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  • 1
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    High-temperature shock formation of N2 and organics on primordial Titan (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Theoretical models suggest that the initial form of nitrogen in Titan's atmosphere may have been NH3. The possible importance of strong shocks produced during high-velocity impacts accompanying the late stages of accretion are investigated as a method for converting NH3 to N2, of which Titan's atmosphere is now primarily composed. The focused beam of a high-power laser is used to simulate the effects of an impact in Titan's atmosphere. For mixtures of 10, 50, and 90 percent NH3, yields of 0.25, 1, and 6 x 20 to the 17th molecules of N2 per joule, respectively, were obtained. It is also found that the yield of HCN is comparable to that for N2. Several other hydrocarbons are produced, many with yields in excess of theoretical high-temperature-equilibrium models. The above yields, when combined with models of the satellite's accretion, result in a total N2 production comparable to that present in TItan's atmosphere and putative ocean.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 332; 520-522
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  • 2
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    Production of organic compounds in plasmas - A comparison among electric sparks, laser-induced plasmas, and UV light (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: In order to ascertain the features of organic compound-production in planetary atmospheres under the effects of plasmas and shocks, various mixtures of N2, CH4, and H2 modeling the atmosphere of Titan were subjected to discrete sparks, laser-induced plasmas, and UV radiation. The experimental results obtained suggest that UV photolysis from the plasma is an important organic compound synthesis process, as confirmed by the photolysis of gas samples that were exposed to the light but not to the shock waves emitted by the sparks. The thermodynamic equilibrium theory is therefore incomplete in the absence of photolysis.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 81; 413-428
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  • 3
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    Laboratory investigations of the aerosols in the stratosphere of Titan (1992)
    In:  CASI
    Details
    Publication Date: 2013-08-29
    Description: Results of experiments in which particles were produced from UV photolysis of C2H2, C2H4, or HCN, separately or in mixtures, modeling Titan's upper atmosphere, are presented. The particles were collected on disks and examined by Scanning Electron Microscopy (SEM). Measurements of particle sizes and shapes and of aggregation were determined from the SEM photographs.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: ESA, Symposium on Titan; p 377-381
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  • 4
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    Shock-induced color changes in nontronite - Implications for the Martian fines (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Shock recovery experiments performed on Riverside nontronite cause a marked color change in the clay, from olive-yellow to strong brown upon recovery from shock loading to peak pressures of 180 to 300 kbar. This color change spans the color range observed in the fine material at the Viking lander sites. The change in color is attributed to a shift in the O(2-)-Fe(3+) charge transfer bands to longer wavelengths, which causes the material to become both redder and darker. The observations that the color change is associated with the dehydroxylation of the clay and the Moessbauer spectra that reveal a lowering of the coordination number of the Fe(3+) as the OH(-) is removed from the structure are seen as suggesting that the movement of the absorption bands into the visible is caused by the formation of 4-fold or distorted 5-fold-like Fe(3+) within the octahedral layers of the clay.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 5
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    Titan's aerosols. I - Laboratory investigations of shapes, size distributions, and aggregation of particles produced by UV photolysis of model Titan atmospheres (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: Experiments in which C2H2, C2H4, and HCN were photolyzed separately and as a mixture in UV light have been conducted in order to ascertain the physical properties of model Titan atmosphere aerosols. Aerosols formed from photolysis of C2H4 were physically similar to those formed from C2H2; protolysis of HCN rapidly generated particles that did not grow to sizes greater than 0.09 microns. While the formation of particles from C4H2 was observed within minutes, formation was slowed by a factor of 4 when C2H2 and HCN were added.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 99; 1; p. 98-105.
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  • 6
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    Chemistry of the outer planets: Investigations of the chemical nature of the atmosphere of Titan (1985)
    In:  CASI
    Details
    Publication Date: 2019-07-13
    Description: It is clear from the experiments that a variety of complex organic models can be produced by lightning in a Titan-like gas mixture. The dominant products were found to be acetylene and hydrogen cyanide, with smaller amounts of many other species. Any aerosol produced by lightning inititated process will consist of a complex mixture of organic compounds, many of which should easily be identified by pyrolytic gas chromatography. Work will continue to expand the data base of molecules produced by lightning and other processes in order to assist in the design of appropriate analytical instruments for the upcoming Saturn/Titan mission and any other planetary probes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-180072 , NAS 1.26:180072
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  • 7
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    Chemistry of the outer planets (1992)
    In:  CASI
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    Publication Date: 2019-07-13
    Description: Various aspects were studied of past or present chemistry in the atmospheres of the outer planets and their satellites using lab simulations. Three areas were studied: (1) organic chemistry induced by kinetically hot hydrogen atoms in the region of Jupiter's atmosphere containing the ammonia cirrus clouds; (2) the conversion of NH3 into N2 by plasmas associated with entry of meteors and other objects into the atmosphere of early Titan; and (3) the synthesis of simple hydrocarbons and HCN by lightning in mixtures containing N2, CH4, and NH3 representing the atmospheres of Titan and the outer planets. The results showed that: (1) hot H2 atoms formed from the photodissociation of NH3 in Jupiter's atmosphere could account for some of the atmospheric chemistry in the ammonia cirrus cloud region; (2) the thermalization of hot H2 atoms in atmospheres predominated by molecular H is not as rapid as predicted by elastic collision theory; (3) the net quantum loss of NH3 in the presence of a 200 fold excess of H2 is 0.02, much higher than was expected from the amount of H2 present; (4) the conversion of NH3 into N2 in plasmas associated with infalling meteors is very efficient and rapid, and could account for most of the N2 present on Titan; (5) the yields of C2H2 and HCN from lightning induced chemistry in mixtures of CH4 and N2 is consistent with quenched thermodynamic models of the discharge core; and (6) photolysis induced by the UV light emitted by the gases in the hot plasmas may account for some, if not most, of the excess production of C2H6 and the more complex hydrocarbons.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-190314 , NAS 1.26:190314
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  • 8
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    The effect of oxygen fugacity on the partitioning of nickel and cobalt between olivine, silicate melt, and metal (1992)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: The effect of oxygen fugacity, f(O2), on the partitioning behavior of Ni and Co between olivine, silicate melt, and metal was investigated in the CaO-MgO-Al2O3-SiO2-FeO-Na2O system, an analogue of a chondrule composition from an ordinary chondrite. The conditions were 1350 C and 1 atm, with values of f(O2) varying between 10 exp -5.5 and 10 exp -12.6 atm (i.e., the f(O2) range relevant for crystal/liquid processes in terrestrial planets and meteorite parent bodies). Results of chemical analysis showed that the values of the Ni and Co partitioning coefficients begin to decrease at values of f(O2) that are about 3.9 log units below the nickel-nickel oxide and cobalt-cobalt oxide buffers, respectively, near the metal saturation for the chondrule analogue composition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 56; 10; p. 3733-3743.
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  • 9
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    Laboratory experiments in the study of the chemistry of the outer planets (1987)
    In:  Other Sources
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    Publication Date: 2019-07-12
    Description: It is shown that much information about planetary chemistry and physics can be gained through laboratory work. The types of experiments relevant to planetary research concern fundamental properties, spectral/optical properties, 'Miller-Urey' syntheses, and detailed syntheses. Specific examples of studies of the chemistry in the atmosphere of Titan are described with attention given to gas phase chemistry in the troposphere and the composition of model Titan aerosols. A list of work that still needs to be done is provided.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 7; 5 19
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