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  • 1
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    Sintering, crystallization, and breccia formation (1975)
    In:  Other Sources
    Details
    Publication Date: 2011-08-16
    Description: The process of breccia formation by viscous sintering in the absence of pressure, advanced by Simonds (1973), is examined in detail. The limitations on the standard model for such sintering are considered. The competing process of crystallization is analyzed kinetically in terms of time-temperature-transformation curves corresponding to various degrees of crystallinity. The analysis is applied to Lunar Composition 15418 to illustrate the approach. The results indicate that close constraints can be placed on the thermal histories of lunar breccias, particularly breccias with modest degrees of crystallinity, from microstructural observations and kinetic measurements.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 2
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    Recent increase in Jupiter's decimetric radio emission (1975)
    In:  Other Sources
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    Publication Date: 2011-08-16
    Description: Observations of the linear polarization properties of Jupiter's decimetric radioemission showed the planet's total intensity to increase between late summer 1973 and July 1974. Measurements were made with the NASA 64-m parabolic antenna operating at a wavelength of 13.1 cm. Data were plotted as a function of the longitude of the central meridian. Both data sets showed similar periodic intensity variation with longitude. However, the 1974 data points were consistently above the corresponding 1973 values. The flux density difference was attributed to the increase in the planet's decimetric radio emission. Measured at wavelengths of 21 cm and 11 to 13 cm the average peak flux densities were plotted as a function of the epoch of each observation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 253; Jan. 10
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  • 3
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    Saturn's microwave spectrum: Implications for the atmosphere and the rings (1978)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Measurements of Saturn's disk temperature are compiled to determine the planet's microwave spectrum from 1 mm to 100 cm wavelength. The data were adjusted to conform with a common flux density scale. A model of Saturn's rings is used to remove the effects of the rings from the atmospheric component at centimeter and decimeter wavelengths. Theoretical spectra for a number of convective atmospheric models were computed and compared with the observed spectrum. Radiative-convective models with approximately solar composition and with an effective temperature of approximately 89 K are in good agreement with the observations. The agreement between the observed and theoretical spectra is a strong indication that gaseous ammonia is present in Saturn's atmosphere. A good fit to the data is obtained with an ammonia mixing ratio of approximately 5 x 10,0001. A comparison of the millimeter wavelength data with the best-fitting atmospheric spectrum indicates that the thermal component of the ring brightness temperature near 1 mm wavelength is approximately 25 k.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Its The Saturn System; p 195-216
    Format: application/pdf
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  • 4
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    Viscous flow, crystallization behavior, and thermal histories of lunar breccias 70019 and 79155 (1975)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 17, 1975 - Mar 21, 1975; Houston, TX
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  • 5
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    Matrix glass vs. intruded glass in lunar breccia 15286 (1977)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The viscous flow and crystallization behavior of the matrix composition of breccia 15286 have been determined in the 1159-1307 C and 644-770 C temperature ranges. The Shaw (1972) model and, to a slightly lesser extent, the semiempirical Bottinga and Weill (1972) model describe the variation of viscosity with temperature. The crystal growth rate has been determined over the temperature range 821-1185 C. Time-temperature-transformation, logarithmic cooling, and continuous cooling curves were constructed; a nucleation barrier of 60 kT at a relative undercooling of 0.2 is assumed. It is estimated that the matrix of 15286 breccia cooled at a rate greater than 80 K/min through the glass transition region. The increase in density that occurs when the matrix glass is annealed suggests that the breccia was formed by cooling from the molten state rather than by direct shock-induced transition from crystal to glass. Viscous sintering under continuous cooling and logarithmic cooling conditions is analyzed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 6
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    Crystallization kinetics, viscous flow, and thermal history of lunar breccia 67975 (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-07-13
    Description: The maximum crystal growth rate for the 67975 matrix composition, about 0.00073 cm/min, was found to occur at about 990 C (undercooling 220 C). The Shaw (1972) model and, to a slightly lesser extent, the Bottinga and Weill (1972) model indicate the variation of viscosity with temperature. Time-temperature-transformation and continuous cooling curves were constructed from the measured crystal growth rates and viscosities and used to estimate the cooling rate required to form bodies with the degree of crystallinity observed in the matrix of the breccia. It is estimated on the basis of kinetic analysis that the 67975 breccia cooled at a rate of about 0.06 C/min over the temperature range below the liquidus. Heat flow analyses indicate that the 67975 breccia did not cool in the size of the lunar sample but as part of a much larger body. Viscous singering as well as cooling of a melt-clast mixture are investigated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 7
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    Venus - Detection of variations in stratospheric carbon monoxide (1978)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The reported observations of the J = 0-1 rotational transition (115271.2 MHz) of carbon monoxide in the Venusian atmosphere indicate that the distribution of stratospheric CO is variable. Observations were obtained with a 11-m antenna on several days in February 1977, when Venus was near maximum eastern elongation (k approximately 0.4), and in April 1977 during inferior conjunction (k approximately 0.01). Differences in the line intensities and shapes for the two data sets are described. The results are interpreted to suggest that on the nightside of Venus there is relatively more CO at higher altitudes and relatively less CO at lower altitudes than on the dayside of the planet.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: In: Symposium on Planetary Atmospheres; Aug 16, 1977 - Aug 19, 1977; Ottawa; Canada
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  • 8
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    Crystallization kinetics, viscous flow, and thermal histories of lunar breccias 15286 and 15498 (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 15, 1976 - Mar 19, 1976; Houston, TX
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  • 9
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    The kinetics of lunar glass formation, revisited (1976)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The nucleation frequency of Lunar Composition 70019, a lithified soil breccia from the center of a small crater in the Taurus-Littrow Valley, is determined using a relation that describes nucleation throughout the volume of a liquid together with measurements of the time required at temperatures of 780 to 930 C to obtain sensibly crystalline bodies. Curves indicating the time required at a given temperature to reach a particular fraction crystallized are shown to have the general form predicted by kinetic analysis. Nucleation frequencies are evaluated by applying such analysis to a curve representing the transition between glassy material and material with a sensible degree of crystallinity. The results obtained are found to be in excellent agreement with the values expected from the classical theory of homogeneous nucleation, indicating that such nucleation represents the dominant contribution to crystal formation, at least over the range of undercoolings covered (250 to 400 C).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 15, 1976 - Mar 19, 1976; Houston, TX
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  • 10
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    Jupiter's atmosphere - Observations and interpretation of the microwave spectrum near 1.25-cm wavelength (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Measurements of Jupiter's disk-temperature spectrum in the 20- to 24-GHz (1.5 cm less than lambda less than 1.25 cm) region are reported. These data are combined with previously published data to produce a uniformly calibrated thermal spectrum of Jupiter in the wavelength interval 0.85 to 2.1 cm. Model studies are carried out to determine optimum pressure-temperature profiles for an assumed radiative-convective temperature structure. It is found that the temperature at the 1-bar total effective pressure level is between 140 and 165 K, with a most probable value of 153 K, provided that NH3 is uniformly saturated in the clouds on a global scale. We show that the temperature profile for the microwave model is approximately 20 K cooler than the profiles derived from infrared data. An explanation of this discrepancy is discussed in terms of a model which invokes different NH3 distributions in the belts and zones.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 35; July 197
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