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  • LUNAR AND PLANETARY EXPLORATION  (1,153)
  • 1990-1994
  • 1980-1984  (1,153)
  • 1965-1969
  • 1925-1929
  • 1983  (552)
  • 1981  (601)
  • 1929
Collection
Keywords
Years
  • 1990-1994
  • 1980-1984  (1,153)
  • 1965-1969
  • 1925-1929
Year
  • 101
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    Radio emission signature of Saturn immersions in Jupiter's magnetic tail (1983)
    In:  Other Sources
    Details
    Publication Date: 2011-08-18
    Description: During the interval from about May through August 1981, when Voyager 2 was inbound to Saturn, the Planetary Radio Astronomy instrument measured repeated, dramatic decreases in the intensity of the Saturn Kilometric Radiation (SKR). The emission dropouts averaged two orders of magnitude below mean energy levels and varied from about 1 to 10 Saturn rotations in duration. Comparison with pre-Saturn encounter Voyager 1 observations (June to November, 1980) shows that the SKR dropouts were unique to the Voyager 2 observing interval, consistent with the closer proximity of Saturn to Jupiter's distant magnetotail in 1981. Further, the dropouts occurred on the average at times when Voyager 2 is known to have been within or near Jupiter's magnetic tail.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; Sept. 1
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  • 102
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    Solar related waves in the Venusian atmosphere from the cloud tops to 100 km (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A quasi-linear diagnostic model using observed solar-related temperatures and a specified solar mean circulation and surface structure to find the solar-related circulation above the clouds of Venus is presented. Despite the greater dependence of model-derived, solar-related circulation on the mean flow than is the case for terrestrial tides, as well as the uncertainty concerning this mean flow, significant conclusions are drawn for the solar-related circulation and thermal structure of Venus. An anomalously large response is found in the polar regions, due to the model's requirement of a process such as dissipation which will act as a major sink for momentum. Dissipation is specified in the model as Rayleigh friction with an unknown free parameter coefficient. In view of this, dissipation is either very efficient by terrestrial standards and accompanied by small solar-related circulation, or similar to that of earth and possessed of a circulation large enough to have an impact on the mean circulation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of the Atmospheric Sciences (ISSN 0022-4928); 40; June 198
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  • 103
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    Vertical distribution of scattering hazes in Titan's upper atmosphere (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Radial intensity scans of a Voyager 2 high phase angle image of Titan have been inverted to yield vertical extinction profiles at 1 deg intervals around the limb. A detached haze layer with peak particle number densities of about 0.2 cu/cm exists at all latitudes south of about 45 N, and at an altitude of 300-350 km. The optical depth 0.01 level lies at a radius of 2932 + or - 5 km at the equator and at a radius of 2915 + or - 10 km over the poles (altitudes of 357 + or - 5 and 340 + or - 10 km, respectively). In addition to the haze layer at 300-350 km, there is a small enhancement in the extinction at about 450 km which exists at all latitudes between 75 deg S and about 60 deg N.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 55; July 198
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  • 104
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    Saturn meteorology - A diagnostic assessment of thin-layer configurations for the zonal flow (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Voyager imaging, infrared, and radio observations for Saturn have been recently interpreted by Smith et al. (1982) as an indication that the jet streams observed at the cloud tops extend to depths greater than the 10,000-bar level. This analysis assumes a maximum latitudinal temperature contrast of a few percent, a mean atmospheric rotation rate at depth given by Saturn's ratio period, and no variation with latitude of the bottom pressure level for the zonal flow system. These assumptions are not, however, firmly constrained by observation. The diagnostic analysis of plausible alternative configurations for Saturn's atmospheric structure demonstrates that a thin weather layer system (confined at mid to high latitudes to levels above 200 bar) cannot be excluded by any of the available observations. A quantitative estimate of the effects of moisture condensation (including the differentiation of mean molecular weight) suggests that these might provide the buoyancy contrasts necessary to support a thin-layer flow provided that Saturn's outer envelope is enriched approximately 10 times in water abundance relative to a solar composition atmosphere and strongly differentiated with latitude at the condensation level.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0019-1035)
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  • 105
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    The atmosphere of Titan - An analysis of the Voyager 1 radio occultation measurements (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The equatorial atmosphere of Titan was probed by means of two coherently related radio signals transmitted from Voyager 1 at 13.0 and 3.6 cm wavelengths during the November 12, 1980 occultation of the spacecraft by the Saturn satellite. An analysis of the differential dispersive frequency measurements did not reveal any ionization layers in the upper atmosphere of Titan. The gas refractivity data, which extend from the surface to about 200 km altitude, were interpreted in two different ways. In the first, it is assumed that N2 makes up virtually all of the atmosphere, with small amounts of CH4 and other hydrocarbons present. In the second interpretation of the refractivity data, it is assumed that the 3.5 km altitude level corresponds to the bottom of a CH4 cloud layer and that N2 and CH4 were perfectly mixed below this level.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 106
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    The role of dissipation in shepherding of ring particles (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A discussion is presented on the gravitational interaction between ring systems and nearby satellites. A shepherd satellite lacking damping mechanisms will force oscillations in the motion of a ring particle that are symmetrical with respect to the encounter geometry. If such damping mechanisms as density wave propagation or a dissipative medium are present, a lag in particle response provides the asymmetry that exerts a net torque on the rings. While the torque on a given particle depends on the degree of damping, that dependence disappears when the torque is averaged over a range of orbits spanning resonances if the degree of damping is within a certain range. A torque that is much lower than the standard formula results from excessively weak or strong damping.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 107
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    High-energy particles (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is pointed out that the magnetosphere of Jupiter is in many respects quite different from that of the earth. The energy required to drive the Jovian magnetosphere is apparently extracted from Jupiter's rotational energy rather than from the solar wind. Jupiter is a strong source of energetic charged particles which can be detected as far away as the orbit of Mercury. The structure and dynamics of the energetic particle distribution in the inner magnetosphere is discussed, taking into account observations, transport and losses in the inner magnetosphere, satellite interactions, and electron synchrotron radiation. The subsolar hemisphere is considered, giving attention to particle fluxes in the subsolar magnetosphere, conditions in the middle magnetosphere, and the characteristics of the outer magnetosphere. A description of the predawn magnetosphere is also provided.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 108
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    Ionosphere (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The original interest in an ionosphere on Jupiter was generated by the discovery of strong radio-frequency emissions at approximately 20 MHz which were thought to be plasma frequencies associated with Jupiter's ionosphere. The ionosphere of Jupiter provides a means to couple the magnetosphere to the atmosphere by virtue of its high conductivity and collisional interaction with the neutral atmosphere. The Pioneer and Voyager have provided direct measurements of profiles of electron concentration at selected locations on Jupiter. Attention is given to basic principles regarding the characteristics of the Jovian ionosphere, the ionization sources, aspects of ion recombination, ion chemistry, observations of Jupiter's ionosphere, the structure of Jupiter's upper atmosphere, and questions of ionospheric modeling. On the basis of the Pioneer and Voyager observations it appears that Jupiter's ionosphere and thermosphere undergo significant solar cycle changes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 109
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    Venus -Mesospheric hazes of ice, dust, and acid aerosols (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Four distinct types of particles are suggested to be present in the upper atmosphere of Venus. The lowest and densest haze may consist of a submicron sulfuric acid aerosol which extends above the cloud tops, up to about 80 km, representing an extension of the upper cloud deck. Temperature structure measurements in the 70-120 km altitude range indicate the occasional appearance of two independent water ice layers, of which the lower may form between 80 and 100 km and is probably the detached haze layer noted in high contrast limb photography. A nucleation of this ice layer on sulfuric acid aerosols is hypothesized. Temperatures of the Venus mesopause, near 120 km altitude, are frequently cold enough to allow ice nucleation on meteoric dust or ambient ions, yielding a haze (analogous to noctilucent clouds on earth) which is expected to be tenuous to the point of optical invisibility.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 110
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    Phosphine photochemistry in Saturn's atmosphere (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The phosphine photochemistry on Saturn is studied with a 1D photochemical model. The PH3 concentration is rapidly depleted with height (scale height 3.5 km) in the upper troposphere. Formation of P, a probable precursor of P4, (a potential red chromophore in the atmosphere), is highly improbable unless the rate constant for the recombination reaction PH + H2 + M yields PH3 + M is less than 10 to the -41st cm exp 6/molecule-squared sec. Coupling of PH3 and hydrocarbon photochemistry, specifically the C2H2 catalyzed photodissociation of CH, is important. Column production rates of the organophosphorus compounds CH3PH2 and HCP of 3 x 10 to the 8th/sq cm sec are predicted, with potentially observable column densities of greater than 1 x 10 to the 17th/sq cm.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; Oct. 198
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  • 111
