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  • Inorganic Chemistry  (7,653)
  • LUNAR AND PLANETARY EXPLORATION  (3,679)
  • Ertrag
  • 1975-1979  (7,458)
  • 1930-1934  (3,902)
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Year
  • 101
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    Energetic protons in the Jovian magnetosphere (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Time histories, angular distributions and energy spectra of energetic protons were observed over an energy range of 0.2 to 20 MeV for the four passes of Pioneers 10 and 11 through the Jovian magnetosphere. The energetic particle data from these four passes are remarkably different. Azimuthal anisotropies appear to dominate with time variations also contributing to the very complex topology. On the inbound P-10 pass the expected corotation anisotropy was not observed in the outer magnetosphere. The simplest explanation is that the particle reference frame (the magnetospheric plasma) is moving nearly radially, suggesting the existence of a planetary wind at that time.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; June 1
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  • 102
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    Evidence for lightning on Venus (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Evidence for lightning on Venus obtained by the Pioneer Venus 1 Orbiter is presented. The first indications of lightning were detected by the electric field detector on board the Orbiter when the spacecraft periapsis, which is well within the ionosphere, moved into the night side of the planet. Impulsive wave signals were primarily detected at altitudes less than 25 km, and were found to be strongest at frequencies corresponding to propagation in the whistler mode, occurring at an average rate of about 0.5/sec. The signals were often observed during intervals of low and variable electron densities. It is tentatively concluded on the basis of the above observations that the impulsive events were caused by Venusian lightning.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 279; June 14
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  • 103
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    Temperature structure of the Uranian upper atmosphere (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The temperature structure of the upper atmosphere of Uranus at two locations on the planet was determined from observations of the occultation of the star SAO158687 by Uranus on 10 March 1977, carried out at the Kuiper Airborne Observatory. The temperature-pressure relationships obtained from the immersion and emersion data for 7280 A channel show peak-to-peak variations of 45 K for immersion and 35 K for emersion. The mean temperature for both immersion and emersion profiles is about 100 K, which shows that Uranus has a temperature inversion between 0.001 mbar and the 100 mbar level probed by IR measurements. Both profiles show wavelike temperature variations, which may be due to dynamical or photochemical processes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 278; May 24
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  • 104
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    Magnetic field studies at Jupiter by Voyager 1 - Preliminary results (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results obtained by the Goddard Space Flight Center magnetometers on Voyager 1 are described. These results concern the large-scale configuration of the Jovian bow shock and magnetopause, and the magnetic field in both the inner and outer magnetosphere. There is evidence that a magnetic tail extending away from the planet on the nightside is formed by the solar wind-Jovian field interaction. This is much like earth's magnetosphere but is a new configuration for Jupiter's magnetosphere not previously considered from earlier Pioneer data. The analysis and interpretation of magnetic field perturbations associated with intense electrical currents (approximately 5 million amperes) flowing near or in the magnetic flux tube linking Jupiter with the satellite Io and induced by the relative motion between Io and the corotating Jovian magnetosphere are reported. These currents may be an important source of heating the ionosphere and interior of Io through Joule dissipation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 204; June 1
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  • 105
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    On the configuration of the nightside Venus ionopause (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Nightside measurements of electron and ion concentrations by instruments on the Pioneer Venus Orbiter have revealed an ionopause which is highly dynamic and whose global configuration is surprisingly complex. Inbound crossing which occur at high northern latitudes encounter the ionopause at an average altitude of 870 km in the late afternoon sector. The average ionopause altitude increases slightly near 100 deg solar zenith angle (SZA) followed by a nightside compression to well below 500 km. The outbound crossings of the ionopause occur at about 20 deg south of the equator. The ionospause at this latitude is found at an average altitude of 800 km in the afternoon-evening sector between 65 and 110 deg SZA, followed by a pronounced rise to altitudes as high as 3000 km in a pronounced bulge near 130 deg SZA.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; May 1979
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  • 106
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    Tharsis Province of Mars - Geologic sequence, geometry, and a deformation mechanism (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Tharsis development apparently involved two stages: (1) an initial rapid topographic rise accompanied by the development of a vast radial fault system and (2) an extremely long-lived volcanic stage apparently continuing to the geological present. A deformation model is proposed in which a first-order mantle convection cell caused early subcrustal erosion and foundering of the low third of the planet. Underplating and deep intrusion by the eroded materials beneath Tharsis caused isostatic doming. Minor radial gravity motions of surficial layers off the dome produced the radial fault system. The hot underplate eventually affected the surface to cause the very long-lived volcanic second stage.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 38; June 197
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  • 107
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    The effect of surface roughness on the transmission of microwave radiation through a planetary surface (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: To account for surface roughness, the transmission of microwave radiation through a planetary surface to an observer is treated by a Monte Carlo technique. Sizable effects are found near the limb of the planet, and they should be included in analyses of high-resolution observations and high-precision integrated disk observations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 38; June 197
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  • 108
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    Four-planet meteorology (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: All planets with atmospheres have common characteristics which are helpful in understanding weather and climate on earth. Of the terrestrial planets, Mars displays the most earth-like characteristics. The feedback mechanism of the Martian Great Dust Storms may control climate on a global scale and shows some parallels to the water cycle on the earth. Venus, on the other hand, has atmosphere motions and characteristics far different from those of earth but appears to be valuable for comparative meteorology and it seems to be a simple weather machine due to absence of axial tilt. A completely gaseous Jupiter also can help because its atmosphere, driven by internal heat, flows round-and-round, showing the same general patterns for years at a time. Results of studying extraterrestrial atmospheres are most important for understanding earth's multi-year weather cycles such as the droughts in the American West every 22 years or effects of the Little Ice Age (1450-1915) on agriculture in the North Hemisphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Spaceflight; 21; June 197
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  • 109
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    A beaming model of the Io-independent Jovian decameter radiation based on multipole models of the Jovian magnetic field (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A geometrical model is presented in which the apparent source locations of the Io-independent decameter radiation are computed. The calculations assume that the radiation is produced by stably trapped electrons radiating near the local electron gyrofrequency and that the emission is then beamed onto a conical surface. The maximum occurrence probability of noise storms is associated with regions in the Jovian magnetosphere where the axis of the emission cone is most inclined toward the Jovian equatorial plane. The calculations utilize and compare two of the octopole spherical harmonic expansions of the Jovian magnetic field constructed from data accumulated by the fluxgate and vector helium magnetometers on board Pioneer 11.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 229
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  • 110
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    The seasonal variation of ozone density in the Martian atmosphere (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A one-dimensional, time-dependent model has been developed to investigate seasonal variations in ozone density in the Martian atmosphere. The model utilizes data for atmospheric temperature, pressure, and water vapor abundance observed by Viking. The results indicate that a high ozone density is not produced near the winter solstice but is in rather late winter, when the amount of water vapor is still small and the solar radiation can penetrate more deeply. A similar condition met in early winter does not necessarily produce a high ozone density because of the predicted higher HO2 density. Seasonal variations in ozone abundance are discussed in terms of the abundances of H2O and H2 and the seasonal variations in their reaction products H2O2 and HOx. The roles of transport, the effects of ozone loss to the surface, and the differences between northern and southern hemisphere ozone distributions are also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Apr. 1
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  • 111
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    Deep radio occultations and 'evolute flashes' - Their characteristics and utility for planetary studies (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Deep radio occultation signals from spacecraft passing behind planets may provide data on atmospheric absorption, turbulence, and structure, as well as information on the effects of planetary gravitational moments, rotation and zonal winds on the atmospheric shape. The strength of radio signals from a spacecraft passing behind a planet will at first decrease because of defocusing in the atmosphere, but then increase as the evolute of the planetary limb is neared, due to focusing caused by limb curvature within the evolute. Within the evolute, the availability of four simultaneous signal paths over four limb positions may render focused signals instantaneously great. The passage of Voyager 1 behind Jupiter and Voyager 2 behind Saturn will provide a test of deep radio occultation studies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 37; Mar. 197
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  • 112
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    Climatic change on the terrestrial planets (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observational data related to climatic change on Venus, earth and Mars are reviewed. The channel features on Mars suggest an early to intermediate epoch of warmer and wetter climate, while the layered polar deposits imply more recent periodic variations in climate. A more reducing atmosphere, which would have produced an enhanced greenhouse effect, may have been responsible for warmer periods in the early history of Mars and earth. Detailed calculations relating atmospheric pressure and composition to the temperature state of Mars are presented. The possibility of a runaway greenhouse effect on Venus resulting in the emplacement of volatiles entirely in the atmosphere is also examined. Periodic variations in orbital eccentricity and axial obliquity may have contributed to alternating glacial and interglacial periods on earth. Mechanisms accounting for the laminated terrain of Mars, and the influence of Martian tectonic distortions on the planet's climate also receive attention.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 37; Mar. 197
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  • 113
