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  • Inorganic Chemistry  (785)
  • LUNAR AND PLANETARY EXPLORATION  (715)
  • 1985-1989  (1,500)
  • 1985  (1,500)
Collection
Keywords
Publisher
Years
  • 1985-1989  (1,500)
Year
  • 1
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    The Venus ionosphere (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Physical properties of the Venus ionosphere obtained by experiments on the US Pioneer Venus and the Soviet Venera missions are presented in the form of models suitable for inclusion in the Venus International Reference Atmosphere. The models comprise electron density (from 120 km), electron and ion temperatures, and relative ion abundance in the altitude range from 150 km to 1000 km for solar zenith angles from 0 to 180 deg. In addition, information on ion transport velocities, ionopause altitudes, and magnetic field characteristics of the Venus ionosphere, are presented in tabular or graphical form. Also discussed is the solar control of the physical properties of the Venus ionosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 11, 1
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  • 2
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    Particulate matter in the Venus atmosphere (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The paper presents a summary of the data currently available (June 1984) describing the planet-enshrouding particulate matter in the Venus atmosphere. A description and discussion of the state of knowledge of the Venus clouds and hazes precedes the tables and plots. The tabular material includes a precis of upper haze and cloud-top properties, parameters for model-size distributions for particles and particulate layers, and columnar masses and mass loadings.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 11, 1
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  • 3
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    Models of Venus neutral upper atmosphere - Structure and composition (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Models of the Venus neutral upper atmosphere, based on both in situ and remote sensing measurements, are provided for the height interval from 100 to 3500 km. The general approach in model formulation was to divide the atmosphere into three regions: 100-150 km, 150-250 km, and 250-3500 km. Boundary conditions at 150 km are consistent with both drag and mass spectrometer measurements. A paramount consideration was to keep the models simple enough to be used conveniently. Available observations are reviewed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 11, 1
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  • 4
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    The interplanetary micrometeoroid flux and lunar primary and secondary microcraters (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: It is proposed that considerable care is required to properly interpret either spacecraft in situ data or lunar crater data as well as near-earth data; in the case of the former, complications may arise which may be attributed to secondary lunar ejecta impacts, in the latter, they may result from impacting earth-orbiting debris. Experimental evidence suggests that most impact pits on lunar rocks with pit diameters smaller than 7 micrometers have been generated by lunar secondary ejecta impacts and not by primary meteoroid impacts. It is also found that lunar crater production rates are more accurate when deduced from meteoroid space experiments and not from solar flare track ages. It is concluded that in so far as all of the above qualifications are taken into account, a self-consistent meteoroid flux versus mass distribution is obtained.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 5
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    Energy conversion processes in the outer planets (1985)
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    Publication Date: 2011-08-19
    Description: Energy conversion processes which are potentially important in the outer planets at pressures greater than obut 0.1 bar are reviewed. Generation of buoyancy contrasts by condensation of various constituents is discussed with emphasis on the possible significance of phase changes in substances such as Si and Mg compounds at deep levels. It is demonstrated that, in the absence of nonequilibrium thermodynamic processes, strong kinetic energy generation must accompany the transport of heat out of the high temperature planetary interiors. The possibly dominant role of lagged parahydrogen conversion in the convective transport of heat at levels where T is less than 300 K is discussed. Measurements which may ultimately contribute to a better understanding of energy conversion processes are summarized.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 6
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    Photochemistry and clouds of Jupiter, Saturn and Uranus (1985)
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    Publication Date: 2011-08-19
    Description: Photochemistry of ammonia, methane, phosphine, hydrogen sulfide, methylamine, hydrogen cyanide and carbon monoxide in the atmospheres of Jupiter, Saturn and Uranus is discussed. Condensation of ammonia, ammonium hydrosulfide, water, methane, ethane and acetylene below and near the tropopause of these planets is formulated. Whenever necessary, new calculations are included. Candidates for the upper atmospheric hazes, and the reddish-brown chromosphore in the clouds of Jupiter and Saturn are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 7
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    Mars missions and bases - A recent look (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper discusses some of the key options for Mars programs, missions, bases, elements, and systems. Program and mission options include Mars flyby, orbiting, and landing missions; they include near-term 'sortie' missions, and later, longer-duration Mars-base missions. Key program and mission parameters include the mix of manned/unmanned elements, the number and types of space vehicles used, types of science done, trajectory options and implications launch timing and schedules, etc. The key mission parameters strongly affect the nature, sizing, and quantity of earth-to-orbit (ETO) vehicles. On-orbit assembly of space vehicles (SVs) is also an important related consideration. The potential degree of utilization of the Space Station (SS) and other then-existing elements is a key question, and several possibilities are discussed in this paper. Several configurations of SVs are provided. Several options are identified for the Mars base infra-structure, and parametric data is shown for buildup of bases as a function of mission and vehicle type. Technologies required for the missions are also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 8