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    The inner edge of Saturn's B ring (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The sharp, 90-km wide transition from an optical depth of 0.2 in the C ring to 1 in the B ring begins at 91,970 km from Saturn's center. This radius is found to be almost exactly at the inward stability limit of charged particles launched in the ring plane at the local Kepler velocity, provided these particles have large charge to mass ratio. The zonal harmonic models of Saturn's magnetic field from the Voyager data and the gravitational field model from Pioneer data are essential to get the very close agreement between theory and observation. The theoretical stability limits are 91,973 + or - 145 km from Voyager 1 magnetic field data and 91,991 + or 145 km from Voyager 2 magnetic data. The zonal harmonic magnetic field lines are not perpendicular to the ring plane. Therefore, in addition to the magnetic mirror, gravitational, and centrifugal forces, an unknown force must be postulated to produce equilibrium in the ring plane and make the stability calculation meaningful.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; Aug. 1
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  • 112
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    Martian gases in an Antarctic meteorite? (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Significant abundances of trapped argon, krypton, and xenon have been measured in shock-altered phases of the achondritic meteorite Elephant Moraine 79001 from Antarctica. The relative elemental abundances, the high ratios of argon-40 to argon-36 (equal to or greater than 2000), and the high ratios of xenon-129 to xenon-132 (equal to or greater than 2.0) of the trapped gas more closely resemble Viking data for the Martian atmosphere than data for noble gas components typically found in meteorites. These findings support earlier suggestions, made on the basis of geochemical evidence, that shergottites and related rare meteorites may have originated from the planet Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 221; Aug. 12
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  • 113
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    Io's 4-micron band and the role of adsorbed SO2 (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The role of adsorbed SO2 on Io's surface particles in producing the observed spectral absorption band near 4 microns in Io's reflectance spectrum is explored. Calculations show that a modest 50 percent monolayer coating of adsorbed So2 molecules on submicron grains of sulfur or alkali sulfide, assumed to make up Io's uppermost optical surface ('radialith'), will result in a nu 1 + nu 3 absorption band near 4 microns with depth about 30 percent below the adjacent continuum, consistent with the observed strength of the Io band. The precise wavelength position of the nu 1 + nu 3 band of SO2 in different phase states such as frost, ice, adsorbate, and gas are summarized from the experimental literature and compared with the available telescopic measurements of the Io band position. The results suggest that the 4-micron band in Io's full disk spectrum can best be explained by the presence on Io's surface of widespread SO2 in the form of adsorbate rather than ice or frost.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 54; June 198
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  • 114
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    HCN formation on Jupiter - The coupled photochemistry of ammonia and Acetylene (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: HCN formation in the upper troposphere and lower stratosphere of Jupiter is presently modeled in terms of UV pyrolysis of the C2H5N isomer aziridine, which is a product of the NH2 and C2H3 radicals that originate from ammonia photolysis and the addition of H atoms to acetylene, respectively. The sensitivity of the HCN column density to the individual rate constants and the eddy diffusion coefficient profile is considered, along with the possibility that additional HCN-yielding pathways may exist. Both ammonia and phosphine are strongly depleted by photolysis.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 54; June 198
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  • 115
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    Does Venus breathe? (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: It is speculated that the periodic absorption and desorption of CO2 by the soil of Venus may buffer daily temperature, pressure and wind variations in the lower atmosphere, effectively eliminating the net tidal torque on the atmosphere. The redistribution of mass would still generate a sizable torque, however, which may serve as a balance for that which is caused by the gravitationally induced tide. This novel tidal mechanism represents a somewhat weaker competitor to the atmospheric tides which have previously been studied.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 54; June 198
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  • 116
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    Thermal structure of Saturn from Voyager infrared measurements - Implications for atmospheric dynamics (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 117
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    Theories of radio emissions and plasma waves (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The complex region of Jupiter's radio emissions at decameter wavelengths, the so-called DAM, is considered, taking into account the basic theoretical ideas which underly both the older and newer theories and models. Linear theories are examined, giving attention to direct emission mechanisms, parallel propagation, perpendicular propagation, and indirect emission mechanisms. An investigation of nonlinear theories is also conducted. Three-wave interactions are discussed along with decay instabilities, and three-wave up-conversio. Aspects of the Io and plasma torus interaction are studied, and a mechanism by which Io can accelerate electrons is reviewed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 118
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    Jupiter's magnetic field and magnetosphere (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Among the planets of the solar system, Jupiter is unique in connection with its size and its large magnetic moment, second only to the sun's. The Jovian magnetic field was first detected indirectly by radio astronomers who postulated its existence to explain observations of nonthermal radio emissions from Jupiter at decimetric and decametric wavelengths. Since the early radio astronomical studies of the Jovian magnetosphere, four spacecraft have flown by the planet at close distances and have provided in situ information about the geometry of the magnetic field and its strength. The Jovian magnetosphere is described in terms of three principal regions. The inner magnetosphere is the region where the magnetic field created by sources internal to the planet dominates. The region in which the equatorial currents flow is denoted as the middle magnetosphere. In the outer magnetosphere, the field has a large southward component and exhibits large temporal and/or spatial variations in magnitude and direction in response to changes in solar wind pressure.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 119
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    Nutritional characteristics of moon dust for soil microorganisms (1983)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Approximately 46% of the lunar sample (10084,151), 125.42 mg, was solubilized in 680 ml 0.01 M salicylic acid. Atomic absorption spectroscopic analysis of the solubilized lunar sample showed the following amount of metal ions: Ca, 3.1; Mg, 4.0; K, 0.09; Na, 0.67; Fe, 7.3; Mn, 1.6; Cu, Ni, Cr, less than 0.1 each. All are in ppm. Salicylic acid used to solubilize the lunar sample was highly inhibitory to the growth of mixed soil microbes. However, the mineral part of the lunar extract stimulated the growth. For optimal growth of the soil microbes the following nutrients must be added to the moon extract; sources of carbon, nitrogen, sulfur, phosphorus, and magnesium in addition to water.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Johnson (Lyndon B.) Space Center The 1983 NASA/ASEE Summer Faculty Fellowship Research Program Research Reports; NASA. Johnson (Lynd
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  • 120
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    Global empirical model of the Venus thermosphere (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Direct measurements of neutral CO2, O, CO, N2, He, and N densities from the Pioneer Venus Orbiter Neutral Mass Spectrometer are described in terms of a spherical harmonic representation (latitude and local time coordinates) of exospheric temperature and number densities at 150 km, using modified Bates temperature profiles. The exospheric temperatures are determined from the altitude variations of atomic oxygen. A global average temperature of 228 K is derived with a first harmonic variation of 5%. The altitude profiles are extended downward to 100 km by using empirical formulas to provide a transition through the turbopause region (simulating the effect of eddy diffusion and vertical flows) and matching entry probe density data. The model reflects the observed variations of temperature and density with the 10.7 cm radio flux index. For a given change in flux at the planet, the exospheric temperature on Venus changes by only 10% of the change seen in the terrestrial thermosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 88; Jan. 1
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  • 121
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    Modulation of Venus ion densities associated with solar variations (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The dayside ion concentrations in the Venus ionosphere obtained by the Pioneer Venus orbiter ion mass spectrometer exhibit a modulation corresponding to the 27-day solar variation. Comparisons were made of the amplitudes of modulation of CO(2(+), C(+), and O2(+), with the amplitudes of the 27-day variation in the 10.7-cm solar radio flux and the simultaneously measured EUV fluxes at He II (304 A) and Lyman-beta(1026 A), together with a theoretical analysis of the effects of solar variability on the ionosphere and neutral atmosphere of Venus. This analysis leads to the conclusion that the observed modulation of dayside ion densities is primarily due to the variability in the ionizing EUV radiations and, to a much lesser extent, the result of the variability with solar activity of the neutral atmosphere via the variability in exospheric temperature. In this connection, it is also shown theoretically why the percentage variation of exospheric temperature on Venus (as observed in the ONMS data) for a given variation in the 10.7-cm radio flux is only half of the exospheric temperature variation for earth.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 8; July 198
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  • 122
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    Sulfur dioxide and other cloud-related gases as the source of the microwave opacity of the middle atmosphere of Venus (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Spacecraft radio occultation measurements imply the presence of a nonuniformly mixed gaseous absorber within, but mostly below, the main cloud layer of sulfuric acid-water droplets measured by Pioneer-Venus. Preliminary considerations of the amount, distribution, and effects of sulfur dioxide and other gases, which apparently are associated with and produce the cloud, indicate that they constitute an important, and probably the predominant, source of the observed microwave opacity of the middle atmosphere of Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 46; Apr. 198
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  • 123
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    Titan (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The paper reviews current knowledge about Titan's atmosphere, surface, interior, and nearby environment. An attempt is made to place the satellite's history within the context of the formation of the Saturn system and to describe possible evolutionary paths for its atmosphere and interior.
