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  • LUNAR AND PLANETARY EXPLORATION  (1,220)
  • 1980-1984  (1,220)
  • 1925-1929
  • 1983  (552)
  • 1980  (668)
  • 1
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    Solar system history as recorded in the Saturnian ring structure (1983)
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    Publication Date: 2011-08-18
    Description: Holberg's analysis of the Voyager Saturn photographs in reflected and transparent light, and occultation data of stars seen through the rings are discussed. A hyperfine structure with 10,000 ringlets can be explained by the Baxter-Thompson negative diffusion. This gives the ringlets a stability which makes it possible to interpret them as fossils which originated at cosmogonic times. It is shown that the bulk structure can be explained by the combined cosmogonic shadows of the satellites Mimas and Janus and the Shepherd satellites. This structure originated at the transition from the plasma phase to the planetesimal phase. The shadows are not simple void regions but exhibit a characteristic signature. Parts of the fine structure, explained by Holberg as resonances with satellites, are interpreted as cosmogonic shadow effects. However, there are a number of ringlets which can neither be explained by cosmogonic nor by resonance effects. Analysis of ring data can reconstruct the plasma-planetesimal transition with an accuracy of a few percent. Previously announced in STAR as N84-12013
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysics and Space Science (ISSN 0004-640X); 97; 1, No; 79-94
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  • 2
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    Stability of streams and lakes on Mars (1983)
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    Publication Date: 2011-08-18
    Description: The freezing of small Martian streams is modelled for a variety of climatic conditions, on the supposition that the Martian atmosphere may have been considerably thicker in the past, at the time of the formation of the valley networks. This model examines the energy balance at the upper and lower surfaces of ice on streams, in order to determine the rate at which ice thickens with time. Results indicate that freezing rates are not strongly dependent on atmospheric pressure, and, under windy conditions, dependence on atmospheric pressure is even weaker. It is noted that the main problem in valley formation is in initiating the flow. Groundwater seepage alone is inadequate, due to the difficulty of groundwater system replenishment.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 56; 476-495
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  • 3
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    Large amplitude MHD waves upstream of the Jovian bow shock (1983)
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    Publication Date: 2011-08-18
    Description: Observations of large amplitude MHD waves upstream of Jupiter's bow shock are analyzed. The waves are found to be right circularly polarized in the solar wind frame, which suggests that they are propagating in the fast magnetosonic mode. A complete spectral and minimum variance eigenvalue analysis of the data was performed. The power spectrum of the magnetic fluctuations contains several peaks. The fluctuations at 2.3 MHz have a direction of minimum variance anti-parallel to the direction of the average magnetic field. Several harmonics at 6, 9, and 12 MHz are also present. The direction of minimum variance of these fluctuations lies at approximately 40 deg to the magnetic field. It is argued that these fluctuations are waves excited by protons reflected off the Jovian bow shock. The inferred speed of the reflected protons is about two times the solar wind speed in the solar wind frame. A linear instability analysis is presented that suggests an explanation for many of the observed features of the observations. The fluctuations apparently contain a significant fraction of magnetic energy that is linearly polarized and in the Alfven mode.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 9989-999
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  • 4
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    Light element geochemistry and spallogenesis in lunar rocks (1983)
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    Publication Date: 2011-08-18
    Description: Abundance and isotopic compositions are measured for the very volatile elements carbon, nitrogen and sulfur in 11 lunar rocks representing a wide spectrum of textures and compositions. Samples were combusted sequentially at three temperatures in order to remove terrestrial contaminants before melting the lunar rock and liberating lunar volatiles. The combustion results indicate very little terrestrial sulfur contamination, with sulfur contents correlated with the TiO2 contents of the basalts analyzed. Sulfur isotopic compositions are remarkably uniform and similar to the Canon Diablo meteorite standard. Nitrogen levels are found to be no greater than those obtained with procedural blanks, corresponding to abundances less than 0.1 microg/g. Stable nitrogen isotope measurements indicate a spallogenic N-15 production rate of 4.1 x 10 to the -6th microg N-15/g sample/million years, in agreement with previous estimates. No indigenous carbon in excess of procedural blank levels of about 0.7 microg/g is found in lunar basalts. Levels of 1 to 5 microg/g found in highland rocks may derive from meteoritic or terrestrial sources. The average measured spallogenic C-13 production rate is 4.1 x 10 to the -6th microg C-13/g sample/million years.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 47; 1769-178
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  • 5
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    The flux and source of energetic protons in Saturn's inner magnetosphere (1983)
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    Publication Date: 2011-08-18
    Description: The flux of energetic protons in Saturn's inner magnetosphere was observed in two channels from 48 to 63 and 63 to 160 MeV. Absorption features due to the G ring and the satellites Enceladus and Mimas were easily identifiable. The flux observed in the absorption slot of Mimas can be maintained by the decay of a cosmic ray albedo neutron flux of 0.007/sq cm/s/sr. This flux is entirely consistent with calculations of the neutron flux produced by galactic cosmic ray interactions with the rings of Saturn. The omnidirectional proton flux of 0.0082/sq cm/s at 2.734 R sub s requires a residence time of 30 years. Both the residence time and the energy spectrum are comparable to those found in the inner radiation belt of the Earth. The angular distribution is nearly isotropic in the Mimas slot and beyond 4R sub s. Otherwise the pitch angle distribution is pancake and is approximated by sin(n)theta with n in the range 2 to 7. This distribution is consistent with an isotropic neutron source in the ring plane. Previously announced in STAR as N83-22084
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 8923-893
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  • 6
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    Survey of low-energy plasma electrons in Saturn's magnetosphere - Voyagers 1 and 2 (1983)
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    Publication Date: 2011-08-18
    Description: The low energy plasma electron environment within Saturn's magnetosphere was surveyed by the Plasma Science Experiment (PLS) during the Voyager encounters with Saturn. Over the full energy range of the PLS instrument (10 eV to 6 keV) the electron distribution functions are clearly non-Maxwellian in character; they are composed of a cold (thermal) component with Maxwellian shape and a hot (suprathermal) non-Maxwellian component. A large scale positive radial gradient in electron temperature is observed, increasing from less than 1 eV in the inner magnetosphere to as high as 800 eV in the outer magnetosphere. Three fundamentally different plasma regimes were identified from the measurements: (1) the hot outer magnetosphere, (2) the extended plasma sheet, and (3) the inner plasma torus. Previously announced in STAR as N83-34872
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 8847-887
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  • 7
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    The Z3 zonal harmonic model of Saturn's magnetic field Analyses and implications (1983)
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    Publication Date: 2011-08-18
    Description: The planetary magnetic field of Saturn has been studied by the spacecraft Pioneer 11 in 1979, Voyager 1 in 1980, and Voyager 2 in 1981. The field is found to be primarily dipolar and axially coincident with the rotation axis, but with significant quadrupole and octupole moments. The harmonic terms are g1(0) = 21535 nT, g2(0) = 1642 nT, and g3(0) = 2743 nT. This model field, Z3, in conjunction with a model for an equatorial ring current, represents very precisely the in situ magnetic-field measurements and data on charged-particle absorption by satellites and rings within 8 Saturn radii of the planet. However, this axisymmetric model fails to explain the periodic modulation of Saturn's kilometric radiation or Saturn's electrostatic discharges. This enigma of Saturn's magnetosphere remains unsolved in spite of extensive reconsideration of all available data bearing on this issue.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 8771-877
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  • 8
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    Photometry and polarimetry of Saturn at 2640 and 7500 A (1983)
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    Publication Date: 2011-08-18
    Description: Voyager 2 photometric and polarimetric data are reduced and tabulated, with spatially resolved limb-to-terminator scans across Saturn's equatorial zone providing information on the altitude distribution of UV-absorbing hazes, together with the phase function and polarizing properties of stratospheric and tropospheric aerosols. It is found that the UV photometry and polarimetry are best fit by Rayleigh's phase matrix. A stratospheric haze of small particles is allowed as long as the optical depth is near unity or less, and the center of the haze layer is in the 30 to 70 mbar region. The altitudes presently derived for three latitudes agree with those obtained by ground-based methane band studies and analyses from Pioneer 11. A high altitude absorber is abundant in the polar regions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 8679-869
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  • 9
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    Morphology and chemistry of projectile residue in small experimental impact craters (1983)
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    Publication Date: 2011-08-18