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    Lava tubes - Potential shelters for habitats (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Natural caverns occur on the moon in the form of 'lava tubes', which are the drained conduits of underground lava rivers. The inside dimensions of these tubes measure tens to hundreds of meters, and their roofs are expected to be thicker than 10 meters. Consequently, lava tube interiors offer an environment that is naturally protected from the hazards of radiation and meteorite impact. Further, constant, relatively benign temperatures of -20 C prevail. These are extremely favorable environmental conditions for human activities and industrial operations. Significant operational, technological, and economical benefits might result if a lunar base were constructed inside a lava tube.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 9
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    Solar and thermal radiation in the Venus atmosphere (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Attention is given to the solar and thermal radiation fields of Venus. Direct measurements and the results of numerical models based on direct measurements are presented. Radiation outside the atmosphere is considered with emphasis placed on global energy budget parameters, spectral and angular dependences, spatial distribution, and temporal variations of solar and thermal radiation. Radiation fluxes inside the atmosphere below 90 km are also considered with attention given to the solar flux at the surface, solar and thermal radiation fluxes from 100 km to the surface, and radiative heating and cooling below 100 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 11, 1
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  • 10
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    Models of the structure of the atmosphere of Venus from the surface to 100 kilometers altitude (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: From a critical comparison and synthesis of data from the four Pioneer Venus Probes, the Pioneer Venus Orbiter, and the Venera 10, 12, and 13 landers, models of the lower and middle atmosphere of Venus are derived. The models are consistent with the data sets within the measurement uncertainties and established variability of the atmosphere. The models represent the observed variations of state properties with latitude, and preserve the observed static stability. The rationale and the approach used to derive the models are discussed, and the remaining uncertainties are estimated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 11, 1
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  • 11
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    Atmospheric circulation of Venus (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observational data of Venus are utilized to study rotational effects on atmospheric circulations. The high surface temperature and planetary-scale turbulent motion at cloud tops, and the relation between energy and momentum budget are examined. The limited amount of data available on the vertical and horizontal distribution of net radiative heating, the zonal wind structure, and waves affects the study of the temperature and motion on Venus. The limitations of the scaling analysis used to estimate the properties of the circulation as regards the cyclostrophic balance, the extent of the Hadley circulation, large-scale wave transport, vertical propagation of waves, convection, and turbulence are considered. Hypotheses concerned with the deep, cloud-level, and upper atmospheres of Venus are proposed. Future research in the areas of propagating planetary- scale waves, zonal flow and planetary-scale wave instability processes, and convection is suggested.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 12
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    The use of radar and visual observations to characterize the surface structure of the planet Mercury (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An analysis is conducted of available topographic profiles and scattering parameters derived from earth-based S- and X-band radar observations of Mercury, in order to determine the nature and origin of regional surface variations and structures that are typical of the planet. Attention is given to the proposal that intercrater plains on Mercury formed from extensive volcanic flooding during bombardment, so that most craters were formed on a partially molten surface and were thus obliterated, together with previously formed tectonic features.
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  • 13
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    Advanced geologic exploration supported by a lunar base - A traverse across the Imbrium-Procellarum region of the moon (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An example of extended traverse of a lunar region, the Imbrium-Procellarum, for the purpose of geological exploration is described. The necessary field support is discussed, including transportation and logistical support, analytical instrumentation, and field equipment. The various sites of special geological interest in the region are mentioned individually in the order in which they would be visited, indicating what questions are of particular scientific interest at each site.
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  • 14
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    Mass extinctions and cosmic collisions - A lunar test (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The possibility has been considered that some or all major mass extinctions in the geologic record of earth are caused by the collision of massive, cosmic objects. Thus, it has been proposed that the unusual concentration of siderophile elements in strata at which the boundary between the Cretaceous (K) and Tertiary (T) geologic time periods has been placed must represent the remnants of a gigantic meteorite. However, a large 65-m.y.-old crater which could have been the result of the impact of this meteorite is not presently known on earth. One approach to evaluate the merits of the collisional hypothesis considered is based on the study of the probability of collision between a cosmic object of a suitable size and the earth. As moon and earth were subject to the same bombardment history and the preservation of craters on the moon is much better than on earth, a consideration of the lunar cratering record may provide crucial information.