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  • 124
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    Diminished tektite ablation in the wake of a swarm (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Observations of ablation markings on tektite surfaces reveal that a large variation in aerodynamic heating must have occurred among the members of a swarm during atmospheric entry. In a few cases, the existence of jagged features indicates that these tektite surfaces may have barely reached the melting temperature. Such an observation seems to be incompatible with the necessarily large heating rates suffered by other tektites which exhibit the ring wave melt flow. A reconciliation is proposed in the form of a wake shielding model which is a natural consequence of swarm entry. Calculations indicate that the observed ablation variations are actually possible for swarm entry at greater than escape velocity. This aerodynamic conclusion provides support for the arguments favoring extraterrestrial origin of tektites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; June 10
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  • 125
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    Jupiter - Structure and composition of the upper atmosphere (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The Voyager ultraviolet stellar occultation data yield a temperature of 200 + or - 50 K at about 400 km, and the solar occultation data give 1100 + or - 200 K at 1450 km above the ammonia cloud tops. The temperature gradient between 400 and 1450 km is approximately 1 K/km. The mesospheric temperature structure gives no strong indication of an earth-like mesopause. The heating of the upper atmosphere appears to result from a combination of magnetospheric charged particle precipitation, ion drag, inertia gravity waves, and solar EUV. The volume mixing ratios of CH4 and C2H6 at 325 km are measured to be 2.5(+3, -2) x 10 to the -5th and 2.5(+2.0, -1.5) x 10 to the -6th, respectively, which are lower than in the stratosphere. The C2H2 volume mixing ratio is not greater than 5 x 10 to the -6th at 300 km. The homopause value of the equatorial eddy diffusion coefficient is found to be 1-2 x 10 to the -6th sq cm/s.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 247
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  • 126
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    New magnetic results from Allende C3/V/ (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Thermomagnetic analyses of Allende C3(V) suggest that magnetic phases contributing about 15% to saturation magnetization with transition temperatures not greater than 320 C, also contribute about 90% to natural remanence (NRM) and about 80% to the saturation isothermal remanence (SIRM). Phases carrying the dominating part of of the NRM are found to be intergrown, magnetically interacting, and thermally unstable, beginning at temperatures as low as 50 C. The ratio of the NRM/SIRM ranges from 0.004 to 0.006 for the bulk meteorite and from 0.0004 to 0.005 for chondrules of all sizes. The remanent coercive force behavior suggests coexisting magnetic phases with differing Curie points or with the low temperature transitions being due to transformation of a thermally metastable phase.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 127
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    Solar wind origin of Ar-36 on Venus (1981)
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    Publication Date: 2011-08-18
    Description: An examination is conducted concerning the circumstances under which the difference between earth and Venus (and Mars) fits naturally into theories in which the terrestrial planets formed by the gradual sweeping up of planetesimals in an essentially gas-free protoplanetary swarm. The primary purpose of the reported investigation is to use observational data to define restrictions on planetary formation theories that would be imposed if most of Venus' inert gases come from the solar wind. The observational data support the suggestion that the abundances of Ar, Kr, and Xe on Venus have been augmented by a component of solar composition. Solar wind implantation at an early stage of accumulation provides a natural way of producing the observed extreme heliocentric distribution of this component, provided that accumulation occurred after dissipation of solar gas from the solar nebula
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 46; Apr. 198
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  • 128
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    Thermal response of Saturn's ring particles during and after eclipse (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The investigation is based on data which were obtained on May 18, 1978, at the 5-m Hale telescope on Palomar Mountain. A Ge:Ga bolometer was used at the f/70 Gregorian focus; a cold interference filter limited the wavelength response to between 16 and 26 micrometers. A brightness asymmetry is observed between the ansae of all three rings; the largest asymmetry occurs in the C ring. The simplest explanation of such asymmetries is just the eclipse cooling and subsequent heating of similar particles at different radial distances from Saturn, coupled with the different travel times from eclipse exit to east ansa. The observed eclipse cooling and subsequent heating in Saturn's B ring support the idea that the uppermost surface of the particles is of low-conductivity water frost, similar to the uppermost surface of the Galilean satellites (omitting Io).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 46; Apr. 198
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    The magnetic field of Jupiter - A generalized inverse approach (1981)
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    Publication Date: 2011-08-18
    Description: The estimation of planetary magnetic fields from observations of the magnetic field gathered along a spacecraft flyby trajectory is examined with the aid of generalized inverse techniques, with application to the internal magnetic field of Jupiter. Model non-uniqueness resulting from the limited spatial extent of the observations and noise on the data is explored and quantitative estimates of the model parameter resolution are found. The presence of a substantial magnetic field of external origin due to the currents flowing in the Jovian magnetodisc is found to be an important source of error in estimates of the internal Jovian field, and new models explicitly incorporating these currents are proposed. New internal field models are derived using the vector helium magnetometer observations and the high field fluxgate observations of Pioneer 11, and knowledge of the external current system gained from the Pioneer 10 and Voyagers 1 and 2 encounters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Sept. 1
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  • 130
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    Comment on 'Azimuthal magnetic field at Jupiter' by J. L. Parish, C. K. Goertz, and M. F. Thomsen (1981)
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    Publication Date: 2011-08-18
    Description: In the first paper, an alternative to one of the models of current flow giving rise to the azimuthal component of the Jupiter magnetic field considered by Parish et al. (1980) is proposed which takes into account the magnetic fields due to return currents and is consistent with Pioneer 10 observations. In the present model, currents enter the equatorial sheet at both poles and then flow radially outward, with a total current flowing into the polar regions of about 1.4 x 10 to the 8th A. In the reply, it is contended that, although the return currents must be present, their net effects almost exactly cancel and their contributions to the near-equatorial field may be neglected for regions sufficiently far from the field lines on which the return current flows. Furthermore, the difference in the total currents estimated by Parish et al. and in the first paper is attributed to the uncertainties and inadequacy of the fit of either model to the observations and to a difference in mathematic expressions used for the field rather than a significant difference between models.
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    Type: Journal of Geophysical Research; 86; Sept. 1
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  • 131
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    Partition coefficients for REE between garnets and liquids - Implications of non-Henry's Law behaviour for models of basalt origin and evolution (1981)
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    Publication Date: 2011-08-18
    Description: An experimental investigation of Ce, Sm and Tm rare earth element (REE) partition coefficients between coexisting garnets (both natural and synthetic) and hydrous liquids shows that Henry's Law may not be obeyed over a range of REE concentrations of geological relevance. Systematic differences between the three REE and the two garnet compositions may be explained in terms of the differences between REE ionic radii and those of the dodecahedral site into which they substitute, substantiating the Harrison and Wood (1980) model of altervalent substitution. Model calculations demonstrate that significant variation can occur in the rare earth contents of melts produced from a garnet lherzolite, if Henry's Law partition coefficients do not apply for the garnet phase.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 45; Sept
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  • 132
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    Polygon patterns on Europa (1981)
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    Publication Date: 2011-08-18
    Description: The formation of polygon patterns in the development of crack networks in cooling basalt flows and similar contracting systems, and under natural conditions in an essentially unbounded basalt flow, are analyzed, and the characteristics of hexagonal and pentagonal patterns in isotropic stress fields are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 291; May 28-J
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  • 133
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    Pioneer fly-by of Saturn and its rings (1981)
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    Publication Date: 2011-08-18
    Description: Results acquired by the imaging photopolarimeter on board Pioneer 11 during the spacecraft fly-by of Saturn and its rings on September 1, 1979 are reviewed. Analysis of the broadband photometry and polarimetry obtained of the Saturn atmosphere has been used to determine a cloud top height of 300 mb and a scale height of the aerosol distribution about 1/4 that of the ambient gas, and to point out differences between the forward scattering and belt and zone characteristics of the Saturn and Jupiter atmospheres. Images of Saturn's rings have been used to derive a profile of ring optical depth between 1.22 and 2.35 Saturn radii, and reveal new divisions and thin rings and azimuthal variations in the brightness of the A ring not observable from earth. Linear polarization observations of Titan in red and blue light reveal that the aerosols near the top of the atmosphere have radii less than about 0.09 micron and that the optical thickness of the small aerosol layer is about 0.6 above an effectively depolarizing surface, and indicate radii of 2845 + or - 25 km and 2880 + or - 22 km in red and blue light, respectively. Earth-based and spacecraft data are consistent with the formation of rings structures as a result of Poynting-Robertson drag and gravitational satellite resonances with the original ice and rock particles.
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  • 134
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    Upper atmosphere of Jupiter - A post Voyager perspective (1981)
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    Publication Date: 2011-08-18
    Description: Some significant upper atmosphere features of Jupiter are discussed with reference to the Voyager observations of 1979. From the time of Pioneer observations in 1973-1974, the Jovian upper atmospheric temperature has increased by about 30%, the eddy diffusion coefficient at the homopause decreased by a factor of 100, the equatorial disk Lyman alpha intensity increased by a factor of 30, and the equatorial ionosphere became more extensive and showed diurnal variation. Important potential candidates for upper atmosphere energetics are thought to be the penetration of the magnetospheric soft electrons, Joule heating mechanism, and auroral electrons.
