Study of the structure of silica film by infrared spectroscopy and electron diffraction analyses

Amorphous silicon oxide films have been studied on the basis of electron diffraction (ED) analyses and infrared (IR) spectroscopy in order to elucidate the relationship between the structures. After the heat treatment of the film in air at 300 and 500°C, the ED pattern showed halo rings, and the IR spectra clearly changed. Intensity analysis of the ED pattern provided evidence for the structural change of the amorphous film. It was concluded that the spectral changes in the ranges of 9.2–10.2, 12.5–13.5 and 19.5–22.5 μm were the result of phase transitions of the microcrystallites of α-cristobalite to β-cristobalite, and α- or β-quartz. Astrophysical implications have been discussed.     

Relationship among O, Mg isotopes and the petrography of two spinel-bearing compound chondrules

The petrological properties, and O and Al-Mg isotopic compositions of two spinel-bearing chondrules from the Allende CV chondrite were investigated using scanning electron microscopy and secondary ion mass spectrometry. A coarse spinel grain in a barred-olivine (BO) chondrule is less enriched in ¹⁶O (Δ¹⁷O ∼ −5‰; Δ¹⁷O = δ¹⁷O - 0.52 δ¹⁸O), whereas smaller spinel grains in a plagioclase-rich chondrule member of a compound chondrule are extremely ¹⁶O-rich (Δ¹⁷O ∼ −17‰) and the spinels have a strongly serrated character. The petrological features and ¹⁶O-enrichments of the spinels in the plagioclase-rich chondrule indicate that spinels originating in coarse-grained Ca-Al-rich Inclusions (CAIs) were incorporated into chondrule precursors and survived the chondrule-forming event. The degree of ¹⁶O-excesses among minerals within each chondrule is correlated to the crystallization sequences. This evidence suggests that the O isotopic variation among minerals may have resulted from incomplete exchange of O isotopes between ¹⁶O-rich chondrule melt and ¹⁶O-poor nebular gas. Aqueous alteration also has changed the O-isotope compositions in the mesostasis. The feldspathic mesostasis in the BO chondrule shows a disturbed Mg-Al isochron indicating that the BO chondrule experienced secondary alteration. While plagioclase in the plagioclase-rich chondrule member of the compound chondrule shows slight ²⁶Mg-excesses corresponding to (²⁶Al/²⁷Al)₀ = [4.6±4.0(2σ)] × 10⁻⁶, nepheline formed by secondary alteration shows no detectable excess. The Al-Mg isotopic system of these chondrules was disturbed by aqueous alteration and thermal metamorphism on the Allende parent body.     

Deflection and Rotation of CMEs from Active Region 11158

Between 13 and 16 February 2011, a series of coronal mass ejections (CMEs) erupted from multiple polarity inversion lines within active region 11158. For seven of these CMEs we employ the graduated cylindrical shell (GCS) flux rope model to determine the CME trajectory using both Solar Terrestrial Relations Observatory (STEREO) extreme ultraviolet (EUV) and coronagraph images. We then use the model called Forecasting a CME’s Altered Trajectory (ForeCAT) for nonradial CME dynamics driven by magnetic forces to simulate the deflection and rotation of the seven CMEs. We find good agreement between ForeCAT results and reconstructed CME positions and orientations. The CME deflections range in magnitude between \(10^{\circ }\) and \(30^{\circ}\). All CMEs are deflected to the north, but we find variations in the direction of the longitudinal deflection. The rotations range between \(5^{\circ}\) and \(50^{\circ}\) with both clockwise and counterclockwise rotations. Three of the CMEs begin with initial positions within \(2^{\circ}\) from one another. These three CMEs are all deflected primarily northward, with some minor eastward deflection, and rotate counterclockwise. Their final positions and orientations, however, differ by \(20^{\circ}\) and \(30^{\circ}\), respectively. This variation in deflection and rotation results from differences in the CME expansion and radial propagation close to the Sun, as well as from the CME mass. Ultimately, only one of these seven CMEs yielded discernible in situ signatures near Earth, although the active region faced toward Earth throughout the eruptions. We suggest that the differences in the deflection and rotation of the CMEs can explain whether each CME impacted or missed Earth.     