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  • 15
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    Saturn's rings - Particle size distributions for thin layer model (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A model incorporating limited interaction between the incident energy and particles in the ring is considered which appears to be consistent with the multiple scattering process in Saturn's rings. The model allows for the small physical thickness of the rings and can be used to relate Voyager 1 observations of 3.6- and 13-cm wavelength microwave scatter from the rings to the ring particle size distribution function for particles with radii ranging from 0.001 to 20 m. This limited-scatter model yields solutions for particle size distribution functions for eight regions in the rings, which exhibit approximately inverse-cubic power-law behavior.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 64; 531-548
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  • 16
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    Supersonic meteorology of Io - Sublimation-driven flow of SO2 (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The horizontal flow of SO2 gas from the day side to the night side of IO is calculated on the basis of a hydrodynamic model. The flow speed is found to be supersonic for all realistic values of the parameters. The surface pressure follows the frost vapor pressure within a factor of 2 in spite of day-night pressure ratios of 10,000 or more. Atmospheric temperature is generally below the surface temperature due to decompression in the expanding flow. The greatest sensitivity of the solution is connected with the frost temperature at the subsolar point. The quantities that involve the mass of the atmosphere (density, pressure, mass transport, and condensation rate) all vary as the vapor pressure of the frost, which is a sensitive function of frost temperature.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 64; 375-390
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  • 17
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    Empirical model of the composition of the Venus ionosphere Repeatable characteristics and key features not modeled (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: In-situ measurements of positive ion composition of the ionosphere of Venus are combined in an empirical model which is a key element for the Venus International Reference Atmosphere (VIRA) model. The ion data are obtained from the Pioneer Venus Orbiter Ion Mass Spectrometer (OIMS) which obtained daily measurements beginning in December 1978 and extending to July 1980 when the uncontrolled rise of satellite periapsis height precluded further measurements in the main body of the ionosphere. For this period, measurements of 12 ion species are sorted into altitude and local time bins with altitude extending from 150 to 1000 km. The model results exhibit the appreciable nightside ionosphere found at Venus, the dominance of atomic oxygen ions in the dayside upper ionosphere and the increase in prominence of atomic oxygen and deuterium ions on the nightside. Short term variations, such as the abrupt changes observed in the ionopause, cannot be represented in the model.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 9, 19
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  • 18
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    Thermal net flux measurements on the Pioneer Venus entry probes (1985)
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    Publication Date: 2011-08-19
    Description: Corrected thermal net (upward minus downward flux) radiation data from four Pioneer Venus probes at latitudes of 4 deg and 60 deg N, and 27 deg and 31 deg S, are presented. Comparisons of these fluxes with radiative transfer calculations were interpreted in terms of cloud properties and the global distribution of water vapor in the lower atmosphere of Venus. The presence of an as yet undetected source of IR opacity is implied by the fluxes in the upper cloud range. It was also shown that beneath the clouds the fluxes at a given altitude increase with latitude, suggesting greater IR cooling below the clouds at high latitudes and a decrease of the water vapor mixing ratios toward the equator.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Advances in Space Research (ISSN 0273-1177); 5; 9, 19
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  • 19
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    The thermal release of Hg from chondrites and their thermal histories (1985)
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    Publication Date: 2011-08-19
    Description: A quantitative treatment and implications of isothermal and linear heating data on Hg in meteorites are given as a sequel to a more qualitative analysis of meteorite thermal histories (Reed and Jovanovic, 1968). Studies of Hg in terrestrial metamorphic rocks establish that thermal events to which meteorites were subjected fall in the same temperature range, of 400-900 C, as exists during terrestrial metamorphism. Hg diffusion parameters based on data from the linear and isothermal heating experiments are calculated. The conclusions are: (1) Meteorites experienced thermal events of the same magnitude as those measured by primarily mineralogical metamorphic indicators reviewed by Dodd (1969); (2) no correspondence with mineralogical-petrological metamorphic grade is evident; (3) Hg data for some chondrites correlate with shock facies (non-thermal) indicators (Dodd and Jarosewich, 1979); (4) small Hg activation energies (6-14 kcal/mole) require that the meteorites must have been stored in closed systems until low temperatures were attained. Hg must be presented as an involatile mineral(s) or as a substituent in a host phase at temperatures below 100 C. Consistent with this interpretation is the fact that despite diffusion times of 100-1,000,000 years at 200 K, Hg was retained in small objects over cosmic ray exposure periods of a hundred-million years.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 49; 1743-175
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  • 20
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    Pole orientation of 16 Psyche by two independent methods (1985)