    Description: Small-scale impact craters (5-7 mm in diameter) were produced with a light gas gun in high purity Au and Cu targets using soda lime glass (SL) and man-made basalt glass (BG) as projectiles. Maximum impact velocity was 6.4 km/s resulting in peak pressures of approximately 120-150 GPa. Copious amounts of projectile melts are preserved as thin glass liners draping the entire crater cavity; some of this liner may be lost by spallation, however. SEM investigations reveal complex surface textures including multistage flow phenomena and distinct temporal deposition sequences of small droplets. Inasmuch as some of the melts were generated at peak pressures greater than 120 GPa, these glasses represent the most severely shocked silicates recovered from laboratory experiments to date. Major element analyses reveal partial loss of alkalis; Na2O loss of 10-15 percent is observed, while K2O loss may be as high as 30-50 percent. Although the observed volatile loss in these projectile melts is significant, it still remains uncertain whether target melts produced on planetary surfaces are severely fractionated by selective volatilization processes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 88; B353-B36
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  • 10
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    The production curve for agglutinates in planetary regoliths (1983)
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    Publication Date: 2011-08-18
    Description: Models for the production of agglutinates are developed that can be applied to the lunar surface or to any planetary or asteroidal body lacking an atmosphere. Models are developed using rate equations for progressively more complex situations and range from Model 1, which is a simple linear increase of agglutinate content with time, to Model 4, which includes provision for recycling of existing agglutinates and replenishment and burial of exposed soil. Model 4 has some aspects of a steady state because, depending on the rate constants, agglutinate content may be limited to an intermediate value, even for long exposure times. In an extreme case, agglutinate content may be limited to a value near zero. These models predict that agglutinates should be low in abundance in areas of thin regolith, such as the Lunokhod-2 site on the moon, and on asteroids. The models may also help explain the apparent low agglutinate abundances of lunar regolith breccias and meteorite regolith breccias.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 88; B193-B19
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  • 11
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    Ancient crustal components in the Fra Mauro breccias (1983)
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    Publication Date: 2011-08-18
    Description: Texturally pristine clasts preserve primary petrographic relationships and mineral compositions, yielding insights into igneous processes of the early lunar crust that cannot be gained from highly shocked and brecciated 'chemically pristine' samples. The use of texture as a prime criterion allows for expansion of the data base derived solely from chemical criteria, and provides complementary data. Texturally pristine clasts from the Apollo 14 site studied here include anorthosite, troctolites, gabbronorites, and basalts. Alkali anorthosites are plagioclase orthocumulates and may form by flotation in Mg-suite plutons. Ferroan anorthosite was cataclastically deformed and metamorphosed to granulite facies. Troctolites include both 01 + Plg and 01 + En + Plg cumulates. Major and trace element analyses of two troctolites reveal 'eastern' geochemical affinities that contrast other 'western' troctolites. Gabbronorites are Pig + Plg + or - Sp cumulates whose parent magmas may range from high-Al to intermediate-Ti mare basalt. At least three varieties of mare basalt are found at Apollo 14: high-Al, low-Ti; low-Al, intermediate-Ti; and low-Al, Ti VHK basalt. VHK (Very High Potassium) basalt is a new variety indigenous to Apollo 14.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 88; B177-B19
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  • 12
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    An upper bound on the radius of a highly electrically conducting lunar core (1983)
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    Publication Date: 2011-08-18
    Description: Parker's (1980) nonlinear inverse theory for the electromagnetic sounding problem is converted to a form suitable for analysis of lunar day-side transfer function data by: (1) transforming the solution in plane geometry to that in spherical geometry; and (2) transforming the theoretical lunar transfer function in the dipole limit to an apparent resistivity function. The theory is applied to the revised lunar transfer function data set of Hood et al. (1982), which extends in frequency from 10 to the -5th to 10 to the -3rd Hz. On the assumption that an iron-rich lunar core, whether molten or solid, can be represented by a perfect conductor at the minimum sampled frequency, an upper bound of 435 km on the maximum radius of such a core is calculated. This bound is somewhat larger than values of 360-375 km previously estimated from the same data set via forward model calculations because the prior work did not consider all possible mantle conductivity functions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 88; B97-B102
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  • 13
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    Atmospheric tides on Venus. III - The planetary boundary layer (1983)
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    Publication Date: 2011-08-18
    Description: Diurnal solar heating of Venus' surface produces variable temperatures, winds, and pressure gradients within a shallow layer at the bottom of the atmosphere. The corresponding asymmetric mass distribution experiences a tidal torque tending to maintain Venus' slow retrograde rotation. It is shown that including viscosity in the boundary layer does not materially affect the balance of torques. On the other hand, friction between the air and ground can reduce the predicted wind speeds from about 5 to about 1 m/sec in the lower atmosphere, more consistent with the observations from Venus landers and descent probes. Implications for aeolian activity on Venus' surface and for future missions are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 56; 165-175
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  • 14
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    Structure and dynamics of Saturn's outer magnetosphere and boundary regions (1983)
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    Publication Date: 2011-08-18
    Description: In 1979-1981, the three USA spacecraft Pioneer 11 and Voyagers 1 and 2 discovered and explored the magnetosphere of Saturn to the limited extent possible on flyby trajectories. Considerable variation in the locations of the bow shock (BS) and magnetopause (MP) surfaces were observed in association with variable solar wind conditions and, during the Voyager 2 encounter, possible immersion in Jupiter's distant magnetic tail. The limited number of BS and MP crossings were concentrated near the subsolar region and the dawn terminator, and that fact, together with the temporal variability, makes it difficult to assess the three dimensional shape of the sunward magnetospheric boundary. The combined BS and MP crossing positions from the three spacecraft yield an average BS-to-MP stagnation point distance ratio of 1.29 +/- 0.10. This is near the 1.33 value for the Earth's magnetosphere, implying a similar sunward shape at Saturn. Study of the structure and dynamical behavior of the outer magnetosphere, both in the sunward hemisphere and the magnetotail region using combined plasma and magnetic field data, suggest that Saturn's magnetosphere is more similar to that of Earth than that of Jupiter. Previously announced in STAR as N83-30346
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 88; 8791-880
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  • 15
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    Channels and valleys on Mars (1983)
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    Publication Date: 2011-08-18
    Description: Tentative conclusions about the origins of channels and valleys on Mars based on the consensus of investigators who have studied the problem are presented. The morphology of outflow channels is described in detail, and the morphology, distribution, and genesis of Martian valleys are addressed. Secondary modification of channels and valleys by mass-wasting phenomena, eolian processes, cratering, and mantling by lava flows is discussed. The physics of the flows needed to account for the immense volumes of Martian outflow channels is considered in detail, including the possible influence of debris flows and mudflows, glaciers, and ice sheets. It is concluded that Mars once probably possessed an atmosphere with higher temperatures and pressures than at present which played an essential role in an active hydrological cycle.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geological Society of America, Bulletin (ISSN 0016-7606); 94; 1035-105
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  • 16
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    Three Mars years - Viking Lander 1 imaging observations (1983)
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    Publication Date: 2011-08-18
    Description: The Mutch Memorial Station (Viking Lander 1) on Mars acquired imaging and meteorological data over a period of 2245 martian days (3.3 martian years). This article discusses the deposition and erosion of thin deposits (ten to hundreds of micrometers) of bright red dust associated with global dust storms, and the removal of centimeter amounts of material in selected areas during a dust storm late in the third winter. Atmospheric pressure data acquired during the period of intense erosion imply that baroclinic disturbances and strong diurnal solar tidal heating combined to produce strong winds. Erosion occurred principally in areas where soil cohesion was reduced by earlier surface sampler activities. Except for redistribution of thin layers of materials, the surface appears to be remarkably stable, perhaps because of cohension of the undisturbed surface material.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 222; 463-468
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  • 17
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    Stability and capture of asteroids (1983)
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    Publication Date: 2011-08-18
    Description: The problem of stability of asteroids is treated from the point of view of Hill's stability-concept and using Lyapunov's Characteristic Numbers. The quantitative measure of stability (S) introduced earlier is evaluated for over 300 asteroids and a surprisingly simple relation is established between the semi-major axes of some of the asteroids' orbits and S. A detailed analysis is presented of the Lyapunov Characteristic Numbers for two minor planets and the time-variation of these numbers is discussed. The technology of capture of asteroids is vitally dependent on their orbital stability, therefore, these two problems, i.e., capture and stability, are closely related. In fact, some predictable instabilities may be properly utilized to capture and/or change asteroidal orbits to accomplish collisions with the Earth.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Sao Paulo Univ. The Motion of Planets and Nat. and Artificial Satellites, Volume 2; p 39-46
