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Abstract: Raman analyses are reported of μm-sized areas of 103 individual carbonaceous presolar grains (“graphite grains”) from three different density fractions of the Murchison meteorite. Few of the grains (2 or 3 of each density fraction) have Raman spectra typical for non-crystalline sp2-bonded carbon (i.e., “organic carbon”) with extremely wide 1st-order and no (or very subdued) 2nd-order peaks, similar to the ones found for terrestrial kerogens. Based on depth profiles of isotopic ratios measured with the NanoSIMS, it is unlikely that such kerogen-type Raman signatures are caused by contamination of the presolar grains with insoluble organic material from the Murchison matrix that stuck to the surfaces of the grains. Rather, the kerogen-type grains are considered to be a new type of presolar carbon grains, which are made up of organic (PAH-like) sp2-bonded carbon. However, most of the other studied presolar carbon grains (95 of 103) have spectra with very narrow 1st-order peaks (called D and G peaks) and very strong 2nd-order peaks typical for inorganic sp2-bonded carbon. Based on their D/G intensity ratios, those grains were grouped into the following Raman types: (fairly well ordered) “graphite” (D/G<0.5), “disordered graphite” (0.51.1), and “unusual sp2-bonded graphitic carbon” (with extremely intense 2nd-order peaks relative to the 1st-order peaks). Grains from the low-density fraction KFA1 (2.05–2.10g/cm3) have predominantly “cauliflower” morphology and Raman spectra characteristic of either very disordered graphite or “glassy carbon” (i.e., the latter is amorphous from the Raman spectroscopic perspective), whereas most grains from the high-density fraction KFC1 (2.15–2.20g/cm3) have “onion” morphology and Raman spectra characteristic of well-crystalline graphite. The KFB1 grains with intermediate density (2.10–2.15g/cm3) are mixed, both in terms of their morphology and their Raman spectra but are closer to KFC1 than to KFA1 grains. The correlation of the Raman results with both morphology and isotopic data show that presolar sp2-bonded carbon grains from different stellar sources differ in their crystalline structure. Grains that dominate the high density fractions and whose isotopic ratios indicate an origin in AGB stars consist of well crystallized graphite, whereas grains that dominate the low-density fraction and whose isotopic ratios indicate a supernova origin consist of very disordered graphite or even of amorphous “glassy carbon”. [Copyright &y& Elsevier]

Abstract: Comprehensive spectroscopic characterization of interior and exterior chips of the lherzolitic shergottite Y-984028 has been performed using results from six techniques. Data from UV–visible–near-IR reflectance spectra, thermal (mid-IR) emission spectra, attenuated total reflectance (ATR) spectra, transmission FTIR spectra, Raman microprobe spectra, and Mössbauer spectra of whole rock and mineral separates from this meteorite are integrated and compared. Five of these analytical techniques accurately determined the ∼Fo65 composition of the olivine within ±10 mol%. Both transmission FTIR and ATR spectra show broad features near 3500 cm−1 indicating the presence of OH/H2O that does not arise from surface water adsorption. The brown color of the Y-984028 olivine is likely due to the presence of nanophase metallic iron particles (npFe0) dispersed throughout the olivine during a major shock event on Mars. Y-984028 olivine also contains a significant amount of Fe3+, but this cannot be distinguished from Fe3+ that is present in pyroxene and possibly clay minerals. This meteorite and the nakhlite MIL03346 are the two most oxidized of the SNC meteorites studied to date, with Fe3+ contents consistent with high-temperature equilibration near the QFM oxygen buffer. [ABSTRACT FROM AUTHOR]

Laser Raman microprobe spectroscopy, which characterizes the molecular structure of a mineral, was used to analyze microscopically small regions of bioapatite in mouse femora in order to study the effect of mouse age and in vitro fluoride treatment on the bone mineral (i.e., mineral identity and degree of crystallinity). Both femora that had and those that had not undergone in vitro NaF treatment underwent point analysis of 1 micron spots in the center of the compact bone's cross-section. The Raman spectra of bones treated with fluoride showed a peak up-shift of the PO4 vibration mode from 961 to 964 delta cm-1 indicating a conversion from a carbonated hydroxylapatitic to a carbonated fluorapatitic mineral phase. The spectral band width of the 961 delta cm-1 PO4 vibration in femora of 4-, 10-, and 24-week-old mice showed that aging, as well as in vitro treatment with 1.5 M NaF for 12 hours, significantly increases the degree of crystallinity of the bioapatite. In vitro fluoridation of 10-week-old mouse femora increased the bioapatite's degree of crystallinity to about the same degree as did aging to 24 weeks. Four-point bending tests indicated that the age-related increase in crystallinity of untreated bones was associated with decreased deformation to failure, i.e., increased brittleness. In contrast, the increased crystallinity following fluoridation of 10-week-old bones was associated with increased deformation, i.e., increased ductility, perhaps due to the altered mineral composition. This study shows that the laser Raman microprobe readily detects the conversion of carbonated hydroxylapatite to carbonated fluorapatite, as well as changes in crystallinity of either mineral phase, in microscopically small regions of a bone sample. [ABSTRACT FROM AUTHOR]

We have extensively modified and successfully used a laser Raman spectrometer (DORISS, deep-ocean Raman in situ spectrometer) for geochemical studies in the deep ocean. The initial instrument, from Kaiser Optical, was separated into three components: an optical head, a laser-power supply telemetry unit, and the spectrometer. These components were modified to fit into custom designed pressure housings, and connected by deep-sea cables and optical penetrators designed to minimize signal loss. The instrument ensemble has been field deployed on remotely operated vehicles (ROVs) for a variety of experiments and observations, with successful operation at 1.6°C, 3600 m depth. Power supply, instrument control, and signal telemetry are provided through the ROV tether, which contains copper conductors and single mode optical fibers. The optical head is deployable by the ROV robotic arm for sample analysis; the remaining components are fixed within the vehicle tool-sled. Challenges of system calibration at depth, temperature and pressure artifacts, and system control through over 4 km of cable were successfully overcome. We present exemplary spectra obtained in situ of gas, liquid, and solid specimens, and of the ubiquitous signal of sea water itself. Future challenges include weight and size reduction, and advances in precise beam positioning on mineral targets on the sea floor. [Copyright &y& Elsevier]