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    Publication Date: 2011-08-19
    Description: Nineteen new lightcurves of 16 Psyche are presented along with a pole orientation derived using two independent methods, namely, photometric astrometry and magnitude-amplitude-shape-aspect. The pole orientations found using these two methods agree to within 4 deg. The results from applying photometric astrometry were prograde rotation, a sidereal period of 0.1748143 days + or - 0.0000003 days, and a pole at longitude 223 deg and latitude +37 deg, with an uncertainty of 10 deg, and, from applying magnitude-amplitude-shape-aspect a pole at 220 + or - 1 deg, +40 + or - 4 deg, and a modeled triaxial ellipsoid shape (a greater than b greater than c) and a/b = 1.33 + or - 0.07. The discrepancy between the high-pole latitude found here and the low latitudes reported by Lupishko et al. (1982) and Zhou and Yang (1982) is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 61; 241-251
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  • 21
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    Chemical zoning and homogenization of Pasamonte-type pyroxene and their bearing on thermal metamorphism of a howardite parent body (1985)
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    Publication Date: 2011-08-19
    Description: The Mg-Fe zoning of pyroxenes in Pasamonte and Juvinas eucrites is examined in order to gain a better understanding of the metamorphism in the surface layer of a eucrite/howardite parent body. Three distinct types of Ca-Mg-Fe zoning of Pasamonte pyroxenes are identified. The wide compositional range of the zoned pyroxenes suggests that Pasamonte is less metamorphosed than previously believed. It is also found that a Pasamonte-type pyroxene may yield a Juvinas-type pyroxene by thermal metamorphism. Calculations imply that the homogenization of Juvinas pyroxenes may have occurred during later reheating events rather than during initial cooling.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; C629-C63
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  • 22
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    Bibliography (1985)
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    Publication Date: 2011-08-19
    Description: Articles entered into the data base and Lunar and Planetary Institute Library in the period from May to October, 1983 are listed in annotated bibliography. The topics of the articles include asteroids, comets, and meteorites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth, Moon, and Planets (ISSN 0167-9295); 32; 193-237
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  • 23
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    Conjecture about a hurricane system in the Jovian atmosphere (1985)
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    Publication Date: 2011-08-19
    Description: Arguments are presented in support of the hypothesis that the Great Red Spot (GRS) of Jupiter is a giant hurricane, and that the same decription might apply to the smaller vortices such as the white and brown ovals (barges) on the surface of Jupiter. Estimates of the spin-down times constants for the white and brown oval vortices, indicate that the motions must be sustained by the continued release of internal energy. In analogy with the CISK mechanism for terrestrial hurricanes, transport of water vapor is identified as a possible latent energy source. On the basis of the large size and long life time of the GRS, (indicating extreme depth), it is suggested that the hurricane GRS hurricane may have been induced by meteor impact. Voyager 1 images of the GRS are provided.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth, Moon, and Planets (ISSN 0167-9295); 32; 183-192
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  • 24
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    Gravity field of the Jovian system from Pioneer and Voyager tracking data (1985)
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    Publication Date: 2011-08-19
    Description: Data sets from the Voyager and Pioneer flybys of Jupiter and the Galilean satellites are employed to characterize the Jovian magnetic field and the effects of the Io torus on transmissions. Both optical and Doppler radio data are considered, except for periods when the Jovian radiation environment disturbed the oscillator stability of the radio transmitters. Account is taken of small accelerations of the spacecraft by tidal forces of a single rising satellite, density differences in the Great Red Spot producing a columnar gravitational change, and three unknown objects in the inner Jovian system. Correction parameters are developed for the effects on the S-band data induced by the Jovian plasmasphere inwards from the Io torus. Calculations are then made of the planet and satellite masses, gravity harmonic coefficients, and orientation of the rotational pole. Large reductions in the uncertainties in previous mass estimates are obtained.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal (ISSN 0004-6256); 90; 364-372
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  • 25
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    Large arcuate scars: A geological legacy of the Earth's accretionary past (1985)
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    Publication Date: 2011-08-19
    Description: Immediately following accretion, the surface of the Earth was densely patterned with circular scars which were the surface expressions of 3-D craterform structures. In the course of geological time these structures would have become less and less visible due to the workings of the Earth's atmosphere, surface waters, and plate tectonics regime but there is no compelling reason to assume that they have been entirely eradicated. Furthermore, a very imperfect analogy with the other inner planets suggests that geological processes may not in fact be capable of totally erasing such deep features. Some illustrative examples of arcuate scars are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 71-73
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  • 26
