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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 NTRS2005

Organics in Meteorites, False Biomarkers, and the Search for Life in the Solar System

The tons of extraterrestrial organic material that come to the Earth every day probably helped to made the Earth habitable, and possibly played a role in the origin of life. At the astrochemistry lab (http://www.astrochem.org) we investigate the formation and distribution of organic molecules in space and consider the impact such molecules may have on the habitability of planets and the search for life in the Solar System. The organic compounds in meteorites include amino acids, aromatics of various sorts including purine and pyrimidine bases, and fatty acids that form bi-layer vesicles. The origin of many of these species remains mysterious, but in recent years we and others have performed experiments that suggest low temperature radiation chemistry could account for the presence and deuterium enrichment of many of these molecules.

Bernstein, Todd↗
NASA NTRS2005

Investigation of the Reactions and Distribution of Polycyclic Aromatic Hydrocarbons and Fullerenes in Extraterrestrial Material

The work funded by this research grant includes four specific projects: (1) Mapping the spatial distribution of polycyclic aromatic hydrocarbons (PAHs) in a variety of meteoritic samples and comparing this distribution with mineralogical features of the meteorite to determine whether a correlation exists between the two. (2) Developing a method for detection of fullerenes in extraterrestrial samples using microprobe laser-desorption laser-ionization mass spectrometry ( pL2MS) and utilizing this technique to investigate fullerene presence, while exploring the possibility of spatially mapping the fullerene distribution in these samples through in situ detection. (3) Investigating a possible formation pathway for meteoritic and ancient terrestrial kerogen involving the photochemical reactions of PAHs with alkanes under prebiotic and astrophysically relevant conditions. (4) Studying reaction pathways and identifying the photoproducts generated during the photochemical evolution of PAH-containing interstellar ice analogs as part of an ongoing collaboration with researchers at the Astrochemistry Lab at NASA Ames.

Zare, Richard N.↗
NASA NTRS2005

Spectroscopy of neutral and ionized PAHs. From laboratory studies to astronomical observations

Polycyclic Aromatic Hydrocarbons (PAHs) are an important and ubiquitous component of carbon-bearing materials in space. PAHs are the best-known candidates to account for the IR emission bands (UIR bands) and PAH spectral features are now being used as new probes of the ISM. PAHs are also thought to be among the carriers of the diffuse interstellar absorption bands (DIBs). In the model dealing with the interstellar spectral features, PAHs are present as a mixture of radicals, ions and neutral species. PAH ionization states reflect the ionization balance of the medium while PAH size, composition, and structure reflect the energetic and chemical history of the medium. A major challenge for laboratory astrochemistry is to reproduce (in a realistic way) the physical conditions that are associated with the emission and absorption interstellar zones. An extensive laboratory program has been developed at NASA Ames to assess the physical and chemical properties of PAHs in such environments and to describe how they influence the radiation and energy balance in space and the interstellar chemistry. PAHs, neutrals and ions, are expanded through a pulsed discharge nozzle (PDN) and probed with high-sensitivity cavity ringdown spectroscopy (CRDS). These laboratory experiments provide unique information on the spectra of free, cold large carbon molecules and ions in the gas phase from the ultraviolet and visible range to the near-infrared range. Intrinsic band profiles and band positions of cold gas-phase PAHs can now be measured with high-sensitivity spectroscopy and directly compared to the astronomical data. Preliminary conclusions from the comparison of the laboratory data with astronomical observations of interstellar and circumstellar environments will also be discussed.

Salama, Farid↗
NASA NTRS2005

Ice photochemistry as a source of amino acids and other organic molecules in meteorites, and implications for the origin of life and the search for life in the Solar System

The tons of extraterrestrial organic material that come to the Earth every day probably helped to made the Earth habitable, and possibly played a role in the origin of life. At the astrochemistry lab (http://www.astrochem.orq) we investigate the formation and distribution of organic molecules in space and consider the impact such molecules may have on the habitability of planets and the search for life in the Solar System. The organic compounds in meteorites include amino acids, aromatics of various sorts including purine and pyrimidine bases, and fatty acids that form bi-layer vesicles. The origin of many of these species remains mysterious, but in recent years we and others have performed experiments that suggest low temperature radiation chemistry could account for the presence and deuterium enrichment of many of these molecules. . I will present our laboratory experiments that show the viability of low temperature radiation chemistry as a source of organic molecules such as;amino acids (Nature, 2002, 416, 401-403), amphiphiles (Astrobiology, 2003, 2, 371, Proc. Nat. Acad. Sci. 2001, 98, 815), quinones (Science, 1999, 283, 1135) and other functionalized aromatic compounds (Meteoritics, 2001, 36, 351 ; Astrophysical Journal., 2003, 582, L25), some of which were invoked as potential biomarkers in the Alan Hills 84001 Martian meteorite. Understanding how components of proteins and DNA could form in sterile space environments is also of relevance to our search for life elsewhere in the Solar System, the great task now ahead of NASA. If we find evidence of Life elsewhere in the Solar System it will probably be in form of chemical biomarkers, quintessentially biological molecules that indicate the presence of micro-organisms. While most people think of molecules such as amino acids, and nucleo-bases as good candidate biomarkers, these molecules are produced non-biotically in space and are expected to be present on the surface of other planets even in the absence of Life. Understanding the range of non-biological organic molecules which could act as false biomarkers in space is a prerequisite for any reasonable search for Life on other worlds.