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  • 135
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    The development of future lunar exploration (1981)
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    Publication Date: 2011-08-18
    Description: Selected aspects of the eventual development of lunar exploration leading to the establishment of a human outpost on the moon are discussed. Possible means of spacecraft propulsion and guidance on an earth-moon trajectory are examined, together with likely means of telecommunications, including by laser and lunar-orbiting communications satellites. As yet unexploited orbits in the earth-moon system are pointed out, and the necessity for the increased use of computerized robots for surface navigation is discussed. Favorable locations for a habitat site, particularly the lunar poles are also considered. Implications of the availability of extraterrestrial resources for materials processing techniques and food production in the lunar environment are then indicated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: vol. 34; Jan. 198
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  • 136
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    The DSN radio science system (1981)
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    Publication Date: 2011-08-18
    Description: The Radio Science experiments at Voyager 1 Saturn encounter which included two atmospheric occultations, a planetary ring occultation, and ring scattering experiment were supported by Deep Space Stations in Australia (DSS 43) and Spain (DSS 63). The DSN Radio Science System data flow from receipt of the radio signals at the antenna to delivery of the recorded data to the project are described.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Telecommun. and Data Acquisition; p 89-93
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  • 137
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    Formation of organic molecules on Titan (1981)
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    Publication Date: 2011-08-18
    Description: A mechanism is proposed for the formation of complex organic nitrogen compounds in the dense lower atmosphere of Titan. The mechanism is based on three-body association reactions with HCNH(+) ions formed by the reaction of N(+) with CH4, which lead to the production of ethyl cyanide, vinyl cyanide and cyanoacetylene. Calculations for a model atmosphere consistent with the preliminary interpretation of Voyager 1 data for the region of maximum cosmic ray activated chemistry, corresponding to a temperature between 150 and 160 K and a pressure of 20 mbar, are presented which show substantial organic nitrile and hydrogen cyanide production rates. Based on these production rates, it is expected that significant equilibrium concentrations of these compounds will be found on Titan.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 293; Sept. 3
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  • 138
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    Anomalous C-12H4:C-13H4 strengths in 3 ny sub 3 (1981)
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    Publication Date: 2011-08-18
    Description: The C-12:C-13 ratios in the atmospheres of the outer planets are important parameters with which to test models for isotope formation and fractionation during the early history of the solar system, yielding insight into processes occurring in the primitive solar nebula. The 3 ny sub 3 spectra of methane were obtained using the Kitt Peak Solar Fourier Transform Spectrometer and a 6 m White cell. The experimental results are summarized in a table. The strength ratios for the R-branch of 3 ny sub 3 exhibit strong anomalies, with C-13H4 lines consistently weaker than their C-12H4 counterparts. The C-12:C-13 abundance ratios for the atmospheres of Jupiter and Saturn have been redetermined using the 3 ny sub 3 line-strength ratios measured.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 247
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  • 139
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    Asteroidal agglutinate formation and implications for asteroidal surfaces (1981)
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    Publication Date: 2011-08-18
    Description: The possible role of spallation on the free surfaces of target bodies in asteroid surface evolution in the presence of colliding bodies is considered. The ease of impact melt formation is discussed based on the results of shock recovery experiments, and a difference between collisions with dense, nonporous targets and with porous, particulate powders is demonstrated. It is shown that agglutinate-type glasses can be produced at impact velocities of 5 km/sec, but only in highly comminuted, porous targets and not in dense rocks. The apparent lack of agglutinate-type glasses on asteroid surfaces is explained in terms of coarse-grained asteroidal surfaces acting as dense, nonporous bedrock. It is argued that a possible mechanism inhibiting asteroidal surface comminution so as to inhibit melt formation and the effects of micrometeoroid impacts can be represented by collision processes with finite-sized targets rather than with a semi-infinite half-space as in the case of the moon, which give rise to spallation products rather than crater ejecta.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 46; June 198
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  • 140
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    Saturn's magnetic tail - Structure and dynamics (1981)
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    Publication Date: 2011-08-18
    Description: Voyager 1 magnetic field observations have provided evidence of a Saturnian magnetic tail. Tail current system distributions are inferred through comparison of the observations with a realistic magnetotail current system model. Temporal variations observed in the tail were probably produced by solar wind variations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 292; Aug. 20
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  • 141
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    Surface waves on Saturn's magnetopause (1981)
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    Publication Date: 2011-08-18
    Description: Voyager 1 magnetometer data have shown that small-amplitude surface waves occurred on Saturn's dayside magnetopause, causing multiple inbound crossings of this boundary. These waves were travelling approximately parallel to Saturn's equatorial plane along the magnetopause ('tailward'), suggesting that they were driven by the rotation of Saturn's magnetosphere. Hydromagnetic waves (possibly slow mode) were observed in the adjacent magnetosheath.
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    Type: Nature; 292; Aug. 20
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  • 142
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    Saturn's kilometric radiation - Satellite modulation (1981)
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    Publication Date: 2011-08-18
    Description: There is an episodic 66-h modulation of the Saturn kilometric radiation which is both frequency and Dione-phase dependent. The behavior is significantly different from the way in which Io modulates the Jovian emission.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 292; Aug. 20
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  • 143
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    Saturnian kilometric radiation - Statistical properties and beam geometry (1981)
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    Publication Date: 2011-08-18
    Description: An adequate description of the average statistical properties of Saturn's radio emissions is needed for a study of these emissions. Data regarding these properties are presented, and the implications for source location, beaming, and magnetic surface anomalies are discussed. A description is presented of the average properties of the Saturn kilometric radiation (SKR) as observed from two locations by the Voyager 1 planetary radio astronomy (PRA) instrument for a 2-month period centered on the November 12, 1980 encounter. An analysis of the occurrence pattern of SKR as a function of Saturn's rotation phase has shown that SKR occurrence is not continuous, but variable and roughly periodic. The statistical SKR properties obtained strongly constrain possible source locations. Several source locations are possible, but most intriguing is the region at high latitudes near the noon meridian.
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    Type: Nature; 292; Aug. 20
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  • 144
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    Arc structure in Saturn's radio dynamic spectra (1981)
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    Publication Date: 2011-08-18
    Description: It is pointed out that one of the most spectacular findings of the Voyager 1 planetary radio astronomy experiment (PRA) was the discovery of nested arc-like structures in the dynamic spectra of Jupiter's decametric emission. These arcs have curvature in either a direction towards increasing or decreasing time. Similar arc structures are also evident in Saturn kilometric radiation. These structures appear superimposed on the strong intensity modulation which is controlled by the rotation of the planet and on fast and narrow band fluctuations which give a very large variability to the PRA observations on a 6-s, 20-kHz scale. The characteristics of the arcs are examined and compared with the arc structure in Jupiter. The similarities between Saturn's and Jupiter's arc structures are found to imply that they are probably due to the same physical mechanism.
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    Type: Nature; 292; Aug. 20
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  • 145
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    Saturn's ring current and inner magnetosphere (1981)
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    Publication Date: 2011-08-18
    Description: The Voyager 1 magnetic field observations at Saturn are shown in a graph. The departure of the oberved magnetic field from the field of a dipole is considered. The observed field magnitude is appreciable less than that of the model dipole at small radial distances and greater than the model dipole in the more distant magnetosphere. These characteristics can be understood by introducing a model current system similar to a system originally applied to observations of the Jovian magnetic disk. Saturn's ring current has important implications for charged-particle motion in Saturn's magnetosphere, particularly the absorption of trapped radiation by its many satellites and rings. The absorption signature observed by the Voyager 1 cosmic ray experiment near the orbital position of Rhea illustrates well the effects of Saturn's ring current on charged particle trajectories.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 292; Aug. 20
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  • 146
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    Topology of Saturn's main magnetic field (1981)
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    Publication Date: 2011-08-18
    Description: The reported analysis of Saturn's main magnetic field takes into account the data obtained by Voyager 1 during its close flyby of Saturn in November 1980. A magnetic field model for the analysis of Saturn's main field in which the distributed ring currents are explicitly modelled is constructed. The considered internal field parameters constitute a first approximation to Saturn's main field. Several model current systems that might be expected on physical grounds to be active in Saturn's magnetosphere are considered. It is pointed out that certain aspects of Saturn's main magnetic field relevant to the planet's interior have been discussed by Stevenson (1980). In particular, the unexpectedly small dipole moment seems to be consistent with the gravitational settling of helium, which leads to a much smaller electrically conducting and convecting region than would be expected of a homogeneous distribution of hydrogen and helium.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 292; Aug. 20
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  • 147
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    Low-frequency plasma waves near Saturn (1981)
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    Publication Date: 2011-08-18
    Description: Voyager planetary radio astronomy observations of low frequency emissions detected around the time of closest approach to Saturn and near the outbound ring plane crossing are presented. Near the ring plane an electron density of between 5 and 20 electrons/cu cm at dista
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    Type: Nature; 292; Aug. 20
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  • 148
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    Impulsive radio discharges near Saturn (1981)
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    Publication Date: 2011-08-18
    Description: Nonthermal radio emissions from the Saturn system were first detected by the Voyager planetary radio astronomy (PRA) experiment on board Voyager 1 in January 1980. Since then emission between 100 kHz and 1 MHz from the planet, termed Saturn kilometric radiation (SKR), has been received almost continuously. A description is presented of eight characteristics which have been fairly well defined by the Voyager 1 encounter. These include a very flat broadband frequency spectrum, a period of approximately 10 h 10 min, a change in the envelope shape of episodes between pre and postencounter, an intensity population structure typical of plural populations, and an episodic structure of a width of approximately 180 deg. It was found that postencounter episodes continue for about three times as long as preencounter ones, and that postencounter bursts are left-circularly polarized at high frequencies. At least one episode shows the onset of high frequency events some time before that of lower frequency ones.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 292; Aug. 20
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  • 149
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    Distribution of neutral gas and dust near Saturn (1981)
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    Publication Date: 2011-08-18
    Description: The distribution of neutral gas and dust within the magnetosphere of Saturn has been inferred from the electron velocity distribution functions measured by the Voyager 1 plasma science experiment. Substantial enhancements of neutral material near Titan and in the vicinity of Enceladus are found. The E ring is also shown to be larger than previously thought.
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    Type: Nature; 292; Aug. 20
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  • 150
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    Titan's atmosphere - Temperature and dynamics (1981)
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    Publication Date: 2011-08-18
    Description: In the lower atmosphere of Titan IR brightness temperatures exhibit meridional contrast less than approximately 3 K. Seasonal variations are absent because of the large radiative time constant. In the upper stratosphere meridional contrasts are approximately 20 K, consistent with 100 m/s cyclostrophic zonal winds, and the radiative time constant is short, implying a large seasonal variation in the temperature and wind field. The absence of longitudinal thermal structure implies that zonally symmetric flows effect the meridional transport of heat. A simple model yields meridional velocities approximately 0.04 cm/s and vertical eddy viscosities approximately 1,000 sq cm/s in the lower troposphere, and meridional velocities approximately 5 cm/s in the upper stratosphere.
