the results

Constraining the source regions of lunar meteorites using orbital geochemical data

Lunar meteorites provide important new samples of the Moon remote from regions visited by the Apollo and Luna sample return missions. Petrologic and geochemical analysis of these meteorites, combined with orbital remote-sensing measurements have enabled additional discoveries about the composition and age of the lunar surface on a global scale. However, the interpretation of these samples is limited by the fact that we do not know the source region of any individual lunar meteorite. Here we investigate the link between meteorite and source region on the Moon using the Lunar Prospector Gamma Ray Spectrometer remote sensing dataset for the elements Fe, Ti and Th. The approach has been validated using Apollo and Luna bulk regolith samples and we have applied it to 48 meteorites excluding paired stones. Our approach is able broadly to differentiate the best compositional matches as potential regions of origin for the various classes of lunar meteorites. Basaltic and intermediate-Fe regolith breccia meteorites are found to have the best constrained potential launch sites, with some impact breccias and pristine mare basalts also having reasonably well defined potential source regions. Launch areas for highland feldspathic meteorites are much less well constrained and the addition of another element, such as Mg, will probably be required to identify potential source regions for these

Lunar radiation dose due to cosmic rays and their secondary particles

To be able to safely perform human activities on the lunar surface, it is very important to assess the radiation environment, including the dose from galactic cosmic Rays (GCRs) and large Solar Energetic Particles (SEPs). Especially, large SPEs are highly hazardous to lunar habitants. In this paper, several SPEs have been evaluated in order to estimate the effective dose equivalent on the lunar surface. Several events give more than 1 Sv without any shield