不同类型生态系统水热碳通量的监测与研究

亚太地区环境革新战略项目(APEIS) 在中国5种主要生态系统类型区(草地: 海北、耕地: 禹城、稻田: 桃源、林地: 千烟洲、荒漠: 阜康) 建立了一个以连续观测能量、水分和碳素通量为中心,包括气象、水文、土壤、植被等各项生态要素的监测网络系统,被称之为APEIS-FLUX系统。作者首先对APEIS-FLUX系统的观测数据进行了初步分析,表明该系统稳定可靠,它可以实时地提供高质量、高精度、长期而连续的通量及生态要素的观测数据。对数据的比较清楚地反映出了不同生态系统类型区的水热碳通量的差异性。其次,利用APEIS-FLUX数据对美国航空航天局(NASA) 的MODIS数据产品进行比较验证后发现,除部分产品如地表面温度(MOD11) 等与观测数据较吻合以外,大部分数据产品如土地覆盖(MOD12),叶面积指数(MOD15) 和光合速率与净第一性生产力(MOD17) 等都与观测数据相差深远,有必要对其处理程序和模式进行修正。为此,我们利用APEIS-FLUX的数据作为MOD15和MOD17的生成模型(BIOME-BGC) 的输入数据,并对该模型的有关参数进行了修订。结果表明,该模式在通过修正后,可以很好地模拟植被的生长过程及其相应的水热碳循环过程。     

An experimental study on impact-induced alterations of planetary organic simulants

The present study systematically investigates shock-induced alteration of organic simulants of planetary bodies (OSPBs) as a function of peak shock pressure and temperature by impact experiments. Our results show that the composition and structure of OSPBs are unchanged upon impacts at peak pressures ≤~5 GPa and temperatures ≤~350 °C. On the other hand, these are dramatically changed upon impacts at >7–8 GPa and > ~400 °C, through loss of hydrogen-related bonds and concurrent carbonization, regardless of the initial compositions of OSPBs. Compared with previous results on static heating of organic matter, we suggest that shock-induced alteration cannot be distinguished from static heating only by Raman and infrared spectroscopy. Our experimental results would provide a proxy indicator for assessing degree of shock-induced alteration of organic matter contained in carbonaceous chondrites. We suggest that a remote-sensing signature of the 3.3–3.6 μm absorption due to hydrogen-related bonds on the surface of small bodies would be a promising indicator for the presence of less-thermally-altered (i.e., <350 °C) organic matter there, which will be a target for landing to collect primordial samples in sample-return spacecraft missions, such as Hayabusa2 and OSIRIS-REx.     

Dissolved and labile particulate Zr,Hf, Nb,Ta, Mo and W in the western North Pacific Ocean

Dissolved and labile particulate Zr, Hf, Nb, Ta, Mo and W were determined at stations K1 (51°N, 165°E), K2 (47°N, 160°E), KNOT (44°N, 155°E) and 35N (35°N, 160°E) in the western North Pacific Ocean. A portion of seawater for dissolved species (D) was passed through a 0.2 μm Nuclepore filter and acidified to pH 2.2 with HCl and HF. A portion of seawater for acid-dissolvable species (AD) was acidified without filtration. Labile particulate (LP) species is defined as AD minus D, which represents a chemically labile fraction of particulate species. D-Zr, Hf and Ta increase with depth, Nb shows a slight depletion in surface water, whereas Mo and W have a conservative vertical profile. The concentration range of D-Zr, Hf, Nb, Ta and W is 31–275, 0.14–0.95, 4.0–7.2, 0.08–0.29 and 40–51 pmol kg⁻¹, respectively, whereas that of Mo is 97–105 nmol kg⁻¹. LP-species of Zr, Hf and Ta account for 10–14% of AD in average and increase up to 25% below 4000 m, whereas those for Mo and W are negligible. In contrast, LP-Nb shows maxima (up to 27%) in surface water. We also found that D-Zr/Hf, Nb/Ta and Mo/W mole ratios generally increase in the order continental crust < river water < coastal sea < open ocean.     