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    Martian extratropical cyclones (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Physical properties of summer-season baroclinic waves on Mars are discussed on the basis of vidicon images and infrared thermal mapping generated by Viking Orbiter 1. The two northern-hemisphere storm systems examined here appear to be similar to terrestrial mid-latitude cyclonic storms. The Martian storm clouds are probably composed of water ice, rather than dust or CO2 ice particles.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 278; Apr. 5
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  • 114
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    On inhomogeneous scattering models of Titan's atmosphere (1979)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Podolak and Danielson (1977) discussed the homogeneous model of Titan's atmosphere with the dust and gas uniformly mixed. They were able to reproduce the equivalent widths of the CH4 bands at 4680 and 5430 A but failed to agree with the observations in the near infrared. The present paper develops an inhomogeneous model which has the dust and gas essentially separated; this model agrees fairly well with the near-IR data of Younkin (1974) but does not agree with the data of Lutz et al. (1976) for the 4860-A band and it must be adjusted to match their data for the 5430-A band.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 37; Feb. 197
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  • 115
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    Comet Halley and history (1979)
    In:  CASI
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    Publication Date: 2017-10-02
    Description: A history of Halley's Comet is presented. Comets Kohoutek and Ikeya-Seki are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Space Missions to Comets; p 179-196
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  • 116
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    Ion propulsion and Comet Halley rendezvous (1979)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Cometary rendezvous missions using ion propulsion is considered. The characteristics of the ion engine are discussed including the fuel efficiency and acceleration, and the design of the ion engine is described. The operation of the ion drive engine and an overview of its applications are presented.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Space Missions to Comets; p 197-214
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  • 117
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    Comets, carbonaceous chondrites, and interstellar clouds: Condensation of carbon (1979)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Comets, carbonaceous chondrites, and interstellar clouds are discussed in relation to information on interstellar dust. The formation and presence of carbon in stars, comets, and meteorites is investigated. The existence of graphite in the interstellar medium, though it is predicted from thermodynamic calculations, is questioned and the form of carbon contained in comets is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Space Missions to Comets; p 113-137
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  • 118
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    Scientific returns from a program of space missions to comets (1979)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: A program of cometary missions is proposed. The nature and size of interstellar dust, its origin and evolution; identification of new interstellar molecules; clarification of interstellar chemistry; accretion of grains into protosolar cometesimals; role of a T Tauri wind in the dissipation of the protosolar nebula; record of isotopic anomalies, better preserved in comets than in meteorites; cosmogenic and radiogenic dating of comets; cosmochronology and mineralogy of meteorites, as compared with that of cometary samples; origin of the earth's biosphere, and the origin of life are topics discussed in relation to comet exploration.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Space Missions to Comets; p 139-178
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  • 119
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    Comets: Cosmic connections with carbonaceous meteorites, interstellar molecules and the origin of life (1979)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The ions, radicals, and molecules observed in comets may be derived intact or by partial decomposition from parent compounds of the sort found either in the interstellar medium or in carbonaceous meteorites. The early loss of highly reducing primitive atmosphere and its replacement by a secondary atmosphere dominated by H2O, CO2, and N2, as depicted in current models of the earth's evolution, pose a dilemma for the origin of life: the synthesis of organic compounds necessary for life from components of the secondary atmosphere appears to be difficult, and plausible mechanisms have not been evaluated. Both comets and carbonaceous meteorites are implicated as sources for the earth's atmophilic and organogenic elements. A mass balance argument involving the estimated ratios of hydrogen to carbon in carbonaceous meteorites, comets, and the crust and upper mantle suggests that comets supplied the earth with a large fraction of its volatiles. The probability that comets contributed significantly to the earth's volatile inventory suggests a chemical evolutionary link between comets, prebiotic organic synthesis, and the origin of life.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Space Missions to Comets; p 59-111
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  • 120
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    Scientific need for a cometary mission (1979)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Known facts about comets are reviewed including their organic and inorganic content. Photographs are used to show the differences in the physical appearances of the three types of comets. Space missions will provide the opportunity to determine the sequence of events that led to their formation and that of the solar system; how volatiles arrived on earth; and the basis for the existence of life on earth; and the source of the outer planetary system.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Space Missions to Comets; p 1-31
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  • 121
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    Connections between comets and plasmas in space (1979)
    In:  CASI
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    Publication Date: 2017-10-02
    Description: The dynamical processes in the cometary system represent unusual examples of very important, widespread natural phenomena. Topics covered include: (1) the comet as an obstacle in the solar wind; (2) the nature of the plasma flow; (3) collisionless shocks; and (4) plasma processes in the comet tail.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Space Missions to Comets; p 33-58
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  • 122
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    Convection and lunar thermal history (1979)
    In:  Other Sources
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    Publication Date: 2019-04-02
    Description: The effects of solid interior convection on the thermal history of the moon are examined. Convective models of lunar evolution are calculated to demonstrate the influence of various viscosities, radioactive heat source distributions and initial temperature profiles and tested by means of a thermal history simulation code. Results indicate that solid convection does not necessarily produce a quasi-steady thermal balance between heat sources and surface losses. The state of the lithosphere is found to be sensitive to the efficiency of heat source redistribution, while that of the convecting interior depends primarily on rheology. Interior viscosities of 10 to the 21st to 10 to the 22nd cm/sec are obtained, along with a central temperature above 1100 C. It is suggested that mare flooding could have been the result of magma production by pressure release melting in the upwelling region of convection cells.
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  • 123
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    Solid Convection in the Terrestrial Planets; Workshop, NASA Ames Research Center, Moffett Field, Calif., December 12, 13, 1977, Review Papers and Contributions (1979)
    In:  Other Sources
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    Publication Date: 2019-03-30
    Description: Review papers and specific contributions on the subject of convection in the solid interiors of the terrestrial planets and planetary evolution are presented. Geophysical observations of solid-state convection in the terrestrial planets are reviewed, along with the theory of convection in a layer with a high Prandtl number and numerical approaches to the calculation of convection in planetary interiors. Other papers treat the formation, history and energetics of terrestrial planet cores, the effects of convection on lunar thermal history and the relation between the height of mountains on Venus and the creep properties of Venusian rocks.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Physics of the Earth and Planetary Interiors (ISSN 0031-9201); 19; 2; 107-207
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  • 124
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    Smectite clays in Mars soil - Evidence for their presence and role in Viking biology experimental results (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Evidence for the presence of smectite clays in Martian soils is reviewed and results of experiments with certain active clays simulating the Viking biology experiments are reported. Analyses of Martian soil composition by means of X-ray fluorescence spectrometry and dust storm spectroscopy and Martian geological history strongly suggest the presence of a mixture of weathered ferro-silicate minerals, mainly nontronite and montmorillonite, accompanied by soluble sulphate salts, as major constituents. Samples of montmorillonite and nontronite incubated with (C-14)-formate or the radioactive nutrient medium solution used in the Viking Labeled Release experiment, were found to produce patterns of release of radioactive gas very similar to those observed in the Viking experiments, indicating the iron-catalyzed decomposition of formate as the reaction responsible for the Viking results. The experimental results of Hubbard (1979) simulating the results of the Viking Pyrolytic Release experiment using iron montmorillonites are pointed out, and it is concluded that many of the results of the Viking biology experiments can be explained in terms of the surface activity of smectite clays in catalysis and adsorption.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Molecular Evolution; 14; Dec. 197
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  • 125
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    The distribution of lobate debris aprons and similar flows on Mars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Planet-wide mapping of lobate debris aprons and other similar flows on Mars shows a strong concentration in two latitudinal bands roughly 25 deg wide and centered at 40 deg N and 45 deg S. This distribution supports the idea that these flows form when erosional debris is transported downslope and becomes mixed with ice deposited from the atmosphere, as these latitudes should receive high seasonal H2O frost deposition relative to the rest of the planet. Flows are found in the northern hemisphere band wherever old highland surfaces occur but are found in the southern hemisphere only near the two major impact basins, Argyre and Hellas. These areas are apparently characterized by mass wasting that is rapid relative to most of the southern hemisphere highlands. The rate of mass wasting may be related to the degree of consolidation of highland material.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 126
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    Impact crater and basin control of igneous processes on Mars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The possible role of impact craters in controlling local Martian endogenic activity is reviewed. Martian impact craters exhibiting evidence for endogenic modification are considered, including the style of modification. In addition, the cooling history of a mafic body intruded beneath impact craters of different sizes which contain water-ice deposits are examined, and results are related to modified Martian craters. This analysis is extended to basin-sized structures, and evidence for impact basin control of major volcanic and tectonic provinces is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 127