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    Type: Nature; 292; Aug. 20
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  • 151
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    Mean molecular weight and hydrogen abundance of Titan's atmosphere (1981)
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    Publication Date: 2011-08-18
    Description: The 200-600/cm continuum opacity in the troposphere and lower stratosphere of Titan is inferred from thermal emission spectra from the Voyager 1 IR spectrometer (IRIS). The surface temperature and mean molecular weight are between 94 and 97 K and between 28.3 and 29.2 AMU, respectively. The mole fraction of molecular hydrogen is 0.002 + or - 0.001, which is equivalent to an abundance of approximately 0.2 + or - 0.1 km amagat.
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    Type: Nature; 292; Aug. 20
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  • 152
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    C4H2, HC3N and C2N2 in Titan's atmosphere (1981)
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    Publication Date: 2011-08-18
    Description: Voyager 1 took IR measurements of the atmosphere of Titan, and obtained an average of 346 spectra, mostly from the center of the disk. The compounds C4H2, HC3N, and C2N2 were detected in the atmosphere of Titan. The identification of two compounds containing nitrogen, in addition to HCN, provides further evidence for the abundance of free N2 on Titan. The organic compounds observed in the atmosphere of Titan are summarized in a table, which also indicates the approximate mole fraction for each compound identified previously. The observed compounds originate by reactions of methane and nitrogen radicals in a predominantly nitrogen atmosphere.
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    Type: Nature; 292; Aug. 20
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  • 153
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    C3H8 and C3H4 in Titan's atmosphere (1981)
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    Publication Date: 2011-08-18
    Description: Four bands of propane C3H8 and two of methyl acetylene C3H4 have been identified in the Voyager IR spectrum of Titan. Stratospheric abundances of 2 x 10 to the -5 for C3H8 and 3 x 10 to the -8 for C3H4 have been determined for the mid-latitude region. A feature at 1,154/cm, previously assigned solely to CH3D, is now identified at least in part due to C3H8.
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    Type: Nature; 292; Aug. 20
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  • 154
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    Saturn ionosphere - Theoretical interpretation (1981)
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    Publication Date: 2011-08-18
    Description: Voyager 1 high latitude and Pioneer 11 equatorial ionospheric structure indicate a solar EUV-controlled ionosphere with a possible molecular ion in the topside. Vibrationally excited H2 in the high latitudes may be an important loss mechanism. Dynamical effects are expected to be important for determining the peak density and its location.
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    Type: Nature; 292; Aug. 20
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    Thermal structure and dynamics of Saturn and Jupiter (1981)
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    Publication Date: 2011-08-18
    Description: High resolution Voyager IRIS measurements for Saturn and Jupiter are assembled in meridional cross sections of the retrieved upper tropospheric temperatures. The calculated thermal wind shear in the upper troposphere is highly correlated on both planets with the cloud top winds derived from imaging data. In contrast, temperatures below approximately 300 mbar are not simply related to the zonal jet structure. The upper tropospheric temperatures seem to have been more consistently correlated with cloud top winds than with major albedo features at the time of the Voyager encounters.
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    Type: Nature; 292; Aug. 20
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    Estimates of total quantity of meteorites in the East Antarctic ice cap (1981)
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    Publication Date: 2011-08-18
    Description: Based on a steady-state model of the East Antarctic ice cap, and current estimates of meteorite influx, a model is developed which predicts that the steady-state number of meteorites being carried in or on the ice is at least 760,000. This large meteorite population does not require unusual influx conditions, since the cold, dry climate preserves virtually all meteorites that fall with the exception of the fragile, porous carbonaceous chondrites. Application of the model to the Greenland ice cap yields a steady-state population of about 61,000 meteorites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 292; Aug. 6
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    Eruption mechanics on the earth, moon and Mars (1981)
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    Publication Date: 2011-08-18
    Description: A survey is provided of recent comparative studies on the character of eruption mechanics on earth, the moon and Mars. Among the relevant determinations made are: (1) a source depth for lunar basaltic magmas deeper, at 100 km, than most terrestrial ones; (2) the rising of both lunar and terrestrial magmas to less than 2 km below the surface before gases begin to exsolve; (3) carbon monoxide concentrations in lunar basalts are an order of magnitude lower than the average volatile contents of terrestrial basalts; and (4) unequivocal proof is lacking for the existence of ignimbrites in Martian volcanic formations, which would be formed by the collapse of large eruption columns.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 292; Aug. 6
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    The magnetic fields of Jupiter and Saturn (1981)
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    Publication Date: 2011-08-18
    Description: The magnetic fields of Jupiter and Saturn and the characteristics of their magnetospheres, formed by interaction with the solar wind, are discussed. The origins of both magnetic fields are associated with a dynamo process deep in the planetary interior. The Jovian magnetosphere is analogous to that of a pulsar magnetosphere: a massive central body with a rapid rotation and an associated intense magnetic field. Its most distinctive feature is its magnetodisk of concentrated plasma and particle flux, and reduced magnetic field intensity. The magnetopause near the subsolar point has been observed at radial distances ranging over 50 to 100 Jovian radii, implying a relatively compressible obstacle to solar wind flow. The composition of an embedded current sheet within the magnetic tail is believed to be influenced by volcanic eruptions and emissions from Io. Spectral troughs of the Jovian radiation belts have been interpreted as possible ring particles. The Saturnian magnetosphere appears to be more like the earth in its topology. It is mainly characterized by a dipole axis parallel to the rotational axis of the planet and a magnetic field intensity much less than expected.
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  • 159
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    Ridge systems of Mars (1981)
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    Publication Date: 2011-08-18
    Description: Mare-type ridges on the Planet Mars were mapped and described based on Viking images. The ridges mapped range from 5 to 400 km long and 1 to 8 km wide. Most ridges on Mars are on plains and plateau units; 4,321 ridges with a total length of 153,835 km were mapped on these unit types. Ridges which resemble lunar mare ridges were also mapped in craters, basins, and several volcanic calderas on Mars. Mapping of ridges on a global scale reveals that they are preferentially developed in older, thinner plains units probably of flood basalt origin. Measuring the trends of ridges in plains units on Mars shows that there is a planetwide predominance of north, northwest and northeast trends. It is proposed that ridges are compressional tectonic features which have formed in response to changes in the planet's rotational equilibrium figure early in its history. In addition, the Tharsis uplift has created a regional stress system which accounts for the trends of ridges in areas near by. Ridges in craters and basins are similarly caused by shortening across the basin in response to regional stresses.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Washington Advan. in Planetary Geol.; p 222-364
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  • 160
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    The atmospheres of Jupiter, Saturn and Titan (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Spacecraft observations of Jupiter, Saturn and Titan are discussed. The relative abundance of helium differs for the two planets, being about 10% for Jupiter and 6% for Saturn. These ratios are consistent with the same age of the planets and internal heat fluxes as measured; Saturn emits IR at about 2.5 to 3 times the incident solar flux, while Jupiter emits about 1.8 to 2 times. Jupiter's zonal jet system is more stable than the colorful markings on the planet. Anticyclonic and cyclonic motions are observed, with the Great Red Spot being the most prominent anticyclonic system. Compared with Jupiter, peak zonal velocities on Saturn are three times higher, reaching two-thirds of the speed of sound near the equator. The zonal jets are much wider and do not have any clear relation to the banded structure. Saturn lacks large oval spots, although features of diameter 1000 km are more abundant than on Jupiter. Titan's atmosphere consists of nitrogen (82%) methane (6%) H2 (0.2%) and, possibly, Argon (12%)
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: ESA The Solar System and its Exploration; p 161-163
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  • 161
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    Standing Alfven wave current system at Io - Voyager 1 observations (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The enigmatic control of the occurrence frequency of Jupiter's decametric emissions by the satellite Io has been explained theoretically on the basis of its strong electrodynamic interaction with the corotating Jovian magnetosphere leading to field-aligned currents connecting Io with the Jovian ionosphere. Direct measurements of the perturbation magnetic fields due to this current system were obtained by the Goddard Space Flight Center magnetic field experiment on Voyager 1 on March 5, 1979, when it passed within 20,500 km south of Io. An interpretation in the framework of Alfven waves radiated by Io leads to current estimates of 2.8 x 10 to the 6th A. A mass density of 7400-13,600 proton mass units/cu cm is derived, which compares very favorably with independent observations of the torus composition characterized by 7-9 proton mass units per electron for a local electron density of 1050-1500/cu cm. The power dissipated in the current system may be important for heating the Io heavy ion torus, inner magnetosphere, Jovian ionosphere, and possibly the ionosphere or even the interior of Io.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Sept. 30
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  • 162
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    Observations of electron gyroharmonic waves and the structure of the Io torus (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Narrow-banded emissions observed by the planetary radio astronomy experiment on the Voyager 1 spacecraft as it traversed the Io plasma torus are discussed. It is found that the waves occur between harmonics of the electron gyrofrequency; they are Jovian analogue of electrostatic emissions observed and theoretically studied for the terrestrial magnetosphere. It is noted that the observed frequencies always include the component near the upper hybrid resonant frequency but that the distribution of the other observed emissions varies in a systematic way with position in the torus. A detailed discussion of the observations is given. Also included is a refined model of the electron density variation, based on identification of the upper hybrid resonant frequency line.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Sept. 30
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  • 163
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    Energetic particles in the predawn magnetotail of Jupiter (1981)
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    Publication Date: 2011-08-18
    Description: A detailed account of the energetic electron and proton populations as observed with Voyager 1 and 2 during their passes through the dawn magnetotail of Jupiter is given. As in the case of Pioneer 10, a thin plasma sheet is found at the magnetic equator which was already well developed near 23 Jupiter radii. It is pointed out that the plasma sheet positions in the magnetotail can be represented by a distorted disk which rotates about the Jovian spin axis.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Sept. 30
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  • 164
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    The Jovian magnetotail and its current sheet (1981)
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    Publication Date: 2011-08-18
    Description: A summary is given of the results of a further analysis of the magnetic field measurements in Jupiter's magnetic tail and in the region of the tail current sheet by both V1 and V2. Four studies are discussed. The first is a determination of the variation of the average magnetic field magnitude in the lobes of the magnetotail, that is, outside the plasma sheet, as a function of distance from the planet. The second is an examination of the variation with distance from Jupiter of the ratio of the azimuthal component of the magnetic field to the product of the radial distance and the radial component of the magnetic field. The third is a study of the detailed structure and orientation of the tail current sheet system, including both detailed illustrations of typical sheet crossings and the results of a minimum variance analysis of all V2 tail sheet traversals. The fourth is an investigation of various models which predict the position of the current sheet in the outer Jovian magnetosphere as a function of both time and location.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Sept. 30