Bernstein, Max↗
NASA NTRS2006

Recent Selected Ion Flow Tube (SIFT) Studies Concerning the Formation of Amino Acids in the Gas Phase

Recently the simplest amino acid, glycine, has been detected in interstellar clouds, ISC, although this has since been contested. In order to substantiate either of these claims, plausible routes to amino acids need to be investigated. For gas phase synthesis, the SIFT technique has been employed to study simple amino acids via ion-molecule reactions of several ions of interstellar interest with methylamine, ethylamine, formic acid, acetic acid, and methyl formate. Carboxylic acid type ions were considered in the reactions involving the amines. In reactions where the carboxylic acid and methyl formate neutrals were studied, the reactant ions were primarily amine ion fragments. It was observed that the amines and acids preferentially fragment or accept a proton whenever energetically possible. NH3(+), however, uniquely reacted with the neutrals via atom abstraction to form NH4(+). These studies yielded a body of data relevant to astrochemistry, supplementing the available literature. However, the search for gas phase routes to amino acids using conventional molecules has been frustrated. Our most recent research investigates the fragmentation patterns of several amino acids and several possible routes have been suggested for future study.

Jackson, Douglas M.↗
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.↗
NASA NTRS2007

Quantum Chemical Evaluation of the Astrochemical Significance of Reactions between S Atom and Acetylene or Ethylene

Addition-elimination reactions of S atom in its P-3 ground state with acetylene (C2H2) and ethylene (C2H4) were characterized with both molecular orbital and density functional theory calculations employing correlation consistent basis sets in order to assess the likelihood either reaction might play a general role in astrochemistry or a specific role in the formation of S2 (X (sup 3 SIGMA (sub g) (sup -)) via a mechanism proposed by Saxena and Misra (Mon. Not. R. Astron. Soc. 1995, 272, 89). The acetylene and ethylene reactions proceed through C2H2S ((sup 3)A")) and C2H4S ((sup 3)A")) intermediates, respectively, to yield HCCS ((sup 2)II)) and C2H3S ((sup 2)A')). Substantial barriers were found in the exit channels for every combination of method and basis set considered in this work, which effectively precludes hydrogen elimination pathways for both S + C2H2 and S + C2H4 in the ultracold interstellar medium where only very modest barriers can be surmounted and processes without barriers tend to predominate. However, if one or both intermediates is formed and stabilized efficiently under cometary or dense interstellar cloud conditions, they could serve as temporary reservoirs for S atom and participate in reactions such as S + C2H2S (right arrow) S2 = C2H2 or S + C2H4S (right arrow) S2 + C2H4. For formation and stabilization to be efficient, the reaction must possess a barrier height small enough to be surmountable at low temperatures yet large enough to prevent redissociation to reactants. Barrier heights computed with B3LYP and large basis sets are very low, but more rigorous QCISD(T) and RCCSD(T) results indicate that the barrier heights are closer to 3-4 kcal/mol. The calculations therefore indicate that S + C2H2 or S + C2H4 could contribute to the formation of S2 in comets and may serve as a means to gauge coma temperature. The energetics of the ethylene reaction are more favorable.

Woon, David E.↗
NASA NTRS2010

Formation of Nucleobases from the UV Photo-Irradiation of Pyrimidine in Astrophysical Ice Analogs

Astrochemistry laboratory simulations have shown that complex organic molecules including compounds of astrobiological interest can be formed under interstellarl/circumstellar conditions from the vacuum UV irradiation of astrophysical ice analogs containing H2O, CO, CO2, CH3OH, NH13, etc. Of all prebiotic compounds, the formation of amino acids under such experimental conditions has been the most extensively studied. Although the presence of amino acids in the interstellar medium (ISM) has yet to be confirmed, they have been detected in meteorites, indicating that biomolecules and/or their precursors can be formed under extraterrestrial, abiotic conditions. Nucleobases, the building blocks of DNA and RNA, as well as other 1V-heterocycles, have also been detected in meteorites, but like amino acids, they have yet to be observed in the ISM. In this work, we present an experimental study of the formation of pyrimidine-based compounds from the UV photo-irradiation of pyrimidine in ice mixtures containing H2O, NH3, and/or CH3OH at low temperature and pressure.