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    Plains and channels in the Lunae Planum-Chryse Planitia region of Mars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The Lunae Planum-Chryse Planitia region provides the opportunity to study a sequence of channeling events and to determine their temporal and genetic relationships to plains units in the northern hemisphere of Mars. Two sets of small channels and four major channel systems can be divided into four periods of channeling by superposition and contact relationships to the plains. All of the channels are considered to have formed by water erosion. The first two channeling events occurred early in the history of this area and formed small, narrow channels within the old rugged terrain. These channel events were separated by deposition of a mantle unit. The small channels probably formed by runoff of surface water or by a sapping process. These channels preceded the emplacement of vast volcanic plains in both Lunae Planum and Chryse Planitia. Channels postdating the plains are Vedra, Maumee, Bahram, and Maja valles; the first three of these deposited a sedimentary unit on the western slope of Chryse Planitia that was eroded by Maja Vallis. These large-scale channels were probably formed predominantly by catastrophic floods and may represent two periods of water release from Juventae Chasma. The origin of Bahram Vallis remains uncertain.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 128
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    Development and analysis of a twelfth degree and order gravity model for Mars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Satellite geodesy techniques previously applied to artificial earth satellites have been extended to obtain a high-resolution gravity field for Mars. Two-way Doppler data collected by 10 Deep Space Network (DSN) stations during Mariner 9 and Viking 1 and 2 missions have been processed to obtain a twelfth degree and order spherical harmonic model for the martian gravitational potential. The quality of this model was evaluated by examining the rms residuals within the fit and the ability of the model to predict the spacecraft state beyond the fit. Both indicators show that more data and higher degree and order harmonics will be required to further refine our knowledge of the martian gravity field. The model presented shows much promise, since it resolves local gravity features which correlate highly with the martian topography. An isostatic analysis based on this model, as well as an error analysis, shows rather complete compensation on a global (long wavelength) scale. Though further model refinements are necessary to be certain, local (short wavelength) features such as the shield volcanos in Tharsis appear to be uncompensated. These are interpreted to place some bounds on the internal structure of Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 129
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    Silicon compounds in the Jupiter atmosphere (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The formation of colored silicon compounds under nonequilibrium conditions is discussed with reference to the composition of the Jupiter atmosphere. It is shown that many of these reactions produce strongly colored intermediates that are relatively stable and similar in appearance to those observed on Jupiter. It is suggested that the silicon compounds could substantially contribute to the colors observed on Jupiter. The colored intermediates may be the result of relatively rapid amorphous silicon monoxide formation in vertical atmospheric currents in the region near the red spot and in the red spot itself.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Zeitschrift fuer Naturforschung; vol. 34
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    Scientific exploration of the moon (1979)
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    Publication Date: 2019-06-27
    Description: The paper reviews efforts undertaken to explore the moon and the results obtained, noting that such efforts have involved a successful interdisciplinary approach to solving a number of scientific problems. Attention is given to the interactions of astronomers, cartographers, geologists, geochemists, geophysicists, physicists, mathematicians and engineers. Earth based remote sensing and unmanned spacecraft such as the Ranger and Surveyor programs are discussed. Emphasis is given to the manned Apollo missions and the results obtained. Finally, the information gathered by these missions is reviewed with regards to how it has increased understanding of the moon, and future exploration is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Interdisciplinary Science Reviews; 4; Sept
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    Pyroxenes from planetary basalts - Characterization of 'other' than quadrilateral components (1979)
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    Publication Date: 2019-06-27
    Description: The paper reports on a synthesis of the silicate mineralogy of a planetary basalt suite, which concerns itself only with specific aspects of pyroxene cation substitutional couples. Consideration is given to the mineral chemistry and the basalt suites in an overview fashion. Attention is given to those characteristics of pyroxene chemistry that reflect planetary constraints on the host basalts from which the pyroxenes crystallized. It is concluded that the inspection of a large number of high quality silicate analyses of pyroxenes demonstrates conclusively that these phases carry a signature of the planetary body in which they evolved. In addition, it is noted that there are planetary probes capable of constraining thermodynamic parameters that were obtained during the petrogenesis of their host basaltic liquids
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; Dec. 197
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  • 132
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    Organic chemistry on Titan (1979)
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    Publication Date: 2019-06-27
    Description: Features taken from various models of Titan's atmosphere are combined in a working composite model that provides environmental constraints within which different pathways for organic chemical synthesis are determined. Experimental results and theoretical modeling suggest that the organic chemistry of the satellite is dominated by two processes: photochemistry and energetic particle bombardment. Photochemical reactions of CH4 in the upper atmosphere can account for the presence of C2 hydrocarbons. Reactions initiated at various levels of the atmosphere by cosmic rays, Saturn 'wind', and solar wind particle bombardment of a CH4-N2 atmospheric mixture can account for the UV-visible absorbing stratospheric haze, the reddish appearance of the satellite, and some of the C2 hydrocarbons. In the lower atmosphere photochemical processes will be important if surface temperatures are sufficiently high for gaseous NH3 to exist. It is concluded that the surface of Titan may contain ancient or recent organic matter (or both) produced in the atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Review of Geophysics and Space Physics; 17; Nov. 197
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  • 133
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    Io's sodium cloud - Explanation of the east-west asymmetries (1979)
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    Publication Date: 2019-06-27
    Description: An explanation of the east-west asymmetries of Io's sodium clouds is suggested based upon the force experienced by sodium atoms as they resonantly scatter sunlight and upon the ability of this force to alter the cloud atom orbits, as determined by the gravitational fields of Io and Jupiter. Orbit calculations illustrating the time-dependent changes in the sodium atom trajectories produced by the solar radiation force as a function of Io's orbital location are presented in support of this explanation. This theory agrees with the idea that sodium atoms are emitted from the satellite nonisotropically and at a constant rate. These conclusions may be important in studying the global effects of active volcanoes and the intense satellite plasma torus discovered for Io from Voyager I spacecraft measurements.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 234
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  • 134
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    Atmospheric effects on Martian ejecta emplacement (1979)
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    Publication Date: 2019-06-27
    Description: The paper presents analytical descriptions of crater growth and numerical calculations of aerodynamic drag to evaluate the possible effects of drag on impact crater ejecta emplacement on Mars. The critical particle size below which ejecta deposition is restricted in range increases with crater size; models of ejecta trajectories in the current Martian atmosphere under hydrostatic equilibrium reveal critical particle diameters ranging from 0.4 to 20 cm, noting that ejecta approaching the critical particle size may impact with crater radius of the excavation crater rim. Ejecta larger than the critical particle size are undecelerated and form secondary impact craters modified by the later arriving decelerated ejecta cloud; thus, ejecta emplacement will be multiphased, but the process depends on the ejecta size distribution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 10
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  • 135
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    Serenitatis multi-ringed basin - Regional geology and basin ring interpretation (1979)
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    Publication Date: 2019-06-27
    Description: New topographic data allow a reassessment of the ring structure and distribution of facies of the Serenitatis basin (SB) and correlation with the younger and essentially same-size Orientale basin. Three major rings of the main (southern) SB are mapped: the Linne ring, outlined by mare ridges, average diameter 420 km; the Haemus ring, outlined by basin-facing scarps and massifs with crenulated borders, 610 km; and the Vitruvius ring, outlined by basin-facing linear scarps and massifs, 880 km. The second ring is interpreted as the rim of the transient cavity, while Serenitatis ejecta should be present in significant amounts at the junction of the Serenitatis and Imbrium third rings. The new reconstruction indicates that portions of the SB are better preserved than previously thought, consistent with recent stratigraphic and sample studies that suggest an age (as young as 3.87 plus or minus 0.04 b.y.) for SB which is older than, but close to, the time of formation of the Imbrium basin.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Moon and the Planets vol. 21; Dec. 197
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  • 136
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    Combining paleointensity methods - A dual-valued determination on lunar sample 10017,135 (1979)
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    Publication Date: 2019-06-27
    Description: A single-heating procedure for the determination of two partially independent values of paleofield intensity for one sample is presented. The procedure combines data for Shaw-type and 'ARM-method' determinations furnishing the ratio thermoremanent magnetization (TRM) to ARM acquisition efficiency corrected for physicochemical alteration to the magnetic carriers. Applicability of the Shaw-method to Fe-bearing samples is demonstrated by simulated paleointensity determinations on synthetic samples containing multidomain grains. The combined Shaw-ARM procedure was applied to a linear basalt sample, but the Thellier-Thellier method could not provide a meaningful determination of the neighboring chip. These conflicting findings may be explained by multiple step-wise heatings causing more damage to carriers than a single heating procedure, and by the natural remanent magnetization in this lunar basalt not being a simple TRM.
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    Lunar magnetic anomalies detected by the Apollo subsatellite magnetometers (1979)
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    Publication Date: 2019-06-27
    Description: Properties of lunar crustal magnetization thus far deduced from Apollo subsatellite magnetometer data are reviewed using two of the most accurate available magnetic anomaly maps, one covering a portion of the lunar near side and the other a part of the far side. The largest single anomaly found within the region of coverage on the near-side map correlates exactly with a conspicuous light-colored marking in western Oceanus Procellarum called Reiner Gamma. This feature is interpreted as an unusual deposit of ejecta from secondary craters of the large nearby primary impact crater Cavalerius. The mean altitude of the far-side anomaly gap is much higher than that of the near side map and the surface geology is more complex; individual anomaly sources have therefore not yet been identified. The mechanism of magnetization and the origin of the magnetizing field remain unresolved, but the uniformity with which the Reiner Gamma deposit is apparently magnetized, and the north-south depletion of magnetization intensity across a substantial portion of the far side, seem to require the existence of an ambient field, perhaps of global or larger extent.