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  • 165
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    Modeling the Jovian current sheet and inner magnetosphere (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Voyager 1 and 2 magnetic field observations confirm and extend the earlier Pioneer 10 detection of the Jovian magnetodisc, a region of enhanced charged particles and plasma and reduced magnetic field intensity located near the magnetic equatorial plane. Modeling of the azimuthal current sheet by a finite thickness annulus of inner radius 5 Jovian radii, 5-Jovian radii thickness, and extending to about 50 Jovian radii provides detailed fits of the vector magnetic field perturbations observed in relation to the planetary field for distances less than 30 Jovian radii. Field line geometry is also investigated, and better insight into the phenomena of charged particle absorption by the Galilean satellites is obtained which provides improved explanations of observed effects due to Ganymede.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Sept. 30
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  • 166
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    A survey of the plasma electron environment of Jupiter - A view from Voyager (1981)
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    Publication Date: 2011-08-18
    Description: A survey of the plasma environment within Jupiter's bow shock is given in terms of the in situ calibrated electron plasma measurements made between 10 eV and 5.95 keV by the Voyager Plasma Science Experiment (PLS). The measurements are analyzed and corrected for spacecraft potential variations; the data are reduced to nearly model independent macroscopic parameters of the local electron density and temperature. The electron parameters are derived without reference to or internal calibration from the positive ion measurements made in the PLS experiment. Extensive statistical and direct comparisons with other determinations of the local plasma charge density indicate clearly that the analysis procedures have successfully and routinely discriminated between spacecraft sheath and ambient plasmas.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Sept. 30
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  • 167
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    Physics of planetary atmospheres and ionospheres (1981)
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    Publication Date: 2011-08-18
    Description: The traditional atmospheric regions, the distinction between homosphere and heterosphere, and changing atmospheric composition are discussed. The validity of the barometric law based on a Maxwell-Boltzmann distribution, for the major part of a planetary atmosphere and its breakdown in the exosphere due to escape of atmospheric particles is considered. The formation and maintenance of photochemical and diffusion-controlled ionospheric layers are treated. Their applicability to planetary ionospheres is dealt with. The spatial extent of magnetic and nonmagnetic planet ionospheres is investigated. Thermal and nonthermal processes responsible for the mass loss of planetary atmospheres are surveyed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: ESA The Solar System and its Exploration; p 157-160
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  • 168
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    Scientific results from the Pioneer Saturn infrared radiometer (1981)
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    Publication Date: 2011-08-18
    Description: Data on Saturn and its rings are presented, obtained by the Pioneer 11 infrared radiometer in broadband channels, centered at 20 and 45 microns. Assuming symmetry about the equator and a constant flux poleward of 7.5 deg latitude, an average effective temperature of 96.5 + or - 2.5 K indicates a total emission which is 2.8 times that of the absorbed sunlight. Temperatures at the 1 bar level are 137 and 140 K, and a minimum temperature averaging 87 K is registered near the 0.06 bar level. Ring boundaries and optical depths are consistent with those at optical wavelengths. Ring temperatures are 54-86 K on the south side, approximately 54 K on the north side, and at least 67 K in Saturn's shadow.
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  • 169
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    Study of the ammonia ice cloud layer in the Equatorial Region of Jupiter from the infrared interferometric experiment on Voyager (1981)
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    Publication Date: 2011-08-18
    Description: Spectra from the Voyager 1 infrared interferometer spectrometer (IRIS) obtained near the time of closest approach to Jupiter were analyzed for the purpose of inferring ammonia cloud properties associated with the Equatorial Region. Comparisons of observed spectra with synthetic spectra computed from a radiative transfer formulation, that includes multiple scattering, yielded the following conclusions: (1) very few NH3 ice particles with radii less than 3 microns contribute to the cloud opacity; (2) the major source of cloud opacity arises from particles with radii in excess of 30 microns; (3) column particle densities are between 1 and 2 orders of magnitude smaller than those derived from thermochemical considerations alone, implying the presence of important atmospheric motion; and (4) another cloud system is confirmed to exist deeper in the Jovian troposphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 46; May 1981
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  • 170
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    Saturn's pole - geometric correction based on voyager UVS and radio occultations (1983)
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    Publication Date: 2011-08-18
    Description: Measurements of of the opacity of Saturn's rings acquired during occultation experiments at radio (3.6 cm) and ultraviolet wavelengths were initially reduced to radial position rho using a standard pole vector. Common features in the two data sets from this reduction were offset by distances Delta rho(i). These offsets have been attributed to an error in the pole direction. Because the viewing geometries were quite different for the two experiments, the set of differences of Delta rho(i) provides a sensitive measure of corrections needed to refine the Saturn pole direction. The new standard pole vector in 1950.0 coordinates has right ascension alpha = 38.409 + or - 0.016 deg and declination delta = 83.324 + or - 0.002 deg.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal (ISSN 0004-6256); 88; Oct. 198
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  • 171
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    Laboratory simulation of Venusian lightning (1983)
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    Publication Date: 2011-08-18
    Description: Evidence of lightning activity in the Venusian atmosphere has been obtained from the Venera 9, 11, and 12 spacecraft, and from the Pioneer Venus Orbiter (PVO). However, a search for optical pulses expected from Venusian lightning using the star sensor on the PVO did not detect any signals. It has been suggested that the star sensor did not detect lightning because Venusian lightning does not radiate in the 500- to 900-nm spectral region detected by the star sensor. In this paper, spectra obtained from a laboratory simulation of Venusian lightning are discussed. Both the laboratory spectrum and the results of a theoretical calculation of line intensities show that Venusian lightning can be expected to radiate strongly in the 600- to 900-nm spectral region. Hence, the failure of the star sensor to detect lightning must be caused by the low flashing rate or by the low intensity of Venusian lightning.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; Oct. 198
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  • 172
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    Identification of deuterium ions in the ionosphere of Venus (1983)
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    Publication Date: 2011-08-18
    Description: The dominant mass two ion in the ionosphere of Venus is identified as D(+) through analysis of the height variation of (mass two ion)/(H(+)) measured in the chemical equilibrium region by the ion mass spectrometer on the Pioneer Venus Orbiter. This result leads to (D)/(H) = (2.2 + or - 0.6) x 10 to the -2 at the turbopause, which agrees with the ratio measured in the lower atmosphere by the large probe mass spectrometer. The 100-fold deuterium enrichment supports previous suggestions that Venus has lost at least 0.3 percent of a terrestrial ocean.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; Oct. 198
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  • 173
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    W-shaped occultation signatures - Inference of entwined particle orbits in charged planetary ringlets (1983)
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    Publication Date: 2011-08-18
    Description: A model for the ringlets of Saturn is proposed where concentration of material near the inner and outer radial edges of the ringlets is a natural consequence of particles in entwined elliptical orbits, with the same particles alternately defining both edges. The existence of a collisionless state where particles fly along entwined paths in a compressed helical formation on and within a toroidal surface whose meridional cross section is a very thin ellipse is explained. The cancellation of strong oblateness perturbations by an extremely weak force normal to the orbit planes and directed primarily outward from the major axis of the meridional cross section of the torus is shown, and the possibility that electric repulsion of like-charged particles could provide the expansion force preventing cross-sectional collapse is examined. The model features a large stability domain within which orbital inclinations and arguments of periapse oscillate but do not progress. Features of the model that can be tested experimentally are mentioned.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0019-1035)
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  • 174
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    Planetary magnetic fields (1983)
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    Publication Date: 2011-08-18
    Description: Observations of planetary magnetic fields are synthesized with current knowledge of the composition and evolution of planets and the sources of planetary magnetism. The observations for earth, Jupiter, Saturn, Mercury, Venus, the moon, Mars, and small bodies and meteorites are summarized. The evolution and structure of the terrestrial planets, of Jupiter and Saturn, and of Uranus and Neptune are discussed in detail. Possible sources of planetary magnetism are discussed, and estimates are established which are sufficient in most cases to identify whether an observed field is likely to be the consequence of dynamo generation. Predictions of the existence or nonexistence of dynamos are offered for each large planet or satellite in the solar system.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Reports on Progress in Physics (ISSN 0034-4885); 46; May 1983
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  • 175
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    Summary of several recent chondrite finds from the Texas Panhandle (1983)
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    Publication Date: 2011-08-18
    Description: Eleven recent chondrite finds from the Texas Panhandle have been examined and classified according to mineralogical and petrological criteria: five H's, five L's, and one LL chondrite. Five are distinct from nearby finds, while three remain ambiguous and three are related to previously reported chondrites. In addition, data are provided to classify the Muleshoe, Silverton, and Vigo Park chondrites, all of which were previously undescribed in the literature.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 18; March 31
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  • 176
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    Venus' nighttime horizontal plasma flow, 'magnetic congestion', and ionospheric hole production (1983)
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    Publication Date: 2011-08-18
    Description: A simple rectilinear, two-dimensional MHD model is used to investigate the effects of field-aligned plasma loss and cooling on a dense plasma convecting across a weak magnetic field, in order to illumine the Venus nighttime phenomena of horizontal plasma flow, magnetic congestion and ionospheric hole production. By parameterizing field-aligned variations and explicitly solving for cross magnetic field variations, it is shown that the abrupt horizontal enhancements of the vertical magnetic field, as well as sudden decreases of the plasma density to very low values (which are characteristic of ionospheric holes), can be produced in the presence of field-aligned losses.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 88; Apr. 1
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  • 177
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    Radiative equilibrium model of Titan's atmosphere (1983)
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    Publication Date: 2011-08-18
    Description: The present global radiative equilibrium model for the Saturn satellite Titan is restricted to the two-stream approximation, is vertically homogeneous in its scattering properties, and is spectrally divided into one thermal and two solar channels. Between 13 and 33% of the total incident solar radiation is absorbed at the planetary surface, and the 30-60 ratio of violet to thermal IR absorption cross sections in the stratosphere leads to the large temperature inversion observed there. The spectrally integrated mass absorption coefficient at thermal wavelengths is approximately constant throughout the stratosphere, and approximately linear with pressure in the troposphere, implying the presence of a uniformly mixed aerosol in the stratosphere. There also appear to be two regions of enhanced opacity near 30 and 500 mbar.
