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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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NASA NTRS1986

Chromium isotopic anomalies in the Allende meteorite

Abundances of the chromium isotopes in terrestrial and bulk meteorite samples are identical to 0.01 percent. However, Ca-Al-rich inclusions from the Allende meteorite show endemic isotopic anomalies in chromium which require at least three nucleosynthetic components. Large anomalies at Cr-54 in a special class of inclusions are correlated with large anomalies at Ca-48 and Ti-50 and provide strong support for a component reflecting neutron-rich nucleosynthesis at nuclear statistical equilibrium. This correlation suggests that materials from very near the core of an exploding massive star may be injected into the interstellar medium.

Papanastassiou, D. A.↗
NASA NTRS1986

Correlated isotopic effects near the Fe abundance peak

A special class of refractory inclusions in carbonaceous meteorites show large isotopic anomalies in Ca, Ti, and Cr that are correlated by virtue of having been measured on the same samples. Large excesses in the neutron-rich isotopes Ca-48, Ti-50, and Cr-54 are comparable and consistent with theoretical calculations of the composition of materials produced during neutron-rich nuclear statistical equilibrium nucleosynthesis. This correlation suggests that materials from very near the core of an expoloding massive star may be injected into the interstellar medium.

Papanastassiou, D. A.↗
NASA NTRS1990

The effect of catastrophic collisional fragmentation and diffuse medium accretion on a computational interstellar dust system

The effects of catastrophic collisional fragmentation and diffuse medium accretion on a the interstellar dust system are computed using a Monte Carlo computer model. The Monte Carlo code has as its basis an analytic solution of the bulk chemical evolution of a two-phase interstellar medium, described by Liffman and Clayton (1989). The model is subjected to numerous different interstellar processes as it transfers from one interstellar phase to another. Collisional fragmentation was found to be the dominant physical process that shapes the size spectrum of interstellar dust. It was found that, in the diffuse cloud phase, 90 percent of the refractory material is locked up in the dust grains, primarily due to accretion in the molecular medium. This result is consistent with the observed depletions of silicon. Depletions were found to be affected only slightly by diffuse cloud accretion.

Liffman, Kurt↗
NASA NTRS1989

Continuous infrared emission of proto- and young-planetary nebulae

Evolutionary sequences of planetary nebulae (PNe) were calculated beginning from the moment of shell ejection to its dissipation and IR spectra of the outgoing radiation were obtained for different stages of the evolution. To solve the coupled hydrodynamical and radiation transfer problem a computer code was used in which gas and dust are treated as two separate hydrodynamical components. The models, which are calculated for two grain materials (graphite and silicate) have a size distribution of particles based on that found for the interstellar medium. In the computations, the recent optical properties of graphite and astronomical silicate grains tabulated by Draine (1987) were employed. It was assumed that silicate of graphite grains exist below some critical temperature equal to 1300 or to 1700 K, respectively. Infrared model spectra are compared with the IR radiation emitted by some proto- and some young-planetary nebulae. The observed IR continua can be quite well matched with our models with grains having a reasonable size range.

Szczerba, Ryszard↗
NASA NTRS1992

Quenched carbonaceous composite - Fluorescence spectrum compared to the extended red emission observed in reflection nebulae

The photoluminescence (fluorescence) of a film of the laboratory-synthesized quenched carbonaceous composite (filmy QCC) is shown to have a single broad emission feature with a peak wavelength that varies from 670 to 725 nm, and coincides with that of the extended red emission observed in reflection nebulae. The rapid decay of the filmy QCC red fluorescence in air and of the stable blue fluorescence of the filmy QCC dissolved in liquid Freon suggests that the red fluorescence originates from the interaction of active chemical species and aromatic components in the filmy QCC. A material similar in nature to that of the filmy QCC may be a major component of interstellar dust.

Sakata, Akira↗
NASA NTRS1996

The interstellar medium and the soft X-ray background

The soft X-ray background (SXRB) surface brightness provides data to study the approximately 10(exp 6) K plasma of the local interstellar medium of our Galaxy. Various studies were carried out in order to search for negative correlation, or shadowing, of the SXRB, and were coupled with interstellar medium absorption line studies. The purpose was to determine whether the distances to the shadowing material will lead to a three dimensional mapping of the X-ray emitting, and X-ray absorbing components.