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    A study of the Rima Sirsalis lunar magnetic anomaly (1979)
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    Publication Date: 2019-06-27
    Description: The source of the lunar magnetic anomaly associated with the Rima Sirsalis linear rille has been modelled using the vector field intensities due to arbitrary uniform magnetization in a rectangular prism. It is shown that in order to match the Apollo 16 subsatellite data, the lunar surface near the rille must have a vertical magnetization of 6,000-9,000 G if the anomaly is due to flux leakage from a gap in the crust with the dimensions of the rille. An alternative explanation is that Rima Sirsalis and its surroundings are the site of a vertical magnetization contrast of 100,000-10,000 G which is at least as wide as the rille and extends to a depth of tens of kilometers in the crust. A wider magnetic source reduces the required magnetization (or depth) proportionately, since to first order the field at high altitude is proportional to the magnetic dipole moment per unit length.
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    Constraints on the origins of lunar magnetism from electron reflection measurements of surface magnetic fields (1979)
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    Publication Date: 2019-06-27
    Description: The paper describes a new method of detecting lunar surface magnetic fields, summarizes electron reflection measurements and correlations of surface field anomalies to moon geologic features, and discusses the constraints on the origin of lunar magnetism. Apollo 15 and 16 measurements of lunar surface magnetic fields by the electron reflection method show patches of strong surface fields distributed over the lunar surface, and a positive statistical correlation is found in lunar mare regions between the surface field strength and the geologic age of the surface. However, there is a lack of correlation of surface field with impact craters indicating that the mare does not have a strong large-scale uniform magnetization as may be expected from an ancient lunar dynamo. Fields were found in lunar highlands which imply that the rille has a strong magnetization associated with it as intrusive, magnetized rock or as a gap in a uniformly magnetic layer of rock.
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  • 140
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    Theories for the origin of lunar magnetism (1979)
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    Publication Date: 2019-06-27
    Description: This paper reviews the major theories which have been proposed to explain the remanent magnetism found in the lunar crust. A total of nine different mechanisms for lunar magnetism are discussed and evaluated in light of the theoretical and experimental constraints pertinent to lunar magnetism. It is concluded that none of these theories in their present state of development satisfy all the known constraints. However, the theories which agree best with the present understanding of the moon are meteorite impact magnetization, thermoelectric dynamo field generation, and an early solar wind field.
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    Origin of the magnetic fields in the giant planets (1979)
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    Publication Date: 2019-06-27
    Description: The paper discusses origin of the magnetic fields in the giant planets. Recent data on the generation of these fields provide conclusions on giant planets; the Jovian magnetic field can be of primordial origin or generated by a thermally driven dynamo, and the expected Saturnian field can be accounted for thermally or by a precessionally driven dynamo. The presence of a 0.1 gauss field on Uranus presents a problem because the so far unobserved thermal flux and convection may be too low, and if such a dynamo were to operate then the field should show seasonal variations. A conductive shell on Neptune similar to that on Uranus appears to be much thinner, but it is likely that Neptune has a magnetic field which is too weak to lead to observable electromagnetic variations.
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  • 142
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    The Martian magnetic field (1979)
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    Publication Date: 2019-06-27
    Description: The paper presents an overview of the Martian magnetic field measurements and the criticisms made of them. The measurements of the Mars 2, 3, and 5 spacecraft were interpreted by Dolginov et al. (1976, 1978) to be consistent with an intrinsic planetary magnetic moment of 2.5 times 10 to the 22nd power gauss cu cm, basing this result on the apparent size of the obstacle responsible for deflecting the solar wind and an apparent encounter of the spacecraft with the planetary field. It is shown that if the dependence of the Martian magnetic moment on the rotation rate was linear, the estimate of the moment would be far larger than reported by Dolginov et al. An upper limit of 250 km is calculated for the dynamo radius using the similarity law, compared with 500 km obtained by Dolginov et al. It is concluded that the possible strength of a Martian dynamo is below expectations, and it is likely that the Mars dynamo is not presently operative.
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    On the determination of the Hermaean magnetic moment - A critical review (1979)
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    Publication Date: 2019-06-27
    Description: The determination of Mercury's magnetic moment from the spatially and temporally limited observations obtained by the Mariner 10 mission is dependent upon the assumed nature of both the intrinsic planetary magnetic field and that of the magnetospheric current systems. In this paper the methods that have been used for this purpose are reviewed. The results that have been obtained are then considered in comparison with the constraints placed on the planetary field by the solar wind dynamic pressures and stand-off distances inferred from the Mariner 10 magnetic field data by Slavin and Holtzer (1979) which are consistent with an effective dipole moment of 6 + or - 2 x 10 to the 22nd G cu cm. It is found that the models which fit the observations with substantial quadrupole and octupole moments are not consistent with the magnetospheric boundary conditions, presumably owing to incorrect assumptions regarding the magnetopause position, incorrect assumptions regarding solar wind dynamic pressure, and/or averaging over temporal variations in the Mariner 10 data.
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    Model magnetosphere of Mercury (1979)
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    Publication Date: 2019-06-27
    Description: A three-dimensional quantitative model of Mercury's magnetosphere based on Mariner 10 data is presented. The model assumes that the Mercury surface magnetic field consists of a dipole, a quadrupole, and an octupole. The dipole moment is determined, noting that the intensity of the quadrupole moment is 45% of the dipole, and that of the octupole moment is 29% of the dipole. The model meets four critical tests: (1) it produces the smallest residuals, (2) it can reproduce the crossing of a tail current sheet by Mariner 10, (3) all planetary field lines are confined inside the model magnetosphere, and (4) the size of the model agrees with the magnetopause crossings observed from Mariner 10. In addition, the plasma characteristics and regions of quiet and disturbed signatures observed from Mariner 10 are discussed.
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  • 145
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    Core cooling by subsolidus mantle convection (1979)
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    Publication Date: 2019-06-27
    Description: Although vigorous mantle convection early in the thermal history of the earth is shown to be capable of removing several times the latent heat content of the core, a thermal evolution model of the earth in which the core does not solidify can be constructed. The large amount of energy removed from the model earth's core by mantle convection is supplied by the internal energy of the core which is assumed to cool from an initial high temperature given by the silicate melting temperature at the core-mantle boundary. For the smaller terrestrial planets, the iron and silicate melting temperatures at the core-mantle boundaries are more comparable than for the earth; the models incorporate temperature-dependent mantle viscosity and radiogenic heat sources in the mantle. The earth models are constrained by the present surface heat flux and mantle viscosity and internal heat sources produce only about 55% of the earth model's present surface heat flow.
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  • 146
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    Correlation of lunar far-side magnetized regions with ringed impact basins (1979)
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    Publication Date: 2019-06-27
    Description: By the method of electron reflection, we have identified seven well-defined magnetized regions in the equatorial belt of the lunar far side sampled by the Apollo 16 Particles and Fields subsatellite. Most of these surface magnetic fields lie within one basin radius from the rim of a ringed impact basin, where thick deposits of basin ejecta are observed or inferred. The strongest of the seven magnetic features is linear, at least 250 km long, and radial to the Freundlich-Sharonov basin. The apparent correlation with basin ejecta suggests some form of impact origin for the observed permanently magnetized regions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 46; 1, De; Dec. 197
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    Stellar condensates in meteorites - Isotopic evidence from noble gases (1979)
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    Publication Date: 2019-06-27
    Description: The Murchison carbonaceous chondrite contains three isotopically anomalous noble-gas components of apparently presolar origin: two kinds of Ne-E, (Ne-20)/(Ne-22) less than 0.6, and s-process Kr + Xe (enriched in the even isotopes 82, 84, 86, 128, 130, 132). Their carriers are tentatively identified as spinel and two carbonaceous phases, the principal high-temperature stellar condensates at low and high C/O ratios, respectively.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 234
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    Temporal characteristics of the Jovian atmosphere (1979)
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    Publication Date: 2019-06-27
    Description: Drift scans along the central meridian of Jupiter have been obtained at wavelengths of 7.9, 17.8, and 19.7 microns. These observations indicate a significant north-south temperature asymmetry within the Jovian stratosphere but not within its troposphere, results which agree with the recent Voyager 1 observations. Employing a time-dependent stratospheric model, it is found that the observed north-south asymmetry is consistent with seasonal stratospheric variability. In the model, the primary cause for this variability is the time-dependent absorption of sunlight by aerosols.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 234
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    Variability of Lyman-alpha emission from Jupiter (1979)
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    Publication Date: 2019-06-27
    Description: The Jovian Lyman-alpha emission line was reobserved in 1978 March using the high-resolution spectrometer of the Copernicus satellite. An intensity of 8.3 plus or minus 2.9 kilorayleighs was measured. This value represents a significant increase in intensity over previous (1976) Copernicus observations, but is lower than the recent (1979) values obtained by Voyager 1 and IUE. The increase in intensity has been accompanied by a significant increase in line width giving strong support to the theory that the emission results from resonant scattering of the solar Lyman-alpha line by H atoms in the upper Jovian atmossphere. The strength of Jovian Lyman-alpha emission correlates well with the level of solar activity. The solar extreme ultraviolet radiation varies with the solar cycle. This radiation causes the dissociation of H2 and CH4 into H atoms in the Jovian atmosphere. Therefore, in times of high solar activity, the H column density will increase, causing the observed strong Jovian Lyman-alpha emission.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 234
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    A model of the Venus atmosphere from radio, radar, and occultation observations (1979)
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    Publication Date: 2019-06-27
    Description: A model is presented of the atmosphere and surface of Venus which best fits in the least-squares sense the available radio-brightness, radar cross-section, radio interferometric, and Mariner 5 and 10 radio occultation observations. The determinations of the radius of the planet obtained by others from radar time-delay measurements are included in the data set. The values of the adjusted parameters are: molar fraction of CO2 = 95 plus or minus 3%; fraction of combined nitrogen and argon = 5 plus or minus 3%; total atmospheric opacity at a wavelength of 1 cm = 19.4 plus or minus 1.3; mean radius of the surface = 6050.7 plus or minus 0.8 km; mean dielectric constant of the surface = 4.1 plus or minus 0.2, and percentage of total opacity due to chemical species other than CO2 = 45 plus or minus 12. The model temperature and pressure at the mean surface are 755 K and 91.4 atm, respectively.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 234
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    REE patterns versus the origin of the basaltic achondrites (1979)
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    Publication Date: 2019-06-27
    Description: The spectral uniqueness of asteroid 4 Vesta has led to suggestions that it is the eucrite parent body. However, there exist other basaltic achondrite types besides eucrites; either they also came from Vesta or else there exist other achondrite parent bodies. Howardites appear to be mixtures of eucrites and diogenites, and mesosiderites mixtures of eucrites or howardites and iron; thus one may infer that all four classes come from the same parent body. The REE patterns of eucrites and diogenites are modeled in order to test this hypothesis; eucrites can be made easily, but the patterns of diogenites are more difficult to match. The other basaltic achondrites are so rare that one cannot argue from statistics of abundances against a disrupted parent body for their origin. Pallasites and most irons likely had an origin separate from eucrites, again in parent bodies since disrupted.
