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  • LUNAR AND PLANETARY EXPLORATION  (1.278)
  • 2000-2004
  • 1980-1984  (552)
  • 1975-1979  (726)
  • 1925-1929
  • 1983  (552)
  • 1976  (726)
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  • 2000-2004
  • 1980-1984  (552)
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  • 1
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    Solar system history as recorded in the Saturnian ring structure (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 20
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    External control of planetary radio emission (1983)
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    Publikationsdatum: 2011-08-19
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Exploration of the giant planets by infrared spectroscopy (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The infrared spectrometer and radiometer for the Mariner-Jupiter-Saturn mission is described. Results of Nimbus and Mariner 9 IR spectroscopy of earth and Mars are used as examples to demonstrate the power and diversity of the technique. Determinations of planetary surface compositions, surface temperatures, vertical temperature profiles, surface pressures, and atmospheric constituents are summarized. Applications to Jupiter and Saturn are briefly mentioned.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 22
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    Structure of Mars' atmosphere up to 100 kilometers from the entry measurements of Viking 2 (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Viking 2 entry data on the structure of Mars' atmosphere up to 100 kilometers define a morning atmosphere with an isothermal region near the surface; a surface pressure 10% greater than that recorded simultaneously at the Viking 1 site; and a thermal structure to 100 kilometers at least qualitatively consistent with pre-Viking modeling of thermal tides. The temperature profile exhibits waves whose amplitude grows with altitude, to about 25 K at 90 kilometers. The atmosphere is stable against convection, except possibly in some very local regions. Temperature is everywhere appreciably above the carbon dioxide condensation boundary at both landing sites, precluding the occurrence of carbon dioxide hazes in northern summer at latitudes to at least 50 deg N. Thus, ground-level mists seen in these latitudes would appear to be condensed water vapor.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Dec. 17
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  • 23
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    Scientific results of the Viking missions (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The two Viking missions to Mars have been extraordinarily successful. Thirteen scientific investigations yielded information about the atmosphere and surface. Two orbiters and landers operating for several months photographed the surface extensively from 1500 kilometers and directly on the surface. Measurements were made of the atmospheric composition, the surface elemental abundance, the atmospheric water vapor, temperature of the surface, and meteorological conditions; direct tests were made for organic material and living organisms. The question of life on Mars remains unanswered. The Viking spacecraft are designed to continue the investigations for at least one Mars year.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Dec. 17
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  • 24
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    Estimated grain saltation in a Martian atmosphere (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Mariner 9 spacecraft images showing evidence of variable surface features and surface erosion resulting from atmospheric wind on Mars have caused a renewed interest in the eolian mechanics of saltating grains. To study this phenomenon, both experimental investigation in an atmospheric wind tunnel and numerical solutions of the equations of motion of a single grain under Martian surface conditions were conducted. The numerical solutions for earth were used and empirically adjusted to correlate with existing experimental data for Mars. These modified equations were then solved to estimate grain motion for Mars. These calculations show the importance of a lifting force on the grain to initiate motion in both earth and Mars calculations. Major findings include a comparison of earth and Mars grain trajectories that show Mars length scales to be longer and to fall with a higher terminal grain velocity. The grains in the Mars calculation also made a smaller collision angle with the surface on rebound.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research; 81; Nov. 10
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  • 25
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    Al-26 in Kenna and other ureilites (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: A description is presented of the results of a nondestructive analysis conducted with a 42-g slice of the Kenna ureilite. The sample was analyzed in a gamma-gamma coincidence counting system, using a dual-parameter, 4096-channel pulse height analyzer. Data concerning Al-26 and Ne-22/Ne-21 in ureilites and Chassigny are presented in a table. A graph shows the ratio of measured Al-26 activity to that calculated from elemental production rates vs spallation Ne-22/Ne-21 for ureilites and Chassigny. The significance of the data with respect to findings reported by Wilkening et al. (1973) is discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geochimica et Cosmochimica Acta; 40; Dec. 197
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  • 26
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    On the energy deposition of photoelectrons in the atmosphere of Venus (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Vertical components of photoelectron fluxes in the atmosphere of Venus are computed by solving an appropriate form of the Boltzmann equation in the cases where there is no flux of either photoelectrons or solar-wind particles across the ionopause and where photoelectrons are free to escape from the atmosphere. It is assumed that Venus has no magnetic field and that the atmosphere is composed of carbon dioxide, atomic oxygen, and helium. The results are plotted as a function of altitude for several energies in the range from 100 eV to a cutoff of the order of 1 eV. Heating rates for the two upper boundary conditions and the case of no spatial transport are determined which show that transport effects dominate at altitudes greater than about 200 km. Electron temperatures are calculated for the adopted model atmosphere and ionosphere by solving the pertinent conservation equation, and excitation rates are computed for the CO Cameron band as well as the CO2(+) A and B bands.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research; 81; Oct. 1
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  • 27
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    The 'soil' of Mars /Viking 1/ (1976)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: The immediate environs of the Viking 1 lander are described, and the techniques employed to deduce the properties of the two different 'soil' types there are summarized. It is shown that the surface in the immediate vicinity of the lander consists of an area with fine-grained materials ('Sandy Flats') and a rocky area set in a matrix of finer-grained material ('Rocky Flats'). Estimates are given for the bulk density, particle density, particle size distribution, cohesion, angle of internal friction, and penetration resistance of the surface layer in each area. Footpad penetration into the surface layer is discussed, and wind removal of particles is examined. It is concluded that the surface layer of the Viking 1 landing site contains loess, dune sand, lunar nominal soil, lag gravel, and bare rock.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Oct. 1
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  • 28