On the Application of Mwp in the Near Field and the March 11, 2011 Tohoku Earthquake

Tsunami Warning Centers issue rapid and accurate tsunami warnings to coastal populations by estimating the location and size of the causative earthquake as soon as possible after rupture initiation. Both US Tsunami Warning Centers have therefore been using Mwp to issue Tsunami Warnings 5–10 min after Earthquake origin time since 2002. However, because Mwp (Tsuboi et al., Bulletin of the Seismological society of America 85:606–613, 1995) is based on the far-field approximation to the P-wave displacement due to a double couple point source, we should only very carefully apply Mwp to data obtained in the near field, at distances of less than a few wavelengths from the fault. On the other hand, the surface waves from Great Earthquakes, including those that occur just offshore of populated areas, such as the 2011 Tohoku earthquake, clip seismographs located near the fault. Because the first arriving P-waves from such large events are often on scale, Mwp should provide useful information, even for these Great Earthquakes. We therefore calculate Mwp from 18 unclipped STS-1 broadband P-wave seismograms, recorded at 2–15° distance from the Tohoku epicenter to determine if Mwp can usefully estimate Mw for this earthquake, using data obtained close to the epicenter. In this case there should be a good chance to get reliable Mwp values for stations at epicentral distances of 9–10°, since the source duration for the Tohoku earthquake is less than 200 s and the time window used to estimate Mwp is 120 s in duration. Our analysis indicates that Mwp does indeed give reliable results (Mw ~ 9.1) beginning at about 11° distance from the epicenter. The values of Mwp from seismic waveforms obtained at 11–15° epicentral distance from the Mw 9.1 off the east coast of Tohuku earthquake of March 11, 2011 fell within the range 9.1–9.3, and were available within 4–5 min after origin time. Even the Mwp values of 7.7–8.4, obtained at less than 5° epicentral distance, exceed the PTWC’s threshold of Mw 7.6 for issuing a regional tsunami warning to coastal populations within 1,000 km of the epicenter, and of Mw 6.9 for issuing a local tsunami warning to the coastal populations of Hawaii.     

An experimental study on Fischer‐Tropsch catalysis: Implications for impact phenomena and nebular chemistry

Abstract— Fischer‐Tropsch catalysis, by which CO and H₂ are converted to CH₄ on the surface of transition metals, has been considered to be one of the most important chemical reactions in many planetary processes, such as the formation of the solar and circumplanetary nebulae, the expansion of vapor clouds induced by cometary impacts, and the atmospheric re‐entry of vapor condensate due to asteroidal impacts. However, few quantitative experimental studies have been conducted for the catalytic reaction under conditions relevant to these planetary processes. In this study, we conduct Fischer‐Tropsch catalytic experiments at low pressures (1.3 times 10^?4 bar ≤ P ≤ 5.3 times 10^?1 bar) over a wide range of H₂/CO ratios (0.25–1000) using pure iron, pure nickel, and iron‐nickel alloys. We analyze what gas species are produced and measure the CH₄ formation rate. Our results indicate that the CH₄ formation rate for iron catalysts strongly depends on both pressure and the H₂/CO ratio, and that nickel is a more efficient catalyst at lower pressures and lower H₂/CO ratios. This difference in catalytic properties between iron and nickel may come from the reaction steps concerning disproportionation of CO, hydrogenation of surface carbon, and the poisoning of the catalyst. These results suggest that nickel is important in the atmospheric re‐entry of impact condensate, while iron is efficient in circumplanetary subnebulae. Our results also indicate that previous numerical models of iron catalysis based on experimental data at 1 bar considerably overestimate CH₄ formation efficiency at lower pressures, such as the solar nebula and the atmospheric re‐entry of impact condensate.