Mid-infrared transmission spectra of individual Antarctic micrometeorites and carbonaceous chondrites

Mid-infrared absorption spectra were obtained for 6 carbonaceous chondrites and 6 Antarctic micrometeorites (AMMs) with transmission light using an IR microscope. Obvious absorption bands caused by O-H stretching vibration at 3400cm^ and H-O-H bending vibration at 1640cm^ were detected for CI, CM2,CR2,and CO3 chondrites. All the chondrite samples had Si-O stretching band at around 1000cm^. Allende (CV3) exhibited only Si-O stretching band at near 900cm^ and no O-H bands. Infrared absorption spectra for AMMs showed no O-H stretching vibration reflecting their dry condition, except for F97AC019 and F97AC017 with weak O-H stretching band. Heating experiments on the grains of Murchison and Orgueil with sizes as small as AMMs (∿100μm) were carried out in order to clarify the dehydration effect of micrometeorite during the atmospheric entry. Heating times were 30 and 60s at temperatures every 100℃ from 500℃ to 1000℃. At relatively lower temperature condition (≤700℃), water in carbonaceous chondrites was not depleted. O-H stretching vibration at 3400cm^ was, however, vanished at higher temperature (≥800℃). This might show that AMMs were heated to 800℃ or more during atmospheric entry if our hearting duration is reasonable. Noble gas measurement using laser heating was performed for individual AMMs after the infrared microscopic analyses. Solar-He was detected for 4 samples. F97AC019 with very high concentration of helium (8.1×10^cm^3 STP/g) preserve solar-Ne and primordial trapped argon component. We have discovered an extraordinary AMM, F97AC021,with highly concentrated organic matters. Intense C-H stretching vibration at 2900cm^ and complex absorption pattern appeared in the range from 1400cm^ to 1800cm^ were detected. The AMM might have a potential to have plenty of extraterrestrial organic compounds

Raman frequencies of graphitic carbon in Antarctic ureilites

Raman frequencies for the in-plane lattice vibration of graphite were surveyed for four Antarctic ureilites in order to construct a paradigm for structural properties of graphitic carbon in ureilites. Raman spectra were obtained by point-by-point measurements using a laser microbeam 1μm in diameter. The measured results formed an array in a two-dimensional plot between the E_ frequency and intensity ratio of two graphite-derived Raman bands. The graphitic matter in ALH-78019 gave the averaged E_ frequency at 1582.0 ⊿cm^, which agrees with the well-established wavenumber of the E_ in-plane lattice vibration of graphite. On the contrary, some graphitic matter in the ureilites (ALH-77257,Y-791538 and MET-78008) exhibited considerably up-shifted E_ frequency. Distribution in the array was proved to be closely linked to the extent of shock which the ureilites suffered

In-situ micro Raman studies on graphitic carbon in some Antarctic ureilites

The fine structures of graphitic materials contained in four Antarctic ureilites (ALH-77257,ALH-78019,MET-78008 and Y-791538) were investigated using a laser light (514.5nm), which could be focused onto a spot of 1μm in diameter. Raman spectra obtained differ not only among individual ureilite samples, but also among positions within a single carbonaceous vein of the same specimen. Moreover, one can classify the carbon into several groups on the basis of the spectra concerned. For all samples, both well-ordered graphitic carbon and semi-ordered graphitic carbon were observed. Amorphous carbon was detected in ALH-77257 and MET-78008. The difference in structural ordering among the samples is attributed to the difference in distribution of the components of carbonaceous material, indicating minor difference in genetic conditions or in locality within the parent body. Structural heterogeneity of carbon within a single carbonaceous vein implies the occurrence of two (or three) types of carbonaceous matters which have fairly different physicochemical properties and distinct histories. For the genesis of the carbonaceous matter in ureilites, a two-stage model is proposed assuming the graphite crystallization from metallic phase followed by the inflow of semi-ordered graphitic carbon or amorphous carbon into the well-ordered graphitic carbon produced from the metal

Raman spectroscopic thermometer for carbonaceous material in chondrites

第6回極域科学シンポジウム[OA] 南極隕石11月16日（月）　国立国語研究所 2階 講

An Explanation of Episodic Tremor and Slow Slip Constrained by Crack-Seal Veins and Viscous Shear in Subduction Mélange

Episodic tremor and slow slip (ETS) occurs in the transition zone between the locked seismogenic zone and the deeper, stably sliding zone. Actual mechanisms of ETS are enigmatic, caused by lack of geological observations and limited spatial resolution of geophysical information from the ETS source. We report that quartz‐filled, crack‐seal shear and extension veins in subduction mélange record repeated low‐angle thrust‐sense frictional sliding and tensile fracturing at near‐lithostatic fluid pressures. Crack‐seal veins were coeval with viscous shear zones that accommodated deformation by pressure solution creep. The minimum time interval between thrusting events, determined from a kinetic model of quartz precipitation in shear veins, was less than a few years. This short recurrence time of low‐angle brittle thrusting at near‐lithostatic fluid overpressures within viscous shear zones may be explained by frequent release of accumulated strain by ETS

A fluorenylidene-acridane that becomes dark in color upon grinding – ground state mechanochromism by conformational change

UTokyo FOCUS Articles掲載「力を加えると大きく色が変わる分子を発見 電気の流れやすさも変化」https://www.u-tokyo.ac.jp/focus/ja/articles/z0508_00130.htmlUTokyo FOCUS Articles "New molecule responds to mechanical pressure with drastic color change : Mechanical stimulus also enhances electron mobility" https://www.u-tokyo.ac.jp/focus/en/articles/z0508_00129.htm

An explanation of episodic tremor and slow slip constrained by crack-seal veins and viscous shear in subduction mélange

Episodic tremor and slow slip (ETS) occurs in the transition zone between the locked seismogenic zone and the deeper, stably sliding zone. Actual mechanisms of ETS are enigmatic, caused by lack of geological observations and limited spatial resolution of geophysical information from the ETS source. We report that quartz‐filled, crack‐seal shear and extension veins in subduction mélange record repeated low‐angle thrust‐sense frictional sliding and tensile fracturing at near‐lithostatic fluid pressures. Crack‐seal veins were coeval with viscous shear zones that accommodated deformation by pressure solution creep. The minimum time interval between thrusting events, determined from a kinetic model of quartz precipitation in shear veins, was less than a few years. This short recurrence time of low‐angle brittle thrusting at near‐lithostatic fluid overpressures within viscous shear zones may be explained by frequent release of accumulated strain by ETS

Deep microbial proliferation at the basalt interface in 33.5–104 million-year-old oceanic crust

The upper oceanic crust is mainly composed of basaltic lava that constitutes one of the largest habitable zones on Earth. However, the nature of deep microbial life in oceanic crust remains poorly understood, especially where old cold basaltic rock interacts with seawater beneath sediment. Here we show that microbial cells are densely concentrated in Fe-rich smectite on fracture surfaces and veins in 33.5- and 104-million-year-old (Ma) subseafloor basaltic rock. The Fe-rich smectite is locally enriched in organic carbon. Nanoscale solid characterizations reveal the organic carbon to be microbial cells within the Fe-rich smectite, with cell densities locally exceeding 1010 cells/cm3. Dominance of heterotrophic bacteria indicated by analyses of DNA sequences and lipids supports the importance of organic matter as carbon and energy sources in subseafloor basalt. Given the prominence of basaltic lava on Earth and Mars, microbial life could be habitable where subsurface basaltic rocks interact with liquid water