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Abstract-A new grouplet of primitive, metal-rich chondrites, here called the CB (C, carbonaceous; B, bencubbinite) chondrites, has been recognized. It includes Bencubbin, Weatherford, Hammadah a1 Hamra (HH) 237 and Queen Alexandra Range (QUE) 94411, paired with QUE 94627. Their mineral compositions, as well as their oxygen and nitrogen isotopic compositions, indicate that they are closely related to the CR and CH chondrites, all of which are members of the more inclusive CR clan. CB chondrites have much greater metal/silicate ratios than any other chondrite group, widely increasing the range of metal/silicate fractionation recorded in solar nebular processes. They also have the greatest moderately volatile lithophile element depletions of any chondritic materials. Metal has compositional trends and zoning patterns that suggest a primitive condensation origin, in contrast with metal from other chondrite groups. CB chondrites, as well as other CR clan chondrites, have much heavier nitrogen (higher 15N/14N) than that in other chondrite groups. The primitive characteristics of the CB chondrites suggest that they contain one of the best records of early nebular processes.Another chondrite, Grosvenor Mountains 9555 1, is petrographically similar to the CB chondrites, but its mineral and oxygen and nitrogen isotope compositions indicate that it formed from a different nebular reservoir.

Regolith particles on the asteroid Itokawa were recovered by the Hayabusa mission. Their three-dimensional (3D) structure and other properties, revealed by x-ray microtomography, provide information on regolith formation. Modal abundances of minerals, bulk density (3.4 grams per cubic centimeter), and the 3D textures indicate that the particles represent a mixture of equilibrated and less-equilibrated LL chondrite materials. Evidence for melting was not seen on any of the particles. Some particles have rounded edges. Overall, the particles' size and shape are different from those seen in particles from the lunar regolith. These features suggest that meteoroid impacts on the asteroid surface primarily form much of the regolith particle, and that seismic-induced grain motion in the smooth terrain abrades them over time.

Eucrites are a class of basaltic meteorites that share common mineralogical, isotopic, and chemical properties and are thought to have been derived from the same parent body, possibly asteroid 4 Vesta. The texture, mineralogy, and noble gas data of the recently recovered meteorite, Northwest Africa (NWA) 011, are similar to those of basaltic eucrites. However, the oxygen isotopic composition of NWA011 is different from that of other eucrites, indicating that NWA011 may be derived from a different parent body. The presence of basaltic meteorites with variable oxygen isotopic composition suggests the occurrence of multiple basaltic meteorite parent bodies, perhaps similar to 4 Vesta, in the early solar system.

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No observed data have been found in the Fukushima Prefecture (FP) for the time-series of atmospheric radionuclides concentrations just after the Fukushima Daiichi Nuclear Power Plant (FD1NPP) accident. Accordingly, current estimates of internal radiation doses from inhalation, and atmospheric radionuclide concentrations by atmospheric transport models are highly uncertain. Here, we present a new method for retrieving the hourly atmospheric 137Cs concentrations by measuring the radioactivity of suspended particulate matter (SPM) collected on filter tapes in SPM monitors which were operated even after the accident. This new dataset focused on the period of March 12–23, 2011 just after the accident, when massive radioactive materials were released from the FD1NPP to the atmosphere. Overall, 40 sites of the more than 400 sites in the air quality monitoring stations in eastern Japan were studied. For the first time, we show the spatio-temporal variation of atmospheric 137Cs concentrations in the FP and the Tokyo Metropolitan Area (TMA) located more than 170 km southwest of the FD1NPP. The comprehensive dataset revealed how the polluted air masses were transported to the FP and TMA, and can be used to re-evaluate internal exposure, time-series radionuclides release rates, and atmospheric transport models.

International audienceWe have performed a mineralogical and geochemical study of eight metamorphosed basaltic eucrites. These are classified into granulitic eucrites and type 4–7 eucrites on the basis of their textures and pyroxene mineralogy, and display mineralogical evidence for high temperature metamorphism, including partial melting. In particular, rare earth element (REE) patterns of a number of the eucrites studied show varying degrees of light REE depletion due to partial melting, with subsequent melt extraction. A simple correlation between metamorphic grade, as deduced from pyroxene mineralogy, and the degree of light REE depletion was not detected. This can be explained by the fact that homogenization, exsolution and inversion of pigeonite would have required prolonged heating at moderate temperatures (not, vert, similar800–1000 °C), whereas partial melting would have taken place over a short time interval where temperatures exceeded that of the solidus. The eucrites studied therefore record a two stage thermal regime consisting of short, high temperature reheating events superimposed on long duration global crustal metamorphism. The short reheating events may have been caused by impact events and/or intrusions of hot magmas. The results of this study demonstrate that the thermal history of eucritic crust was more complex than can be explained by a simple burial model alone. In particular, the origin of Stannern trend eucrites requires contamination of Main-Group magmas by partial melts extracted from residual eucrites

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