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    Electromagnetic heating of minor planets in the early solar system (1979)
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    Publication Date: 2019-06-27
    Description: Electromagnetic processes occurring in the primordial solar system are likely to have significantly affected planetary evolution. In particular, electrical coupling of the kinetic energy of a dense T-Tauri-like solar wind into the interior of the smaller planets could have been a major driver of thermal metamorphism. Accordingly a grid of asteroid models of various sizes and solar distances was constructed using dc transverse magnetic induction theory. Plausible parameterizations with no requirement for a high environmental temperature led to complete melting for Vesta with no melting for Pallas and Ceres. High temperatures were reached in the Pallas model, perhaps implying nonmelting thermal metamorphosis as a cause of its anomalous spectrum. A reversal of this temperature sequence seems implausible, suggesting that the Ceres-Pallas-Vesta dichotomy is a natural outcome of the induction mechanism. Highly localized heating is expected to arise due to an instability in the temperature-controlled current distribution. Localized metamorphosis resulting from this effect may be relevant to the production and evolution of pallasites, the large presumed metal component of S object spectra, and the formation of the lunar magma ocean.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 40; Dec. 197
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    The condensation and fractionation of refractory lithophile elements (1979)
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    Publication Date: 2019-06-27
    Description: It is noted that Cr, Mg, and Si are fractionated in chondritic material along with, but to a lesser extent than, a large group of more refractory elements. These patterns are reexamined with the reasoning that this might imply some unique distribution at the time of fractionation. It is shown that apparently two distinct fractionization patterns can be resolved: one involving ordinary and enstatite chondrites and the other involving carbonaceous chondrites, the earth, the moon, and the eucrite parent body. It is noted that the two trends intersect at C1 composition. Attention is given to the range in which the largest fraction of planetary matter condenses. It is concluded that the appearance of large amounts of condensed materials is conceivably in some way related to the fractionization process, although the exact relationship cannot be specified.
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    Type: Icarus; 40; Dec. 197
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    Grooves on asteroids - A prediction (1979)
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    Publication Date: 2019-06-27
    Description: The characteristics of the grooves on Phobos indicate that these features were formed by a large impact, an observation which implies that grooves may occur on other small bodies. Published data on fragmentation experiments suggest that the energy of the impact which produced the grooves on Phobos was in a critical range, strong enough to produce fracturing at large distances from the crater, but too weak to fragment the object. Other small bodies, such as asteroids, which have experienced an impact flux sufficient to include one such critical cratering event should show grooves, unless they have been fragmented subsequently by a more severe impact. It is estimated that between 1/12th and 1/4th of asteroids smaller than 100 km in diameter may have surface features resembling grooves associated with large impact craters. Several morphologically distinct types of grooves can be expected, depending on the thickness and composition of the regolith of the parent body.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 40; Dec. 197
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    Radar observations of asteroid 1 Ceres (1979)
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    Publication Date: 2019-06-27
    Description: Radar observations of asteroid 1 Ceres were made at a 12.6-cm wavelength from the Arecibo Observatory in March/April 1977. The measurements, made with a received circular polarization orthogonal to that transmitted, yield a radar cross section of (0.04 + or- 0.01) piR-squared, for R = 510 km. The corresponding radar reflectivity is less than that measured for any other celestial body. Within the accuracy of measurement, no significant variation of cross section with rotational phase is apparent. The shape of the power spectrum suggests that Ceres is rougher at the scale of the observing wavelength than the moon and inner planets, but smoother than the outer three Galilean satellites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 40; Dec. 197
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    Radar observations of asteroid 1580 Betulia (1979)
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    Publication Date: 2019-06-27
    Description: Radar observations of the asteroid 1580 Betulia, made at a wavelength of 12.6 cm, show a mean radar cross section of 2.2 + or- 0.8 sq km and a total spectral bandwidth of 26.5 + or- 1.5 Hz. Combining bandwidth measurements with the optically determined rotation period sets a lower limit to the asteroid's radius of 2.9 + or- 0.2 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 40; Dec. 197
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  • 157
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    Notes on the origin of the Trojan asteroids (1979)
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    Publication Date: 2019-06-27
    Description: The dynamic plausibility of various ideas on the origin of the Trojans is briefly discussed. We take the point of view that the present, tightly bound population has secularly evolved through some mechanism from less to more tightly bound orbit configurations. The mechanisms considered are changes in the Jovian mass or semimajor axis during planetary formation, collisional interactions with external, asteroidal material, and cometary outgassing.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 40; Dec. 197
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  • 158
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    The Palomar planet-crossing asteroid survey, 1973-1978 (1979)
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    Publication Date: 2019-06-27
    Description: Photographic coverage of about 80,000 sq deg of sky with the Palomar 46-cm Schmidt camera has yielded 12 new planet-crossing asteroids as well as many objects in the main asteroid belt. The estimated population of planet-crossing asteroids includes approximately 100 Atens, 700 + or- 300 Apollos, 1000-2000 Amors, 10,000 + or- 5000 Mars crossers, and approximately 5000 Mars grazers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 40; Dec. 197
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  • 159
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    Wave tilt sounding of multilayered structures (1979)
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    Publication Date: 2019-06-27
    Description: The relationship between the wave tilt and the electrical parameters of a multilayered structure is investigated. Particular emphasis is placed on the inverse problem associated with the sounding planetary surfaces. An inversion technique, based on multifrequency wave tilt, is proposed and demonstrated with several computer models. It is determined that there is close agreement between the electrical parameters used in the models and those in the inversion values.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Radio Science; 14; Nov
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  • 160
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    A possible origin for the grooves of Phobos (1979)
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    Publication Date: 2019-06-27
    Description: A hypothesis that the age and distribution of grooves on the surface of Phobos may be explained by a hybrid origin due to varying tidal stresses induced after a large impact altered the satellite's rotation rate is presented. The theory that these grooves are surface manifestations of internal fractures induced by the decay of Phobos orbit is ruled out because this mechanism would require the grooves to be extremely young features, but their implied age is greater than 10 to the 9th power yr. The location and relationship of grooves to the largest crater, Stickney, indicate that they are related to the Stickney impact, but were formed shortly after that event with orientations determined by the shape of Phobos. If the impact destroyed the condition of synchronous rotation, the changing orientation of Phobos in the gravitational field of Mars would subject its interior to stresses, producing the systems of grooves.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 282; Dec. 13
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  • 161
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    A model for the azimuthal brightness variations in Saturn's rings (1979)
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    Publication Date: 2019-06-27
    Description: The paper presents a model to explain brightness variations in Saturn rings. These variations have been interpreted as implying the presence of large, synchronously rotating particles with elongated shapes or leading-trailing-edge differences although such synchronous rotation appears unlikely. The model given here assumes that the gravitational wakes or waves can be considered as elongated distributions of particles referred to as blobs, and the radiative transfer in the rings will involve both processes internal to the blobs and analogous processes among blobs. This model explains the existence of azimuthal variation in ring brightness, as well as the dependence of their amplitude on geometrical and photometric parameters. The probable photometric effects are outlined assuming the existence of density irregularities as a result of self-gravitation, and the results simplify the geometric discussion of Franklin and Colombo (1978).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 282; Dec. 13
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  • 162
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    Quantitative modeling of planetary magnetospheric magnetic fields (1979)
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    Publication Date: 2019-06-27
    Description: Three new quantitative models of the earth's magnetospheric magnetic field have recently been presented: the Olson-Pfitzer model, the Tsyganenko model, and the Voigt model. The paper reviews these models in some detail with emphasis on the extent to which they have succeeded in improving on earlier models. The models are compared with the observed field in both magnitude and direction. Finally, the application to other planetary magnetospheres of the techniques used to model the earth's magnetospheric magnetic field is briefly discussed.