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    Status of the Viking missions (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: A chronology of Viking 1 lander activities is presented for the first 43 sols (Martian days) of surface sampling and analysis. The orbital insertion of the second Viking spacecraft is reviewed along with the search for the second landing site. A general assessment of the planet is made on the basis of the data thus far obtained. Some of the findings reported are that: (1) there is extensive evidence of volcanism, fluvial and aeolian erosion, and deposition over the entire surface; (2) the floor of Vallis Marineris is significantly younger than the planet's surface; (3) the morphology of Martian crater ejecta is indicative of surface flow rather than ballistic deposition; (4) the rocks in the immediate vicinity of the lander are all covered by a layer of fine red dust; (5) the atmosphere is optically thick and well mixed, with suspended particles giving the sky a pink color; (6) the N and Ar isotopic ratios are different from those on earth; (7) atmospheric water vapor varies with both time of day and location; (8) the summer northern polar regions have a high water concentration in the atmosphere; (9) a large fraction of magnetic material resides in the surface; and (10) no complex organic compounds have been detected in the two samples analyzed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Oct. 1
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  • 29
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    Venus' night side ionosphere - Its origin and maintenance (1976)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A substantial nightside ionosphere has been observed on Venus by both Mariner 5 and Mariner 10. Major dayside ionic species such as O2(+) and other molecular ions have chemical lifetimes much shorter than the 244.3-day rotation period of the planet. Rapid transport of ions from the dayside to the nightside to the extent required seems most unlikely. Consequently, possibilities are investigated for local production of ions on the nightside itself. Constraints imposed by chemical lifetimes require atomic ions with low ionization potentials. It is suggested that metallic ions of meteoric origin are the positive charge carriers, and the plausibility of this mechanism is demonstrated. Other possibilities are examined and shown to be less likely. Meteor ablation on Venus, the aeronomy of metallic species, and the role of negative ions near the electron peaks of the atmosphere are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research; 81; Sept. 1
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  • 30
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    The Viking landing sites - Selection and certification (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: During the past several years the Viking project developed plans to use Viking orbiter instruments and earth-based radar to certify the suitability of the landing sites selected as the safest and most scientifically rewarding using Mariner 9 data. During June and July 1976, the earth-based radar and orbital spacecraft observations of some of the prime and backup sites were completed. The results of these combined observations indicated that the Viking 1 prime landing area in the Chryse region of Mars is geologically varied and possibly more hazardous than expected, and was not certifiable as a site for the Viking 1 landing. Consequently, the site certification effort had to be drastically modified and lengthened to search for a site that might be safe enough to attempt to land. The selected site considered at 47.5 deg W, 22.4 deg N represented a compromise between desirable characteristics observed with visual images and those inferred from earth-based radar. It lies in the Chryse region about 900 kilometers northwest of the original site.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 193; Aug. 27
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  • 31
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    The Halley rendezvous via solar sailing mission description (1976)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: The possibility of using solar sails to achieve a rendezvous with Halley's Comet is explored. Rendezvous trajectories are calculated.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Proc. of the Shuttle-Based Cometary Sci. Workshop; p 251-256
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  • 32
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    QH observations (1976)
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    Publikationsdatum: 2011-08-18
    Beschreibung: A model of the dissociative lifetime of the hydroxyl radical is computed where the H2O and OH velocities are vectorially added. A lifetime of approximately 3 x 100,000 seconds is determined.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA. Marshall Space Flight Center Proc. of the Shuttle-Based Cometary Sci. Workshop; p 222-226
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  • 33
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    High resolution spectral analysis of the Jovian decametric radiation. II - The band-like emissions (1976)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Analysis of the bandlike Jovian decametric emission is presented. A model for the active region that accounts for the observed radiation characteristics is described using the measured parameters of the bandlike emission and a model of the Jovian magnetic field. The active region is characterized not only by the fact that an upward-flowing electron stream is caused to radiate in this region, but the stream itself is broken into radiating electron bunches within the active region. Observed undulations of the emission band on the time-frequency plane are interpreted as motions of the active region along a flux tube. The instantaneous location of the active region along the flux tube shows a dependence on the density of the stream entering the active region. The mechanism responsible for density modulation of the stream appears to be common to both the bandlike and simple-S-burst emission types.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus; 29; Dec. 197
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  • 34
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    High resolution spectral analyses of the Jovian decametric radiation. I - Burst morphology and drift rates (1976)
    In:  Other Sources
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    Publikationsdatum: 2011-08-17
    Beschreibung: Morphological analyses of high-resolution spectral recordings of Jovian decametric radiation show a regime of phenomena not seen at lower resolutions. Observed emissions range from narrow-band (50 kHz) simple quasi-periodic bursts to wide-band emissions (extending over a 500-kHz passband) exhibiting complex structural detail. Assuming gyroemission from electrons in a dipole field for which the magnetic moment is 10 Gauss Jupiter-radius-cubed, drift-rate measurements of the bursts indicate that the source size is of the order of 600 km and its location is near 1.3 Jupiter radii at a colatitude of 27.3 deg. The measurements suggest that the emitting electrons belong to a population having a very specific equatorial pitch angle near 3.5 deg. This study concludes that it may be possible to verify gyroemission as the mechanism responsible for the decametric radiation.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus; 29; Dec. 197
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  • 35
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    The occultation of Mariner 10 by Mercury (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Analysis of Mariner 10 dual-frequency radio-occultation recordings has yielded new information on the radius and atmosphere of Mercury. The ingress measurements, which were conducted near 1.1 deg north latitude and 67.4 deg east longitude on the night side of the planet, gave a value for the radius of 2439.5 + or - 1 km. Egress near 67.6 deg north latitude and 258.4 deg east longitude on the sunlit side yielded a radius of 2439.0 + or - 1 km. The atmospheric measurements showed the electron density to be less than 1000 per cu cm on both sides of the planet. From the latter result one may infer an upper limit to the dayside surface gas density of 1 million molecules per cu cm.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus; 29; Dec. 197
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  • 36
