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  • LUNAR AND PLANETARY EXPLORATION  (7)
  • polymer  (1)
  • 1
    Electronic Resource
    Electronic Resource
    Injection moulding of thermoplastics: Freezing during mould filling (1983)
    Springer
    Rheologica acta 22 (1983), S. 223-236 
    Details
    ISSN: 1435-1528
    Keywords: Injection moulding ; thermoplastic ; freezing ; polymer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract The injection moulding of thermoplastic polymers involves, during mould filling, flows of hot melts into mould networks, the walls of which are so cold that frozen layers form on them. Theoretical analyses of such flows are presented here.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01332374
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    Paper (German National Licenses)
    Fulltext
  • 2
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    Water loss from Venus: Implications for the Earth's early atmosphere (1985)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The atmosphere of Venus outgassed rapidly as a result of planetary heating during accretion, resulting in massive water loss. The processes affecting atmospheric chemistry following accretion have consisted largely of hydrogen escape and internal re-equilibrium. The initial bulk composition of Venus and Earth are assumed to have been roughly similar. Chemical speciation on Venus was controlled by the temperature and oxygen buffering capacity of the surface magma. It is also assumed that the surfaces of planetary bodies of the inner solar system were partly or wholly molten during accretion with a temperature estimated at 1273 to 1573 K. To investigate the range of reasonable initial atmospheric compositions on Venus, limits have to be set for the proportion of total hydrogen and the buffered fugacity of oxygen. Using the C/H ratio of 0.033 set for Earth, virtually all of the water generated during outgassing must later have been lost in order to bring the current CO2/H2O ratio for Venus up to its observed value of 10 sup 4 to 10 sup 5. The proportion of H2O decreases in model atmospheres with successfully higher C/H values, ultimately approaching the depleted values currently observed on Venus. Increasing C/H also results in a rapid increase in CO/H2O and provides an efficient mechanism for water loss by the reaction CO+H2O = CO2 + H2. This reaction, plus water loss mechanisms involving crustal iron, could have removed a very large volume of water from the Venusian atmosphere, even at a low C/H value.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 65-67
    Format: text
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    NASA TECHNICAL REPORTS
  • 3
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    The case for a wet, warm climate on early Mars (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Arguments are presented in support of the idea that Mars possessed a dense CO2 atmosphere and a wet, warm climate early in its history. The plausibility of a CO2 greenhouse is tested by formulating a simple model of the CO2 geochemical cycle on early Mars. By scaling the rate of silicate weathering on Earth, researchers estimated a weathering time constant of the order of several times 10 to the 7th power years for early Mars. Thus, a dense atmosphere could have existed for a geologically significant time period (approx. 10 to the 9th power years) only if atmospheric CO2 was being continuously resupplied. The most likely mechanism by which this could have been accomplished is the thermal decomposition of carbonate rocks induced directly or indirectly by intense, global scale volcanism.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington, Reports of Planetary Geology and Geophysics Program, 1986; p 160
    Format: application/pdf
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  • 4
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    The case for a wet, warm climate on early Mars (1987)
    In:  Other Sources
    Details
    Publication Date: 2011-08-19
    Description: The conditions under which Mars could have had a warm wet climate during its early evolution are explored by means of numerical simulations, incorporating more accurate data on the opacity of gaseous CO2 and H2O in the solar and thermal spectral regions (McClatchey et al., 1971) into the one-dimensional radiative-convective greenhouse model of Kasting and Ackerman (1986). The results are presented in extensive graphs and characterized in detail, with consideration of atmospheric CO2 loss rates, sources of atmospheric CO2, CO2 partitioning between atmosphere and hydrosphere, the Mars volatile inventory, the CO2 geochemical cycle, climate evolution, and observational tests. It is concluded that greenhouse conditions (requiring atmospheric CO2 of 1-5 bar) could have existed for a period of about 1 Gyr if the total surficial inventory of CO2 was 2-10 bar.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 71; 203-224
    Format: text
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  • 5
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    Water loss on Venus - The role of carbon monoxide (1984)
    In:  Other Sources
    Details
    Publication Date: 2019-06-28
    Description: The four-to-fivefold difference in water abundance between the earth and Venus may reflect either initial differences in the bulk volatile content of the two planets, or massive water loss mechanisms on Venus. These two possibilities were investigated by performing thermodynamic calculations on the heterogeneous system C-O-H-N-S, varying C/H upward from its 0.033 terrestrial value. While atmospheric H2O decreases as bulk C/H increases, the latter would have to rise to an improbably high value in order to account for the low water abundance on Venus through initial deficiency alone. Calculations suggest that if the outgassed C/H on Venus was higher than on earth by even a factor of 5, it would have been sufficient for CO to become competitive with FeO as a sink for oxygen. Together with the lower initial water abundance value that follows from a higher C/H ratio, water loss due to CO may have been a major factor.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 60; 307-316
    Format: text
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  • 6
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    The composition of carbonaceous chondrite matrix (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Matrix compositions of 32 of the approximately 40 known carbonaceous chondrites were analyzed using an electron probe defocussed-beam technique. Except in those chondrites that show evidence of metamorphism, matrices are compositionally similar and have correlation coefficients of +0.96 or greater. The implications of these analyses for the chemistry of individual matrix phases and for primitive solar system material are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 41; Aug. 197
    Format: text
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  • 7
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    Vein formation in the C1 carbonaceous chondrites (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Veins in the C1 chondrites Orgueil, Alais, and Ivuna have been deposited during an extended period of impact brecciation and leaching. At least three generations of mineralization, dominated successively by carbonates, calcium sulfate, and magnesium sulfate, can be recognized. Vein minerals are derived locally by closed-system reactions between matrix phyllosilicates and an aqueous fluid, with the result that few, if any, primitive mineral phases still exist in the C1s.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 13; Mar. 31
    Format: text
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  • 8
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    Textural evidence bearing on the origin of isolated olivine crystals in C2 carbonaceous chondrites (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: In some cases the mechanical competence of chondrules in carbonaceous chondrites has been reduced by alteration of their mesostasis glass to friable phyllosilicate, providing a mechanism by which euhedral olivines can be separated from chondrules. Morphological features of isolate olivine grains found in carbonaceous chondrites are similar to those of olivine phenocrysts in chondrules. These observations suggest that the isolated olivine grains formed in chondrules, by crystallization from a liquid, rather than by condensation from a vapor.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 37; 3, Ja; Jan. 197
    Format: text
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