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  • 163
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    On seasonal phenomena in Saturn's atmosphere - New observations of Saturn's 3nu3 methane band (1979)
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    Publication Date: 2019-06-27
    Description: Saturn's 3nu3 CH4 band has been reobserved during April-June 1976, using the same telescope and spectrographic set-up used to study this band during the 1970 apparition. Direct comparison of the ratio spectra Saturn/moon reveals greater absorption in the manifold cores during 1976, but the increase is not as pronounced as that for the stronger CH4 bands. The rotational temperature and effective pressure of this band did not change significantly. These results are interpreted in terms of a possibly seasonal settling of the upper boundary of Saturn's atmospheric haze layer.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Society of the Pacific; vol. 91
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  • 164
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    Petrogenesis of Luna 16 aluminous mare basalts (1979)
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    Publication Date: 2019-06-27
    Description: Bulk compositions, petrology and mineralogy of Luna 16 aluminous mare basalt particles of less than 0.5 mm are described. The data rule out any close genetic relationships between Luna 16 and other major types of lunar mare basalts. Compared to high-Ti mare basalts, the Luna 16 basalts contain lower TiO2 and Ta and higher Al2O3 and REE abundances, suggesting that the Luna 16 source rocks crystallized later than (i.e. stratigraphically above) the ilmenite-bearing high-Ti basalt cumulate source rocks. The REE pattern for the Luna 16 basalts requires that the source material from which they were derived crystallized from a light REE enriched magma.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; Nov. 197
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  • 165
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    A comparison of Pioneer Venus and Venera bow shock observations - Evidence for a solar cycle variation (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Observations by the Venera 9 and 10 orbiters in 1975-76 have been used in previous studies to determine the mean location and shape of the Cytherean bow shock. In addition it has also been reported that the shock is found to be more distant from the planet above regions of the ionosheath where draped IMF field lines are oriented perpendicular to the flow as opposed to parallel. An examination of the dependence of shock altitude in the terminator plane on upstream IMF direction using 86 Pioneer Venus orbiter bow shock crossings in 1978-79 sets an upper limit on this asymmetry of 12% or approximately half that derived earlier from the Venera data. More significantly, the mean distance to the bow shock observed by Pioneer Venus Orbiter is 35% greater than was the case in 1975-76 near solar minimum. As the growth in effective obstacle radius is an order of magnitude larger than can be accounted for in terms of varying ionopause altitude due to all causes, these results strongly suggest that Venus can absorb significantly more of the incident solar wind plasma during solar minimum when EUV flux is low than during the current epoch in which maximum is approaching.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; Nov. 197
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  • 166
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    Position and shape of the Venus bow shock - Pioneer Venus Orbiter observations (1979)
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    Publication Date: 2019-06-27
    Description: Magnetometer data from the Pioneer Venus Orbiter is used to examine the position and shape of this planet's bow shock. Utilizing crossings identified on 86 occasions during the first 65 orbits a mean shock surface is defined for sun-Venus-satellite angles of 60-110 deg. Both the shock shape and variance in location are found to be very similar to the terrestrial case for the range in SVS angle considered. However, while the spread in shock positions at the earth is due predominantly to the magnetopause location varying in response to solar wind dynamic pressure, ionopause altitude variations can have little effect on total obstacle radius. Thus, the Cytherean shock is sometimes observed much closer to or farther from the planet than previously predicted by gasdynamic theory applied to the deflection of flow about a blunt body which acts neither as source nor sink for any portion of the flow.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; Nov. 197
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  • 167
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    On the inference of properties of Saturn's Ring E from energetic charged particle observations (1979)
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    Publication Date: 2019-06-27
    Description: The paper demonstrates that information about Saturn's Ring E particle size is potentially obtainable from observations of Saturnian trapped radiation. It is shown that observations of the radial dependence of the intensities, energy spectra, electron-to-proton intensity ratio, and pitch angle distributions of energetic charged particles trapped outside of Ring A can potentially provide information (1) on the existence of Ring E, (2) on the effective size of the particulate matter therein, and (3) on the magnitude of the radial diffusion coefficient for energetic particles. A parametric study of these possibilities is specialized to the characteristics of the University of Iowa detectors on Pioneer 11 which was scheduled to make a close encounter with Saturn in 1979.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; Nov. 197
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  • 168
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    A history of Mars atmospheric opacity in the southern hemisphere during the Viking extended mission (1979)
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    Publication Date: 2019-06-27
    Description: A history of developing opacity in the Mars southern hemisphere during the Viking extended mission has been compiled using orbiter images obtained at high altitude. Observations of changing contrasts under similar viewing conditions have been modeled by multiple-scattering intensity transfer equations that have produced a temporal description of changes in optical depth and particle-scattering properties within a network of control points. The results are presented in the form of Mercator and perspective plots for various dates.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Nov. 1
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  • 169
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    /Ar-40/-/Ar-39/ dating of inclusions from IAB iron meteorites (1979)
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    Publication Date: 2019-06-27
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 43; Nov. 197
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  • 170
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    Isotopic anomalies in meteorites and their origins. V - Search for fission fragment recoils in Allende sulfides (1979)
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    Publication Date: 2019-06-27
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 43; Nov. 197
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  • 171
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    Alteration in CM carbonaceous chondrites inferred from modal and chemical variations in matrix (1979)
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    Publication Date: 2019-06-27
    Description: The modal abundance of matrix in CM chondrites appears to vary from 57-85 vol%. The concentrations of volatile elements that should occur in matrix remain approximately constant despite differences in the proportions of matrix, suggesting that the differing matrix contents may not be real primary variations but are optical effects due to aqueous alteration processes that make other petrologic components unrecognizable. Apparent matrix content can be used as a qualitative measure of the degree of alteration experienced by each CM chondrite. Fe/Si ratios in matrices decrease progressively with increasing alteration due to the formation of new phyllosilicate phases with higher Mg/Fe ratios and optically recognizable opaque minerals that are not counted as matrix. The aqueous alteration process in CM chondrites appears to have been largely isochemical if the bulk meteorites are considered as the reacting systems, although depletion patterns and isotopic anomalies indicate open-system behavior for a few highly mobile components.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 43; Nov. 197
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  • 172
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    Planetary radio astronomy observations from Voyager 2 near Jupiter (1979)
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    Publication Date: 2019-06-27
    Description: The Voyager 2 Planetary Radio Astronomy experiment to Jupiter has confirmed and extended to higher zenomagnetic latitudes results from the identical experiment carried by Voyager 1. The kilometric emissions discovered by Voyager 1 often extended to 1 megahertz or higher on Voyager 2 and often consisted of negatively, or less frequently, positively drifting narrowband bursts. On the basis of tentative identification of plasma wave emissions similar to those detected by Voyager 1, the plasma torus associated with Io appeared somewhat denser to Voyager 2 than it did to Voyager 1. The paper reports on quasi-periodic sinusoidal or impulsive bursts in the broadcast band range of wavelengths (800 to 1800 kHz). A Faraday effect appears at decametric frequencies, which probably results from propagation of the radiation near its sources on Jupiter. Finally, the occurrence of decametric emission in homologous arc families is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 206; Nov. 23
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  • 173
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    Hot plasma environment at Jupiter - Voyager 2 results (1979)
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    Publication Date: 2019-06-27
    Description: Preliminary results are reported from measurements made with the low-energy charged particle (LECP) instrument on Voyager 2 as it approached and traversed the Jovian magnetosphere. The primary objectives of the LECP instrument were to make measurements of the hot plasma (no less than about 20 keV and no less than about 28 keV for electrons and ions, respectively), to characterize the composition of the hot plasma and energetic-particle population, and to determine the particle flows and spatial distributions. In addition, the effects associated with the possible wake of Ganymede are discussed. Attention is given to inbound and outbound passes, along with Jovian plasma characteristics. The results suggest that the Jovian magnetosphere is confined by a plasma boundary rather than a conventional magnetopause. Inside the plasma boundary there exists a discontinuity at about 50-60 Jupiter radii, and the region inside this discontinuity is termed the 'inner plasmasphere'.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 206; Nov. 23
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  • 174
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    Photometric observations of Jupiter at 2400 angstroms (1979)
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    Publication Date: 2019-06-27
    Description: The photopolarimeter instrument on Voyager 2 was used to obtain a map of Jupiter at an effective wavelength of 2400 angstroms. Analysis of a typical north-south swath used to make this map shows strong absorption at high latitudes by a molecular or particulate constituent in the Jovian atmosphere. At 65 deg north latitude, the absorbing constituent extends to altitudes above the 50-millibar pressure level
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 206; Nov. 23
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  • 175
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    Grain carriers of isotopic anomalies (1979)
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    Publication Date: 2019-06-27
    Description: The dynamics of grain motion through gas are examined in terms of the injection of isotopically anomalous (compared to solar abundances) material into the early solar nebula. Calculations indicate that the injected grains cannot penetrate to the center of any of a range of reasonable configurations, suggesting the formation of an edge region enriched in injected material. Furthermore, the dynamical behavior of grains in turbulent flows indicates that pockets of grains can have some resistance to turbulent diffusion. The constraints developed here are used to delineate a set of consistent, injected-grain models for the origin of the isotopic anomalies in meteorite inclusions.
