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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 91 records · Page 5
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NASA NTRS1976

Aliphatic amines in the Murchison meteorite

The paper reports on the determination of aliphatic amines in water extracts of the Murchison meteorite. The amines were analyzed by gas chromatography both as the free amines and as 2,4-dinitrophenyl (DNP) derivatives. The results give evidence for the presence of all of the possible primary aliphatic monoamines (eight) with fewer than five carbon atoms. Two of the seven possible secondary or tertiary aliphatic monoamines were identified. The identified primary amines total 80 nmol per g meteorite, and seem to be chemically or physically trapped in the meteorite. Similarities between the water-extractable amines and amino acids suggest that (1) a simple carbon compound, methane, for example, is the precursor of meteorite amines and amino acids, and (2) both amines and amino acids are extracted from the meteorite both as such and in the form of acid-hydrolyzable derivative or precursor species.

Jungclaus, G.↗
NASA NTRS1976

The mesosphere

The mesosphere is an atmospheric region characterized by a negative gradient of solar energy absorption and temperature. Although the distribution of most minor constituents is dominated by photochemistry, vertical transport does have a pronounced effect on many of them. The basic dynamic principles are discussed along with their application to the important mesospheric motions: acoustic-gravity waves, tides, planetary-scale waves, and eddy motions. Oxides of nitrogen and hydrogen are also examined which strongly influence the balance of odd oxygen (O and O3). Brief discussions of the chemistry of carbon compounds and of excited species are also included. The chemistry of ionic species in the mesosphere is very important because it strongly influences the propagation and absorption of radio waves. Because of ion clustering and negative-ion formation, such chemistry is extremely complex. The current state of knowledge is discussed in some detail. The principles involved in constructing models for predicting the distribution of minor constituents, both neutral and ionic, are presented.

Poppoff, I. G.↗
NASA NTRS1978

The evolution of the atmosphere of the earth

Computer simulations of the evolution of the earth's atmospheric composition and surface temperature have been carried out. The program took into account changes in the solar luminosity, variations in the earth's albedo, the greenhouse effect, variation in the biomass, and a variety of geochemical processes. Results indicate that prior to two billion years ago the earth had a partially reduced atmosphere, which included N2, CO2, reduced carbon compounds, some NH3, but no free H2. Surface temperatures were higher than now, due to a large greenhouse effect. When free O2 appeared the temperature fell sharply. Had earth been only slightly further from the sun, runaway glaciation would have occurred at that time. Simulations also indicate that a runaway greenhouse would have occurred early in earth's history had earth been only a few percent closer to the sun. It therefore appears that, taking into account the possibilities of either runaway glaciation or a runaway greenhouse effect, the continuously habitable zone about a solar-type star is rather narrow, extending only from roughly 0.95 to 1.01 AU.

Hart, M. H.↗
NASA NTRS1978

The biology instrument for the Viking Mars mission

Two Viking spacecraft have successfully soft landed on the surface of Mars. Each carries one biology laboratory with three different experiments designed to search for evidence of living microorganisms in material sampled from the Martian surface. This 15.5-kg biology instrument which occupies a volume of almost 28.3 dm is the first to carry out an in situ search for extraterrestrial life on a planet. The three experiments are called the pyrolytic release, labeled release, and gas exchange. The pyrolytic release experiment has the capability to measure the fixation of carbon dioxide or carbon monoxide into organic matter. The labeled release experiment detects metabolic processes by monitoring the production of volatile carbon compounds from a radioactively labeled nutrient mixture. The gas exchange experiment monitors the gas changes in the head space above a soil sample which is either incubated in a humid environment or supplied with a rich organic nutrient solution.

Brown, F. S.↗
NASA NTRS1979

An assessment of near-earth asteroid resources

On the basis of remote-sensing evidence and meteorite studies, a substantial fraction of small asteroids in near-earth space should contain abundant volatile (water, carbon, carbon compounds) and/or free metal (nickel-iron) materials. Although there are only about 40 known earth-approaching asteroids, this number could be increased by at least an order of magnitude in a few years by a dedicated search program with a large telescope (48 in. Schmidt). A discovery rate of 20 objects/yr could be expected from a facility costing about $3 million to establish. Relatively high-resolution, broad-wavelength coverage reflectance spectra could be made for many of these objects with a large telescope and instruments under development. Such spectra are necessary for detailed mineralogic, characterizations of these asteroids. Low-resolution survey survey spectra with similar wavelength coverage (UBVRIJHK filters) would provide useful characterizations of fainter objects.