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  • 18
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    A Sr and Nd isotopic study of five Yamato polymict eucrites and a comparison to other Antarctic and ordinary eucrites (1983)
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    Publication Date: 2011-08-19
    Description: Sr and Nd isotopic analysis of five Yamato polymict eucrites indicate that these samples formed at about 4.6 Ga ago with initial Sr and Nd ratios essentially the same as the analyzed non-Antarctic eucrites. The Yamato eucrites have Sr, Sm, and Nd concentrations that consistently lie among the highest found in eucritic samples. This characteristic identifies these Yamato samples as a closely related group. Comparisons between these Yamato samples and other Antarctic polymict eucrites clearly estabishes that they all share some characteristic trace element features. Comparisons of Antarctic polymict eucrites with non-Antarctic ordinary eucrites reveal consistent differences. The most obvious is an enrichment of Rb in the polymict eucrites. These comparisons suggest that the Antarctic polymict eucrites belong to a single large family of material that is itself fairly diverse and distinct from the non-Antarctic eucrites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: National Institute of Polar Research, Memoirs, Special Issue (ISSN 0386-0744); 30, D
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  • 19
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    Condensation of chondrules (1983)
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    Publication Date: 2011-08-19
    Description: Analysis of current experimental results concerned with the kinetic constraints on chondrule formation showed that the major physical properties of chondrules could have been produced by direct condensation of metastable liquid silicates droplets from a hot gas in the primordial nebula. It is argued that such a condensation process would have to be followed by crystallization, accretion, and partial comminution of the droplets. The chemical mechanisms driving this process are described, including: nucleation constraints on comminution and crystallization; slow transformations and chemical reactions in chain silicates; and the slow diffusion of ions. It is shown that the physical mechanisms for chondrule condensation are applicable to a broad spectrum of chondrule sources.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 20
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    External control of planetary radio emission (1983)
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    Publication Date: 2011-08-19
    Description: Recent studies using data from Voyagers 1 and 2 to correlate variations in the Saturn kilometric radiation (SKR) with changes in solar-wind properties are summarized and illustrated with graphs. Best SKR correlations have been obtained with the solar-wind ram pressure and the related kinetic energy flux. It is pointed out that the related phenomenon on earth, the auroral kilometric radiation, occurs mainly in the nightside auroral region (as opposed to the dayside cleft region for SKR) and is best correlated with solar-wind velocity and inverted-V electron-precipitation events, implying a different stimulation process. The evidence for solar-wind control of the non-Io-related decametric radiation of Jupiter is also reviewed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Oesterreichische Akademie der Wissenschaften, mathematisch-naturwissenschaftliche Klasse, Sitzungsberichte, Abteilung 2 (ISSN 0723-9319); 192; 8-10,
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  • 21
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    Saturn - Origin and composition of its inner moons and rings (1980)
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    Publication Date: 2011-08-18
    Description: Theoretical modelling of the contraction of the primitive protosaturnian cloud, using ideas of supersonic turbulent convection, suggests that each of Saturn's inner moons, excepting Rhea, condensed above the ice-point of water and consists primarily of hydrous magnesium silicates. It is predicted that Voyager 1 may find that the satellite mean densities steadily increase towards the planet and that the rocky moons are irregular in shape.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Physics Letters; 80A; Nov. 24
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  • 22
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    Gravity anomalies on Venus (1980)
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    Publication Date: 2011-08-18
    Description: Doppler radio tracking of the Pioneer Venus orbiter has provided gravity measures over a significant portion of Venus. Feature resolution is approximately 300-1000 km within an area extending from 10 deg S to 40 deg N latitude and from 70 deg W to 130 deg E longitude (approximately equal to 200 deg). Many anomalies were detected, and there is considerable correlation with radar altimetry topography (Pettengill et al., 1980). The amplitudes of the anomalies are relatively mild and similar to those on earth at this resolution. Calculations for isostatic adjustment reveal that significant compensation has occurred.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 198
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  • 23
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    Distribution and source of the UV absorption in Venus' atmosphere (1980)
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    Publication Date: 2011-08-18
    Description: The model predictions were compared with the Pioneer Venus probes and orbiter to determine the composition of the UV absorbing materials. The simulations were carried out with radiative transfer codes which included spacecraft constraints on the aerosol and gas characteristics in the Venus atmosphere; gaseous SO2 (a source of opacity at the wavelengths below 0.32 microns), and a second absorber (which dominates above 0.32 microns) were required. The UV contrast variations are due to the optical depth changes in the upper haze layer producing brightness variations between equatorial and polar areas, and to differences in the depth over which the second UV absorber is depleted in the highest portion of the main clouds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 24
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    Measurements of thermal structure and thermal contrasts in the atmosphere of Venus and related dynamical observations - Results from the four Pioneer Venus probes (1980)
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    Publication Date: 2011-08-18
    Description: The thermal structure of the Venus atmosphere and differences in structure with latitude (up to 60 deg) and clock hour (from midnight to 8 AM) have been measured in situ from a height of 126 km to the surface by instruments on the four Pioneer Venus entry probes. It is found that thermal contrasts below 45 km are a few K, with the midlatitudes warmer than both equatorial and high latitudes. Considerable temperature and pressure differences with latitude develop in the clouds (25 K and 20 mbar level). In addition, upward of 110 km, there is evidence of large-amplitude temperature oscillations with altitude, believed to signify the presence of large-amplitude waves, perhaps thermal tides. Agreement of structure data from other Pioneer Venus experiments is generally excellent.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 25
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    Dust in Jupiter's magnetosphere. I - Physical processes. II - Origin of the ring. III - Time variations. IV - Effect on magnetospheric electrons and ions (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The physical processes acting on charged microscopic dust grains in the Jovian atmosphere involve electromagnetic forces which dominate dust particle dynamics and diffusion across field lines resulting from random charge fluctuations of the dust grains. A model of the Jovian ring hypothesizes that the 'visible' ring particles are produced by erosive collisions between an assumed population of kilometer-sized parent bodies and submicron-sized magnetospheric dust particles. Fluctuations in the ring topology and intensity are determined over various time scales, showing that the ring is a quasipermanent and quasistable characteristic of the Jovian system. Finally, the interaction of the Jovian energetic belt electrons and the Jovian plasma with an ambient dust population is examined; the distribution of dust ejected from Io in the inner magnetosphere and losses of magnetospheric ions and electrons due to direct collisions with charged dust particles are calculated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science; 28; Dec. 198
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    Io control of Jovian radio emission (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The possibility of Io controlling Jovian decametric radio emission, particularly in the region below 22 MHz, is discussed. Results of a two-year survey at 26.3 at 26.3 MHz are presented which demonstrate the control of Io over a high-intensity storm component of the radio emission and the independence of a weak radio component from the phase of Io, as was observed at lower frequencies. It is thus hypothesized that Io control is a flux-dependent rather than a frequency-dependent phenomenon, and results of analyses at 18 and 10 MHz which support this hypothesis are presented. The apparent correlation between frequency and Io control is thus shown to result from a selection effect due to the increase of non-Io emission with decreasing frequency and relative antenna detection threshold. This result implies a contiguous Io-controlled source region extending out several Jovian radii along the Io flux tube.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 287; Oct. 30
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  • 27
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    Viscous flow and crystallization behavior of tektite glasses (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The variation of viscosity with temperature was determined in the 200-2000 K range for a Muong Nong tektite material. The viscosity at the liquidus temperature of 1320 C is 20,000 P; treatments between 900 and 1300 C do not result in significant crystallization in the natural sample except when the sample is heated in contact with a synthetic tektite composition. Two synthetic microtektite with lower SiO2 contents than the Muong Nong material were also examined; heat flow calculations were performed for 2.5 to 10 cm spheres of tektite when cooling by radiation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Oct. 10
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  • 28
