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  • LUNAR AND PLANETARY EXPLORATION  (14)
  • 61.10  (1)
  • 1985-1989  (4)
  • 1975-1979  (11)
  • 1
    Electronic Resource
    Electronic Resource
    Direct determination of X-Ray reflection phases for noncentrosymmetric crystals (1985)
    Springer
    Applied physics 37 (1985), S. 57-64 
    Details
    ISSN: 1432-0630
    Keywords: 61.10
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract An experimental method is described for the phase determination of x-ray reflections from noncentrosymmetric crystals. This method results from considerations on the phase dependence of line profiles in three-beam reflection-type diffractions for wavelength λ above and below a critical absorption edgeλ E of the heaviest constituent atom in the crystals. A relationS p =S L ·S R for phase determination is derived theoretically and verified experimentally forλ〈λ E ,S p being the sign of the sine of invariant phase,S L the sign defined from the line profile, andS R determined by the rotation of the crystal lattice.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00617869
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    Paper (German National Licenses)
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  • 2
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    Measurements of physical properties of model Titan atmospheres (1986)
    In:  CASI
    Details
    Publication Date: 2006-02-14
    Description: One aspect of the study of Titan's atmosphere is the elucidation of the chemical and physical nature of the aerosols. In order to facilitate this, a program to produce laboratory synthesized model materials for Titan's aerosol and to study their chemical and physical properties is now in progress. Various processes, including electric discharge, photolysis by ultraviolet light, and irradiation by energetic particles, will be used to produce the materials. A first set of experiments where a nominal Titan mixture (97%N2, 3% CH4, 0.2% H2) was subjected to pulsed high temperature shocks yielded a reddish brown waxy solid. This material was subjected to pyrolysis/gas chromatography, a technique that has been proposed as a method for analysis of the Titan aerosols. Preliminary results show the material to consist of simple hydrocarbons but little else, at least up to temperatures of 600 C. Since the material was colored, compounds other than those mentioned above must be present.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Second Symposium on Chemical Evolution and the Origin and Evolution of Life; p 50
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  • 3
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    Survival of interstellar matter in meteorities - Evidence from carbonaceous material (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: An interstellar origin has been attributed to certain organic and apparently elemental forms of C which occurs in carbonaceous meteorites. Evidence for such an origin comes from anomalous isotopic composition either of the C itself or of elements, such as N, H, or the noble gasses, which are combined with or trapped within the carbonaceous material. Suggested sources for these anomalous compositions include atmospheres of red giant stars, novae and super-novae, and interstellar molecular clouds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 4
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    Chemical and spectroscopic characterization of a suite of Mars soil analogs (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: The National Aeronautics and Space Administration has begun preparations for the flight of the Mars Observer Mission in the early 1990s. An advanced ground-based study is being conducted on a usefully limited suite of Mars Soil Analog Materials (MarSAM) intended to simulate the aeolian material covering the surface of Mars. A series of variably proportioned iron/calcium smectite clays were prepared from a typical montmorillonite clay using the Banin method. The effect of increasing iron on a diverse set of chemical and spectroscopic properties of the suite of clays is discussed. In order to chemically characterize the MarSAM and compare them with the Martian soil studied by Viking, the clays were analyzed for their major and minor elemental compositions by X-ray fluorescence and ion-coupled plasma techniques. It was concluded that the surface iron has a complex and hitherto uninvestigated impact on the catalytic and spectroscopic properties of clays and on the ability of these material to store energy.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., MEVTV Workshop on Nature and Composition of Surface Units on Mars; p 46-48
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  • 5
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    Organic chemistry on Titan (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Observations of nonequilibrium phenomena on the Saturn satellite Titan indicate the occurrence of organic chemical evolution. Greenhouse and thermal inversion models of Titan's atmosphere provide environmental constraints within which various pathways for organic chemical synthesis are assessed. Experimental results and theoretical modeling studies suggest that the organic chemistry of the satellite may be dominated by two atmospheric processes: energetic-particle bombardment and photochemistry. Reactions initiated in various levels of the atmosphere by cosmic ray, Saturn wind, and solar wind particle bombardment of a CH4 - N2 atmospheric mixture can account for the C2-hydrocarbons, the UV-visible-absorbing stratospheric haze, and the reddish color of the satellite. Photochemical reactions of CH4 can also account for the presence of C2-hydrocarbons. In the lower Titan atmosphere, photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH3 to exist. Hot H-atom reactions initiated by photo-dissociation of NH3 can couple the chemical reactions of NH3 and CH4 and produce organic matter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL The Saturn System; p 161-184