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    Relation of a contracting earth to the apparent accelerations of the sun and moon (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: It has been concluded that the theoretical ratio of the apparent secular accelerations of the moon and the sun implied by tidal theory is far higher than the ratio of observed values. This paper shows that the discrepancy can be entirely removed within the range of uncertainty of the various quantities involved if terms making allowance for a secularly decreasing terrestrial moment of inertia are included in the dynamical equations for the apparent secular accelerations. Such a decrease has already been predicted on the basis of the phase-change hypothesis for the nature of earth's core. The development of this hypothesis is reviewed, the modified dynamical equations are derived, and values of tidal couples implied by existing observational data are examined. The numerically determined rate of decrease of earth's moment of inertia is found to be in close agreement with that predicted by the phase-change hypothesis. The results indicate that a diminishing gravitational constant is unlikely, that the moon would have been in close proximity to earth only 1 billion years ago, and that earth's rotation period at that time would have been about 5 hr.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: The Moon; 16; Dec. 197
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  • 37
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    Observational and theoretical temperatures for a total lunar eclipse (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Temperature profiles from seven regions of the moon were recorded during a total eclipse using an infrared radiometer and telescope. The eclipse was visible from beginning to end. Target areas chosen range from mare areas to mountainous highlands. Theoretical temperature curves were calculated using a thermophysical model in which the lunar material properties are variable. These curves are compared with the experimental data. A description of the instrumentation, observations, calibration, signal reduction, and the theoretical model is given. The results show excellent agreement between the observational and theoretical temperatures during the eclipse. The apparent differences between the observed and calculated temperatures during pre- and post-eclipse are minimal after directional radiation is taken into account.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: The Moon; 15; June-Jul
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  • 38
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    Floor-fractured lunar craters (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Observational data concerning floor-fractured craters on the lunar near and far sides are examined, including the morphologic classification of the craters, their spatial and size distributions, and their floor, peak, and rim elevations relative to the maria. Six morphologic classes and two subclasses are delineated on the basis of fracture pattern, crater floor depth, and floor type. These data are used to reconstruct a history of crater modification which accounts for the large differences in affected crater size and age, the small peak-rim elevation differences, remnant central peaks within mare-flooded craters and ringed plains, ridged and flat-topped rim profiles of heavily modified craters and ringed plains, as well as the absence of positive gravity anomalies in most floor-fractured craters and some large mare-filled craters. The results indicate that: (1) impact craters became centers of intrusions and volcanism generally related to periods of basin inundation by mare basalts; (2) some light-plains units in the highlands may be due to both impact ejecta and extrusions of light-colored lava or ash; (3) floor-fractured craters may have become important volcanic vents that contributed to the inundation of the lunar surface by mare basalts; and (4) the lunar highlands probably did not fully escape the epochs of mare flooding.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: The Moon; 15; June-Jul
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  • 39
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    The chemistry of planetary atmospheres (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Present knowledge concerning the chemistry of planetary atmospheres is reviewed along with the theories which attempt to explain observational data. The known gross atmospheric compositions of the terrestrial and giant planets are listed, differences between the atmospheres of earth and Venus are discussed, and the atmospheres of the giant planets are described. The origin and evolution of the atmospheres of earth, Venus, Mars, Jupiter, Saturn, and Uranus are outlined, and chemical processes in the atmospheres are examined, particularly cloud formation. The question of organic synthesis and evolution in the reducing atmospheres of the giant planets is considered. It is noted that laboratory work on the individual chemical processes and reactions involved in the evolution of organic compounds in planetary atmospheres, comets, and interstellar space points to the inevitability of organic-compound synthesis in all these situations and to the pervasiveness of organic chemistry throughout the universe.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Chemical Education; 53; Apr. 197
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  • 40
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    Mars dynamics, atmospheric and surface properties - Determination from Viking tracking data (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Approximately three months of radio tracking data from the Viking landers have been analyzed to determine the lander locations, the orientation of the spin axis of Mars, and a first estimate from Viking data of the planet's spin rate. Preliminary results have also been obtained for atmospheric parameters and radii at occultation points and for properties of the surface in the vicinity of lander 1.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Dec. 17
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  • 41
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    Viking magnetic properties investigation - Further results (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The amounts of magnetic particles held on the reference test chart and backhoe magnets on lander 2 and lander 1 are comparable, indicating the presence of an estimated 3 to 7 percent by weight of relatively pure, strongly magnetic particles in the soil at the lander 2 sampling site. Preliminary spectrophotometric analysis of the material held on the backhoe magnets on lander 1 indicates that its reflectance characteristics are indistinguishable from material within a sampling trench with which it has been compared. The material on the RTC magnet shows a different spectrum, but it is suspected that the difference is the result of a reflectance contribution from the magnesium metal covering on the magnet. It is argued that the results indicate the presence, now or originally, of magnetite, which may be titaniferous.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Dec. 17
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  • 42
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    Spiral structure as an explanation for the asymmetric brightness of Saturn's A ring (1976)
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    Publikationsdatum: 2011-08-17
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature; 264; Nov. 25
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  • 43
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    Tektites and their origin (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Questions concerning the tektite distribution are examined, taking into account the Australasian strewn field, the Ivory Coast strewn field, the Moldavite strewn field, the North American strewn field, the Libyan desert glass, the Aouelloul crater glass, and amerikanites. Attention is given to the shapes of tektites, the internal structure of tektites, the physical properties of tektite glass, the chemical composition of tektites, isotopes, fission tracks, cosmic ray tracks, and arguments in favor and against the terrestrial origin of tektites. It is concluded that tektites cannot be terrestrial in origin. They are probably volcanic ejects, of geologically recent epochs, from one or a number of lunar volcanoes.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 44