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    The occurrence rate, polarization character, and intensity of broadband Jovian kilometric radiation (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper describes the major observational features of one new component of Jupiter's radio emission spectrum, the broadband kilometer wavelength radiation, or bKOM. This study, using the Voyager Planetary Radio Astronomy (PRA) experiments, reveals that the overall occurrence morphology, dynamic spectra, and polarization character of bKOM are strong functions of the latitude and/or local time geometry of the observations. The postencounter data show a decline in the mean occurrence rates and power level of bKOM and, in particular, a depletion in the occurrence rate at those same longitudes where the detection rate is a maximum before encounter. Additionally, the polarization sense undergoes a permanent reversal in sign after encounter, whereas the time-averaged wave axial ratio and degree of polarization remain relatively unchanged. Finally, no evidence of any control by Io is found. The strong dependence of the morphology on local time suggests a source whose beam is nearly fixed relative to the Jupiter-sun line
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Aug. 1
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  • 29
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    The case against UV photostimulated oxidation of magnetite (1980)
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    Publication Date: 2011-08-17
    Description: The kinetics of magnetite oxidation in O2-bearing atmospheres in the presence of electromagnetic radiation was studied. No perceptible oxidation of magnetite by ultraviolet (UV) photostimulation occurred. These results do not corroborate previous conclusions by Huguenin (1973, 1974) as to the occurrence of this process. Therefore, although the possibility that the process actually occurs cannot be ruled out, it is concluded that there is not yet a basis in laboratory experiments for inferring that UV photostimulated oxidation of magnetite occurs naturally on the surface of Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Aug. 198
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  • 30
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    Voyager detection of nonthermal radio emission from Saturn (1980)
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    Publication Date: 2011-08-17
    Description: The planetary radio astronomy experiment on board the Voyager spacecraft has detected bursts of nonthermal radio noise from Saturn occurring near 200 kilohertz, with a peak flux density comparable to higher frequency Jovian emissions. The radiation is right-hand polarized and is most likely emitted in the extraordinary magnetoionic mode from Saturn's northern hemisphere. Modulation that is consistent with a planetary rotation period of 10 hours 39.9 minutes is apparent in the data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 209; Sept. 12
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  • 31
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    Investigation of numerical properties of Hovenier's exit function equation for multiple scattering of light (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A technique of deriving Hovenier's exit function equation (1978) for multiple scattering, starting with a set of invariant imbedding equations, is presented. The feasibility of the exit function equation as a means to obtain reflection and transmission functions is investigated for isotropic, Rayleigh, and Henyey-Greenstein phase functions with emphasis on the numerical stability, accuracy and timing. It is possible to compute the reflection function rather accurately with an efficiency comparable to that of the standard doubling technique for the same phase functions with moderate anisotropy. The resulting transmission is slightly less accurate than the reflection function, but it may be acceptable for practical purposes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysics and Space Science; 69; 1, Ma; May 1980
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  • 32
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    Instability of equatorial protons in Jupiter's mid-magnetosphere (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Two different models for the distribution function are fit to the Jovian protons seen by Pioneer 10 inbound. The models reproduce the observed energy and angular distributions. These models are then used to assess the collisionless mirror instability. Because of the pancake proton angular distributions in the equatorial ring current region, the ring current particle population appears to be mirror unstable at times, with instability growth rates of about 10 min. Such a time is consistent with observed proton flux autocorrelation times. An instability such as this (there are other candidates) may be responsible for the previously established proton flux flowing parallel to the magnetic field away from the equatorial region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Jan. 1
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  • 33
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    Saturn's rings - Particle composition and size distribution as constrained by observations at microwave wavelengths. II - Radio interferometric observations (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Theoretical models are presented of the brightness of Saturn's rings at microwave wavelengths (0.34-21.0 cm) including both intrinsic ring emission and diffuse scattering by the rings of the planetary emission. In addition, several previously existing sets of interferometric observations of the Saturn system at 0.83, 3.71, 6.0, 11.1, and 21.0 cm wavelengths are analyzed. A comparison of models and experimental data make it possible to establish improved constraints on the properties of the rings. In particular, it is found that (1) the maximum optical depths in the rings is 1.5 + or - 0.3 referred to visible wavelengths; (2) a significant decrease in ring optical depths from 3.7 to 21.0 cm makes it possible to rule out the possibility that more than 30% of the cross section of the rings is composed of particles larger than about a meter; and (3) the ring particles cannot be primarily of silicate composition (independently of particle size), and the particles cannot be primarily smaller than about 0.1 cm, independently of composition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Dec. 198
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  • 34
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    Greenhouse models of Venus' high surface temperature, as constrained by Pioneer Venus measurements (1980)
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    Publication Date: 2011-08-18
    Description: Recent measurements conducted from the Pioneer Venus probes and orbiter have provided a significantly improved definition of the solar net flux profile, the gaseous composition, temperature structure, and cloud properties of Venus' lower atmosphere. Using these data, we have carried out a series of one-dimensional radiative-convective equilibrium calculations to determine the viability of the greenhouse model of Venus' high surface temperature and to assess the chief contributors to the greenhouse effect. New sources of infrared opacity include the permitted transitions of SO2, CO, and HCl as well as opacity due to several pressure-induced transitions of CO2. We find that the observed surface temperature and lapse rate structure of the lower atmosphere can be reproduced quite closely with a greenhouse model that contains the water vapor abundance reported by the Venera spectrophotometer experiment. Thus the greenhouse effect can account for essentially all of Venus' high surface temperature. The prime sources of infrared opacity are, in order of importance, CO2, H2O, cloud particles, and SO2, with CO and HCl playing very minor roles.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 35
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    Cloud morphology and motions from Pioneer Venus images (1980)
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    Publication Date: 2011-08-18
    Description: The horizontal and vertical cloud structures, atmospheric waves, and wind velocities at the cloud top level were determined by the Pioneer Venus photopolarimeter images in the UV from January through March 1979. The images indicate long-term evolution of cloud characteristics, the atmospheric dynamics, and rapid small changes in cloud morphology. The clouds show a globally coordinated oscillation relative to latitude circles; retrograde zonal winds of 100 m/s near the equator are determined from the tracking of small-scale cloud properties, but two hemispheres show important variations. The zonal wind velocity in the southern hemisphere is reduced toward the poles at a rate similar to solid body rotation; the midlatitude jet stream noted by Mariner 10 is not observed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 36
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    Pioneer Venus gas chromatography of the lower atmosphere of Venus (1980)
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    Publication Date: 2011-08-18
    Description: A gas chromatograph mounted in the Pioneer Venus sounder probe measured the chemical composition of the atmosphere of Venus at three altitudes. Ne, N2, O2, Ar, CO, H2O, SO2, and CO2 were measured, and upper limits set for H2, COS, H2S, CH4, Kr, N2O, C2H4, C2H6, and C3H8. Simulation studies have provided indirect evidence for sulfuric acid-like droplets and support the possibility of water vapor at altitudes of 42 and 24 km. The paper discusses the implications of these results for the origin, evolution, and present state of Venus' atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 37
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    Dynamic properties of the thermosphere inferred from Pioneer Venus mass spectrometer measurements (1980)
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    Publication Date: 2011-08-18
    Description: The data obtained by the Pioneer Venus spectrometer experiments indicate that the day-night temperature contrast on Venus is associated with wind velocities of about 200 m/s which transport oxygen, helium, and hydrogen toward the night side. A mass exchange with the mesosphere commensurate with an eddy diffusion coefficient of 3 x 10 to the 7th is required to buffer the horizontal advection so as to reproduce the observed day time bulge in oxygen and the small diurnal variations in helium. The observed time response and magnitude of the day-night density variations require transport processes to be effective over time periods between five and ten days, implying a superrotation rate or prevailing winds in excess of 50 m/s at the equator. Nonlinear mass transport results in wave steepening and contributes to the amplification of the density extrema in hydrogen and helium.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 38
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    Electron temperature and heat flow in the nightside Venus ionosphere (1980)
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    Publication Date: 2011-08-18
