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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
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 NTRS1977

Bioorganic chemistry and the emergence of the first cell

It is suggested that the best way to study the evolution of cells from primordial compounds is to attempt to assemble a protocell, i.e., a primordial cell. Simulation of processes that occurred in archaic times would require inductive reasoning and constructionist techniques rather than the analytic approach in which cell components are separated and studied in isolation. Advantages to primordial life which would result from protocell formation are surveyed, and the proteinoid microsphere, a model of the protocell, is discussed. A photoreactive proteinoid is considered.

Fox, S. W.↗
NASA NTRS1981

Possible role of phosphine in chemical evolution

Experiments simulating the formation of organic molecules in model reducing atmospheres including phosphine show that a variety of organic molecules can be synthesized. From the experiments using UV light as an energy source, it appears that the presence of phosphine drastically increases the yield of photolysis of methane and, thus, the yield of the formation of organic matter. The presence of phosphine enhances the formation of organophosphorous compounds, such as methyl and dimethylphosphine.

Raulin, F.↗
NASA NTRS1992

Origin and evolution of planetary atmospheres

This report concerns several research tasks related to the origin and evolution of planetary atmospheres and the large-scale distribution of volatile elements in the Solar System. These tasks and their present status are as follows: (1) we have conducted an analysis of the volatility and condensation behavior of compounds of iron, aluminum, and phosphorus in the atmosphere of Venus in response to publish interpretations of the Soviet Venera probe XRF experiment data, to investigate the chemistry of volcanic gases, injection of volatiles by cometary and asteroidal impactors, and reactions in the troposphere; (2) we have completed and are now writing up our research on condensation-accretion modeling of the terrestrial planets; (3) we have laid the groundwork for a detailed study of the effects of water transport in the solar nebula on the bulk composition, oxidation state, and volatile content of preplanetary solids; (4) we have completed an extensive laboratory study of cryovolcanic materials in the outer solar system; (5) we have begun to study the impact erosion and shock alteration of the atmosphere of Mars resulting from cometary and asteroidal bombardment; and (6) we have developed a new Monte Carlo model of the cometary and asteroidal bombardment flux on the terrestrial planets, including all relevant chemical and physical processes associated with atmospheric entry and impact, to assess both the hazards posed by this bombardment to life on Earth and the degree of cross-correlation between the various phenomena (NO(x) production, explosive yield, crater production, iridium signature, etc.) that characterize this bombardment. The purpose of these investigations has been to contribute to the developing understanding of both the dynamics of long-term planetary atmosphere evolution and the short-term stability of planetary surface environments.

Lewis, John S.↗
NASA NTRS2010

Depth Dose Distribution Study within a Phantom Torso after Irradiation with a Simulated Solar Particle Event at NSRL

The adequate knowledge of the radiation environment and the doses incurred during a space mission is essential for estimating an astronaut's health risk. The space radiation environment is complex and variable, and exposures inside the spacecraft and the astronaut's body are compounded by the interactions of the primary particles with the atoms of the structural materials and with the body itself Astronauts' radiation exposures are measured by means of personal dosimetry, but there remains substantial uncertainty associated with the computational extrapolation of skin dose to organ dose, which can lead to over- or underestimation of the health risk. Comparisons of models to data showed that the astronaut's Effective dose (E) can be predicted to within about a +10% accuracy using space radiation transport models for galactic cosmic rays (GCR) and trapped radiation behind shielding. However for solar particle event (SPE) with steep energy spectra and for extra-vehicular activities on the surface of the moon where only tissue shielding is present, transport models predict that there are large differences in model assumptions in projecting organ doses. Therefore experimental verification of SPE induced organ doses may be crucial for the design of lunar missions. In the research experiment "Depth dose distribution study within a phantom torso" at the NASA Space Radiation Laboratory (NSRL) at BNL, Brookhaven, USA the large 1972 SPE spectrum was simulated using seven different proton energies from 50 up to 450 MeV. A phantom torso constructed of natural bones and realistic distributions of human tissue equivalent materials, which is comparable to the torso of the MATROSHKA phantom currently on the ISS, was equipped with a comprehensive set of thermoluminescence detectors and human cells. The detectors are applied to assess the depth dose distribution and radiation transport codes (e.g. GEANT4) are used to assess the radiation field and interactions of the radiation field with the phantom torso. Lymphocyte cells are strategically embedded at selected locations at the skin and internal organs and are processed after irradiation to assess the effects of shielding on the yield of chromosome damage. The initial focus of the present experiment is to correlate biological results with physical dosimetry measurements in the phantom torso. Further on, the results of the passive dosimetry within the anthropomorphic phantoms represent the best tool to generate reliable data to benchmark computational radiation transport models in a radiation field of interest. The presentation will give first results of the physical dose distribution, the comparison with GEANT4 computer simulations based on a Voxel model of the phantom, and a comparison with the data from the chromosome aberration study.