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    Viking to Mars - Profile of a space expedition (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The Viking spacecraft, operations, and findings are reviewed and numerous pictures are presented in an attempt to capture the atmosphere of the Viking expedition. The details of the two Viking spacecraft, each consisting of an orbiter and lander combination launched a Titan III/Centaur are described and illustrated, along with the Viking ground-data and communications system. The principal conclusions of the Viking mission to date are: detection of nitrogen, argon, krypton, and xenon; determination of isotopic ratios of carbon, nitrogen, oxygen, and argon; uniform diurnal meteorological conditions; determination of major elemental abundances; complex surface chemistry; no ubiquitous organic material; 4 to 7% of the sampled surface material is magnetic; discovery of ancient extensive fluvial activity; north permanent polar cap made of water ice; and significant variations of the atmospheric water vapor, the summer hemisphere being much more humid than the winter hemisphere.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Astronautics and Aeronautics; 14; Nov. 197
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  • 45
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    An example of a thermally metamorphosed agglutinate (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The nature and properties of lunar agglutinates in relation to the kind of metamorphism described by Albee et al. (1973) are briefly considered. The properties of the agglutinates are compared with those of a lunar metaclastic particle which is believed to be the product of the extreme thermal metamorphism of an agglutinate. The results of electronprobe microanalyses of selected agglutinitic glasses are presented in a table. Attention is also given to the bulk chemical composition of some noritic metaclastic rocks and several highland rock types.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Meteoritics; 11; Sept. 30
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  • 46
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    Unlimbering Viking's scoop (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: A number of difficulties which were encountered in deploying the Viking 1 lander's surface-sampler arm are discussed. When the surface sampler jammed during its initial operation, the problem was studied with the aid of tests on a full-scale lander mock-up. It was found that the difficulty was caused by a boom latch pin which had failed to fall clear. The surface-sampler arm could subsequently be freed by modifying the original command sequence. Another difficulty could be overcome by a similar approach.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: IEEE Spectrum; 13; Oct. 197
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  • 47
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    A radar study of the backup Martian landing sites (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The Goldstone radar system at DSS 14 was used to probe the Martian surface at 8495 MHz in a narrow strip between -6 deg and -2 deg latitude. The Viking C landing sites lie in this strip, and their altitudes, rms surface slope, and reflectivity are presented.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: The Deep Space Network; p 49-52
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  • 48
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    A geological basis for the exploration of the planets: Introduction (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The geological aspects of solar-system exploration were considered by first showing how geologic data are related to space science in general, and, second, by discussing the approach used in planetary geology. The origin, evolution, and distribution of matter condensed in the form of planets, satellites, comets, and asteroids were studied. Terrestrial planets, comets, and asteroids, and the solid satellites of the outer planets are discussed. Jupiter and Saturn, in particular, have satellites of prime importance. Geophysics, geochemistry, geodesy, cartography, and other disciplines concerned with the solid planets were all included.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: A Geol. Basis for the Exploration of the Planets; p 1-12
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  • 49
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    Viking magnetic properties investigation - Preliminary results (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Three permanent-magnet arrays are aboard the Viking lander. By sol 35, one array, fixed on a photometric reference test chart on top of the lander, has clearly attracted magnetic particles from airborne dust; two other magnet arrays, one strong and one weak, incorporated in the backhoe of the surface sampler, have both extracted considerable magnetic mineral from the surface as a result of nine insertions associated with sample acquisition. The loose Martian surface material around the landing site is judged to contain 3 to 7 per cent highly magnetic mineral which, pending spectrophotometric study, is thought to be mainly magnetite.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Oct. 1
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  • 50
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    Search for the Viking 2 landing site (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The search for the landing site of Viking 2 is reviewed, emphasizing the characteristics of the various candidate sites and reasons for rejecting unsuitable sites. It is shown that the B3 site in Utopia Planitia was selected because the B latitude band (40 to 50 deg N) was of the highest scientific interest, the site appeared to be smoothed by uniform mantling, and the additional data analysis and acquisition required to land at any other site could have resulted in a landing delay and significant additional operational complexity. It is tentatively concluded that the Viking 2 lander rests in a deflation hollow.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Oct. 1
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    Mapping of lunar surface from side-looking orbital radar images (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Side-looking spacecraft radar imagery has thus far been produced only from an orbit around the moon. This was a part of the Apollo Lunar Sounder Experiment (ALSE) of the Apollo 17 mission in December 1972. This paper reports results of a radargrammetric evaluation of overlapping Apollo 17 synthetic-aperture radar images (wavelength 2 m). The potential to map from single images and to reconstruct three-dimensional stereoscopic models is studied. The relative height accuracy achieved is about + or - 100 m and is thus competitive with that obtained with the vidicon camera presently used for planetary exploration.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: The Moon; 15; June-Jul
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    Martian north pole summer temperatures - Dirty water ice (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Broadband thermal and reflectance observations of the Martian north polar region in late summer yield temperatures for the residual polar cap near 205 K with albedos near 43 percent. The residual cap and several outlying smaller deposits are water ice with included dirt; there is no evidence for any permanent carbon dioxide polar cap.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Dec. 17
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    The Viking seismic experiment (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: A three-axis short-period seismometer is now operating on Mars in the Utopia Planitia region. The noise background correlates well with wind gusts. Although no quakes have been detected in the first 60 days of observation, it is premature to draw any conclusions about the seismicity of Mars. The instrument is expected to return data for at least 2 years.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 194; Dec. 17
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    Discovering Jupiter. I (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The current state of knowledge regarding the planet Jupiter is examined, taking into account data obtained with the aid of the spacecraft Pioneer 11. A description is given of Jupiter's weather. The Pioneer 11 pictures show that the planet's banded cloud structure breaks down above 50 deg latitude, and turns into relatively small, mostly circular cloud features in the polar regions. Attention is given to Jupiter's heat balance, aspects of internal heat flow, questions of atmospheric circulation, the turbulence in Jupiter's atmosphere, the effects of coriolis forces, Jupiter's upper atmosphere, the Great Red Spot, and the Jovian magnetosphere and radiation belts.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Spaceflight; 18; Dec. 197
