Mid-infrared Study of Stones from the Sutters Mill Meteorite

The Sutter's Mill meteorite fell in northern California on April 22, 2012, and numerous pieces have been recovered and studied with several analytical techniques [1]. We present a Fourier-transform infrared (FTIR) spectroscopy analysis of fragments from several stones of the meteorite. Methods and analysis: Infrared spectra of samples SM2 and SM12 were recorded with a Nicolet iN10 MX FTIR microscope in the mid-IR range (4000-650/cm; spectral resolution 4/cm), while samples SM20 and SM30 were analyzed with a synchrotron-based Nicolet Continuum IR microscope in the same range. Samples were deposited on a clean glass slide, crushed with either a stainless steel roller tool or between 2 slides, and placed directly on the focal plane of the microscopes. Results: IR spectra of non-fusion crust samples show several absorption features associated with minerals such as olivines, phyllosilicates, carbonates (calcite and dolomite), and pyroxenes, as well as organics [2]. The carbonates display a main, broad band centered at 1433/cm, with additional bands at 2515/cm, 1797/cm, 882/cm, and 715/cm. Features associated with phyllosilicates include a symmetric Si-O stretching mode band centered at 1011/cm and several O-H stretching mode bandsa broad band centered at 3415/cm that is probably due to adsorbed H2O, and occasionally a much weaker, narrower feature centered near 3680/cm due to structural O-H. Features observed in the 2985-2855/cm range suggest the presence of aliphatic -CH3 and -CH2- groups. However, some of these bands show unusual relative intensities, mainly because of carbonate overtone bands that fall in the same spectral range, which can make the identification of C-H stretching bands problematic. The positions and relative strengths of the aliphatic -CH2- and -CH3 features, where they can be distinguished from overlapping carbonate bands, are consistent with those in interplanetary dust particles (IDPs) and Murchison. Finally, the absence of a strong C=O absorption feature near 1700/cm distinguishes the organics in the Sutter's Mill meteorite from that in most IDPs and in Murchison, but is consistent with the organic matter in Tagish Lake

Water-Rock Interactions in Outer Solar System Bodies: Evidence from the Coordinated Analysis of Interplanetary Dust

NASA has an ongoing program of collecting interplanetary dust particles (IDPs) in the stratosphere using high altitude research aircraft. The collected IDPs are derived from asteroids and comets and here we report studies of a subset of hydrated IDPs rich in carbonaceous matter that are proposed to have a cometary origin. Our studies are aimed at understanding the evolution of oxygen reservoirs in the Solar System and their interaction with cometary minerals and organic matter. The small size (<20 m) and fragility of these IDPs present a number of analytical challenges. We have pioneered techniques for performing chemical, mineralogical, isotopic, and spectroscopic measurements on the same sample in a carefully coordinated sequence. Coordinated analyses of nanogram-size samples is made possible by several delicate sample preparation techniques. To avoid organic contamination, we embed IDPs in elemental sulfur and use ultramicrotomy to partly section the particles (the first few micrometers). Multiple thin sections (50-70 nm thick) are placed on different substrates depending on the analysis technique. We use a JEOL 2500SE scanning, transmission electron microscope (STEM) to determine the mineralogy, microstructure, and elemental compositions of constituent minerals in the thin sections through a combination of high resolution imaging, electron diffraction, quantitative energy-dispersive x-ray mapping, and electron energy-loss spectroscopy. Following the STEM analyses, we use a NanoSIMS 50L for high spatial resolution isotopic measurements of H, C, N, and O to search for presolar grains and to understand the origin of the indigenous organic matter. The isotopic analyses are performed on the same sections analyzed in the STEM in order to correlate isotopic properties with the elemental and mineralogical data. We reserve other thin sections for non-destructive analyses utilizing synchrotron-based techniques including Fourier-transform infrared (FTIR) micro-spectroscopy and X-ray absorption near-edge structure (XANES) analyses, especially for functional group analysis of organic matter in the particles. The remainder of the IDP is extracted from the sulfur bead that was used for microtomy and is pressed into Au foil for quantitative analysis (including light elements) using a JEOL 8530F field emission electron probe microanalyzer (EPMA). After the EPMA measurements, high precision oxygen isotopic analyses are obtained using Cameca IMS1270/1290 instruments at UCLA. The hydrated IDPs in this study are dominated by saponitic clays, with minor magnetite, carbonate and abundant organic matter. The remarkable oxygen isotopic compositions, high carbon contents, and the abundance of isotopically anomalous organic matter, together suggest that the high carbon, hydrated IDPs are derived from primitive sources not yet represented in meteorite collections such as outer main belt P- and D-type asteroids or comets