    Description: A steady-state two-dimensional heat balance model is used to analyze the night side Venusian ionospheric electron temperatures given by the Pioneer Venus orbiter electron temperature probe. The energy calculation includes the solar EUV heating at the terminator, electron cooling to ions and neutrals, and heat conduction within the ionospheric plasma. An optimum magnetic field is derived by solving for the heat flux directions which force energy conservation while constrained by the observed temperatures within the range of 80-170 deg solar zenith angle and 160-170 km. The heat flux vectors indicate a magnetic field that connects the lower night side ionosphere to the day side ionosphere, and connects the upper ionosphere to the ionosheath. The lower ionosphere is heated through conduction of heat from the dayside, and the upper ionosphere is heated by the solar wind in the ionosheath with heat flowing downward and from the nightside to the day side.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 39
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    Mass spectrometric measurements of the neutral gas composition of the thermosphere and exosphere of Venus (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The neutral gas composition and density in the thermosphere of Venus is being measured with a quadrupole mass spectrometer on the Pioneer Venus orbiter. Data are obtained near periapsis once per day approximately 150-250 km above the surface. The principal gases in the thermosphere are CO2, CO, N2, O, N, and He. Atomic oxygen is the major constituent above 155 km on the dayside and also on the nightside up to 180 km when helium becomes the major constituent. The average values of CO2, CO, N2, O, and N remain nearly constant during day and night, but an abrupt change occurs across the terminator from a high dayside value to a low nightside value. The helium density varies in the opposite way, and a distinct bulge was observed at night near the morning terminator. The data have been used as the basis of an empirical model. Large orbit to orbit variations in densities were also observed on the nightside, suggesting perhaps strong turbulent motion in the atmosphere below. Kinetic temperatures inferred from scale heights are approximately 285 K on the dayside and 110 K at night. The average global temperature obtained from the model is 199 K.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 40
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    Empirical models of the electron temperature and density in the Venus ionosphere (1980)
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    Publication Date: 2011-08-18
    Description: The electron temperature and density of the Venus ionosphere is characterized using data from the Pioneer Venus orbiter electron temperature probe experiment for the full range of solar zenith angles and local times. Values for the electron density are nearly uniform across the day side with a sharp decrease in the vicinity of the terminator. The model shows a substantial night side ionosphere which can be accounted for by a combination of several transport processes, and by local production by precipitating particles. The electron temperature model demonstrates the high temperatures seen on both the day side and night side. It is found that the night side is much more variable than the day side, and that there is no obvious north-south asymmetry in either the temperature or the density.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 41
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    Global observations of the composition and dynamics of the ionosphere of Venus - Implications for the solar wind interaction (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The in-situ measurements of the global composition and Venus ionosphere dynamics recorded by the Bennett ion mass spectrometer on the Pioneer Venus orbiter during Dec. 1978-Aug. 1979 are presented. The observations of three plasma regimes show the bowshock-ionosheath region, the thermal ionosphere, and a superthermal flowing ion layer contacting the ionosphere at the ionopause and extending outward to different heights above the planet. An abundant ionosphere dominated by O(+) above 200 km and by O2(+) down to the typical periapsis altitudes of 160 km occur during quiet periods; less disturbed data shows strong day to night changes in the distributions of ions including O(+), O2(+), CO2(+), and N(+). The ionopause is located near the subpolar point at 250-400 km; under disturbed nighttime conditions it may have randomly spaced concentration gradients in the dusk region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 42
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    Dynamical response of the dayside ionosphere of Venus to the solar wind (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Dayside ion composition measurements made by the orbiter ion mass spectrometer and the orbiter electron temperature probe on the Pioneer Venus orbiter are used to infer the dominant processes involved in the dynamic response of the Venus ionosphere to the solar wind. The analysis is confined to the topside ionosphere in the vicinity of the subsolar point, where the ionosphere-solar wind interaction is expected to be maximized. Height profiles of the ion composition and plasma temperatures in the main body of the topside ionosphere, lying between the ionopause and chemical equilibrium regions, reveal that the ionosphere is in a compressed state. This region of the ionosphere is interpreted in terms of a stationary equilibrium where the compression is derived from the ponderomotive force j x B. The estimated magnitude of this force is confirmed by the magnetic field measurements made by the orbiter magnetometer.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 43
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    Pioneer Venus plasma observations of the solar wind-Venus interaction (1980)
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    Publication Date: 2011-08-18
    Description: Collection of data from the Ames plasma analyzer on the Pioneer Venus orbiter has permitted long-term measurements of the interaction of the solar wind with Venus. The paper presents a mapping of the ionosheath flow field, plasma measurements in the distant ionosheath and near the distant plasma cavity, and a summary of observations of jumps in the solar wind proton parameters across Venus' bow shock. Also, the apparent detection of ionospheric O(+) accelerated up to solar wind speeds downstream in Venus' ionosheath is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 44
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    A physical model of Titan's clouds (1980)
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    Publication Date: 2011-08-18
    Description: A physical model of the formation and growth of aerosols in the atmosphere of Titan has been constructed in light of the observed correlation between variations in Titan's albedo and the sunspot cycle. The model was developed to fit spectral observations of deep methane bands, pressures, temperature distributions, and cloud structure, and is based on a one-dimensional physical-chemical model developed to simulate the earth's stratospheric aerosol layer. Sensitivity tests reveal the model parameters to be relatively insensitive to particle shape but sensitive to particle density, with high particle densities requiring larger aerosol mass production rates to produce compatible clouds. Solution of the aerosol continuity equations for particles of sizes 13 A to about 3 microns indicates the importance of a warm upper atmosphere and a high-altitude mass injection layer, and the production of aerosols at very low aerosol optical depths. Limits are obtained for the chemical production of aerosol mass and the eddy diffusion coefficient, and it is found that an increase in mass input causes a decrease in mean particle size.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 43; Sept
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  • 45
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    Hg and Pt-metals in meteorite carbon-rich residues - Suggestions for possible host phase for Hg (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Carbon-rich and oxide residual phases have been isolated from Allende and Murchison by acid demineralization for the determination of their Hg, Pt-metal, Cr, Sc, Co, and Fe contents. Experimental procedures used eliminated the possibility of exogenous and endogenous contaminant trace elements from coprecipitating with the residues. Large enrichments of Hg and Pt-metals were found in Allende but not in Murchison residues. Hg-release profiles from stepwise heating experiments suggest a sulfide as the host for Hg. Diffusion calculations for Hg based on these experiments indicate an activation energy of 7-8 kcal/mol, the same as that for Hg in troilite from an iron meteorite. This is further support for a sulfide host phase for Hg. Equilibration of Hg with this phase at approximately 900 K is indicated. Reasons for the presence of Pt-metals in noncosmic relative abundances are explored.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 44; Oct. 198
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  • 46
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    Endemic isotopic anomalies in titanium (1980)
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    Publication Date: 2011-08-18
    Description: Abundances of the titanium isotopes were determined using a new high-precision technique that shows terrestrial, lunar, and bulk meteorite samples to be indistinguishable. Ca-Al-Ti-rich inclusions in the Allende meteorite are found to contain Ti of widely varying isotopic composition reflecting the presence of at least three nucleosynthetic components. The anomalies in Ti appear to be relatively widespread and, when correlated with Ca data, provide a clue to nucleosynthesis in the neighborhood of the iron peak and to the late-stage nucleosynthetic processes which immediately preceded formation of the solar nebula.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 240
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  • 47
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    Structures far from the head of comet Kohoutek. II - A discussion of the Swan Cloud of January 11 and of the general morphology of cometary plasma tails (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Photographs show that the 'Swan Cloud' observed in comet Kohoutek on January 11, 1974 was an advanced stage of a plasma tail disconnection event, of which the rejected tail appeared to decelerate as it receded from the head. The event commenced with the development of strong tail ray activity followed by the actual tail disconnection, the merging of the disconnected tail with the new tail to form the Swan and the formation of arcade loops in the space between closing tail rays. The observed morphological sequence is easily understood in the sector boundary model (Niedner et al., 1978), and the arcade loops are proposed to be reconnected flux tubes between oppositely polarized tail rays in the incipient new tail which followed the disconnection
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 42; May 1980
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  • 48
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    Some diurnal properties of clouds over the Martian volcanoes (1980)
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    Publication Date: 2011-08-17