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    Stratigraphy and structural geology (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The immediate goal of stratigraphy and structural geology is to reduce the enormous complexity of a planetary surface to comprehensible proportions by dividing the near-surface rocks into units and mapping their distribution and attitude.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: A Geol. Basis for the Exploration of the Planets; p 13-32
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    Geophysics (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Four areas of investigation, each dealing with the measurement of a particular geophysical property, are discussed. These properties are the gravity field, seismicity, magnetism, and heat flow. All are strongly affected by conditions, past or present, in the planetary interior; their measurement is the primary source of information about planetary interiors.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: A Geol. Basis for the Exploration of the Planets; p 63-74
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    Geodesy and cartography (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: Geodesy and cartography provide the geometric framework on which most investigations of planets are ultimately based. Specifically, the products of these disciplines provide information on the following: (1) the dimensions of the planet, (2) a mathematical figure of reference for the planet, (3) the orientation of the body in the celestial coordinate system, (4) the rotational constants, (5) a defined system of coordinates, (6) the location of surface points in the defined coordinate system, (7) the gravity potential expressed in spherical harmonics, (8) topographic and thematic maps, and (9) surface albedo in various wavelengths. The relevance of geodesy and cartography to planetology is discussed, and the requirements of data acquisition and mission design are considered.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA Ames Res. Center A Geol. Basis for the Exploration of the Planets; p 75-84
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    Geochemistry (1976)
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    Publikationsdatum: 2011-08-17
    Beschreibung: The most effective strategy for the geochemical study of a planet is to proceed systematically with the mineralogical and chemical characterization of its materials in accordance with geologically determined priorities. It is insufficient merely to analyze chemically the surface rocks. To appreciate the meaning of a chemical analysis, some assessment must be made of the geologic history of the sample - what its source and mode of origin are and what processes have operated upon the sample to cause chemical fractionation. Determination of mineralogy, texture, lithology, and other properties of the rock that might be relevant to origin is, therefore, necessary.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA Ames Res. Center A Geol. Basis for the Exploration of the Planets; p 33-62
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    Photometry of Venus from Mariner 10 (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Photometry of the upper atmosphere of Venus from Mariner 10 on February 5, 1974 is discussed with respect to in-flight verification of camera linearity, shading, and absolute photometric calibration. Among photometric results are the following: (1) temporal brightness variations were observed in the UV greater than 10% over a few hours due to the rapid rotation of the upper atmosphere, (2) the observed terminator was 4 degrees past the geometric terminator due to detached haze layers at altitudes around 85 km, (3) there were no indications of cloud top elevation variations greater than a few hunderd meters, and (4) in the UV, the bright and dark regions both had low albedos in all scales, showing that the UV absorber is not confined just to dark markings.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of the Atmospheric Sciences; 33; Sept
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    Jupiter at five microns (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The paper summarizes the information obtained in recent maps of Jupiter at 5 microns, a frequency at which the gases in Jupiter have a relatively low opacity. It is highly possible that 5-micron hot spots are breaks in the cloud deck permitting observation of the hot lower layers of the atmosphere. Many 5-micron sources coincide with blue visual features, but the details of the correspondence need further investigation. Large-scale changes in the appearance of the planet occur at 5 microns on time scales of months; these changes are sufficiently dramatic to produce detectable variations in the whole-disk flux from the planet. Their correspondence to large-scale changes in visual features is not yet determined.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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    Bow shock and magnetosheath waves at Mercury (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Mariner 10 measurements at the Mercury bow shock provide examples where the magnetic field is approximately parallel or perpendicular to the bow shock normal. Upstream of a broad irregular parallel shock, left-hand circularly polarized waves are observed which cut off very sharply at about 4 Hz. Upstream of a perpendicular shock, righ-hand circularly polarized waves are observed which persist up to the Nyquist frequency of 12 Hz. Determination of the wave propagation vector as a function of frequency helps to identify conclusively the waves as whistler mode waves propagating from the shock. The magnetosheath downstream of the parallel shock is disturbed more than that downstream of the perpendicular shock, particularly below 1 Hz. In the latter case, regular left-hand-polarized waves observed slightly above the proton gyrofrequency are identified as ion cyclotron waves with wavelengths of about 300 km which have been Doppler shifted up to their observed frequency.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research; 81; Aug. 1
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    Mars - Wind friction speeds for particle movement (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Wind friction threshold speeds for particle movement were determined in a low pressure boundary layer wind tunnel at an atmospheric pressure of 5.3 mb. The results imply that for comparable pressures on Mars, the minimum wind friction threshold speed is about 2.5 m/sec, which would require free-stream winds of 50 to 135 m/sec, depending on the character of the surface and the atmospheric conditions. The corresponding wind speeds at the height of the Viking lander meteorology instrument would be about a factor of two less than the free-stream wind speed. The particle size most easily moved by winds on Mars is about 160 microns; particles both larger and smaller than this (at least down to about 5 microns) require stronger winds to initiate movement.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geophysical Research Letters; 3; Aug. 197
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    The first Viking mission to Mars (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The paper outlines the major goals and present achievements of the Viking 1 mission to Mars. The construction and instrumentation of the orbiter and lander are described. The criteria used to select the optimum landing site are discussed together with orbit adjustments and the landing process. Special attention is given to constraints on surface coverage and observation conditions.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science; 193; Aug. 27
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    A new estimate of volatile outgassing on Mars (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The presence of 28% argon on Mars, as calculated by Levine and Riegler (1974) and indirectly inferred from Soviet Mars-6 lander data, has important implications for the outgassing history of H2O, CO2, and N2 on Mars. Even if the terrestrial volatile outgassing ratio is only approximately valid for Mars, then large quantities of H2O (of the order of 100,000 g/sq cm), about 10,000 g/sq cm of CO2 (about 1000 times more CO2 than found at present in the Martian atmosphere), and some 450 g/sq cm of N2 may have outgassed over the history of Mars.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus; 28; June 197