Snowden, S. L.↗
NASA NTRS2014

Final Reports of the Stardust ISPE: Seven Probable Interstellar Dust Particles

The Stardust spacecraft carried the first spaceborne collector specifically designed to capture and return a sample of contemporary interstellar dust to terrestrial laboratories for analysis [1]. The collector was exposed to the interstellar dust stream in two periods in 2000 and 2002 with a total exposure of approximately 1.8 10(exp 6) square meters sec. Approximately 85% of the collector consisted of aerogel, and the remainder consisted of Al foils. The Stardust Interstellar Preliminary Examination (ISPE) was a consortiumbased effort to characterize the collection in sufficient detail to enable future investigators to make informed sample requests. Among the questions to be answered were these: How many impacts are consistent in their characteristics with interstellar dust, with interplanetary dust, and with secondary ejecta from impacts on the spacecraft? Are the materials amorphous or crystalline? Are organics detectable? An additional goal of the ISPE was to develop or refine the techniques for preparation, analysis, and curation of these tiny samples, expected to be approximately 1 picogram or smaller, roughly three orders of magnitude smaller in mass than the samples in other small particle collections in NASA's collections - the cometary samples returned by Stardust, and the collection of Interplanetary Dust Particles collected in the stratosphere.

Allen, Carlton↗
NASA NTRSDate not supplied

Morphological Comparison of Debris Recovered Searching for the 2018 Meteorite Fall into the Pacific with Those Recovered From the Purportedly Interstellar 2014 Fall

On 08 Jan 2014 a bolide was detected by US DoD sensors over the Pacific north of Papua New Guinea. A claim was subsequently made that this event arose from a meteoroid of interstellar origin based on fireball parameters, although that interpretation has been challenged. A seagoing expedition recovered material from the seafloor at a location calculated to be the fall site, and that material included small melted spherules. The spherules were claimed to be of extrasolar origin based on appearance and composition. A recent publication finds a favorable composition match between the retrieved spherules and coal ash, a ubiquitous contaminant on Earth’s surface and seafloor.

M D Fries↗
NASA NTRS1994

The nature of the dense obscuring material in the nucleus of NGC 1068

High spatial and spectral resolution observations of the distribution, physical parameters, and kinematics of the molecular interstellar medium toward the nucleus of the Seyfert 2 galaxy NGC 1068 are reported. The data consist of 2.4 by 3.4 arcseconds resolution interferometry of the 88.6 GHz HCN J = 1 towards 0 line at 17 km/s spectral resolution, single dish observations of several mm/submm isotopic lines of CO and HCN, and 0.85 arcseconds imaging spectroscopy of the 2.12 micron H2 S(1) line at a velocity resolution of 110 km/s. The central few hundred parsecs of NGC 1068 contain a system of dense (N(H2) approximately 10(exp 5) cm(exp -3)), warm (T greater than or equal to 70 K) molecular cloud cores. The low density molecular envelopes have probably been stripped by the nuclear wind and radiation. The molecular gas layer is located in the plane of NGC 1068's large scale disk (inclination approximately 35 deg) and orbits in elliptical streamlines in response to the central stellar bar. The spatial distribution of the 2 micron H2 emission suggests that gas is shocked at the leading edge of the bar, probably resulting in gas influx into the central 100 pc at a rate of a few solar mass per year. In addition to large scale streaming (with a solid body rotation curve), the HCN velocity field requires the presence of random motions of order 100 km/s. We interpret these large random motions as implying the nuclear gas disk to be very thick (scale height/radius approximately 1), probably as the result of the impact of nuclear radiation and wind on orbiting molecular clouds. Geometry and column density of the molecular cloud layer between approximately 30 pc to 300 pc from the nucleus can plausibly account for the nuclear obscuration and anisotropy of the radiation field in the visible and UV.