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  • 178
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    Albedo, internal heat flux, and energy balance of Saturn (1983)
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    Publication Date: 2011-08-18
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  • 179
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    The evolution of Enceladus (1983)
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    Publication Date: 2011-08-18
    Description: Evidence is adduced for several episodes of geologic resurfacing and extensional tectonism spreading over much of the history of the small, icy Saturn moon Enceladus. Resurfacing was the product of fresh material eruptions that may have contained ammonia, which may also have made melting in the interior more likely. Tidal dissipation seems to be the only heating mechanism capable of melting Enceladus. For the thermal properties of pure H2O, the orbital eccentricity would have to be higher than the present value of 0.0044 by a factor of 5-7 in order to maintain a molten interior, and may have to be greater by a factor of 20 in order to cause melting in an initially frozen body. Removal of eccentricity forcing would result in rapid eccentricity damping, freezing, and the cessation of tectonic activity.
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  • 180
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    Lightning generation in planetary atmospheres (1983)
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    Publication Date: 2011-08-18
    Description: The possibilities of lightning generation on other planets are considered, and the basic conditions that exist in terrestrial clouds during lightning discharges and the various theories of charge separation are reviewed. The properties of terrestrial clouds that produce lightning, the properties of lightning itself, and the fairweather field are first reviewed. The general requirements and the different proposed charging mechanisms for electrification of terrestrial clouds are discussed. The mechanisms of electrical breakdown and whistler production are considered, and recent observations of extraterrestrial lightning and of clouds on other planetary bodies are summarized. Circumstances likely to account for lightning activity on Jupiter and Venus and for electrical activity on Mars and in the rings of Saturn are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 56; 80-115
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  • 181
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    Io (1983)
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    Publication Date: 2011-08-18
    Description: A report on the continuing investigation of Io is presented. Gravitational resonance is discussed as the cause of Io's volcanism, and the volcanic activity is explained in terms of sulfur chemistry. Theories concerning the reasons for the two main types of volcanic eruptions on Io are advanced and correlated with geographical features of the satellite. The sulfur and silicate models of the calderas are presented, citing the strengths and weaknesses of each. Problems of the gravitational resonance theory of Io's heat source are then described. Finally, observations of Io planned for the Galileo mission are summarized.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Scientific American (ISSN 0036-8733); 249; 56-67
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  • 182
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    Bunte Breccia of the Ries - Continuous deposits of large impact craters (1983)
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    Publication Date: 2011-08-18
    Description: The 26-km-diameter Ries impact crater in south Germany and the mechanism of ejection and emplacement associated with its formation about 15 Myr ago are discussed in detail, and the implications of the findings for models of crater formation on earth, moon, and planets are considered. Field observations and laboratory tests on 560-m core materials from nine locations are reported. The continuous deposits (Bunte Breccia) are found to be a chaotic mixture resulting from deposition at ambient temperatures in a highly turbulent environment, probably in the ballistic scenario proposed by Oberbeck et al. (1975), with an emplacement time of only about 5 min. Further impact parameters are estimated using the 'Z model' of Maxwell (1977): initial radius = 6.5 km, excavation depth = 1650 m, excavation volume = 136 cu km, and transient cavity volume = 230 cu km. The interpretation of lunar and planetary remote-sensing and in situ evidence from impact craters is reviewed in the light of the Ries findings. Numerous photographs, maps, diagrams, and tables illustrate the investigation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Reviews of Geophysics and Space Physics (ISSN 0034-6853); 21; 1667-172
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  • 183
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    On the habitability of Europa (1983)
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    Publication Date: 2011-08-18
    Description: It is pointed out that the Voyager flybys of Jupiter produced remarkable images of Europa, one of the four large Galilean satellites. Taking into account information provided by these Voyagers flybys and other data and investigations, a study is conducted regarding the suitability of Europa as a habitat for living organisms. The performed calculations indicate, that for a plausible physical model of Europa, the general conditions for the survival of biological organisms could exist, at least in some regions, highly restricted in both space and time.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 56; 246-254
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  • 184
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    Evidence for disequilibrium of ortho and para hydrogen on Jupiter from Voyager IRIS measurements (1983)
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    Publication Date: 2011-08-18
    Description: Preliminary results of an analysis of the ortho state/para state ratio (parallel/antiparallel) for molecular H2 in the Jovian atmosphere using Voyager IR spectrometer (IRIS) data are reported. The study was undertaken to expand the understanding of the thermodynamics of a predominantly H2 atmosphere, which takes about 100 million sec to reach equilibrium. IRIS data provided 4.3/cm resolution in the 300-700/cm spectral range dominated by H2 lines. Approximately 600 spectra were examined to detect any disequilibrium between the hydrogen species. The results indicate that the ortho-para ratio is not in an equilibrium state in the upper Jovian troposphere. A thorough mapping of the para-state molecules in the upper atmosphere could therefore aid in mapping the atmospheric flowfield.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 306; 571
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  • 185
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    C-12H3D rovibrational intensities and the Jovian D/H ratio (1983)
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    Publication Date: 2011-08-18
    Description: A tabulation is given of line intensities for the nu(2) band of CH3D which have absolute accuracies of + or - 3 percent. Using these intensities, some of the previous Jovian D/H determinations are reinterpreted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 273; L47-L49
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  • 186
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    Size estimates of Titan's aerosols based on Voyager high-phase-angle images (1983)
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    Publication Date: 2011-08-18
    Description: Limits on the physical properties of the scattering haze near the top of Titan's atmosphere are derived from data obtained from seven high-phase-angle images from Voyager 1 and 2. From the ratio of the intensities observed at two different high phase angles, an estimate can be made of the forward-scattering lobe of the single-scattering phase function. Comparing the forward-scattering estimate with diffraction lobes from particles of different radii, it is concluded that the average radius of the particles found in the upper few tenths of an optical depth exceeds 0.19 micron. Judging from data observed at four different phase angles, the haze particles probably have a refractive index near 1.6 and a mean size of about 0.5 micron, if the widths of their diffraction peaks are close to those for equal-volume spheres. However, the highly polarizing nature of the particles over a broad wavelength-bandpass (Tomasko and Smith, 1982; West et al, 1983) combined with their forward-scattering behavior makes it very unlikely that the particles are spherical. The nonsphericity contributes to the uncertainty about the radii of the particles, but it is thought that the average radius is several tenths of a micron.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 8721-872
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  • 187
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    The relationship between Saturn kilometric radiation and the solar wind (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Voyager spacecraft radio, interplanetary plasma, and interplanetary magnetic field data are used to show that large amplitude fluctuations in the power generated by the Saturn kilometric radio emission are best correlated with solar wind ram pressure variation. In all, thirteen solar wind quantities previously found important in driving terrestrial magnetospheric substorms and other auroral processes were examined for evidence of correlations with the Saturn radio emission. The results are consistent with hydromagnetic wave or eddy diffusion processes driven by large scale solar wind pressure changes at Saturn's dayside magnetopause. Previously announced in STAR as N83-24445
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 8999-900
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  • 188
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    Energetic atomic and molecular ions in Saturn's magnetosphere (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Voyager 1 and 2 sensor data are analyzed in order to derive the composition, energy spectra, and spatial distribution of energetic ions in the Saturn magnetosphere. In order of abundance, the major species are H, H2(+), He, H3(+), C, and O. The fluxes of all species decreased inside the orbit of Dione, and nearly vanished in the 'slot' region within the orbit of Tethys. Both satellite absorption and precipitation due to pitch angle scattering may be important loss processes in that region. In the outer magnetosphere, photodissociation rapidly destroys a large fraction of the H2(+) ions, but dissociation by impact with neutral H atoms is faster for H2(+) ions in the lowest vibrational state. The ground state lifetime of about 23 days places a limit of about 10-100 days on the mean overall residence time for energetic ions in Saturn's magnetosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 8905-892
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  • 189
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    Currents in Saturn's magnetosphere (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A model of Saturn's magnetospheric magnetic field is obtained from the Voyager 1 and 2 observations. A representation consisting of the Z sub 3 zonal harmonic model of Saturn's planetary magnetic field together with an explicit model of Saturn's planetary magnetic field and a model of the equatorial ring current fits the observations well within r 20 R sub S, with the exception of data obtained during the Voyager 2 inbound pass. Previously announced in STAR as N83-30345
