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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

A Fluorescent Aerogel for Capture and Identification of Interplanetary and Interstellar Dust

Aerogels are extremely low-density solids whose superiority as capturing media for hypervelocity (v > 0.5 km/s) grains has been well established. A prominent example is the use of silica aerogel as the collecting medium for cometary and interstellar grains on NASA s Stardust mission. Aerogel collectors have been deployed in low-earth orbit, but severe background from anthropogenic orbital debris has so far prevented the identification of more than a handful of interplanetary particles. No interstellar particles have been identified so far. Since they are on hyperbolic orbits, extraterrestrial particles are faster than orbital debris, so could in principle be identified on that basis, but existing aerogels give little information on impact velocity. With this in mind, we have developed a novel calorimetric aerogel which passively records the kinetic energy of captured hypervelocity particles.

Dominguez, Gerardo↗
NASA NTRS1989

Identification of relict phases in a once-molten Allende inclusion

Fassaite rims around spinel grains that are enclosed entirely by normally zoned cores of melilite crystals are interpreted as relict grains which predate the melting of Allende type B1 refractory inclusions. Nonrelict subliquidus fassaite did not begin crystallizing from melts of these compositions until the onset of precipitation of the reversely zoned melilite mantles around the same melilite crystal cores. Relict fassaite is fractionated and highly enriched in REE and other refractory lithophiles compared to subliquidus fassaite in the same inclusion. Mass balance suggests that the relict fassaite represents only 3 percent of the original premelt amount of fassaite, and that melilite and at least one other phase were additional condensate precursors of these inclusions.

Kuehner, Scott M.↗
NASA NTRS1979

Scientific returns from a program of space missions to comets

A program of cometary missions is proposed. The nature and size of interstellar dust, its origin and evolution; identification of new interstellar molecules; clarification of interstellar chemistry; accretion of grains into protosolar cometesimals; role of a T Tauri wind in the dissipation of the protosolar nebula; record of isotopic anomalies, better preserved in comets than in meteorites; cosmogenic and radiogenic dating of comets; cosmochronology and mineralogy of meteorites, as compared with that of cometary samples; origin of the earth's biosphere, and the origin of life are topics discussed in relation to comet exploration.

Delsemme, A. H.↗
NASA NTRS1982

Carbon in the Allende meteorite - Evidence for poorly graphitized carbon rather than carbyne

A carbon-rich acid residue from the Allende carbonaceous chondrite was examined by high-resolution transmission electron microscopy (HRTEM) and also by analytical electron microscopy. A TEM mount of this residue that has previously been reported to contain carbyne forms of carbon was shown to contain sheet silicate contaminants. These sheet silicate grains give electron diffraction patterns similar to those reported for carbynes, thus raising questions about the previous report of carbynes in this residue. Furthermore, two crystals from a glacier microspherule, which had previously been identified as carbyne VIII, were shown by microanalysis to be talc. In view of these observations it is suggested that identifications of carbyne by electron diffraction should be supported by microanalyses of the individual grains. HRTEM investigations of the Allende carbon indicate that it is a poorly crystalline graphite, structurally similar to 'glassy' carbon

Smith, P. P. K.↗
NASA NTRS1989

Identification of solar nebula condensates in interplanetary dust particles and unequilibrated ordinary chondrites

Orthopyroxene and olivine grains, low in FeO, but containing MnO contents up to 5 wt percent were found in interplanetary dust particles (IDP) collected in the stratosphere. The majority of olivines and pyroxenes in meteorites contain less than 0.5 wt percent MnO. Orthopyroxenes and olivines high in Mn and low in FeO have only been reported from a single coarse grained chondrule rim in the Allende meteorite and from a Tieschitz matrix augite grain. The bulk MnO contents of the extraterrestrial dust particles with high MnO olivines and pyroxenes are close to CI chondrite abundances. High MnO, low FeO olivines and orthopyroxenes were also found in the matrix of Semarkona, an unequilibrated ordinary chondrite. This may indicate a related origin for minerals in extraterrestrial dust particles and in the matrix of unequilibrated ordinary chondrites.

Kloeck, W.↗
NASA NTRS1993

A study of carbonates, sulfates, and phosphates using thermal emission spectroscopy

Thermal emission spectroscopy is useful for identifying mineralogies including carbonates, sulfates, and phosphates. Each of these groups of minerals has a distinct emissivity profile that allows for general identification (e.g., carbonate). Laboratory data are being collected that suggest the potential for determining specific composition of these minerals (e.g., calcite, magnesite). Previous studies of Mars suggest that the above groups of minerals should be present. On Mars fine-grained mineralogies are likely to be intimately mixed due to aeolian activity. Mixtures of calcite with palagonite will be studied to determine the volume percent requirement for salt identification and to understand the complexities of fine-grained mixtures observed by thermal emission. Further work with mixtures will include sulfate and phosphate mineralogies.