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  • 176
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    Solar-wind interactions with the moon - Role of oxygen ions (1979)
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    Publication Date: 2019-06-27
    Description: The role of oxygen ions in the solar-wind interactions with the lunar surface due to tenuous atmosphere and magnetic field is examined. The interaction results in an absorption of the solar-wind corpuscles producing no upstream bowshock but a cavity downstream, and the oxygen ionic species undergo a set of reactions with the lunar minerals and the solar-wind derived trapped gases. The oxygen concentrations in the lunar surface material and the solar-wind species flux are discussed, noting that for the contributions of oxygen from the lunar surface grains to the atmosphere, the diffusion coefficients of oxygen atom and molecules should be known. The coefficients are calculated by using the apparent lifetimes of oxygen in the lunar material, and the atmospheric concentration of oxygen atoms and molecules near the lunar surface were compared with the Apollo 17 lunar orbital data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Moon and the Planets; 21; Nov. 197
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  • 177
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    Planetary seismology and interiors (1979)
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    Publication Date: 2019-06-27
    Description: This report briefly summarizes knowledge gained in the area of planetary seismology in the period 1969-1979. Attention is given to the seismic instruments, the seismic environment (noise, characteristics of seismic wave propagation, etc.), and the seismicity of the moon and Mars as determined by the Apollo missions and Viking Lander experiments, respectively. The models of internal structures of the terrestrial planets are discussed, with the earth used for reference.
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  • 178
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    Does Venus wobble (1979)
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    Publication Date: 2019-06-27
    Description: The free wobble damping time for Venus due to solar tides and rotational flexing is found to be approximately 700,000 times Q sub omega years, where Q sub omega is the dissipation function associated with the wobble frequency. The slow spin and expected small (nonhydrostatic) J2 predict a very long wobble period of about 100,000 years. As a result, a simple scaling of the earth's Chandler wobble excitation rate to that of Venus suggests that an appreciable wobble could exist. Detection (or lack thereof) of a free wobble may thus place constraints on the dynamic activity (e.g., mantle convection, Venusquakes, etc.) of the Venus interior.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 233
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  • 179
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    New isotopic clues to solar system formation (1979)
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    Publication Date: 2019-06-27
    Description: The presence of two new extinct nuclides Al-26 and Pd-107 with half lives of approximately one million years in the early solar system implies that there were nucleosynthetic activities involving a great many elements almost at the instant of solar system formation. Rate gas and oxygen isotopic abundance variations ('anomalies') relative to the 'cosmic' composition were observed in a variety of planetary objects, which indicates that isotopic heterogeneities caused by the incomplete mixing of distinct nucleosynthesis components permeate the entire solar system. These new results have major implications for cosmochronology, nucleosynthesis theory, star formation, planetary heating, and the genetic relationship between different planetary bodies
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  • 180
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    The distribution of titanium on the lunar surface (1979)
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    Publication Date: 2019-06-27
    Description: Titanium concentrations derived from the lunar-orbiting gamma-ray experiment on Apollo 15 and 16 by analyzing a spectral interval in which the titanium signal is relatively enhanced are presented. Landing site soil values provide the reference for a regression curve from which Ti concentrations in 137 regions of adequate counting statistics are calculated. Mare Tranquillitatis contains the highest, and Mare Crisium the lowest Ti concentration, and regional values in the western maria range from 1.1% to 4.1%. Highland Ti concentrations suggest a north-south symmetry which is not consistent with previously reported Fe and Th results. Comparisons with telescopic spectral reflectance studies of the maria do not show complete agreement and suggest that effects due to Fe may not have been fully removed from the reflectance data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 45; 1, Oc; Oct. 197
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  • 181
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    Solubility of noble gases in serpentine - Implications for meteoritic noble gas abundances (1979)
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    Publication Date: 2019-06-27
    Description: An investigation of the solubilities of the noble gases from synthesis and solubility studies of the sheet silicate mineral serpentine in carbonaceous chondrites is presented. Hydrothermal synthesis and exchange experiments were made at 340C and 1 kbar with noble gas partial pressures from 2 times 10 to the -8th power to 0.1 atm. The measured distribution coefficients for noble gases are not sufficiently high to account for the trapped noble gases in carbonaceous chondrites by exchange in solar nebula if meteoritic minerals have comparable distribution coefficients. Also, serpentine gains and loses noble gases to approach equilibrium values with the terrestrial atmosphere, indicating that this exposure may have influenced the noble gas abundances in phyllosilicate minerals of these chondrites. The dispersion of K-Ar ages of carbonaceous chondrites could be the result of phyllosilicates approaching equilibrium solubility of atmospheric Ar-40.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 45; 1, Oc; Oct. 197
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  • 182
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    The phase of the ten-hour modulation in the Jovian magnetosphere /Pioneers 10 and 11/ (1979)
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    Publication Date: 2019-06-27
    Description: The paper describes the study of the phase of the 10-hour modulation of energetic electrons seen by Pioneers 10 and 11 in the Jovian magnetosphere. Attention is given to the peaks rather than the valleys of each cycle because the peaks are where physically interesting features occur, such as particle acceleration, current sheets, etc. To identify the peaks, it is required that the instantaneous intensity be higher than the 5-hour running average and the 5-hour running average be greater than the 10-hour running average. These criteria select an interval rather than a point and it is determined that this interval is an appropriate estimate of the experimental uncertainty. When the phases of the peaks are plotted together, they create patterns which are discussed in terms of disk-like, clock-like, and rotating anomaly models of the magnetosphere. Each model fits some of the data, but no model explains all of the data convincingly. It is concluded that there is still no understanding of the configuration of the outer Jovian magnetosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Oct. 1
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  • 183
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    A model of the neutral and ion nitrogen chemistry in the daytime thermosphere of Venus (1979)
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    Publication Date: 2019-06-27
    Description: Density profiles of N(4S), NO, N(2D), NO(+), and N(+) are calculated for the thermosphere of Venus. The results show that N(4S) is the dominant odd nitrogen species throughout the thermosphere and has a maximum density of 18 million atoms/cu cm at 132 km. The calculated NO(+) density agrees well with recent Pioneer Venus measurements, but the calculated N(+) densities are a factor of two to five less than the measurements. The production of N(4S) atoms generated in the model is adequate to explain recent measurements of the nitric oxide chemiluminescent emission on the night side of Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; Oct. 197
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  • 184
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    An isostatic model for the Tharsis province, Mars (1979)
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    Publication Date: 2019-06-27
    Description: A crust-upper mantle configuration is proposed for the Tharsis province of Mars which is isostatic and satisfies the observed gravity data. The model is that of a low density upper mantle compensating loads at both the surface and crust-mantle boundary. Solutions are found for lithospheric thickness greater than about 300 km, for which the stress differences are less than 750 bars. This model for Tharsis is similar to the compensation mechanism under the Basin and Range province of the western United States. These provinces also compare favorably in the sense that they are both elevated regions of extensional tectonics and extensive volcanism.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; Oct. 197
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  • 185
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    Determination of secondary electron emission characteristics of lunar soil samples (1979)
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    Publication Date: 2019-06-27
    Description: A procedure is described for the determination of the 'apparent crossover voltage', i.e. the value of the primary (bombarding) electron energy at which an insulating sample surface changes the average sign of its charge. This apparent crossover point is characteristic of the secondary emission properties of insulating powders such as the lunar soil samples. Lunar core samples from well-defined, distinct soil layers are found to differ significantly in their secondary emission properties. This observation supports the suggestion that soil layers were deposited by an electrostatic transport process.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 45; 1, Oc; Oct. 197
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  • 186
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    Voyager encounters Jupiter (1979)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Images of Jupiter and its satellites are presented. The photographs were taken by the Voyager 1 Spacecraft and the Voyager 2 Spacecraft. A brief description of the Voyager project is given.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-163607 , JPL-400-24
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  • 187
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    Silt-clay aggregates on Mars (1979)
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    Publication Date: 2019-06-27
    Description: Viking observations suggest abundant silt and clay particles on Mars. It is proposed that some of these particles agglomerate to form sand size aggregates that are redeposited as sandlike features such as drifts and dunes. Although the binding for the aggregates could include salt cementation or other mechanisms, electrostatic bonding is considered to be a primary force holding the aggregates together. Various laboratory experiments conducted since the 19th century, and as reported here for simulated Martian conditions, show that both the magnitude and sign of electrical charges on windblown particles are functions of particle velocity, shape and composition, atmospheric pressure, atmospheric composition and other factors. Electrical charges have been measured for saltating particles in the wind tunnel and in the field, on the surfaces of sand dunes, and within dust clouds on earth. Similar, and perhaps even greater, charges are proposed to occur on Mars, which could form aggregates of silt and clay size particles
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Oct. 10
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  • 188
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    Crystallization, flow and thermal histories of lunar and terrestrial compositions (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Contents: a kinetic treatment of glass formation; effects of nucleating heterogeneities on glass formation; glass formation under continuous cooling conditions; crystallization statistics; kinetics of crystal nucleation; diffusion controlled crystal growth; crystallization of lunar compositions; crystallization between solidus and liquidus; crystallization on reheating a glass; temperature distributions during crystallization; crystallization of anorthite and anorthite-albite compositions; effect of oxidation state on viscosity; diffusive creep and viscous flow; high temperature flow behavior of glass-forming liquids, a free volume interpretation; viscous flow behavior of lunar compositions; thermal history of orange soil material; breccias formation by viscous sintering; viscous sintering; thermal histories of breccias; solute partitioning and thermal history of lunar rocks; heat flow in impact melts; and thermal histories of olivines.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-162445
