Deep-sea record of impact apparently unrelated to mass extinction in the Late Triassic.

The 34-million-year (My) interval of the Late Triassic is marked by the formation of several large impact structures on Earth. Late Triassic impact events have been considered a factor in biotic extinction events in the Late Triassic (e.g., end-Triassic extinction event), but this scenario remains controversial because of a lack of stratigraphic records of ejecta deposits. Here, we report evidence for an impact event (platinum group elements anomaly with nickel-rich magnetite and microspherules) from the middle Norian (Upper Triassic) deep-sea sediment in Japan. This includes anomalously high abundances of iridium, up to 41.5 parts per billion (ppb), in the ejecta deposit, which suggests that the iridium-enriched ejecta layers of the Late Triassic may be found on a global scale. The ejecta deposit is constrained by microfossils that suggest correlation with the 215.5-Mya, 100-km-wide Manicouagan impact crater in Canada. Our analysis of radiolarians shows no evidence of a mass extinction event across the impact event horizon, and no contemporaneous faunal turnover is seen in other marine planktons. However, such an event has been reported among marine faunas and terrestrial tetrapods and floras in North America. We, therefore, suggest that the Manicouagan impact triggered the extinction of terrestrial and marine organisms near the impact site but not within the pelagic marine realm.

A primordial noble gas component discovered in the Ryugu asteroid and its implications.

Ryugu is the C-type asteroid from which material was brought to Earth by the Hayabusa2 mission. A number of individual grains and fine-grained samples analysed so far for noble gases have indicated that solar wind and planetary (known as P1) noble gases are present in Ryugu samples with concentrations higher than those observed in CIs, suggesting the former to be more primitive compared to the latter. Here we present results of analyses of three fine-grained samples from Ryugu, in one of which Xe concentration is an order of magnitude higher than determined so far in other samples from Ryugu. Isotopically, this Xe resembles P1, but with a much stronger isotopic fractionation relative to solar wind and significantly lower 36Ar/132Xe ratio than in P1. This previously unknown primordial noble gas component (here termed P7) provides clues to constrain how the solar composition was fractionated to form the planetary components.

Noble gases and nitrogen in samples of asteroid Ryugu record its volatile sources and recent surface evolution.

The near-Earth carbonaceous asteroid (162173) Ryugu is expected to contain volatile chemical species that could provide information on the origin of Earth's volatiles. Samples of Ryugu were retrieved by the Hayabusa2 spacecraft. We measured noble gas and nitrogen isotopes in Ryugu samples and found that they are dominated by presolar and primordial components, incorporated during Solar System formation. Noble gas concentrations are higher than those in Ivuna-type carbonaceous (CI) chondrite meteorites. Several host phases of isotopically distinct nitrogen have different abundances among the samples. Our measurements support a close relationship between Ryugu and CI chondrites. Noble gases produced by galactic cosmic rays, indicating a ~5 million year exposure, and from implanted solar wind record the recent irradiation history of Ryugu after it migrated to its current orbit.

Time-series variations in 129I concentrations and 129I/137Cs ratios in suspended particulate matter collected in eastern Japan immediately after the 2011 nuclear accident in Fukushima, Japan.

We have determined the hourly atmospheric concentrations of 129I in aerosols dispersed into the atmosphere by the nuclear accident at the Fukushima Daiichi Nuclear Power Plant (FD1NPP) on March 11, 2011. Data were obtained by measuring the quantity of 129I in suspended particulate matter (SPM) collected on filter tapes at 41 SPM monitoring stations in Fukushima and other prefectures in eastern Japan, including the metropolitan area of Tokyo and the surrounding area. After scrutiny, 500 out of 920 hourly SPM samples were determined to be reliable (i.e., devoid of cross-contamination), and these were subjected to further analysis and discussion. Based on the data from these samples, especially data from the four SPM sampling sites located close to the FD1NPP (Futaba, Naraha, Haramachi and Nihonmatsu), the time-series variations in the atmospheric concentration of 129I and the activity ratio of 129I/137Cs were reconstructed by using 137Cs concentration data in the literature. 129I and 137Cs were observed to be continuously and sometimes explosively dispersed into the atmosphere in aerosols transported by radioactive plumes from the FD1NPP. The highest activity concentrations of 129I and 137Cs were observed in the SPM sample at the Futaba SPM station (3.2 km west-northwest of the FD1NPP) at 14:00-15:00 on March 12 after the venting of Unit 1. Systematically high 129I/137Cs activity ratios were observed at the Futaba and Haramachi stations from March 12 to 14, suggesting that radioactive masses released from the FD1NPP during the first few days after the nuclear accident were relatively enriched in radioiodine. High activity ratios of 129I/137Cs were also measured starting on March 21 at Naraha (17.5 km south of FD1NPP) and from March 22-23 in the metropolitan area which must have been caused by a different type of emission event(s) on those days at the FD1NPP, as previously reported. The 129I data from this study are highly effective in the validation and elaboration of the modelling of the atmospheric dispersion of radioiodine. They further contribute to assessing the internal exposure due to inhalation of 131I estimated by means of such elaborate atmospheric diffusion models.

Data on atmospheric 129I concentrations and 129I/137Cs ratios for suspended air particulate matter dispersed in eastern Japan just after the 2011 nuclear accident in Fukushima, Japan.