Milam, S. N.↗
NASA NTRS2011

Planetary Geochemistry Techniques: Probing In-Situ with Neutron and Gamma Rays (PING) Instrument

The Probing In situ with Neutrons and Gamma rays (PING) instrument is a promising planetary science application of the active neutron-gamma ray technology so successfully used in oil field well logging and mineral exploration on Earth. The objective of our technology development program at NASA Goddard Space Flight Center's (NASA/GSFC) Astrochemistry Laboratory is to extend the application of neutron interrogation techniques to landed in situ planetary composition measurements by using a 14 MeV Pulsed Neutron Generator (PNG) combined with neutron and gamma ray detectors, to probe the surface and subsurface of planetary bodies without the need to drill. We are thus working to bring the PING instrument to the point where it can be flown on a variety of surface lander or rover missions to the Moon, Mars, Venus, asteroids, comets and the satellites of the outer planets.

Parsons, A.↗
NASA NTRS2010

Ultraviolet Irradiation of Pyrimidine in Interstellar Ice Analogs: Formation and Photo-Stability of Nucleobases

Astrochemistry laboratory experiments recently showed that molecules of prebiotic interest can potentially form in space, as supported by the detection of amino acids in organic residues formed by the UV photolysis of ices simulating interstellar and cometary environments (H2O, CO, CO2, CH3OH, NH3, etc.). Although the presence of amino acids in the interstellar medium (ISM) is still under debate, experiments and the detection of amino acids in meteorites both support a scenario in which prebiotic molecules could be of extraterrestrial origin, before they are delivered to planets by comets, asteroids, and interplanetary dust particles. Nucleobases, the informational subunits of DNA and RNA, have also been detected in meteorites, although they have not yet been observed in the ISM. Thus, these molecules constitute another family of prebiotic compounds that can possibly form via abiotical processes in astrophysical environments. Nucleobases are nitrogen-bearing cyclic aromatic species with various functional groups attached, which are divided into two classes: pyrimidines (uracil, cytosine, and thymine) and purines (adenine and guanine). In this work, we study how UV irradiation affects pyrimidine mixed in interstellar ice analogs (H2O, NH3, CH3OH). In particular, we show that the UV irradiation of H2O:pyrimidine mixtures leads to the production of oxidized compounds including uracil, and show that both uracil and cytosine are formed upon irradiation of H2O:NH3:pyrimidine mixtures. We also study the photostability of pyrimidine and its photoproducts formed during these experiments.

Nuevo, Michel↗
NASA NTRS2011

Astrobiology and the Chemistry of the Early Solar System

The field of astrochemistry investigates the origin of the chemicals necessary for the formation of life. Astrochemists use remote observations, laboratory simulations, and analysis of extraterrestrial samples to understand the inventory of pre biotic chemicals present on the early Earth. Among the problems investigated by astrochemists is the origin of homo chirality in terrestrial life. Analysis of meteorites shows that they may have delivered an excess of L-amino acids to the Earth's surface, perhaps leading to homochirality.

Cook, Jamie Elsila↗
NASA NTRS2012

The Atomic to Molecular Transition in the Interstellar Medium

Study of H2 in UV and IR continues to surprise us with complexity of excitation state, OPR, and role in astrochemistry. Atomic H in molecular clouds is a very powerful tool suggesting that they are not "young" but that it takes millions of years to convert primarily atomic hydrogen clouds to 99.9% molecular form. Laboratory data suggests that H2 formation is efficient over broader range of temperatures than thought to be the case a few years ago, but range is still limited. Issues of complex grain morphology and surface structure make this a very difficult field in which to obtain definitively meaningful results. Ongoing and future observations of CI and CII will improve our understanding of the structure of clouds, their total mass, and how they have evolved and will continue to do so.

interstellar medium↗
NASA NTRS2014

Cold Water Vapor in the Barnard 5 Molecular Cloud

After more than 30 yr of investigations, the nature of gas-grain interactions at low temperatures remains an unresolved issue in astrochemistry. Water ice is the dominant ice found in cold molecular clouds; however, there is only one region where cold ((is) approximately 10 K) water vapor has been detected-L1544. This study aims to shed light on ice desorption mechanisms under cold cloud conditions by expanding the sample. The clumpy distribution of methanol in dark clouds testifies to transient desorption processes at work-likely to also disrupt water ice mantles. Therefore, the Herschel HIFI instrument was used to search for cold water in a small sample of prominent methanol emission peaks. We report detections of the ground-state transition of o-H2O (J = 110-101) at 556.9360 GHz toward two positions in the cold molecular cloud, Barnard 5. The relative abundances of methanol and water gas support a desorption mechanism which disrupts the outer ice mantle layers, rather than causing complete mantle removal.