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  • 189
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    Introduction to the Apollo collections: Part 2: Lunar breccias (1979)
    In:  CASI
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    Publication Date: 2019-06-27
    Description: Basic petrographic, chemical and age data for a representative suite of lunar breccias are presented for students and potential lunar sample investigators. Emphasis is on sample description and data presentation. Samples are listed, together with a classification scheme based on matrix texture and mineralogy and the nature and abundance of glass present both in the matrix and as clasts. A calculus of the classification scheme, describes the characteristic features of each of the breccia groups. The cratering process which describes the sequence of events immediately following an impact event is discussed, especially the thermal and material transport processes affecting the two major components of lunar breccias (clastic debris and fused material).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-162559
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  • 190
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    Preliminary results of penetrator field test program, Tonopah, Nevada, 16-28 April 1979 (1979)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Subscale (0.63 scale) penetrators impacted various sizes of volcanic rocks resting on and within compacted plays sediments. All penetrators were identical in size, shape, weight, and impact velocity. Although minor variations in impact angle were documented, the final orientation of the buried penetrators was primarily a consequence of the size, shape, and depth of the rocks encountered during impact. In situ measurements of impacted penetrators revealed that surface and buried layers of rocks having diameters up to 3 times the penetrator diameter caused only small ( 10 deg) angles of deflection. Only large single rocks greater than 10 times the penetrator diameter caused deflections appreciably greater than 10 deg. The large deflection angles followed by the penetrator were strongly influenced by fracture planes that developed in the rock as it broke apart. No catastrophic failure of the penetrator occurred during these tests. A cross section of the path of each penetrator through the ground is shown together with details on orientation before, during, and after the tests. Comparisons are made with results of previous subscale penetrator tests, and conclusions are drawn with respect to full-scale Mars penetrator performance.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-58222 , JSC-16221
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  • 191
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    Mars in the solar wind (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Recent spacecraft observations and model calculations of the solar wind interaction (SWI) at Mars have shown that the particle pressure is not large enough to stand off the solar wind unless the electron temperature is 4 times the ion temperature in the ionosphere, but the additional pressure is presumably magnetic, provided by a planetary magnetic field. In addition, a planetary field corresponding to a surface field of about 20 gammas, and a dipole moment of about 8 x 10 to the 21st gauss per cu cm are implied. Calculations indicate that 60-70% of the pressure is supplied by the magnetic field, and 30-40% by the ionosphere. Thus, the SWI at Mars is unique, being an interaction both with the atmosphere and with the planetary magnetic field.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 192
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    Is the Martian lithosphere sulfur rich (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Several models are proposed to explain the abundance of sulfurand chlorine-containing compounds in the Martian fines. Preliminary analyses attributed the S and Cl enrichment to the upward migration of soluble salt. Alternative possibilities are examined, including remnant primitive lithosphere, a primitive component in the regolith, and trapping of volcanic gases. The alternative models encompass various features of the accretion chemistry thermal history, and core size-mass relationships that have been proposed for Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 193
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    The planet Mars as seen at the end of the Viking mission (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The paper presents a summary of new knowledge about Mars obtained from Mariner and Viking missions. Specific subjects include Martian geologic features, composition of the surface, the atmosphere, and the polar caps, and Martian meteorology, including temperatures, pressures, tides, dust storms, and atmospheric water vapor. The program of further Mars exploration is outlined. The major element of the program will be a sample return mission, utilizing orbiters and limited-range rovers with enough instrumentation to identify, acquire, and return well documented samples from two or more sites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 194
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    Grooves on Phobos - Their distribution, morphology and possible origin (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The global distribution, morphology, age, possible origin and significance of the long, linear depressions termed grooves on the surface of Phobos are discussed, based on Viking Orbiter data. The grooves, which consist of linear strings of coalesced and separate depressions in a loose regolith up to 100-200 m in depth, are observed to define the intersection of several sets of parallel planes with the surface of Phobos, with the widest and deepest grooves occurring just outside the rim of the 10-km crater, Stickney. The superposition of the grooves on older craters, crater density within the grooves and the intersections of groove sets suggest that the grooves are all of the same age, with their formation closely following that of Stickney. The evidence of groove morphology and distribution is used to attribute their formation to the enlargement of preexisting fractures or the formation of new fractures by the Stickney impact, causing the mobilization of the regolith along the fractures. The lack of observable grooves on Deimos is explained by the absence of a crater large enough to have severly fractured its surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 195
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    The relative humidity of Mars' atmosphere (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: As a general rule, Mars' atmosphere contains as much water vapor as it can hold on a daily basis; it reaches saturation at night, and the vapor appears to be distributed throughout the lowest several kilometers. Interesting exceptions to this occur when there are temperature inversions in the arctic springtime and during dust-storm activity. As contrasted to the northern hemisphere there appears to be no local source of water in the southern temperate and arctic areas.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 196
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    Recession of Martian north polar cap - 1977-1978 Viking observations (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The regression curve for the 1977-1978 sublimation of the north polar cap of Mars is extracted from Viking orbiter imaging data. The recession observed during the spring season is quite consistent with previous observations and is in excellent agreement with telescopic data obtained concurrently. A receding late winter boundary is identified, but owing to hood obscuration this boundary cannot be definitely attributed to a surface cap.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 197
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    Volcano-ice interactions on Mars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Central volcanic eruptions beneath terrestrial glaciers have built steep-sided, flat-topped mountains composed of pillow lava, glassy tuff, capping flows, and cones of basalt. Subglacial fissure eruptions produced ridges of similar composition. In some places the products from a number of subglacial vents have combined to form widespread deposits. The morphologies of these subglacial volcanoes are distinctive enough to allow their recognition at the resolutions characteristic of Viking orbiter imagery. Analogs to terrestrial subglacial volcanoes have been identified on the northern plains and near the south polar cap of Mars. The polar feature provides probable evidence of volcanic eruptions beneath polar ice. A mixed unit of rock and ice is postulated to have overlain portions of the northern plains, with eruptions into this ground ice having produced mountains and ridges analogous to those in Iceland. Subsequent breakdown of this unit due to ice melting revealed the volcanic features. Estimated heights of these landforms indicate that the ice-rich unit once ranged from approximately 100 to 1200 m thick.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 198
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    Erosional processes in channelized water flows on Mars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A hypothesis is investigated according to which the Martian outflow channels were formed by high-velocity flows of water or dynamically similar liquid. It is suggested that the outflow channels are largely the result of several interacting erosional mechanisms, including fluvial processes involving ice covers, macroturbulence, streamlining, and cavitation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 199
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    Mars - The north polar sand sea and related wind patterns (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: Viking Orbiter 2 images of the north polar region reveal an enormous sand sea (erg) covering an area of greater than 500,000 sq km around the perennial ice cap. All dunes are either transverse or barchan. The various dune morphologies and modifications of primary dune types reflect a wind regime having more than one wind direction. In the summer, two major wind directions prevail: (1) off-pole winds that become easterly due to coriolis forces and (2) on-pole winds that become westerly. During the winter and/or spring, only the on-pole winds exist. Strong winds greater than 75 m/s are required for sand accumulation to form the thick transverse dunes. The strongest winds in the north polar region are thought to exist during summer over the transverse dune field between 110 deg and 220 deg W; this area is a relatively warm belt (temperature greater than 230 K) between two ice zones (temperature less than 220 K). The lack of well-developed longitudinal dunes implies that the dune field is young. The relationship of the present dune field to the perennial ice indicates that the dunes began to form after the formation of the present ice cap.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 200
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    Landslides in Valles Marineris, Mars (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: The morphology of the landslides in the Martian equatorial troughs, the geologic structure of the troughs, the time of emplacement, the similarity to terrestrial landslides, and the origin and mechanism of transport are analyzed. About 35 large landslides well-resolved on Viking images were examined, and it is found that the major landslides cover 31,000 sq km of the trough floors, and individual slides range in area from 40 to 7000 sq km. The morphologic variations of the landslides can be attributed mainly to their degree of confinement on trough floors. Many prominent landslides appear to be of similar age and were emplaced after a major faulting that dropped the trough floors. Most sliding occurred after the created scarps were dissected into spurs, gullies, and tributary canyons. Emplacement of the landslides approximately coincided with a late episode of major eruptive activity of the Tharsis volcanoes, and it is suggested that the slides may have originated as gigantic mudflows with slump blocks at their heads. The large size of many landslides is due to the fault scarps as high as 7 km on which they formed in the absence of vigorous fluvial erosion. The landslides suggest that Mars is earthlike in some respects, which may be important for further evaluations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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