    Format: application/pdf
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  • 6
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    Comets: Cosmic connections with carbonaceous meteorites, interstellar molecules and the origin of life (1979)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: The ions, radicals, and molecules observed in comets may be derived intact or by partial decomposition from parent compounds of the sort found either in the interstellar medium or in carbonaceous meteorites. The early loss of highly reducing primitive atmosphere and its replacement by a secondary atmosphere dominated by H2O, CO2, and N2, as depicted in current models of the earth's evolution, pose a dilemma for the origin of life: the synthesis of organic compounds necessary for life from components of the secondary atmosphere appears to be difficult, and plausible mechanisms have not been evaluated. Both comets and carbonaceous meteorites are implicated as sources for the earth's atmophilic and organogenic elements. A mass balance argument involving the estimated ratios of hydrogen to carbon in carbonaceous meteorites, comets, and the crust and upper mantle suggests that comets supplied the earth with a large fraction of its volatiles. The probability that comets contributed significantly to the earth's volatile inventory suggests a chemical evolutionary link between comets, prebiotic organic synthesis, and the origin of life.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Space Missions to Comets; p 59-111
    Format: application/pdf
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  • 7
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    Organic chemistry on Titan (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Features taken from various models of Titan's atmosphere are combined in a working composite model that provides environmental constraints within which different pathways for organic chemical synthesis are determined. Experimental results and theoretical modeling suggest that the organic chemistry of the satellite is dominated by two processes: photochemistry and energetic particle bombardment. Photochemical reactions of CH4 in the upper atmosphere can account for the presence of C2 hydrocarbons. Reactions initiated at various levels of the atmosphere by cosmic rays, Saturn 'wind', and solar wind particle bombardment of a CH4-N2 atmospheric mixture can account for the UV-visible absorbing stratospheric haze, the reddish appearance of the satellite, and some of the C2 hydrocarbons. In the lower atmosphere photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH3 to exist. It is concluded that the surface of Titan may contain ancient or recent organic matter (or both) produced in the atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Review of Geophysics and Space Physics; 17; Nov. 197
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  • 8
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    Elimination of chromite and novel sulfides as important carriers of noble gases in carbonaceous meteorites (1978)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 9
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    The distribution of methylamine in the Jovian atmosphere (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: An estimate has been made of the methylamine concentration in the Jupiter atmosphere on the basis of the possible overlap between the regions of hydrocarbon and ammonia photochemistry. It was found that the maximum production rate of 6 x 10 to the 4th/cu cm/Jovian day occurs in the vicinity of 60 km above the ammonia cloud layer. The volumetric mixing ratio is 3 x 10 to the -11th, if the downward transport of methylamine equals the production rate.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 4; May 1977
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  • 10
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    Light element geochemistry of the Apollo 16 site (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The abundance and isotopic composition of carbon, sulfur, and nitrogen, the abundance of helium and hydrogen, and the content of metallic iron are reported for lunar surface samples from the Apollo 16 landing site at Cayley-Descartes. The light elements show marked interstation variability at the site. The abundances in soils of C, N, He, and H are apparently controlled mainly by exposure to the solar wind, through implantation or stripping processes. Carbon abundances (but not observed isotopic distributions) are compatible with a model in which equilibrium is established after 10,000-100,000 yr between solar wind input and loss by proton stripping. Sulfur abundances in soils are apparently controlled by abundances in local country rocks, but the lunar S cycle is quite complex. A metallic iron component may have originated by solar wind reduction of lunar Fe(2+).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 39; Feb. 197
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