Wenrich, M. L.↗
NASA NTRS1993

Identification of new meteorite, Mihonoseki (L), from broken fragments in Japan

New meteorite of Mihonoseki fallen in Shimane-ken was identified by fine broken pieces by using an energy-dispersive scanning electron microprobe analyzer. It shows fusion-crust (i.e. Fe-Si melt), meteoritic minerals (kamacite, taenite, troilite, amorphous plagioclase etc.) and chrondrule with clear glassy rim. Mineralogical, and petrological data of several fine grains suggest that broken fragments of Mihonoseki are L3/4 chondritic meteorite which is the first identification in a Japanese fallen meteorite. The prompt identification method of meteorite-fragments will be applied to the next lunar, Martian and asteroid explorations, as well as meteorite falls on the terrestrial surface.

Miura, Y.↗
NASA NTRS1996

Observations of Ices in Star-Forming Regions

Ground-based, air-borne, and space-based infrared spectra of protostars show prominent absorption features at 3.08, 3.54, 4.23, 4.67, 4.9, 6.0, 6.85, and 7.6 micrometers. These features are due to simple molecules such as H2O, CH3OH, CO2, CO, OCS, and CH4 in accreted icy grain mantles. These studies have revealed the presence of several independent ice components, often along the same line of sight. The observations and proposed identifications will be reviewed with the emphasis on recent results from ISO and on the organic inventory of interstellar ices. These molecular grain mantles are thought to form by accretion and reaction of gas phase species on a grain surface. Observed abundances will be compared with theoretical calculations and the important grain surface routes will be delineated. The importance of the 'diffusion' limit will be emphasized.

Tielens, Alexander G. G. M.↗
NASA NTRS2013

Complex Indigenous Organic Matter Embedded in Apollo 17 Volcanic Black Glass Surface Deposits

Papers presented at the first Lunar Science Conference [1] and those published in the subsequent Science Moon Issue [2] reported the C content of Apollo II soils, breccias, and igneous rocks as rang-ing from approx.50 to 250 parts per million (ppm). Later Fegley & Swindle [3] summarized the C content of bulk soils from all the Apollo missions as ranging from 2.5 (Apollo 15) to 280 ppm (Apollo 16) with an overall average of 124+/- 45 ppm. These values are unexpectedly low given that multiple processes should have contributed (and in some cases continue to contribute) to the lunar C inventory. These include exogenous accretion of cometary and asteroidal dust, solar wind implantation, and synthesis of C-bearing species during early lunar volcanism. We estimate the contribution of C from exogenous sources alone is approx.500 ppm, which is approx.4x greater than the reported average. While the assessm ent of indigenous organic matter (OM) in returned lunar samples was one of the primary scientific goals of the Apollo program, extensive analysis of Apollo samples yielded no evidence of any significant indigenous organic species. Furthermore, with such low concentrations of OM reported, the importance of discriminating indigenous OM from terrestrial contamination (e.g., lunar module exhaust, sample processing and handling) became a formidable task. After more than 40 years, with the exception of CH4 [5-7], the presence of indigenous lunar organics still remains a subject of considerable debate. We report for the first time the identification of arguably indigenous OM present within surface deposits of black glass grains collected on the rim of Shorty crater during the Apollo 17 mission by astronauts Eugene Cernan and Harrison Schmitt.

Thomas-Keprta, Kathie L.↗
DOE OSTI2025

Nanoscale Phase Identification Using Two-Dimensional Pair Correlation Functions: A Case Study on Hafnium Oxide

Accurate identification of local phases in nanocrystalline materials is essential for understanding their functional properties, but it remains a significant challenge for polymorphic materials to locally differentiate them at nanoscale. This challenge is further compounded in polycrystalline materials with randomly oriented grains and the coexistence of multiple phases. In this report, we present a methodology for phase and orientation identification at the nanoscale by leveraging vector pair correlation functions extracted from atomically resolved scanning transmission electron microscopy (STEM) images. We demonstrate the accuracy of the methodology on both simulated and experimental data from HfO 2 -based films, a material that exhibits multiple coexisting phases in films with thicknesses ranging from 5 to 20 nm. While demonstrated on HfO 2 films, the methodology can be extended to other polymorphic nanocrystalline systems with complex phase coexistence.

36 MATERIALS SCIENCE↗
NASA NTRS1979

Analysis of ultraviolet spectrophotometric data from Copernicus

Ultraviolet spectral data from the OAO 3 satellite are being used to study interstellar absorption lines and stellar and circumstellar lines in hot stars. The interstellar data are beneficial in analyzing the depletions of heavy elements from the gas phase and in elucidating how these depletions depend on physical conditions. Abundances in separate velocity components were determined from line profiles. Observations were carried out for interstellar abundances, both atomic and molecular, towards a number of stars. The better quality data are being analyzed for profile information and the lesser data are being used in curve-of-growth analyses. Molecular observations were carried out as well, N2 was sought; interstellar C2 was detected and its rotational excitation utilized to establish limits in interstellar cloud temperatures. An extensive search for H2O resulted in a tentative identification which will produce new information on chemical reaction rates. Interstellar depletions and grain properties in the rho Ophiuchi cloud, stellar wind variability, and circumstellar lines are also under study.