    Description: The diurnal properties of cloud systems over Martian volcanoes observed by the Viking Orbiter spacecraft are discussed. Photographic sequences of diurnal cloud development are presented for clouds in the vicinity of Elysium Mons and Ascraeus Mons, and the rapid growth of cloudiness starting at 11.23 LT is noted. The low-lying fogs and convective afternoon clouds observed are characterized as water ice clouds, while the cirrus-type clouds may be composed of CO2. The diurnal development of the clouds is then explained in terms of local atmospheric stability and circulation as influenced by surface topography and thermal properties. Consideration is also given to possible reasons for the pronounced seasonal variations in cloudiness.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 286; July 24
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  • 49
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    Saturn - Tropospheric ammonia and nitrogen (1980)
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    Publication Date: 2011-08-17
    Description: Photochemical calculations based on recent data on the Saturn temperature structure and Lyman-alpha albedo indicate that detectable amounts of gaseous ammonia may exist between 20 and 35 km above the cloud tops. An instrument that might be able to observe this gas is the spectrometer on board the International Ultraviolet Explorer satellite. The calculations also yield a maximum nitrogen mixing ratio at the cloud tops between 1.8 x 10 to the -10th to 6 x 10 to the -8th by volume, depending upon the degree of supersaturation of ammonia and hydrazine. Even the lower limit could produce intense emissions if electrical discharges such as those observed on Jupiter by Voyager are also present on Saturn, or if high energy particles penetrate to the Saturnian troposphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; June 198
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  • 50
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    Thermal diffusion calculations for the ionosphere of Venus (1980)
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    Publication Date: 2011-08-17
    Description: Simplified multicomponent diffusion calculations are made for the ionosphere of Venus. Large differences in temperature between electrons and ions and appreciable temperature gradients that are near those of recent measurements are used. Compositions for which binary thermal diffusion coefficients for ions are the same as multi-ion ones are examined as well as those that are quite different. An attempt to combine binary coefficients to give multi-ions ones has not been particularly successful.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Jan. 1
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  • 51
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    Comment on absorbing regions in the atmosphere of Venus as measured by radio occultation (1980)
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    Publication Date: 2011-08-18
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Dec. 198
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  • 52
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    Evolution of Io's volatile inventory (1980)
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    Publication Date: 2011-08-18
    Description: Voyager data are used to make crude estimates of the rate at which Io loses volatiles, by a variety of processes, to the surrounding magnetosphere, for the case of both the current, SO2-dominated atmosphere and hypothetical paleoatmospheres in which such other gases as N2 may have been the dominant constituent. Among the mechanisms making significant contributions to the prodigious rate at which Io is losing volatiles are: the interaction of the magnetospheric plasma with volcanic plume particles and the background atmosphere; the sputtering of ices on the surface, if the nightside atmospheric pressure is low enough; and Jeans' escape of O as a dissociation product of SO2 gas. It is also argued that in the case of paleoatmospheres only the first two alternatives would have been possible and, nevertheless, insufficient to account for N2 loss over the life of the satellite.
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  • 53
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    The clouds of Venus - A synthesis report (1980)
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    Publication Date: 2011-08-18
    Description: The results presented represent a synthesis of data from those Pioneer Venus experiments directed toward studying cloud problems. These orbiter and multiprobe experiments show the cloud system to consist of three altitude regions populated by cloud particles and smaller haze particles which extend above and below as well as coexist with the cloud particles. The optical properties derived are only consistent with the largest particles, having platelike morphology. The smallest particles are shown to require changes in chemical composition to explain observed behavior. The medium-sized H2SO4 droplets of 2 micrometers diameter appear to be the least volatile and are the best understood. The role of the cloud particles in precipitation dynamical processes, lightning, and radiation are all discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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    The thermal balance of Venus in light of the Pioneer Venus mission (1980)
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    Publication Date: 2011-08-18
    Description: Pioneer Venus orbiter and probes measured many of the properties of the Venus atmosphere which control its thermal balance and support its high surface temperature. Estimates based on orbiter data yield an effective radiating temperature of Venus of 228 + or - 5 K, corresponding to a solar emission of 153 + or - 13 W/sq cm. A mode of submicron particles is suggested as an important source of thermal opacity near the cloud tops to explain the orbiter and probe thermal flux measurements. A comparison of the measured solar flux profile with thermal fluxes computed from the measured temperature structure and composition shows that the greenhouse mechanism explains essentially all of the 500-K difference between the surface and radiating temperatures of Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 55
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    The structure of the clouds of Venus - Results of the Pioneer Venus nephelometer experiment (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: The nephelometer measurements by the four Pioneer Venus probes reveal an upper haze area in the vertical cloud structure with several less clearly delineated layers in the main cloud bank. Concentrated sulfuric acid is the main component of the majority of the particulate matter in the clouds; the near UV radiation is absorbed by the clouds. The particles ejected from the planet surface are in the 10 to 100 micron range.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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    Venus upper atmosphere structure (1980)
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    Publication Date: 2011-08-18
    Description: Atmospheric densities of Venus were measured from the orbital decay of the Pioneer Venus from Dec. 9, 1978 to Aug. 7, 1979 near the 16 deg latitude between 140 and 190 km during the entire day. Comparative atmospheric densities on earth at 150 km are higher by a factor of 3.5 with only a 1% diurnal variation; an atmospheric composition, temperature, and density model based on the orbiter atmospheric drag (OAD) vertical structure is presented. The model shows that atomic oxygen is the major component in the Venus atmosphere above 145 km at night and above 160 km during the day with mixing ratios over 0.1 near 140 km; drag measurements indicate O concentrations from 1 x 10 to the 9th/cu cm in daytime to 3 x 10 to the 7th/cu cm at night. It is concluded that the neutral upper atmosphere of Venus is surprisingly insensitive to solar extreme UV variations and changes in the solar wind.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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    Electromagnetic heating of Io (1980)
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    Publication Date: 2011-08-18
    Description: The electromagnetic heating of the Io interior is considered as an alternative to tidal dissipation to account for the observed volcanic activity. The characteristics of the time-varying magnetic field of Jupiter as seen from Io are discussed, and the range of possible rock conductivities is examined. Interior heating due to the transverse electric and transverse magnetic modes is calculated. It is found that the TM mode appears to be insignificant as a heating source due to the high conductivity of the ionosphere, even when TM heating is concentrated in local hot regions. The TE mode is a more promising source of heating, although electromagnetic heating by either mode does not appear significant in comparison with other heat sources at present.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 10
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    History of the mass of Mercury (1980)
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    Publication Date: 2011-08-18
    Description: This paper discusses the calculation of the masses of planets, as a means to construct reliable tables for their positions. Emphasis is placed on the four inner planets and the moon, with additional consideration given to the history of the masses of Jupiter and Saturn. A smooth curve can be drawn with the logarithm of the masses of the earth, Venus, Mars, and the moon, but the point for Mercury lies substantially off the curve. An investigation of the material content, surface examination, and planet radius for the planets leads to a reexamination of the history of the value for the mass of Mercury.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Royal Astronomical Society; vol. 21
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    Possible determination of the deceleration parameter using lunar occultations and laser ranging observations (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 241
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  • 60
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    Carbonaceous chondrites. II - Carbonaceous chondrite phyllosilicates and light element geochemistry as indicators of parent body processes and surface conditions (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Petrographic analyses of CM matrices characterized four phyllosilicates in Murray and Murchison meteorites and Fe- and Mg-serpentines in Nogoya. All phyllosilicates and bulk matrices show enrichment of K relative to Na when compared with bulk meteorites; the loss of Na and some Cl, and the addition of H2O, CO2, and water-soluble organics during alteration indicates a partially open system. Synthesis of soluble organic materials may have occurred in CM matrices before aqueous alteration of the precursive phases. Nogoya was 95% altered and has a bulk C content of 5.2%, higher than any meteorite; also, it has the lowest measured C-13/C-12 ratio of any carbonaceous chondrite except for Karoonda.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 44; Oct. 198