Berger, Thomas↗
NASA NTRS2011

Composition of LHB Comets and Their Influence on the Early Earth Atmosphere Composition

Two main processes were responsible for the composition of this atmosphere: chemical evolution of the volatile fraction of the accretion material forming the planet and the delivery of gasses to the planetary surface by impactors during the late heavy bombardment (LHB). The amount and composition of the volatile fraction influences the outgassing of the Earth mantle during the last planetary formation period. A very weakened form of outgassing activity can still be observed today by examining the composition of volcanic gasses. An enlightenment of the second process is based on the sparse records of the LHB impactors resulting from the composition of meteorites, observed cometary comas, and the impact material found on the Moon. However, for an assessment of the influence of the outgassing on the one hand and the LHB event on the other, one has to supplement the observations with numerical simulations of the formation of volatiles and their incorporation into the accretion material which is the precursors of planetary matter, comets and asteroids. These simulations are performed with a combined hydrodynamic-chemical model of the solar nebula (SN). We calculate the chemical composition of the gas and dust phase of the SN. From these data, we draw conclusions on the upper limits of the water content and the amount of carbon and nitrogen rich volatiles incorporated later into the accretion material. Knowing these limits we determine the portion of major gas compounds delivered during the LHB and compare it with the related quantities of the outgassed species.

Tornow, C.↗
NASA NTRS2013

1,2-Dichlorohexafluoro-Cyclobutane (1,2-c-C4F6Cl2, R-316c) a Potent Ozone Depleting Substance and Greenhouse Gas: Atmospheric Loss Processes, Lifetimes, and Ozone Depletion and Global Warming Potentials for the (E) and (Z) stereoisomers

The atmospheric processing of (E)- and (Z)-1,2-dichlorohexafluorocyclobutane (1,2-c-C4F6Cl2, R-316c) was examined in this work as the ozone depleting (ODP) and global warming (GWP) potentials of this proposed replacement compound are presently unknown. The predominant atmospheric loss processes and infrared absorption spectra of the R-316c isomers were measured to provide a basis to evaluate their atmospheric lifetimes and, thus, ODPs and GWPs. UV absorption spectra were measured between 184.95 to 230 nm at temperatures between 214 and 296 K and a parametrization for use in atmospheric modeling is presented. The Cl atom quantum yield in the 193 nm photolysis of R- 316c was measured to be 1.90 +/- 0.27. Hexafluorocyclobutene (c-C4F6) was determined to be a photolysis co-product with molar yields of 0.7 and 1.0 (+/-10%) for (E)- and (Z)-R-316c, respectively. The 296 K total rate coefficient for the O(1D) + R-316c reaction, i.e., O(1D) loss, was measured to be (1.56 +/- 0.11) × 10(exp −10)cu cm/ molecule/s and the reactive rate coefficient, i.e., R-316c loss, was measured to be (1.36 +/- 0.20) × 10(exp −10)cu cm/molecule/s corresponding to a approx. 88% reactive yield. Rate coefficient upper-limits for the OH and O3 reaction with R-316c were determined to be <2.3 × 10(exp −17) and <2.0 × 10(exp −22)cu cm/molecule/s, respectively, at 296 K. The quoted uncertainty limits are 2(sigma) and include estimated systematic errors. Local and global annually averaged lifetimes for the (E)- and (Z)-R-316c isomers were calculated using a 2-D atmospheric model to be 74.6 +/- 3 and 114.1 +/-10 years, respectively, where the estimated uncertainties are due solely to the uncertainty in the UV absorption spectra. Stratospheric photolysis is the predominant atmospheric loss process for both isomers with the O(1D) reaction making a minor, approx. 2% for the (E) isomer and 7% for the (Z) isomer, contribution to the total atmospheric loss. Ozone depletion potentials for (E)- and (Z)-R-316c were calculated using the 2-D model to be 0.46 and 0.54, respectively. Infrared absorption spectra for (E)- and (Z)-R-316c were measured at 296 K and used to estimate their radiative efficiencies (REs) and GWPs; 100-year time-horizon GWPs of 4160 and 5400 were obtained for (E)- and (Z)-R-316c, respectively. Both isomers of R-316c are shown in this work to be long-lived ozone depleting substances and potent greenhouse gases.