Mineralogy and petrology of comet 81P/wild 2 nucleus samples

The bulk of the comet 81P/Wild 2 (hereafter Wild 2) samples returned to Earth by the Stardust spacecraft appear to be weakly constructed mixtures of nanometer-scale grains, with occasional much larger (over 1 micrometer) ferromagnesian silicates, Fe-Ni sulfides, Fe-Ni metal, and accessory phases. The very wide range of olivine and low-Ca pyroxene compositions in comet Wild 2 requires a wide range of formation conditions, probably reflecting very different formation locations in the protoplanetary disk. The restricted compositional ranges of Fe-Ni sulfides, the wide range for silicates, and the absence of hydrous phases indicate that comet Wild 2 experienced little or no aqueous alteration. Less abundant Wild 2 materials include a refractory particle, whose presence appears to require radial transport in the early protoplanetary disk

Chemical composition of the graphitic black carbon fraction in riverine and marine sediments at sub-micron scales using carbon X-ray spectromicroscopy

Author Posting. © The Authors, 2005. This is the author's version of the work. It is posted here by permission of Elsevier B.V. for personal use, not for redistribution. The definitive version was published in Geochimica et Cosmochimica Acta 70 (2006): 1483-1494, doi:10.1016/j.gca.2005.12.001.The chemical composition of the graphitic black carbon (GBC) fraction of marine organic matter was explored in several marine and freshwater sedimentary environments along the west coast of North America and the Pacific Ocean. Analysis by carbon x-ray absorption near edge structure (C-XANES) spectroscopy and scanning transmission x-ray microscopy (STXM) show the GBC-fraction of Stillaguamish River surface sediments to be dominated by more highly-ordered and impure forms of graphite, together forming about 80% of the GBC, with a smaller percent of an aliphatic carbon component. Eel River Margin surface sediments had very little highly-ordered graphite, and were instead dominated by amorphous carbon and to a lesser extent, impure graphite. However, the GBC of surface sediments from the Washington State Slope and the Mexico Margin were composed almost solely of amorphous carbon. Pre-anthropogenic, highly-oxidized deep-sea sediments from the open Equatorial Pacific Ocean contained over half their GBC in different forms of graphite as well as highly-aliphatic carbon, low aromatic/highly-acidic aliphatic carbon, low aromatic/highly aliphatic carbon, and amorphous forms of carbon. Our results clearly show the impact of graphite and amorphous C phases in the BC fraction in modern riverine sediments and nearby marine shelf deposits. The pre-anthropogenic Equatorial Pacific GBC fraction is remarkable in the existence of highly-ordered graphite.This work was supported by NSF grants OCE-0221295 and OCE-0118036 (JAB), and OCE-9310364 (SGW), by a NSF Graduate Research Fellowship to A.F.D., and the Canadian National Science and Engineering Research Council to Y.G

Styrene oligomerization as a molecular probe reaction for Brønsted acidity at the nanoscale

The Brønsted acid-catalyzed oligomerization of 4-fluorostyrene has been studied on a series ofH-ZSM-5 zeolite powders, steamed under different conditions, with a combination of UV-Vismicro-spectroscopy and Scanning Transmission X-ray Microscopy (STXM). UV-Vis microspectroscopyand STXM have been used to monitor the relative formation of cyclic and lineardimeric carbocations as a function of the steaming post-treatment (i.e., parent vs. steaming at600, 700 and 800 1C). It was found that the UV-Vis band intensity ratios of linear to cyclicdimeric species increase from 0.79 (parent H-ZSM-5) over 1.41 (H-ZSM-5 steamed at 600 1C) and1.88 (H-ZSM-5 steamed at 700 1C) to 2.33 (H-ZSM-5 steamed at 800 1C). STXM confirms thistrend in reaction product selectivity, as the relative intensities of the transitions attributed to thepresence of the cyclic dimer in the carbon K-edge spectra decrease with increasing severity of thesteaming post-treatment. Furthermore, STXM reveals spatial heterogeneities in reaction productformation within the H-ZSM-5 zeolite powders at the nanoscale. More specifically, a shrinkingcarbon core–shell distribution was detected within the zeolite aggregates, in which the relativeamount of cyclic dimeric species is higher in the core relative to the shell of the zeolite aggregateand the relative amount of cyclic dimeric species in the zeolite core gradually decreases withincreasing severity of the steaming post-treatment. These differences are rationalized in terms ofspatial differences in Brønsted acidity within H-ZSM-5 zeolite powders as well as by changes inthe formation process of linear and dimeric carbocations within H-ZSM-5 micro- and mesopores

Instrumentation developments iin scanning soft x-ray microscopy at the NSLS (invited) Mark Rivers