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    On the relationship between secular brightness changes of Titan and solar variability (1980)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Titan's geometric albedo varied noticeably from 1972 to 1978, in phase with variations in solar activity (Lockwood and Thompson, 1979). A series of radiative transfer and aerosol formation calculations were made to demonstrate the feasibility of the following scenario for these secular brightness changes. Solar activity changes, especially in the UV output of the sun, result in alterations to the mass production rate of aerosols in Titan's atmosphere, which lead to modifications of their microphysical properties. The latter, in turn, cause the albedo to vary. Current estimates of the change in the solar UV radiation below the dissociation limit of methane imply alterations to the mean radius of the aerosols over an 11-yr solar cycle that are consistent in sign and magnitude with those required to explain the observed secular brightness changes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Oct. 198
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  • 62
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    Properties of the Io plasma torus inferred from Voyager EUV data (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A physical model for the Io plasma torus is constructed to explain the EUV radiative emission observed by the Voyager UV spectrometer. Electron impact excitation rate coefficients for electronic transitions of S III, S IV, O II and O III are calculated by the method of distorted waves (Davis, Kepple, and Blaha, 1976); these coefficients account for the asymmetric shape of the 686 A feature. It is concluded that the electron gas must have a distribution function with a non-Maxwellian tail. An approximate representation of the distribution function as two temperature components requires a cold component of 3.5-4 eV and density of 2000 per cu cm and a hot component of about 100 eV and density of 50-100 per cu cm to satisfy observational constraints.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 238
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  • 63
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    Cometary collisions on the moon and Mercury (1980)
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    Publication Date: 2011-08-17
    Description: Unusual swirl patterns of bright and dark material on the moon and Mercury are proposed to be remnants of collisions with gas/dust-rich regions within a cometary coma. This interpretation provides important new clues for understanding cometary fine structure, impact effects of low-density material, and the origin of certain pronounced magnetic anomalies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 284; Mar. 6
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    Atomic nitrogen in the upper atmosphere of Venus (1980)
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    Publication Date: 2011-08-17
    Description: Atomic nitrogen has been detected in the upper atmosphere of Venus by the Pioneer-Venus Orbiter Neutral Mass Spectrometer (ONMS). Surface recombination of atomic nitrogen with atomic oxygen to form nitric oxide in the ion source allows it to be detected at mass 30. The scale height temperature of the mass 30 peak agrees with the scale height temperatures of the other species if it is assumed to be derived from atomic nitrogen. The diurnal variation of atomic nitrogen is approximately proportional to that of atomic oxygen with an estimated N/O ratio of 1.5% at 150 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Jan. 198
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    Measurements of wind vectors, eddy momentum transports, and energy conversions in Jupiter's atmosphere from Voyager 1 images (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Voyager 1 narrow-angle images were used to obtain displacements of features down to 100 to 200 km in size over intervals of 10 hours. A global map of velocity vectors and longitudinally averaged zonal wind vectors as functions of the latitude, is presented and discussed
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 7; Jan. 198
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    Bibliography (1983)
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    Publication Date: 2011-08-18
    Description: A bibliography of articles entered into the data base at the Lunar and Planetary Institute Library from November 1982 through January 1983 is presented. An abstract of each article is given. The subjects covered by the articles include: the motion of the moon and dynamics of the earth-moon system: shape and gravity field of the moon; the physical structure of the moon, its thermal and stress history; the morphology of the lunar surface, the origin and stratigraphy of lunar formations, and mapping of the moon; the chemical composition of the moon, lunar petrology, mineralogy, and crystallography; electromagnetic properties of the moon; the planets; and other objects, including asteroids, comets, meteorites, and cosmic dust.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Moon and the Planets (ISSN 0165-0807); 29; 237-327
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  • 67
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    Atmospheric storm explanation of saturnian electrostatic discharges (1983)
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    Publication Date: 2011-08-18
    Description: Saturn electrostatic discharges (SED) monitored by the Voyager 1 were investigated to determine the source of the phenomena. Consideration has been given to two sources: the atmosphere at equatorial latitudes, where the cloud-top wind velocities correspond to the Saturn 10 hr 10 min rotation period; and the rings at 1.8 Saturn radius. The data were analyzed in terms of time and frequency, revealing a time-varying frequency, few detectable discharges outside of a low threshold, and the appearances and disappearances of the SED with no correlation with frequency. The periodicity of the SED episodes indicated that the source was occulted between revolutions, which ruled out the ring source. The SED signals were only detected on the dayside, suggesting the signals propagated through the dayside ionosphere. Diurnal variations in the ion densities could prohibit the signals from escaping on the nightside, a factor supported by detection of low frequency SED only during close passage of the Voyager. Ray tracing experiments have demonstrated that storm sources have emissions observable with the storm on the limb at the observed 30-40 MHz interval.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 303; May 5
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    Speculation on Martian north polar wind circulation and the resultant orientations of polar sand dunes (1983)
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    Publication Date: 2011-08-18
    Description: When seen at frost cap minimum, Martian north polar erg dunes north of 80 deg N record east winds, while those south of that latitude record west winds. Many of the transverse dunes are considered to be reversing dunes, and dunes in the two fields may have reversed at least once during the lifetime of the Viking Orbiters. It is proposed that the average polar winds are strong, off-pole northwest winds in the fall, moderate west winds in winter, latitude-dependent weak-to-strong off-pole northeast winds in spring, and weak west winds in summer, as has been largely confirmed by Viking images of near polar clouds. Over millenia, the combination of reversing west and east winds could produce the biomodal distributions of dune orientations observed at the north pole.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 55; Sept
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    Formation and photochemistry of methylamine in Jupiter's atmosphere (1983)
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    Publication Date: 2011-08-18
    Description: In the upper troposphere and lower stratosphere of Jupiter, translationally hot H atoms are produced in the photolysis of ammonia, phospine, and acetylene which react with methane to form methyl radicals. The latter combine with NH2 to form methylamine. It is presently shown that the combined production of methylamine and subsequent photolysis to HCN is unlikely to account for the HCN observed near Jupiter's tropopause. The recommendation of NH2 and C2H3 radicals to yield C2H5N, followed by photolysis to HCN, is the preferred path. An upper limit column density on CH3PH2 is estimated to be about 10 to the 13th/sq cm, as compared to 10 to the 15th/sq cm for CH3NH2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 55; Sept
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    Modeling of the 10-micron natural laser emission from the mesospheres of Mars and Venus (1983)
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    Publication Date: 2011-08-18
    Description: The NLTE radiative transfer problem is solved to obtain the 00 deg 1 vibrational state population. This model successfully reproduces the existing center-to-limb observations, although higher spatial resolution observations are needed for a definitive test. The model also predicts total fluxes which are close to the observed values. The strength of the emission is predicted to be closely related to the instantaneous near-IR solar heating rate.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 55; Sept
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    Observations of the 10-micron natural laser emission from the mesospheres of Mars and Venus (1983)
    In:  Other Sources
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    Publication Date: 2011-08-18
    Description: Observations of the total flux and center to limb dependence of the nonthermal emission occurring in the cores of the 9.4 and 10.4 micrometers CO2 bands on Mars are compared to a theoretical model based on this mechanism. The model successfully reproduces the observed center to limb dependence of this emission, to within the limits imposed by the spatial resolution of the observations of Mars and Venus. The observed flux from Mars agrees closely with the prediction of the model; the flux observed from Venus is 74 percent of the flux predicted by the model. This emission is used to obtain the kinetic temperatures of the Martian and Venusian mesospheres. For Mars near 70 km altitude, a rotational temperature analysis using five lines gives T = 135 + or - 20 K. The frequency width of the emission is also analyzed to derive a temperature of 126 + or - 6 K. In the case of the Venusian mesosphere near 109 km, the frequency width of the emission gives T = 204 + or - 10 K.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 55; Sept
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    Some dynamical properties of vortex streets in Saturn's atmosphere from analyses of Voyager images (1983)
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    Publication Date: 2011-08-18