Tacconi, L. J.↗
NASA NTRS1984

HEAO 3 discovery of Al-26 in the interstellar medium

A new analysis technique was used with HEAO 3 satellite gamma ray data to quantify the galactic 1809 keV emission. A method of bins was applied in summing for specific scan directions, followed by fitting the source and background components. The 1809 keV line of Al-26 was significant because of the recent discovery that Al-26 was overabundant in meteoritic material and implanted during solar system formation. The HEAO 3 flux indicated a current decay of 3 solar masses of Al-26 per year in the interstellar medium, possibly occurring in red giants and massive main sequence stars. The ratio of the observed Al-26 to the Al-27 flux was similar to that measured in meteorites, which suggests that the ratio is normal for the galactic medium and that no supernova triggered the protosolar nebular collapse.

Mahoney, W. A.↗
NASA NTRS1974

The origin of life

Research in the areas of precambrian paleontology, chemical evolution of genetically important monomers, prebiotic dehydration-condensation reactions, organic compounds in meteorites and interstellar space, and biological exploration of the planets is summarized. Fossils in precambrian cherts and findings of eukaryotic cells are described, and recent investigations of prebiotic conditions, energy sources, and starting materials for genetic molecules are outlined. Studies of homogeneous and heterogeneous dehydrations and of nonaqueous thermal dehydrations are described. The detection of amino acids, purines, and pyrimidines in meteorites and of biologically significant molecules in interstellar clouds is discussed, as well as the possibilities of life on Jupiter, Mars, and Titan.

Horowitz, N. H.↗
NASA NTRS1987

The planetary and interstellar components of meteorites - A review

Recent analyses show that, although most meteorites are collisional debris of asteroids, three meteorites collected on the Antarctic ice sheet were projected to earth from the highlands of the moon, and eight meteorites have chemical and isotopic compositions suggestive of derivation from Mars. Although meteorites are primarily of interest to planetary scientists for the abundance of clues they hold to the materials and processes that formed the solar system, they have begun to engage the attention of astrochemists because of isotopic and mineralogical indications that they contain interstellar components. Although each individual observation to this effect is inconclusive, the body of evidence is becoming ever more persuasive. This paper reviews the main classes of meteorites and their probable sources, with special emphasis on components that appear to be exotic to the solar system.

Marvin, Ursula B.↗
NASA NTRS1991

Carbon stars with oxygen-rich circumstellar material

The IUE satellite was used to search for companions to two carbon-rich stars with oxygen-rich circumstellar envelopes, EU And and V778 Cyg. Depending upon the amount of interstellar extinction and distances (probably between 1 and 2 kpc from the Sun) to these two stars, upper limits were placed between approx. 1.5 and 6 solar mass to the mass of any main sequence companions. For the 'near' distance of 1 kpc, it seems unlikely that there are white dwarf companions because the detection would be expected of ultraviolet emission from accretion of red giant wind material onto the white dwarf. A new model is proposed to explain the oxygen-rich envelopes. If these stars have a high nitrogen abundance, the carbon that is in excess of the oxygen may be carried in the circumstellar envelopes in HCN rather than C2H2 which is a likely key seed molecule for the formation of carbon grains. Consequently, carbon particles may not form; instead, oxygen-rich silicate dust may nucleate from the SiO present in the outflow.

Jura, Michael↗
NASA NTRS1983

The kinematics and structure of N49

The present investigation of N49, which is located in the Large Magellanic Cloud (LMC), makes use of an analysis of optical emission-line profiles. Echelle spectrograph observations indicate the large-scale kinematic and structural properties of N49. It is found that this supernova remnant (SNR) is evolving in a clumpy interstellar medium (ISM), probably as many other remnants are. The very high resolution spectra of this remnant show three kinds of spectral feature, called broad bands, narrow bands, and spikes. It is shown that N49 can be regarded as the product of a supernova explosion in a heterogeneous interstellar medium. The heterogeneity is indicated in low-speed and high-speed systems of shocked material in N49.

Shull, P., Jr.↗
NASA NTRS1996

Raman Spectrum of Quenched Carbonaceous Composites

Quenched Carbonaceous Composites (QCC's) are products from the ejecta of a hydrocarbon plasma. Two types of QCC, dark QCC and thermally-altered (heated) filmy QCC, have been shown to have a 220 nm absorption feature similar to that seen in the interstellar extinction curve. We present here Raman spectra of the QCCs and compare them with various carbonaceous materials to better understand the structure QCC. We find that structure of QCC is different from that of graphite and more similar to carbonaceous material found in some interplanetary dust particles and chondritic meteorites.