UV cross section↗
NASA NTRSDate not supplied

The Impact of Atmospheric Dynamics and Anthropogenic Very Short-Lived Chlorine Species on the Recovery of Extra-Polar Ozone

The successful implementation of the Montreal Protocol has led to a decrease in the atmospheric abundance of ozone-depleting substances and a slowing in the destruction of the ozone layer. Previous studies have suggested that atmospheric dynamics, or a rise in compounds not regulated by the Montreal Protocol, such as very short-lived chlorine species (VSL Cl), may lead to a slower than expected recovery of the ozone layer. In this presentation, we examine the expected recovery of total column ozone (TCO) and stratospheric column ozone (SCO) to values observed in 1980 using a novel multiple linear regression (MLR) model that involves a month-by-month regression. The MLR model is trained to TCO anomalies from six data records (SBUV v8.7 MOD, SBUV v8.6 COH, WOUDC, GSG, GTO-ECV, MSR-2) over 1979 to 2021 for the Northern Hemisphere (35N – 60N), the Southern Hemisphere (60S – 35S) and the Tropics (20S – 20N), and SCO anomalies from ML-TOMCAT for these same zonal bands. The MLR includes the effect of halogens (equivalent effective stratospheric chlorine (EESC)), total solar irradiance, stratospheric aerosol optical depth, quasi-biennial oscillation, and the El Niño Southern Oscillation as regressors. We also include the effect of atmospheric dynamics such as the Brewer-Dobson Circulation, Arctic Oscillation, and the Antarctic Oscillation, and VSL Cl species in the formulation of EESC. We use a novel approach to the MLR framework, by separating the observed and regressor time series into the respective months (separating all of the Januarys, Februarys, etc.). Then we conduct a regression for each month from 1979 to 2021 for the three zonal bands denoted above. The model results for each month are combined together to achieve a full monthly time series from 1979 to 2021. We use this novel approach to ascertain the effect of atmospheric dynamics on TCO and SCO, since the dynamical proxies affect ozone in a distinctly different manner for various months. In this presentation, we will quantify the role of both the inclusion of VSL Cl species in the formulation of EESC as well as atmospheric dynamics in explaining the slower than expected recovery of extra-polar TCO and SCO over the past decade.

Laura A. McBride↗
NASA NTRS1973

Composition and dynamics of lunar atmosphere

The model of lunar atmosphere is updated to take into account new information on the dynamics and amounts of H2, He-4, Ne-20, Ar-36, and Ar-40. Helium and neon appear to be in close balance with the solar wind, although Ar-36 is depleted in the atmosphere, suggesting that surface materials are not saturated with argon. Atmospheric carbon compounds, which should result from the solar wind influx of carbon, remain undetected, as do nitrogen compounds. However, evidence of a volcanic gas release is presented, which suggests the transient presence of these elements.