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 8779-878
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  • 190
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    Jupiter and Io - A binary magnetosphere (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: A qualitative assessment is presented of Voyager 1 and 2 data analysis and theoretical interpretation, regarding the Io torus and Jovian aurora, dominant magnetospheric components, plasma waves and radio emissions, with emphasis on the difficulty of accounting for either the Jupiter aurora or Io torus EUV emission luminosities in energetic terms. Jupiter's middle atmosphere is also considered, with attention to observations of corotating ions, their ambiguities and their implications. After a discussion of the question of Jupiter's interaction with the solar wind, as manifested by its magnetic tail, terrestrial magnetospherics are invoked in the construction of a tentative unification of observed phenomena which is within the latitude afforded by the current state of data reduction.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Vistas in Astronomy; 25; pt. 3
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  • 191
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    Photochemistry in planetary atmospheres (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Widely varying paths of evolutionary history, atmospheric processes, solar fluxes, and temperatures have produced vastly different planetary atmospheres. The similarities and differences between the earth atmosphere and those of the terrestrial planets (Venus and Mars) and of the Jovian planets are discussed in detail; consideration is also given to the photochemistry of Saturn, Uranus, Pluto, Neptune, Titan, and Triton. Changes in the earth's ancient atmosphere are described, and problems of interest in the earth's present troposphere are discussed, including the down wind effect, plume interactions, aerosol nucleation and growth, acid rain, and the fate of terpenes. Temperature fluctuations in the four principal layers of the earth's atmosphere, predicted decreases in the ozone concentration as a function of time, and spectra of particles in the earth's upper atmosphere are also presented. Finally, the vertical structure of the Venus cloud system and the thermal structure of the Jovian planets are shown graphically.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: EOS; 62; Dec. 15
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  • 192
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    Planetary-scale wave structure in the Martian atmosphere (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Wave-like perturbations are found in the Mariner 9 IRIS atmospheric temperature data during late Northern Hemisphere winter in a latitude band between 45 deg N and 65 deg N. The nature of the data base prevents a unique separation of spatial and temporal behavior, but Fourier analysis of the data constrains the waves to discrete combinations of planetary wavenumber and period. One major spectral component possesses a meridional amplitude cross section with a maximum near the 1 mbar level at 60 deg N and is strongly correlated with the circumpolar jet observed in thermal winds calculated from the mean meridional temperature cross section. This feature is consistent with the low-wavenumber baroclinic waves observed in Viking Lander data, and the vertical structure reflects the behavior anticipated for a vertically penetrating quasi-geostrophic disturbance. Other possible origins for the wave cannot be ruled out, however. Among these is a stationary wave forced by wavenumber-2 topographic relief.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 48; Nov. 198
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  • 193
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    Mars atmospheric opacity effects observed in the Northern Hemisphere by Viking orbiter imaging (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Viking orbiter television camera observations of Mars contrasts show variations of atmospheric opacity in the Southern Hemisphere. The study is extended into the Northern Hemisphere, over a longer time period, and results in a detailed description of photometric changes at the lander sites, as seen from orbit. During the period of January 1977 to April 1978, a series of four storms at 202 deg, 264 deg, 40 deg and 86 deg latitudes have provided photometric changes and planetwide aerosol distributions for 18 months. It is found that the large, forward-scattering particles did not enter the atmosphere at the storm's onsets. A reduction of atmospheric transmission by over 20% at visual wavelengths remained for nearly one Martian year.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 86; Dec. 1
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  • 194
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    Isotopic and REE studies of lunar basalt 12038 - Implications for petrogenesis of aluminous mare basalts (1981)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Sr, Nd, and Sm isotopic studies of lunar basalt 12038, one of the so-called aluminous mare basalts, are reported. The evolution of the Sr and Nd isotopic compositions and the rare earth element (REE) abundances is successfully modeled within the framework of the model developed by Nyquist et al. (1977, 1979) for Apollo 12 olivine-pigeonite and ilmenite basalts. It is pointed out that the isotopic and trace element features of 12038 can by modeled as produced by partial melting of a cumulate mantle source which crystallized from a lunar magma ocean with a chondrite-normalized REE pattern of constant negative slope. Chondrite-normalized La/Yb is equal to 2.2 for this hypothetical magma ocean pattern.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 55; 3, No; Nov. 198
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  • 195
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    The R asteroids reconsidered (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: JHK infrared photometry shows that R asteroids have two distinct infrared color domains. Most R asteroids have JHK and visual colors and albedos that fall amongst those observed for S asteroids, but a small subset is clearly different. These are designated as a new A class of asteroids.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 55; July 198
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  • 196
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    The role of seasonal reservoirs in the Mars water cycle. I Seasonal exchange of water with the regolith. II - Coupled models of the regolith, the polar caps, and atmospheric transport (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 55; July 198
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  • 197
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    Uranus - Variability of the microwave spectrum (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Radio astronomical observations of Uranus show that the radio emission spectrum is evolving in time. Ammonia vapor must be depleted in the Uranian atmosphere as Gulkis et al. (1978) previously suggested. Since 1965, ammonia either has been decreasing in time or is a decreasing function of latitude, or both, provided that the radio emission is atmospheric in origin. If Uranus has an observable low-emissivity 'surface', these trends may be reversed. The microwave observations made in 1965, at the time when the spin axis of Uranus was nearly perpendicular to the sun-Uranus line, are consistent with an atmospheric opacity profile that would be produced by saturated ammonia vapor in a predominantly hydrogen atmosphere. At the present time, when the spin axis of Uranus is nearly aligned with the sun-Uranus line, the measurements require an opacity that would be produced by saturated water vapor. A large thermal gradient between the pole and equator is ruled out.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 221; July 29
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  • 198
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    Entwined and parallel bundled orbits as alternative models for narrow planetary ringlets (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Particle orbits can be bundled in two different ways to produce narrow, Uranus-type ringlets. The usual assumption is that they are packed in a parallel manner in a structure that is essentially only two-dimensional, but it is then difficult to explain the large numbers of particles per unit area of the ring plane that are inferred from the observations. The alternative of a bundle of entwined orbits produces a three-dimensional structure of potentially large projected areal density. A start has been made in identifying possible mechanisms for stabilizing these structures, but much remains to be done, particularly for the less-studied model of entwined orbits. The two models might be discriminated observationally by differences in the motion of the line of intersection of the orbital and equatorial planes, and by the predicted radial reversal (entwined) or nonreversal (parallel) of features in occultation signatures taken at certain longitudes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 221; July 22
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  • 199
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    The magnetosphere of Saturn (1983)
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    Publication Date: 2011-08-18
    Description: Characterizations of the Saturn magnetospheric activities that have been made possible through data gathered by means of the Pioneer 11 and Voyagers 1 and 2 flybys are reviewed. The spacecraft data confirmed the presence of a Saturn magnetosphere, which features inward diffusion and energization of trapped energetic particles as well as cosmic ray albedo neutron decay as a source of inner belt protons. A dense plasma was identified in the region covering the outer magnetosphere to the magnetopause, which extends outward 17.3-23.6 Saturn radii on the sunward side and from 30.3-70 radii on the far side, according to the satellite measurements. Characteristics of the particle populations and behaviors of the outer magnetosphere, the slot region, the inner magnetosphere, and the ring region are reviewed, as are those of the magnetic field, the solar wind-magnetospheric interaction, and the Titan-magnetospheric interaction are described. Further investigation of the longitudinal asymmetry of decimetric radio emissions from Saturn is recommended.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0034-6853)
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  • 200
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    The Jovian magnetosphere (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Research on Jovian magnetospheric physics from 1979 through 1982 is surveyed, with a focus on the observations of Voyagers 1 and 2. Jovian fields and plasmas are characterized in the order of their distance from the planet, and special emphasis is given to the Io plasma torus (IPT) in the 4.9-8-Jovian-radius region and to the extended Jovian magnetotail. Topics reviewed include synchrotron radiation, magnetic-field models, Na and S emissions in the IPT, aurora, the magnetic-anomaly model, IPT plasma diffusion-convection, Io-generated Alfven wave, plasma configuration beyond the IPT, low-energy charged particles, cosmic-ray-energy particles, particle acceleration, magnetic configuration, tail current sheet and plasma disc, magnetopause and magnetosheath, interplanetary ions of Jovian origin, and the Jovian magnetosphere at Saturnian distances.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: (ISSN 0034-6853)
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