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    On the calculation of cosmic-ray exposure ages of stone meteorites (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Abundances of cosmic ray-produced noble gases and Al-26, including some new measurements, have been compiled for some 23 stone meteorites with exposure ages less than 3,000,000 yr. Concentrations of cosmogenic He, Ne, and Ar in these meteorites have been corrected for differences in target element abundances by normalization to L-chondrite chemistry. Combined noble gas measurements in depth samples of the Keyes and St. Severin chondrites are utilized to derive equations for normalizing the production rates of cosmogenic He-3, Ne-21, and Ar-38 in chondrites to an adopted 'average' shielding. The measured unsaturated AL-26 concentrations and the calculated equilibrium Al-26 for these meteorites are combined to estimate exposure ages. These exposure ages are statistically compared with chemistry- and shielding-corrected concentrations of cosmogenic He, Ne, and Ar to derive absolute production rates for these nuclides, which are found to be roughly 25% higher than production rates used in the past. From these production rates and relative chemical correction factors, production rates for other classes of stone meteorites are derived.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geochimica et Cosmochimica Acta; 40; July 197
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    Possibility of detecting magnetospheric radio bursts from Uranus and Neptune (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The intensity of magnetospheric radio bursts (MRBs) is scaled to solar-wind input into planetary magnetospheres and the frequency of emission is scaled to polar surface magnetic-field strength in order to estimate the possibility of detecting MRBs from Uranus and Neptune. A scaling law is derived which relates the ratio of power radiated in MRBs to the solar-wind input for earth, Jupiter, and Saturn. Power-flux spectra of MRBs from these three planets are plotted, and it is shown that Jupiter and Saturn may radiate 1% to 5% of the solar-wind energy input into their magnetospheres. The properties of MRBs from Uranus and Neptune are estimated by assuming a conversion efficiency of 1% to 5%, a bandwidth of half the peak frequency, and conformity of Uranus' and Neptune's dipole moments with the magnetic Bode's law. Based on the results, it is suggested that detection of MRBs from these two planets may be a reasonable cruise-mode radio-astronomy objective on future missions to the outer solar system.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature; 261; May 27
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    Aliphatic amines in the Murchison meteorite (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The paper reports on the determination of aliphatic amines in water extracts of the Murchison meteorite. The amines were analyzed by gas chromatography both as the free amines and as 2,4-dinitrophenyl (DNP) derivatives. The results give evidence for the presence of all of the possible primary aliphatic monoamines (eight) with fewer than five carbon atoms. Two of the seven possible secondary or tertiary aliphatic monoamines were identified. The identified primary amines total 80 nmol per g meteorite, and seem to be chemically or physically trapped in the meteorite. Similarities between the water-extractable amines and amino acids suggest that (1) a simple carbon compound, methane, for example, is the precursor of meteorite amines and amino acids, and (2) both amines and amino acids are extracted from the meteorite both as such and in the form of acid-hydrolyzable derivative or precursor species.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature; 261; May 13
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    Polarization of the reflected light of asteroid 433 Eros (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Linear polarizations measured for asteroid 433 Eros at various wavelengths and at solar phase angles ranging from 9 to 53 deg are presented. The polarization results are entirely typical of main-belt S asteroids, and indicate a dusty surface with geometric albedo 0.20. The derived effective diameter at photometric maximum is 21 km. Eros is quite uniform polarimetrically; no dependence on aspect is detected, and the polarization is shown to be constant during a single rotation with a precision of one part in forty.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus; 28; May 1976
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    Lightcurves and the axis of rotation of 433 Eros (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Ten lightcurves and UBV photometry of 433 Eros were obtained between August 1972 and May 1975. The absolute magnitude of the lightcurve maximum is 10.75 and the phase coefficient is 0.025 mag/deg. There may be a small difference in B-V color between the northern and southern hemispheres. The pole of the axis of rotation is directed toward 16 deg, ecliptic longitude and 12 deg ecliptic latitude, respectively, and the rotation is direct with a sidereal period of 5 hr 16 min 13.4 sec. The dimensions derived from the polarimetric albedo and the lightcurve amplitudes are 12 km by 12 km by 31 km for a smooth cylinder with hemispherical ends.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus; 28; May 1976
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    Investigation of a new stony meteorite from Mauritania with some additional data on its find site - Aouelloul crater (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The Zerga meteorite, a small stony meteorite found at Aouelloul crater, is a fragment of a larger mass with a pre-atmospheric radius between 20 and 125 cm. The meteorite is a typical amphoterite, with monomict brecchia which has undergone at least one recrystallization episode. The terrestrial age of the meteorite is roughly an order of magnitude smaller than the K-Ar gas-retention age (about 3.1 million years) of the glassy impactite found at the crater, which is close to the age of the nearby Tenoumer crater (about 2.5 million years). The similar ages of the two craters, together with their alignment with the Temimichat Ghallaman crater, suggest a simultaneous triple impact following the disruption of a large meteorite moving on a very shallow earth trajectory. The unusually shallow original depths inferred for two of the craters may be explained by low impact angles.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Earth and Planetary Science Letters; 30; 2, Ma; May 1976
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    Physical properties of asteroid 433 Eros (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Newly available photometric, polarimetric, spectroscopic, thermal-radiometric, radar, and occultation results are synthesized in order to derive a coherent model for Eros. The geometric albedo is 0.19 plus or minus 0.01 at the visual wavelength, and the overall dimensions are approximately 13 by 15 by 36 km. The rotation is about the short axis, in the direct sense, with a sidereal period of 5 hr 16 min 13.4 sec. The pole of rotation lies within a few degrees of ecliptic coordinates 16 deg longitude and beta = +11 deg latitude. Eros is uniformly coated with a particulate surface layer several millimeters thick. It has an iron-bearing silicate composition, similar to that of a minority of main-belt asteroids, and probably identifiable with H-type ordinary chondrites.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus; 28; May 1976
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    Martian atmospheric lee waves (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Areas of extensive mountain lee wave phenomenon in the northern midlatitudes during late winter are observed in Mariner 9 television pictures of Mars. The lee wave pattern is due to the discrete spectrum of waves generated by a crater ridge in an airstream. The cloud patterns resulting from the waves generated by the flow across a mountain or crater are dependent on the velocity profile of the airstream and the vertical stability of the atmosphere. A two-layer velocity model of the airstream is used in calculations based on the theory of mountain lee waves. Regardless of the simple model used for the airstream, the calculations appear to be capable of reproducing the observed wave patterns. The many observations of lee waves suggest that the near surface wind speeds as implied by the lower stream velocities do not greatly exceed, and most of the time are less than, 40 m/sec in the northern midlatitudes during late winter except possibly on a very localized scale. Results are in agreement with circulation models, especially the Leovy and Mintz (1969) two-layer numerical model.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus; 27; Apr. 197