Gaffey, M. J.↗
NASA NTRS1981

Observing chemical abundances in comets

The atomic resonance lines of the major elements were observed in the atmospheres of a few comets, by using vacuum ultraviolet spectrographs on board rockets or orbiting observatories. Dust-to-gas ratios were also deduced for two comets through a Finson-Probstein's analysis of their dust-tail isophotes. The geometric albedo of the dust for the phase angle alpha of the observations is not accurately known but, the dust-to-gas ratio is not overly sensitive to the actual value of this albedo. Infrared observations of the dust head of some comets show that the bulk of cometary dust must be silicates, although a minor component (5-10 percent) of carbon compounds is rather likely, because of poor dielectric properties of the grains. This interpretation is confirmed by the fact that interplanetary dust probably of cometary origin, that was collected in the stratosphere by NASA-U2 Spacecraft, is chondritic in nature. Metal abundances in the head of a sungrazing comet support the chondritic hypothesis.

Delsemme, A. H.↗
NASA NTRS1982

Photochemistry of NH3, CH4 and PH3 - Possible applications to the Jovian planets

It is found that the photolysis of NH4 at 185 nm in the presence of a two-fold excess of CH4 results in the loss of about 0.25 mole of CH4 per mole of NH3 decomposed. The loss is shown to arise from the abstraction of hydrogen atoms from CH4 by photolytically generated hot hydrogen atoms. It is concluded that NH3 photolysis in the H2-abundant atmosphere of Jupiter is not responsible for the presence of the carbon compounds observed there, such as ethane, acetylene, and hydrogen cyanide, but may have had a role in the early atmosphere of Titan. Also, it is found that the photolysis of PH3 with a 206 nm light source gives P2H4, which in turn is converted to a red-brown solid. The course of the photolysis is not changed appreciably when the temperature is lowered to 157 K except that the concentration of P2H4 increases, while the presence of H2 has no effect on the P2H4 yield. Photolysis of 9:1 NH3:PH3 is found to give a rate of decomposition of PH3 that is comparable with that observed by the direct photolysis of PH3 and comparable amounts of the red-brown solid and P2H4 are observed. In addition, the implications of these results for the structures of the compounds responsible for the wide array of colors observed in the atmosphere of Jupiter are examined.

Ferris, J. P.↗
NASA NTRS1983

Chemical evolution and the origin of life

A review is presented of recent advances made in the understanding of the formation of carbon compounds in the universe and the occurrence of processes of chemical evolution. Topics discussed include the principle of evolutionary continuity, evolution as a fundamental principle of the physical universe, the nuclear synthesis of biogenic elements, organic cosmochemistry and interstellar molecules, the solar nebula and the solar system in chemical evolution, the giant planets and Titan in chemical evolution, and comets and their interaction with the earth. Also examined are carbonaceous chondrites, environment of the primitive earth, energy sources available on the primitive earth, the synthesis of biochemical monomers and oligomers, the abiotic transcription of nucleotides, unified prebiotic and enzymatic mechanisms, phospholipids and membranes, and protobiological evolution.

Oro, J.↗
NASA NTRS1986

Radioactivities in returned lunar materials and in meteorites

A preliminary C-14 study on lunar soil was carried out with the University of Toronto Iso Trace accelerator mass spectrometer. This accelerator was recommended for C-14 work by Dr. R. Schneider of A.S. and E., who was the field engineer during the assemblage and start-up operation of the accelerator. After the preliminary study using CO2 from 10084,937 soil, which had previously been counted with low-level mini-proportional counters, it became clear that the Toronto accelerator could carry out C-14/C-13/C-12 ratio measurements on 1 gram meteorite and lunar samples and that the C-14 measurements are done with higher precision and better reliability than elsewhere. A collaborative program with the University of Toronto Iso Trace accelerator group, which is expected to be scientifically fruitful. Arrangements have been made for Dr. R.P. Beukens of the Toronto Accelerator Group to extract the carbon compounds from Antarctic meteorite and lunar samples and to convert the compounds to CO2. During the past two years, a uranium-series dating method was developed for polar ice, which method is being applied to ice from the Allan Hills site, Byrd core, and the Beardsmore glacier.

Fireman, E. L.↗
NASA NTRS1989

Chemical evolution: A solar system perspective

During the last three decades major advances were made in the understanding of the formation of carbon compounds in the universe and of the occurrence of processes of chemical evolution in the solar system and beyond. This was made possible by the development of new astronomical techniques and by the exploration of the solar system by means of properly instrumented spacecraft. Some of the major findings made as a result of these observations are summarized.

Oro, J.↗
NASA NTRS1988

Carbon recycling in materially closed ecological life support systems

Results of studies are presented of materially closed energetically open microbial ecosystems or 'closed ecosystems'. These are natural marine ecosystems that have been sealed in glass containers to prevent material exchange with the environment but allow energy to pass freely through them. They represent model life support systems for the future human habitation of space. The results are discussed analytically and indicate that these ecosystems, when subjected to a constant energy flux, seem to be reliable and self-sufficient systems for recycling of biologically produced carbon compounds.