    Description: The first observations of a vortex street in an atmosphere other than that of the earth are presented, made from a sequence of images of Saturn taken by Voyager 2 in August 1981. The analysis of these images shows that the feature sits at the maximum of the westward jet and suggests that it may be produced by material rising up from below the level of the visible clouds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; Sept
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    Ferromagnetic resonance and magnetic properties of ALHA 81005 (1983)
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    Publication Date: 2011-08-18
    Description: Seven chips of primarily matrix material from the Antarctic meteorite ALHA 81005 were analyzed by ferromagnetic resonance (FMR) and magnetic hysteresis techniques. The FMR spectra of two chips have a resonance at g of about 2.1 that resembles the g of about 2.1 resonance that is characteristic of lunar soils. Thus the FMR spectra are consistent with the lunar regolith being a progenitor for the matrix material. For the two chips, the FMR surface exposure (maturity) index was about 5 units, which is equivalent to a value for an immature lunar soil. The total concentration of metallic iron is on the order of 0.11 equivalent wt. pct, which is within the observed range for Apollo 16 rocks and soils.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; Sept
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    Recent cosmic ray exposure history of ALHA 81005 (1983)
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    Publication Date: 2011-08-18
    Description: Measurements of the Be-10 and Al-26 contents of ALHA 81005 constrain the length and conditions of its exposure to cosmic rays. Calculations based on one-step irradition models imply that the time spent by this object in space is shorter than that spent by most 'asteroidal' meteorites. On the other hand the results are readily consistent with a lunar origin for ALHA 81005.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; Sept
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    Trapped noble gases indicate lunar origin for Antarctic meteorite (1983)
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    Publication Date: 2011-08-18
    Description: The isotopic abundances of the noble gases (He, Ne, Ar, Kr, Xe) are reported for Antarctic ALHA 81005. It contains solar wind-implanted gases whose absolute and relative concentrations are quite similar to lunar regolith samples but not to other meteorites. ALHA 81005 also contains a large excess Ar-40 component which is identical to the component in lunar fines implanted from the lunar atmosphere. Large concentrations of cosmogenic Ne-21, Kr-82, and Xe-126 in ALHA 81005 indicate a total cosmic ray exposure age of at least 200 million years. The noble gas data alone are strong evidence for a lunar origin of this meteorite.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 10; Sept
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    The Tunguska event - No cometary signature in evidence (1983)
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    Publication Date: 2011-08-18
    Description: It is suggested that existing data on the 1908 Tunguska fall precludes an interpretation of the object as an either active or extinct comet fragment. Because a fireball of the Tunguska mass is not efficiently decelerated by the earth's atmosphere, it would at an entry velocity of about 30 km/sec have had to resist aerodynamic pressures greater than one billon dyn/sq cm before disintegrating. The inherently extremely fragile cometary material could not have survived a load of this magnitude. The data on Type II fireballs with prominent terminal flares are extrapolated, to estimate Tunguska's critical dynamic pressure at the same time of explosion as being of the order of 200 million dyn/sq cm, and its preexplosion velocity as about 10 km/sec, thereby ruling out a comet-like orbit. The Tunguska object is most consistently described as a small Apollo-type asteroid, 90-190 m across.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal (ISSN 0004-6256); 88; Sept
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    Radio emission signature of Saturn immersions in Jupiter's magnetic tail (1983)
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    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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    Solar related waves in the Venusian atmosphere from the cloud tops to 100 km (1983)
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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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    Vertical distribution of scattering hazes in Titan's upper atmosphere (1983)
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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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    Saturn meteorology - A diagnostic assessment of thin-layer configurations for the zonal flow (1983)
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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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    The atmosphere of Titan - An analysis of the Voyager 1 radio occultation measurements (1983)
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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.
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    The role of dissipation in shepherding of ring particles (1983)
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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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  • 83
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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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  • 84
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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.
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  • 85
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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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  • 86
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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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  • 87
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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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  • 88
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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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  • 89
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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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  • 90
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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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  • 91
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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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  • 92
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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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  • 93
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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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  • 94
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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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  • 95
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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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  • 96
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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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  • 97
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    Primordial refractory metal particles in the Allende meteorite (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Refractory metal particles containing Os, Re, W, Mo, Ir, and Ru were observed in a Ca-Al-rich inclusion in the Allende meteorite. These particles are the closest to unaltered primordial metal condensates from a nebula yet reported, and appear to have been isolated from the nebula before the condensation of refractories was complete. Computer calculations of condensation indicate that the temperature of isolation appears to be close to the calculated temperature of first formation of oxides (about 1620 K at 0.0001 atm) indicating that isolation may have been effected by coating of the particles by oxides.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 44; Feb. 198
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  • 98
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    Comments on 'A three-dimensional model of dynamical processes in the Venus atmosphere' (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of the Atmospheric Sciences; 37; Jan. 198
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  • 99
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    Preliminary results on the plasma environment of Saturn from the Pioneer 11 plasma analyzer experiment (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Ames Research Center Pioneer 11 plasma analyzer experiment provided measurements of the solar wind interaction with Saturn and the character of the plasma environment within Saturn's magnetosphere. It is shown that Saturn has a detached bow shock wave and magnetopause quite similar to those at earth and Jupiter. The scale size of the interaction region for Saturn is roughly one-third that at Jupiter, but Saturn's magnetosphere is equally responsive to changes in the solar wind dynamic pressure. Saturn's outer magnetosphere is inflated, as evidenced by the observation of large fluxes of corotating plasma. It is postulated that Saturn's magnetosphere may undergo a large expansion when the solar wind pressure is greatly diminished by the presence of Jupiter's extended magnetospheric tail when the two planets are approximately aligned along the same solar radial vector.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 207; Jan. 25
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  • 100
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    Noble-gas-rich separates from ordinary chondrites (1980)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Acid-resistant residues were prepared by HCl-HF demineralization of three H-type ordinary chondrites: Brownfield 1937 (H3), Dimmitt (H3, 4), and Estacado (H6). These residues were found to contain a large proportion of the planetary-type trapped Ar, Kr, and Xe in the meteorites. The similarity of these acid residues to those from carbonaceous chondrites and LL-type ordinary chondrites suggests that the same phase carries the trapped noble gases in all these diverse meteorite types. Because the H group represents a large fraction of all meteorites, this result indicates that the gas-rich carrier phase is as universal as the trapped noble-gas component itself. When treated with an oxidizing etchant, the acid residues lost almost all their complement of noble gases.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 44; Feb. 198
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