Hodges, R. R., Jr.↗
NASA NTRS1989

Observational astrochemistry - Recent results

More than 80 molecular species have now been observed in the dense interstellar clouds where stars and planets form or in the envelopes expelled by evolved stars. Elemental constituents of these compounds include all of the biogenic elements, H, C, N, O, S and P. In addition, Si is found in several molecules, and a series of metal halides have recently been detected in the outflowing envelope of a nearby carbon star. Knowledge of the chemical reservoirs for the major volatile elements and a comparison between observed molecular abundances and theoretical models are both discussed.

Irvine, W. M.↗
NASA NTRS1991

AIAA/IKI Microgravity Science Symposium, 1st, Moscow, USSR, May 13-17, 1991, Proceedings

The state of the art of microgravity science is examined in reviews and reports. Consideration is given to fluid physics; modeling and numerical analysis; crystal growth of electronic materials, proteins, metals, alloys, glasses, and ceramics; biotechnology, combustion science, microgravity hardware, and fundamental phenomena; and education. Particular attention is given to containerless science and technology, a low-gravity two-phase flow with heat transfer, numerical investigation on Benard instability in a finite liquid layer, synthesis and crystallization of refractory compounds from solutions in metallic melts under microgravitation conditions, the long duration protein crystallization experiment aboard the Mir Space Station, directional solidification in immiscible systems, formation of periodic layer structure in oxide melts under different gravity values, opposed flow flame spread in normal, enhanced, and reduced gravity, automatic equipment for semiconductor production in space, and consort and joust sounding rocket missions.

Source record↗
NASA NTRS2000

The Composition of Organics and Volatiles in the Interstellar Medium

Tremendous progress has been made in our understanding of the composition of interstellar dust through the combined use of telescopic observations, theoretical models, laboratory studies of analogs, and the analysis of interstellar samples found in meteorites. It is increasingly clear that the interstellar medium (ISM) contains an enormous diversity of materials created by a wide range of chemical and physical processes. This paper reviews some of our current knowledge of the organic and volatile materials thought to exist in the ISM. These compounds supply a significant portion of the material that makes up the interstellar dense molecular clouds from which new stars and planetary systems are formed, and thus represents an important reservoir of material that could play key roles in the formation and evolution of life. This paper will largely focus on solid materials, as opposed to gases, since solids contain a major fraction of the heavier elements in clouds and because solids are most likely to survive incorporation into new planetary systems in identifiable form. The paper concludes with a brief discussion of the astrobiological relevance of some of the compounds now known or suspected to be present in the ISM.

Sandford, Scott A.↗
NASA NTRS2003

Understanding Organics in Meteorites and the Pre-Biotic Environment

(1) Refinement of the analytic capabilities of our experiment via characterization of molecule-specific response and the effects upon analysis of the type of sample under investigation; (2) Measurement of polycyclic aromatic hydrocarbons (PAHs) with high sensitivity and spatial resolution within extraterrestrial samples; (3) Investigation of the interstellar reactions of PAHs via the analysis of species formed in systems modeling dust grains and ices; (4) Investigations into the potential role of PAHs in prebiotic and early biotic chemistry via photoreactions of PAHs under simulated prebiotic Earth conditions. To meet these objectives, we use microprobe laser-desorption, laser-ionization mass spectrometry (MuL(exp 2)MS), which is a sensitive, selective, and spatially resolved technique for detection of aromatic compounds. Appendix A presents a description of the MuL(exp 2)MS technique. The initial grant proposal was for a three-year funding period, while the award was given for a one-year interim period. Because of this change in time period, emphasis was shifted from the first research goal, which was more development-oriented, in order to focus more on the other analysis-oriented goals. The progress made on each of the four research areas is given below.