ISM: molecules↗
NASA NTRS2015

The Formation of Organic Compounds of Astrobiological Interest by the Irradiation Processing of Astrophysical Ices

Many environments in space contain very low temperature mixed molecular ices that are exposed to ionizing radiation in the form of cosmic rays and high-energy photons. While traditional chemistry would not be expected to occur at the temperatures typical of these ices (T < 50 K), ionizing radiation can break bonds in the original molecules in the ices to form highly reactive ions and radicals. These ions and radicals are subsequently free to react despite the low temperatures of the original ices. Laboratory experiments, many of them carried out at the Astrochemistry Laboratory at NASA-Ames, show that the irradiation of ices made of even simple molecules like H2O, CO, CO2, CH4, NH3, etc. can result in the robust formation of large numbers of far more complex organic compounds. Many of these new products are of direct interest to astrobiology. For example, the irradiation of mixed molecular ices has been shown to produce amino acids, amphiphiles, quinones, sugars, heterocyclic compounds, and nucleobases, all molecular building blocks used by terrestrial life. Insofar as the presence of these materials plays a role in the origin of life on planets, this has profound implications for the potential abundance of life in the universe since these experiments simulate universal conditions that are expected to be found wherever new stars and planets form.

Astrobiology↗
NASA NTRS2015

The Formation of N- and O-Heterocycles from the Irradiation of Benzene and Naphthalene in H2O/NH3- Containing Ices

Aromatic hydrocarbons are an important class of molecules for both astrochemistry and astrobiology (Fig. 1). Within this class of molecules, polycyclic aromatic hydrocarbons (PAHs) are known to be ubiquitous in many astrophysical environments, and are likely present in interstellar clouds and protostellar disks. In dense clouds, PAHs are expected to condense onto grains as part of mixed molecular ice mantles dominated by small molecules like H2O,CH3OH, NH3, CO, and CO2. These ices are exposed to ionizing radiation in the form of cosmic rays and ambient high-energy X-ray and UV photons.

Ice Irradiation↗
NASA NTRS2016

A Search for O2 in CO-Depleted Molecular Cloud Cores With Herschel

The general lack of molecular oxygen in molecular clouds is an outstanding problem in astrochemistry. Extensive searches with the Submillimeter Astronomical Satellite, Odin, and Herschel have only produced two detections; upper limits to the O2 abundance in the remaining sources observed are about 1000 times lower than predicted by chemical models. Previous atomic oxygen observations and inferences from observations of other molecules indicated that high abundances of O atoms might be present in dense cores exhibiting large amounts of CO depletion. Theoretical arguments concerning the oxygen gas-grain interaction in cold dense cores suggested that, if O atoms could survive in the gas after most of the rest of the heavy molecular material has frozen out onto dust, then O2 could be formed efficiently in the gas. Using Herschel HIFI, we searched a small sample of four depletion cores-L1544, L694-2, L429, and Oph D-for emission in the low excitation O2 N(sub J)=3(sub 3)-1(sub 2) line at 487.249 GHz. Molecular oxygen was not detected and we derive upper limits to its abundance in the range of N(O2)/N (H2) approx. = (0.6-1.6) x10(exp -7). We discuss the absence of O2 in the light of recent laboratory and observational studies.

ISM: abundances↗
NASA NTRS2017

Laboratory Investigations into the Spectra and Origin of Propylene Oxide: A Chiral Interstellar Molecule

Propylene oxide was recently identified in the interstellar medium, but few laboratory results are available for this molecule to guide current and future investigations. To address this situation, here we report infrared spectra, absorption coefficients, and band strengths of solid propylene oxide along with the first measurement of its refractive index and a calculation of its density, all for the amorphous solid form of the compound. We present the first experimental results showing a low-temperature formation pathway for propylene oxide near 10 K in interstellar ice analogs. Connections are drawn between our new results and the interstellar molecules propanal and acetone, and predictions are made about several as yet unobserved vinyl alcohols and methylketene. Comparisons are given to earlier laboratory work and a few applications to interstellar and solar system astrochemistry are described.

molecular processes↗