Data of the atmospheric activity concentrations (in Bq/m3) of 129I dispersed into the environment as aerosol immediately after the nuclear accident at Fukushima Daiichi Nuclear Power Plant in 2011 are presented. The radioactivity of 129I was determined in suspended particulate matter (SPM) collected on filter tapes at 41 SPM monitoring sites in Fukushima and other prefectures in eastern Japan including the metropolitan area. For quantitative determination of 129I in SPM samples by accelerator mass spectrometry (AMS), 129I was chemically separated. Prior to the 129I measurement, the 137Cs activity was determined for the same SPM sample by gamma-ray spectrometry using Ge-semiconductor detectors. Combining activity concentrations of the two nuclides, an activity ratio of 129I/137Cs (in Bq/Bq) was calculated for each SPM sample. In our research project, atmospheric activity concentrations of 129I and 137Cs, and their activity ratios were obtained for 920 SPM samples. Scientific discussion related to those data was described in the research article entitled "Time-series variations of atmospheric 129I concentrations and 129I/137Cs ratios in eastern Japan just after the 2011 nuclear accident in Fukushima, Japan" (Ebihara et al. 2022), where 363 data sets were presented. The remaining 557 data sets are presented in this article, so this data article makes up for the original research article (Ebihara et al. 2022). Blank values were obtained for whole analytical procedure. In addition, those for reagents and filters (both bland-new and used filters) were analyzed for assessing the contribution of the 129I activity from these samples. Those data also are presented in this article.

Dual functional catalysis of [Nb6O19]8--modified Au/Al2O3.

A catalyst prepared by modifying the surface of Au nanoparticles (NPs) on Al2O3 with [Nb6O19]8- clusters had specific base and reduction abilities, and the reduction of p-nitrophenol to p-aminophenol using H2 as a reductant proceeded efficiently with the dual functional catalyst. At the interface between Au NPs and basic [Nb6O19]8-, heterolytically cleaved hydrogen species are generated, which can efficiently react with nitrophenolate ions generated by base catalysis. Moreover, this surface modification strategy was applicable to the reduction of other nitro compounds.

First asteroid gas sample delivered by the Hayabusa2 mission: A treasure box from Ryugu.

The Hayabusa2 spacecraft returned to Earth from the asteroid 162173 Ryugu on 6 December 2020. One day after the recovery, the gas species retained in the sample container were extracted and measured on-site and stored in gas collection bottles. The container gas consists of helium and neon with an extraterrestrial 3He/4He and 20Ne/22Ne ratios, along with some contaminant terrestrial atmospheric gases. A mixture of solar and Earth's atmospheric gas is the best explanation for the container gas composition. Fragmentation of Ryugu grains within the sample container is discussed on the basis of the estimated amount of indigenous He and the size distribution of the recovered Ryugu grains. This is the first successful return of gas species from a near-Earth asteroid.

Determination of trace rare earth elements in rock samples including meteorites by ICP-MS coupled with isotope dilution and comparison methods.

Combining isotope dilution mass spectrometry with a calibration method and choosing appropriate internal standard elements, 14 lanthanides (rare earth elements, REEs) were precisely and accurately determined for rock samples by using quadruple ICP-MS instruments. An enriched spike of 149Sm was used to determine Sm content by an isotope dilution method. Simultaneously, Sm content was determined by a calibration method and the ratio of the two Sm values was used for correcting the preparation loss of the other REEs, which were analyzed only by a calibration method. Indium and Tl were chosen for use as internal standard elements. Applying the procedure developed in this study to the homogenized Allende meteorite powder sample prepared by the Smithsonian Institution, Washington, D. C., US and several geological reference samples issued by the Geological Survey of Japan and the US geological Survey, precision and accuracy of the data obtained were evaluated and the accuracy was found to be equivalent to isotope dilution values obtained by thermal ionization mass spectrometry. Rare earth element concentrations in several meteorite samples were determined, and results indicate that our procedure is appropriate for a wide variety of whole rock compositions.

Development of a sample holder for synchrotron radiation-based computed tomography and diffraction analysis of extraterrestrial materials.

A sample holder for a suite of synchrotron radiation measurements on extraterrestrial materials, which are fragile and irregularly shaped, was developed using carbon nanotubes and polyimide. The holder enables investigation of such samples with multiple analytical instruments, which means that we can reduce the number of sample transfers between holders. The holder developed in our study also enables investigation of such samples without exposure to the terrestrial atmosphere, which contains abundant contaminants, such as water vapor and organic substances. The stability of the samples in the holder during the measurements and disturbance of the analysis result by the holder were evaluated, which showed that sample drift motion and image disturbance due to x-ray attenuation and scattering of the holder materials are insignificant.

A new approach for reconstructing the 131I-spreading due to the 2011 Fukushima nuclear accident by means of measuring 129I in airborne particulate matter.

To retrieve the diffusion trajectory of the 131I dispersed in the environment by the nuclear power plant accident in Fukushima in 2011, airborne particulate matter (APM) samples collected in the Tokyo metropolitan area were analyzed for their 129I contents by means of accelerator mass spectrometry. In evaluating blank levels of chemicals and filters used for collecting APM, we established the analytical procedure for determining the 129I activity of as low as 10-8 Bq for a small piece of filter samples (about 0.1 cm2). Coupled with 131I data determined just after the accident, activity ratios of 129I/131I were obtained with a mean value of 2.29 × 10-8 (±28% of a standard deviation). This value is systematically smaller than a mean value of soil samples by 16-24% and the inventory data by 27%, suggesting that 129I was partly lost from APM. As 129I can be a proxy of 131I for APM, it is possible to trace how 131I in the particulate phase spread in eastern Japan and, furthermore, evaluate the internal radiation exposure due to 131I by inhalation of 131I-containing airborne particulates.