Zare, Richard N.↗
NASA NTRS2019

Land–Atmosphere Feedbacks Exacerbate Concurrent Soil Drought and Atmospheric Aridity

Compound extremes such as cooccurring soil drought (low soil moisture) and atmospheric aridity (high vapor pressure deficit) can be disastrous for natural and societal systems. Soil drought and atmospheric aridity are 2 main physiological stressors driving widespread vegetation mortality and reduced terrestrial carbon uptake. Here, we empirically demonstrate that strong negative coupling between soil moisture and vapor pressure deficit occurs globally, indicating high probability of cooccurring soil drought and atmospheric aridity. Using the Global Land Atmosphere Coupling Experiment (GLACE)-CMIP5 experiment, we further show that concurrent soil drought and atmospheric aridity are greatly exacerbated by land– atmosphere feedbacks. The feedback of soil drought on the atmosphere is largely responsible for enabling atmospheric aridity extremes. In addition, the soil moisture–precipitation feedback acts to amplify precipitation and soil moisture deficits in most regions. CMIP5 models further show that the frequency of concurrent soil drought and atmospheric aridity enhanced by land–atmosphere feedbacks is projected to increase in the 21st century. Importantly, land– atmosphere feedbacks will greatly increase the intensity of both soil drought and atmospheric aridity beyond that expected from changes in mean climate alone.

Compound extreme events↗
NASA NTRS1985

Biologically produced volatile compounds: N2O emissions from soils

Tropospheric nitrous concentration has increased by 0.2 0.4% per year over the period 1975 to 1982, amounting to net addition to the atmosphere of 2.8 - 5.6 Tg N2O-N per year. This perturbation, if continued into the future, will affect stratospheric chemical cycles, and the thermal balance of the Earth. In turn it will have direct and indirect global effects on the biosphere. Though the budget and cycles of N2O on Earth are not yet fully resolved, accumulating information and recent modelling efforts permit a more complete evaluation and better definition of gaps in our knowledge.

Banin, A.↗
NASA NTRS1979

Applications of Modern Hydrodynamics to Aeronautics. Part 1: Fundamental Concepts and the Most Important Theorems. Part 2: Applications

A discussion of the principles of hydrodynamics of nonviscous fluids in the case of motion of solid bodies in a fluid is presented. Formulae are derived to demonstrate the transition from the fluid surface to a corresponding 'control surface'. The external forces are compounded of the fluid pressures on the control surface and the forces which are exercised on the fluid by any solid bodies which may be inside of the control surfaces. Illustrations of these formulae as applied to the acquisition of transformations from a known simple flow to new types of flow for other boundaries are given. Theoretical and experimental investigations of models of airship bodies are presented.

Prandtl, L.↗
NASA NTRS1979

The elemental and isotopic abundances of H, C, N, O in comets

The elemental abundances of light elements in comets is discussed by considering gas and dust separately. It is noted that the icy conglomerate model of the nucleus (Whipple, 1957) has been confirmed, and that the dust-to-gas mass ratio has been estimated within a factor of two for two recent comets. It is found that the total amount of oxygen available is also nominally in solar abundance; this implies that the oxygen of the solar nebula has probably been quantitatively bound in compounds that have been completely condensed and accreted in cometary nuclei. In addition, the amount of hydrogen is clearly depleted by a factor of 2,000, suggesting that the only hydrogen present is that linked in molecular compounds of H, C, N and O.

Delsemme, A. H.↗
NASA NTRSDate not supplied

Atmospheric Formaldehyde Trend and Its Source Attributions in the Recent Decades

Formaldehyde (CH 2 O) is one of the most important reactive trace gases in the atmosphere with an important role in tropospheric chemistry and in the control of surface air quality. Sources of CH 2 O includes direct emissions and in situ production from the oxidation of volatile organic compounds (VOCs). In this study, we investigate spatial-temporal variations in atmospheric CH 2 O and how changes in CH 2 O couple with tropospheric ozone variability during the past two decades using recently available retrievals from the Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite and the RefD1 simulation from the NASA Goddard Earth Observing System Chemistry Climate Model (GEOSCCM). Our initial analysis provides evidence of significant increases in atmospheric CH 2 O concentrations over several of the world’s major anthropogenic regions, including China, India, and the Middle East, and several biomass burning regions, including South America, southern Africa, boreal regions and Indonesia. We furthermore will identify regional source contributions to CH 2 O trends, including anthropogenic VOCs emissions, biogenic isoprene emissions and open fires. In particular, we will focus on anthropogenic emission regions to examine the role of changing anthropogenic VOC emissions on CH 2 O abundance.

Atmospheric Formaldehyde↗