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    Thermal emission spectra of 24 asteroids and the Galilean satellites (1976)
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    Publikationsdatum: 2011-08-16
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus; 27; Apr. 197
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    Radiometric diameter and albedo of the remarkable asteroid 1976AA (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: It is pointed out that the minor planet 1976AA discovered on January 7, 1976, is the first asteroid found with an orbital period of less than a year. A description is given of a study in which the diameter and the albedo of the asteroid were determined with the aid of infrared radiometry. It is concluded that on the basis of its albedo 1976AA can probably be classed with the stony group of asteroids.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature; 260; Apr. 22
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    New theory of the Great Red Spot from solitary waves in the Jovian atmosphere (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: It is shown that many characteristics of the Great Red Spot (GRS) and numerous other features that have been observed on Jupiter can be explained by solitary waves on a horizontally sheared zonal flow in a rotating, stratified atmosphere. Streamline patterns for waves corresponding to combined depression-elevation solitary waves (D-E solitrons) show a strong resemblence to the flow around the GRS. The morphology and flow pattern of the South Tropical Disturbance indicate that it was a D solitron. Numerous spot-like features situated in regions between cloud bands where horizontal shear forces might be expected have the morphology of E solitrons. Restrictions placed on the atmospheric parameters by the model are consistent with available models and observations.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature; 260; Apr. 8
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    Minor planets and related objects. XIX - Shape and pole orientation of /39/ Laetitia (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Results are reported for analyses of UBV photoelectric photometric data and light curves of the asteroid Laetitia. The pole orientation is determined using a technique for reducing the scatter in the magnitude-phase relation. No significant variations in color are found over the surface, and the light curves are found to indicate topographic elements (peaks, scarps, or depressions) approximately 10 km in radius. It is shown that the light-curve amplitudes as well as the wide scatter in observed magnitude and phase relation can be explained by a triaxial ellipsoidal figure with a dimensional ratio of about 15:9:5. It is concluded that the size, shape, and composition of this asteroid are highly suggestive of a major collisional fragment from a substantially more massive differentiated parent body.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Astronomical Journal; 81; Jan. 197
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    Diurnal tide in the Martian atmosphere (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Classical atmospheric tidal theory is extended to include the effects of large-amplitude planetary-scale variations of the terrain height. Utilizing simple models of the thermotidal forcing, the resulting technique is used to compute the diurnal tide in both the dust-free and the dust-laden Martian atmosphere. The main effect of the Martian variable terrain is to drive topographic tidal modes which can propagate vertically and to excite the possibly resonant diurnal Kelvin mode. The resulting surface wind can exceed 20 m/sec and may determine the preferred location for the initiation of global dust storms. In the middle Martian atmosphere (30-80 km) static and shear instabilities embedded within the tidal fields will generate extensive, though variable, regions of turbulence. Vertical mixing by this turbulence and transport by the tide itself may help to stabilize the middle Martian atmosphere against photolysis.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of the Atmospheric Sciences; 33; Feb. 197
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    New vistas in planetary radio astronomy (1976)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: Recent progress in planetary radio astronomy is reviewed, where the most significant advances have come from spacecraft observations. The low-frequency radio spectra of the earth, Jupiter, and Saturn are compared, and the striking similarity in shapes is noted. New radio data are examined which provide a way to compare the magnetic field strengths of the planets. More detailed information on the radio structures of Jupiter and Saturn, and possibly on Uranus, is expected from the 1977 Mariner Jupiter-Saturn mission.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Sky and Telescope; 51; Mar. 197
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  • 79
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    Early lunar magnetism (1976)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: A new method (Shaw, 1974) for investigating paleointensity (the ancient magnetic field) was applied to three subsamples of a single, 1-m homogeneous clast from a recrystallized boulder of lunar breccia. Several dating methods established 4 billion years as the age of boulder assembly. Results indicate that the strength of the ambient magnetic field at the Taurus-Littrow region of the moon was about 0.4 oersted at 4 billion years ago. Values as high as 1.2 oersted have been reported (Collison et al., 1973). The required fields are approximately 10,000 times greater than present interplanetary or solar flare fields. It is suggested that this large field could have arisen from a pre-main sequence T-Tauri sun.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature; 260; Mar. 18
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  • 80
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    The journey to Jupiter (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The Pioneer missions to Jupiter are reviewed, and the observations made by the two probes are discussed. The spacecraft are described along with their launches, instrument packages, and trajectories. The major results of the micrometeorite, plasma, magnetic-field, and charged-particle experiments are summarized. The structure of Jupiter's magnetosphere is illustrated, spectroscopic and photometric observations by the Pioneers are discussed, and measurements of the Jovian atmosphere and gravitational field are examined. The measured masses and densities of the Galilean satellites are given, and future prospects for the Pioneer spacecraft are noted, including the possibility that Pioneer 10 may still be in contact with earth when it crosses the boundary between the solar system and interstellar space.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Endeavour; 35; Jan. 197
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  • 81
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    Crater populations in the early history of Mercury (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Crater populations on two major geologic units of Mercury have been classified into three morphologic types which characterize their state of degradation. The results indicate that one or more processes either prior to or contemporary with the formation of the 1300-km-diameter Caloris Planitia reduced the population of fresh craters smaller than 70 to 80 km in diameter and totally erased the population of fresh craters smaller than 20 to 30 km.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geophysical Research Letters; 3; Mar. 197
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  • 82