Obenhuber, D. C.↗
NASA NTRS1989

Vega-Giotto flyby missions and cometary cosmogony

The most important implication of the Vega/Giotto flyby missions to Halley's Comet for cometary cosmogony is the opportunity to absorb the results of the in-situ measurements as made onboard the spacecrafts. Unfortunately the exploration of ejecta form the nucleus was unable to provide an unambiguous definition of the chemical-mineralogical nature of the nucleus: it failed to provide information comparable to that which was expected from a sample return mission. However, the obtained results are significant enough to affect and redirect cosmogonical thinking. Accordingly, the understanding of the cometary-matter dichotomy is modified as deduced from the distiction of water-dominated volitiles and silicate-based non-volitiles. Organic carbon compounds emerge as a major constituent of cometary nuclei. Presently, it is likely that the revision of Whipple's classic concept of the icy conglomerate cannot be avoided. Affected by the Vega/Giotto flyby missions to Hally's Comet, cometary cosmogony seems to enter a new conceptual period. The results of the in-situ measurements (mass spectrometric, UV spectroscopic, and IR spectroscopic) appear to be of basic importance. A chemical explanation is employed to explain the occurrence inside the nuclei of the variety of species, as inferred from the mass spectrometric data, to predict the results of the processes possibly involved. A cosmochemical factor is postulated to operate behind the observed cometary phenomena. The chemistry of the interstellar medium, covering the circumstellar and interstellar dust, advances cometary cosmogony.

Lang, Bruno↗
NASA NTRS1991

Characterization of low albedo asteroids

Three asteroid classes were defined from the early spectral surveys of the asteroids: C for carbonaceous, M for metallic, and S for stony. Subsequent spectral studies have defined new asteroid classes and have shown that the original classes can be divided into a number of additional asteroid types. The low albedo asteroids are now classified as types B, C, D, F, G, K and P. These types are concentrated in the middle asteroid belt and beyond. Their visible and near infrared spectra are generally featureless and dark, with a red slope in the ultraviolet. Some of them show water absorption features in the mid-infrared, indicating the presence of bound water. The lack of absorption features in the telescopic reflectance spectra has made it difficult to determine the mineralogy of the low albedo asteroids. Some of the asteroid spectra closely resemble laboratory spectra of carbonaceous chondrite meteorites, implying similar mineralogy. These meteorites are chemically primitive, composed of fine-grained matrix material which includes hydrous silicates, complex carbon compounds, olivine and pyroxene, combined with olivine and/or pyroxene chondrules. The main belt low albedo asteroids are probably very similar to these asteroids, but no meteoritic analogues exist for the most distant asteroid types.

Lebofsky, Larry A.↗
NASA NTRS1991

The states of carbon and nitrogen atoms after photodissociation of CN, CH, CH(+), C2, C3, and CO in comets

The photodissociation of carbon compounds by solar UV radiation at a heliocentric distance of 1 AU is examined, comparing published observational data with the predictions of theoretical models and results from laboratory experiments. It is shown that species other than CO, including CN, CH, CH(+), C2, and C3, can contribute to the observed brightness of the VUV lines of C I (156.1, 165.7, and 193.1 nm) and C II (133.5 nm) in comet comae. CN photodissociation is also found to produce metastable 2D0 and 2P0 N I atoms, possibly leading (at heliocentric distances less than 0.25 AU) to 143.9-nm emission via resonance fluorescence.

Singh, P. D.↗
NASA NTRS1991

Photochemical reactions of cyanoacetylene and dicyanoacetylene: Possible processes in Titan's atmosphere

Titan has an atmosphere which is subject to dramatic chemical evolution due mainly to the dramatic effect of the UV flux from the Sun. The energetic solar photons and other particles are converting the methane-nitrogen atmosphere into the unsaturated carbon compounds observed by the Voyager probes. These same solar photons are also converting some of these unsaturated reaction products into the aerosols observed in the atmosphere which obscure the view of the surface of Titan. In particular, the photochemical reactions of cyanoacetylene, dicyanoacetylene, acetylene and ethylene may result in the formation of the higher hydrocarbons and polymers which result in the aerosols observed in Titan's atmosphere. Polymers are the principal reaction products formed by irradiation of cyanoacetylene and dicyanoacetylene. Irradiation of cyanoacetylene with 185 nm of light also yields 1,3,5-tricyanobenzene while irradiation at 254 nm yields 1,2,4-tricyanobenzene and tetracyano cyclooctatetraenes. Photolyses of mixtures of cyanoacetylene and acetylene yields mono- and di- cyanobenzenes. The 1-Cyanocyclobutene is formed from the photochemical addition of cyanoacetylene with ethylene. The photolysis of dicyanoacetylene with acetylene yields 2,3-dicyano-1,3-butadiene and 1,2-dicyanobenzene. Tetracyano cyclooctatetraene products were also observed in the photolysis of mixtures of dicyanoacetylene and acetylene with 254 nm light. The 1,2-Dicyano cyclobutene is obtained from the photolysis dicyanoacetylene and ethylene. Reaction mechanisms will be proposed to explain the observed photoproducts.