Snow, T. P., Jr.↗
NASA NTRS1985

Relationships between microstructure and microfissuring in alloy 718

Microfissures which occur in the weld heat affected zone of alloy 718 can be a limiting factor in the material's weldability. Several studies have attempted to relate microfissuring susceptibility to processing conditions, microstructure, and/or heat-to-heat chemistry differences. The present investigation studies the relationships between microstructure and microfissuring by isolating a particular microstructural feature and measuring microfissuring as a function of that feature. Results to date include the identification of a microstructure-microfissure sequence, microfissuring susceptibility as a function of grain size, and microfissuring susceptibility as a function of solution annealing time.

Thompson, R. G.↗
DOE OSTI2026

A new self-adaptive reconstruction method to identify defects through Wigner–Seitz approach

A new self-adaptive reconstruction method based on local atomic structure at any given molecular dynamics (MD) step has been developed in this article. The method can be used in Wigner–Seitz defect analysis approach to correctly and efficiently explore the information of both point defects and complex defect clusters (e.g. dislocation loops and voids) formed after a displacement cascade where the cascade interacts with grain boundaries and/or dislocations. The algorithm and validation are provided in detail. Results for identification of radiation defects during and after cascades interacting with a dislocation network show that the new method can well recognize all simple and complex defects and defect clusters. Thus, this new method provides a totally new way to explore the density and size of radiation defects at atomic scale after complex MD evolution processes, providing correct information to understand and predict radiation damage in materials through atomic simulations.

72 PHYSICS OF ELEMENTARY PARTICLES AND FIELDS↗
NASA NTRS1987

Bright sand/dark dust: The identification of active sand surfaces on the Earth and Mars

Field studies and analysis of LANDSAT Thematic Mapper data in the Gran Desierto, Mexico may shed light on a technique to distinguish active from inactive (relict) sand surfaces. Active sand bodies in the study area are consistently brighter (by an average of 20%) at visual and near infrared wavelengths and darker at thermal infrared wavelengths than compositionally similar inactive sands. The reasons for the albedo difference between active and inactive sands are reviewed and the mixing model of Johnson et al. is examined for tracing the provenance of sands based on albedo and spectral variations. Portions of the wavelengths covered by the Mars Orbiter correspond to the Thematic Mapper data. The identification of active sands on Earth, with a priori knowledge of bulk composition and grain size distribution, may allow the remote mapping of active sand surfaces on Mars. In conjuction with thermal infrared remote sensing for composition, it may also provide a method for the remote determination of grain size distributions within sand/silt mixtures.

Blount, H. G., II↗
NASA NTRS2000

Identification of Crystalline Minerals in Volcanic Alteration Products and Applications to the Surface of Mars

Visible, infrared and Mossbauer spectra have been measured for fine-grained alteration products of volcanic tephra and ash. Comparison of the spectral and chemical properties for different size separates and related samples provides information about the crystalline materials in these samples and how they may have formed. Hydrothermal processes can increase the alteration rates of the primary minerals and glass and provide S, Fe and/or water for formation of sulfates and hydrated minerals. Identification of crystalline alteration minerals on Mars may indicate hydrothermal alteration and sites of interesting geologic processes.

Bishop, J. L.↗
NASA NTRS1994

Spectral reflectance properties of carbon-bearing materials

The 0.3-2.6 micrometers spectral reflectance properties of carbon polymorphs (graphite, carbon black, diamond), carbides (silicon carbide, cementite), and macromolecular organic-bearing materials (coal, coal tar extract, oil sand, oil shale) are found to vary from sample to sample and among groups. The carbon polymorphs are readily distinguishable on the basis of their visible-near infrared spectral slopes and shapes. The spectra of macromolecular organic-bearing materials show increases in reflectance toward longer wavelengths, exceeding the reflectance rise of more carbon-rich materials. Reflectance spectra of carbonaceous materials are affected by the crystal structure, composition, and degree of order/disorder of the samples. The characteristic spectral properties can potentially be exploited to identify individual carbonaceous grains in meteorites (as separates or in situ) or to conduct remote sensing geothermometry and identification of carbonaceous phases on asteroids.

Cloutis, Edward A.↗
NASA NTRS2002

Luminescence from VUV Irradiated Cosmic Ice Analogs and Organic Residues

The optical luminescent properties for a variety of vacuum-ultraviolet (VUV) irradiated cosmic ice analogs and the complex organic residues produced from irradiation might be applicable to Solar System and interstellar observations and processes for various astronomical objects with an ice heritage. Some examples include grain temperature determination and vaporization rates, nebula radiation balance, albedo values, color analysis, and biomarker identification. Detailed results are presented for the mixed molecular ice: H2O:CH3OH:NH3:CO (100:50:1:1), a realistic representation for an interstellar/precometary ice. The irradiated ices and the room-temperature residues resulting from this energetic processing have remarkable photoluminescent properties in the visible (520-570 nm). The luminescence dependence on temperature, thermal cycling, and VUV exposure of the residue is described.

Gudipati, Murthy S.↗