The Scanning Transmission Soft X-ray Microscope at the NSLS has been instrumented for the following new forms of imaging: (1) XANES microscopy for the mapping of chemical constituents and for absorption spectroscopy of small specimen areas; (2) luminescence microscopy for locating visible light emitting labels at the resolution determined by the size of the x-ray microprobe: and (3) dichroism microscopy for mapping the alignment of molecules whose absorption spectra are polarization dependent. Since the instrument is used mostly for the imaging of biological and other radiation sensitive materials, a cryostage is being planned to accommodate frozen hydrated specimens. 0 1995 American Institute of Physics. THE SCANNING SOFT X-RAY MICROSCOPE AT THE NSLS The Scanning Transmission Soft X-ray Microscope (STXM) has been operating on the NSLS XlA beamline since 1989, with zone plates fabricated by E. Anderson (Center for X-ray Optics, LBL). The Xl soft x-ray undulator serves as the bright tuneable source and the zone plate forms a microprobe that provides the 50 nm resolution of the instrument.&apos; [ Scanning microscopy is among the major beneficiaries of high brightness, in that the, speed of image acquisition is proportional to the coherent flux, which in turn is proportional to the brightness. Coherent illumination is required to form the finest (diffraction limited) microprobe that the zone plate is capable of producing. At the NSLS the emittance of the electron beam is such that roughly 0.3% of the undulator output is coherent in the 20-40 nm wavelength range. The excess output is put to good use partly by splitting the radiation cone into two beamlines&quot; (and splitting off a third one is being planned), and partly to overfill the apertures and thereby improve the stability of the illumination. Transmission images are taken in digital form, suitable for quantitative analysis. One study which used standard Van t&apos;Hof and S. Lamm, involved measurements on several hundred images of chromosomes from three plants and one mammal.3 Based on the data and independent information on the size of the genome in these species, the DNA fraction in the chromosomes was measured. In spite of the fourfold variation in genome size, the DNA fraction was found to be 39% within experimental error in all cases. This suggests a conservation of the DNA packaging mechanism. II. RECENT INSTRUMENTATION DEVELOPMENTS The following new instrumentation developments have added significantiy to the capabilities of the microscope. A. XANES microscopy By scanning the monochromator with the x/y scan of the sample stopped, an absorption spectrum can be taken from a small (submicron) specimen area. Because the zone plate is highly chromatic (focal length proportional to photon energy), the focus must track the monochromator to keep the exposed spot in focus. Absorption spectra near elemental edges (XANES) often exhibit resonances or other features that are characteristic of the chemical environment of the absorbing atom. Based on the observed spectral structure one selects characteristic energies at which to image the specimen to map its chemical components. The technique was demonstrated by delineating the morphology of pollymer blend.4 Applications to other polymeric systems, to biological specimen&amp;&apos; and to coal7 soon followed. Up to now we have been limited to the carbon K and the calcium L edges, but the dbstacles to work at the nitrogen and oxygen edges (air, silicon nitride windows, and quartz mirrors) should be removed within the next year

Oxidation is Key for Black Carbon Surface Functionality and Nutrient Retention in Amazon Anthrosols

Aims: Soil black carbon (BC) has been shown to possess large amounts of cation exchange sites and surface charge, and is viewed as a potential soil amendment to improve nutrient retention and for pollutant remediation. This study investigated the nano-scale distribution of reactive functional groups and the binding of cations on the surface of micron-size BC particles, identified the key processes, and explored the sources of surface functionality and their relative contribution to cation exchange capacity (CEC). Materials and Methods: Elemental microprobe and synchrotron-based Scanning Transmission X-ray Spectromicroscopy (STXM) coupled with Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy were used for nano-scale mapping of cations and reactive functional groups, and further distinction of the sources of reactive functional groups generated either by oxidation of BC surfaces or by adsorption of non-BC organic matter onto the BC surfaces. Their respective contribution to cation adsorption was obtained using a depth profile of a BC-rich Anthrosol from the central Amazon, Brazil. Results and Discussion: Adsorption of Non-BC organic matter is more dominant on the surface of BC particle in topsoil as evidenced by a stronger signal of microbial biomass and humic substances extracts. In comparison, a greater level of oxidation was found on the outerlayer of BC particles in subsoil horizons. Organic C in subsoils was found to generate 23-42% more CEC per unit C than topsoil. Based on CEC per unit C, the capacity of BC in creating CEC was 6-7 times higher than Non-BC, and the BC in deeper horizons had up to 20% higher CEC than the topsoil horizon. Near BC surfaces, higher ratios of Ca/C and K/C in subsoil than topsoil horizons reinforce the observation that BC in subsoil horizons had a higher capacity in binding cations and creating CEC than in the topsoil horizon. Conclusions: Oxidation of BC is suggested to be more efficient and important for creating CEC than the adsorption of non-BC onto BC surfaces, thus identified as being key for BC surface functionality and nutrient retention in Amazon Anthrosols