Ferris, J. P.↗
NASA NTRS1993

Theoretical calculations on the electron absorption spectra of selected Polycyclic Aromatic Hydrocarbons (PAH) and derivatives

As a theoretical component of the joint effort with the laboratory of Dr. Lou Allamandola to search for potential candidates for interstellar organic carbon compound that are responsible for the visible diffuse interstellar absorption bands (DIB's), quantum mechanical calculations were performed on the electron absorption spectra of selected polycyclic aromatic hydrocarbons (PAH) and derivatives. In the completed project, 15 different species of naphthalene, its hydrogen abstraction and addition derivatives, and corresponding cations and anions were studied. Using semiempirical quantum mechanical method INDO/S, the ground electronic state of each species was evaluated with restricted Hartree-Fock scheme and limited configuration interaction. The lowest energy spin state for each species was used for electron absorption calculations. Results indicate that these calculations are accurate enough to reproduce the spectra of naphthalene cation and anion observed in neon matrix. The spectral pattern of the hydrogen abstraction and addition derivatives predicted based on these results indicate that the electron configuration of the pi orbitals of these species is the dominant determinant. A combined list of 19 absorptions calculated from 4500 A to 10,400 A were compiled and suggested as potential candidates that are relevant for the DIB's absorptions. Continued studies on pyrene and derivatives revealed the ground state symmetries and multiplicities of its neutral, anionic, and cationic species. Spectral calculations show that the cation (B(sub 3g)-2) and the anion (A(sub u)-2) are more likely to have low energy absorptions in the regions between 10 kK and 20 kK, similar to naphthalene. These absorptions, together with those to be determined from the hydrogen abstraction and addition derivatives of pyrene, can be used to provide additional candidates and suggest experimental work in the search for interstellar compounds that are responsible for DIB's.

Du, Ping↗
NASA NTRS1994

The Diffuse Interstellar Bands: Contributed papers

Drawing a coherent picture of the observational characteristics of the Diffuse Interstellar Bands (DIB's) and the physical and chemical properties of its proposed carriers was the focus of this NASA sponsored conference. Information relating to absoption spectra, diffuse radiation carriers, carbon compounds, stellar composition, and interstellar extinction involving T-Tauri stars, Reflection Nebulae, Red Giants, and accretion discs are discussed from those papers presented at the conference, which are included in this analytic.

Tielens, Alexander G. G. M.↗
NASA NTRS1999

Synthesis of Large Molecules in Cometary Ice Analogs: Physical Properties Related to Self-Assembly Processes

The combination of realistic laboratory simulations and infrared observations have revolutionized our understanding of interstellar dust and ice-the main component of comets. Since comets and carbonaceous micrometeorites may have been important sources of volatiles and carbon compounds on the early Earth, their organic composition may be related to the origin of life. Ices on grains in molecular clouds contain a variety of simple molecules. The D/H ratios of the comets Hale-Bopp and Hyakutake are consistent with a primarily interstellar ice mixture. Within the cloud and especially in the presolar nebula through the early solar system, these icy grains would have been photoprocessed by the ultraviolet producing more complex species such as hexamethylenetetramine, polyoxymethylenes, and simple keones. We reported at the 1999 Bioastronomy meeting laboratory simulations studied to identify the types of molecules which could have been generated in pre-cometary ices. Experiments were conducted by forming a realistic interstellar mixed-molecular ice (H2O, CH3OH, NH3 and CO) at approximately 10 K under high vacuum irradiated with UV light from a hydrogen plasma lamp. The gas mixture was typically 100:50:1:1, however when different ratios were used material with similar characteristics was still produced. The residue that remained after warming to room temperature was analyzed by HPLC, and by several mass spectrometric methods. This material contains a rich mixture of complex compounds with mass spectral profiles resembling those found in IDPs and meteorites. Surface tension measurements show that an amphiphilic component is also present. These species do not appear in various controls or in unphotolyzed samples. Residues from the simulations were also dispersed in aqueous media for microscopy. The organic material forms 10-40 gm diameter droplets that fluoresce at 300-450 nm under UV excitation. These droplets have a morphology and internal structure which appear strikingly similar to those produced by extracts of the Murchison meteorite. Together, these results suggest a link between organic material photochemically synthesized on the cold grains in dense, interstellar molecular clouds and compounds that may have contributed to the organic inventory of the primitive Earth. For example, the amphiphilic properties of such compounds permit self-assembly into the membranous boundary structures that required for the first forms of cellular life.

Dworkin, Jason P.↗