Wada, S.↗
NASA NTRS2004

Identifying Organic Molecules in Space: The AstroBiology Explorer (ABE) Mission Concept

The AstroBiology Explorer (ABE) mission concept consists of a modest dedicated space observatory having a 60 cm class primary mirror cooled to T less than 50 K equipped with medium resolution cross-dispersed spectrometers having cooled large format near- and mid-infrared detector arrays. Such a system would be capable of addressing outstanding problems in Astrochemistry and Astrophysics that are particularly relevant to Astrobiology and addressable via astronomical observation. The mission's observaticxiai program woiild make fundamental scieztific: prngress in establishing the nature, distribution, formation and evolution of organic and other molecular materials in the following extra-terrestrial environments: 1) The Outflow of Dying Stars; 2) The Diffuse Interstellar Medium (DISM); 3) Dense Molecular Clouds, Star Formation Regions, and Young Stellar/Planetary Systems; 4) Planets, Satellites, and Small Bodies within the Solar System; and 5) The Interstellar Media of Other Galaxies ABE could make fundamental progress in all of these area by conducting a 1 to 2 year mission to obtain a coordinated set of infrared spectroscopic observations over the 2.5 - 20 micron spectral range at a spectral resolution of R greater than 2500 of about 1500 galaxies, stars, planetary nebulae, young stellar objects, and solar system objects.

Ennico, Kimberly↗
NASA NTRS2004

Identifying Organic Molecules in Space: The AstroBiology Explorer (ABE) Mission Concept

The AstroBiology Explorer (ABE) mission concept consists of a dedicated space observatory having a 60 cm class primary mirror cooled to T < 50 K equipped with medium resolution cross-dispersed spectrometers having cooled large format near- and mid-infrared detector arrays. Such a system would be capable of addressing outstanding problems in Astrochemistry and Astrophysics that are particularly relevant to Astrobiology and addressable via astronomical observation. The mission s observational program would make fundamental scientific progress in establishing the nature, distribution, formation and evolution of organic and other molecular materials in the following extra-terrestrial environments: 1) The Outflow of Dying Stars, 2) The Diffuse Interstellar Medium, 3) Dense Molecular Clouds, Star Formation Regions, and Young StellarPlanetary Systems, 4) Planets, Satellites, and Small Bodies within the Solar System, and 5 ) The Interstellar Media of Other Galaxies. ABE could make fundamental progress in all of these areas by conducting a 1 to 2 year mission to obtain a coordinated set of infrared spectroscopic observations over the 2.5-20 micron spectral range at a spectral resolution of R > 2000 of about 1500 objects including galaxies, stars, planetary nebulae, young stellar objects, and solar system objects. Keywords: Astrobiology, infrared, Explorers, interstellar organics, telescope, spectrometer, space, infrared detectors

Ennico, K. A.↗
NASA NTRS2002

The AstroBiology Explorer (ABE) MIDEX Mission Concept: Using Infrared Spectroscopy to Identify Organic Molecules in Space

One of the principal means by which organic compounds are detected and identified in space is by infrared spectroscopy. Past IR telescopic and laboratory studies have shown that much of the carbon in the interstellar medium (ISM) is in complex organic species but the distribution, abundance and evolutionary relationships of these materials are not well understood. The Astrobiology Explorer (ABE) is a MIDEX mission concept designed to conduct IR spectroscopic observations to detect and identify these materials and address outstanding problems in astrobiology, astrochemistry, and astrophysics. ABE's core science program includes observations of planetary nebulae and stellar outflows, protostellar objects, Solar System objects, and galaxies, and lines of sight through dense molecular clouds and the diffuse ISM. ABE is a cryogenically-cooled 60 cm diameter space telescope equipped with 3 cross-dispersed R-2000 spectrometers that share a single common slit. Each spectrometer measures one spectral octave and together cover the entire 2.5-20 micron region simultaneously. The spectrometers use state-of-the-art InSb and Si:As 1024x1024 pixel detectors. ABE would operate in a heliocentric, Earth drift-away orbit and have a core science mission lasting approximately 1.5 years. ABE is currently under study at NASA's Ames Research Center in collaboration with Ball Aerospace and Technologies Corp.

Sandford, Scott A.↗