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    Shock-loading meteoritic b.c.c. metal above the pressure transition - Remanent-magnetization stability and microstructure (1976)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: The paper describes the remanent-magnetization stability and microstructure associated with samples of b.c.c. Fe-Ni from the Odessa meteorite which were shock loaded at 200, 400, 600, 800, and 1000 kbar. The samples include those which were transformation hardened as well as those which were altered by varying thermal levels associated only with the shock levels themselves. Demagnetization curves for an unshocked Odessa sample and for samples shocked at each level are presented along with saturation isothermal remanence demagnetization curves for samples shocked at 600 and 1000 kbar. It is found that: (1) the 200-kbar sample was shock-hardened with no significant thermal effects; (2) stability to demagnetization decreased in the 400- and 600-kbar specimens, indicating that recovery took place; and (3) the specimens shocked at 800 and 100 kbar had the greatest demagnetization stability. These three levels of shock effects are shown to be delimited by discrete levels of microhardness, microstructure, and stability of remanence to demagnetization. It is concluded that the first level is simply a consequence of antiferromagnetic-ferromagnetic reversal and that the other two levels contain a thermal component.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Physics of the Earth and Planetary Interiors; 11; 3, Ja; Jan. 197
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  • 83
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    Microcraters formed in hot glass by hypervelocity projectiles (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Microcraters were formed in heated soda-lime glass by the normal incidence of spheres of plastic or fused silica with diameters between 0.8 and 4.5 microns and velocities between 2.5 and 10 km/s. The morphology of the craters in targets at temperatures up to 800 C is little different from those formed in unheated glass. Spallation still occurs to the same extent and above the same velocity threshold, but the spalls sag and sharp edges become dull in a few seconds at temperatures above the softening point. There is a small increase in the flow of glass from the central pit into a narrow lip at the higher temperatures, but this lip is often removed by spallation, especially at the higher velocities of impact. There is no evidence of a splashed lip with strings of melt overlying the spalled area. The results in conjunction with other evidence suggest that most lunar craters of micrometer size with a smooth central pit, splashed lip, and a spallation zone are the result of primary impacts.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: The Moon; 15; Jan
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  • 84
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    Diurnal variation of the Jovian ionosphere (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: The time-dependent structure of the Jovian ionosphere is examined. Diurnal variation of appreciable magnitude is revealed in the lower ionosphere. The upper ionosphere remains more or less intact at nighttime, as in the case of the earth's ionosphere. There is considerable difference in the height-integrated electrical conductivities on the day and night sides.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Astronomical Society of Japan; vol. 28
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  • 85
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    Directivity and stimulation in Jovian decametric radiation (1976)
    In:  Other Sources
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    Publikationsdatum: 2011-08-16
    Beschreibung: Analysis of an 18-year synoptic monitoring record compiled at the University of Texas Radio Astronomy Observatory (UTRAO) reveals the existence of distinct Io-controlled and Io-independent source mechanisms which differ in second-order morphology and in intrinsic emission directivity. After a discussion of statistical models and estimation, the UTRAO 1974 analysis catalog is described, Io-controlled and Io-independent sources are defined, and their morphology is described and compared. The sources are distinguished on the basis of their directivity, and the conditions for Io control are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research; 81; July 1
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  • 86
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    Airborne ultraviolet studies of Venus (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Airborne ultraviolet studies of Venus were carried out during the NASA-ESO Space Shuttle simulation program. The primary wavelength region monitored was between 2950 and 3350 A in the third order. Measurements of solar radiation reflected from Venus were obtained on five flights at elevation angles of 15-30 deg. Direct solar and lunar spectra were obtained for the same elevation angles during two of the flights. Typical solar and Venutian spectra are presented.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature; 261; May 6
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  • 87
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    Explanation for the very low Ga and Ge concentrations in some iron meteorite groups (1976)
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    Publikationsdatum: 2011-08-16
    Beschreibung: Parallels between the abundance patterns of moderately volatile elements in iron meteorites and ordinary chondrites are pointed out and discussed in relation to condensation processes in the solar nebula. The discussion is centered around a graph in which As, Cu, Ga, Ge to Ni ratios, normalized to CI chondrites, are compared for IVB, IVA, IVB, and IIIAB irons and H-group ordinary chondrites. The patterns suggest that the same volatile loss mechanism was at work for both IVB irons and ordinary chondrites, but was more efficient in the IVB process. A picture for the process at the IVB location is proposed, according to which condensation occurred when temperature decreased rapidly and trace metals condensed as a fine aerosol that was later blown away by a T-Tauri solar storm. Condensation at the H-group location was more complete because of a less rapid temperature decrease, allowing trace metals to diffuse deeper into Fe-Ni grains. Possible ways in which IVA conditions may have differed from IIIAB or H conditions are also proposed and discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature; 261; May 13
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  • 88
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    Bibliography (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Moon and the Planets (ISSN 0165-0807); 29; 237-327
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  • 89
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    Atmospheric storm explanation of saturnian electrostatic discharges (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature (ISSN 0028-0836); 303; May 5
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  • 90
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    Speculation on Martian north polar wind circulation and the resultant orientations of polar sand dunes (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 55; Sept
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  • 91
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    Formation and photochemistry of methylamine in Jupiter's atmosphere (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 55; Sept
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  • 92
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    Modeling of the 10-micron natural laser emission from the mesospheres of Mars and Venus (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 55; Sept
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  • 93
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    Observations of the 10-micron natural laser emission from the mesospheres of Mars and Venus (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 10; Sept
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  • 95
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    Ferromagnetic resonance and magnetic properties of ALHA 81005 (1983)
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Astronomical Journal (ISSN 0004-6256); 88; Sept
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  • 99
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    Radio emission signature of Saturn immersions in Jupiter's magnetic tail (1983)
    In:  Other Sources
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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: 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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    Publikationsdatum: 2011-08-18
    Beschreibung: 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.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of the Atmospheric Sciences (ISSN 0022-4928); 40; June 198
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