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    Lunar and Martian impact basins: Exposed records of terrestrial bombardment? (1985)
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    Publication Date: 2011-08-19
    Description: The unrecycled surfaces of the Moon, Mercury, and Mars preserve the very early history of impact bombardment and its effect on crustal evolution. Previous studies indicated that the post accretion impact flux by large bodies on Mars may have been dificient, but systematic studies recently have revealed that this deficiency is largely the result of active erosional and depositional processes during the first 0.8 by. Ancient Martian impact basins larger than 300 km in diameter are revealed by subtle but unequivocal topographic and structural control of drainage patterns. In addition, the largest basins have left a deep seated imprint of concentric and radial structural patterns that control the occurrence of most Martian volcanic and tectonic provinces. If 10(-6)/km(2) is considered to be a reasonable approximation for the density of impact basins ( 300 km) of the Moon and Mars, then the Earth should have recorded more than 500 impacts that resulted in basins larger than 300 km in diameter over its post accretion geologic history. If calibrated with the Moon, then most of these impacts occurred prior to 3.8 by.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 74-75
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  • 27
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    Water loss from Venus: Implications for the Earth's early atmosphere (1985)
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    Publication Date: 2011-08-19
    Description: The atmosphere of Venus outgassed rapidly as a result of planetary heating during accretion, resulting in massive water loss. The processes affecting atmospheric chemistry following accretion have consisted largely of hydrogen escape and internal re-equilibrium. The initial bulk composition of Venus and Earth are assumed to have been roughly similar. Chemical speciation on Venus was controlled by the temperature and oxygen buffering capacity of the surface magma. It is also assumed that the surfaces of planetary bodies of the inner solar system were partly or wholly molten during accretion with a temperature estimated at 1273 to 1573 K. To investigate the range of reasonable initial atmospheric compositions on Venus, limits have to be set for the proportion of total hydrogen and the buffered fugacity of oxygen. Using the C/H ratio of 0.033 set for Earth, virtually all of the water generated during outgassing must later have been lost in order to bring the current CO2/H2O ratio for Venus up to its observed value of 10 sup 4 to 10 sup 5. The proportion of H2O decreases in model atmospheres with successfully higher C/H values, ultimately approaching the depleted values currently observed on Venus. Increasing C/H also results in a rapid increase in CO/H2O and provides an efficient mechanism for water loss by the reaction CO+H2O = CO2 + H2. This reaction, plus water loss mechanisms involving crustal iron, could have removed a very large volume of water from the Venusian atmosphere, even at a low C/H value.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 65-67
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  • 28
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    The origin of continental crust: Outlines of a general theory (1985)
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    Publication Date: 2011-08-19
    Description: The lower continental crust, formerly very poorly understood, has recently been investigated by various geological and geophysical techniques that are beginning to yield a generally agreed on though still vague model (Lowman, 1984). As typified by at least some exposed high grade terranes, such as the Scottish Scourian complex, the lower crust in areas not affected by Phanerozoic orogeny or crustal extension appears to consist of gently dipping granulite gneisses of intermediate bulk composition, formed from partly or largely supracrustal precursors. This model, to the degree that it is correct, has important implications for early crustal genesis and the origin of continental crust in general. Most important, it implies that except for areas of major overthrusting (which may of course be considerable) normal superposition relations prevail, and that since even the oldest exposed rocks are underlain by tens of kilometers of sial, true primordial crust may still survive in the lower crustal levels (of. Phinney, 1981).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 54-56
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    Implications for the Earth of the early dynamical environment (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The formation of the Earth, was mainly from sizeable bodies: perhaps moon sized. Models of interaction among small planetesimals which take into account only close encounters all lead to the formation of moon sized objects, thus leading to several 100 in the inner solar system. Longer term interactions, such as secular resonance sweepings, are needed to get these planetesimals together to form the observed terrestrial bodies. After the accumulation of the Earth, during which core formation certainly occurred, further impacts probably influenced the locations of rifting centers in the system of mantle convection and crustal differentiation. They may have affected craton stabilization by promoting lateral heterogeneity, but had little influence on the key problem of early recycling of sial.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 45-47
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  • 30
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    A review of tectonic aspects of the Limpopo belt and other Archean high-grade gneissic terranes (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Published information on the Archean high grade terrains varies a great deal in the detail available. Such information as exists indicates marked differences in the lithic types and proportions present in the central Limpopo belt compared with the better studies of the other Archean high grade terrains. These differences may be important because they are expressed by the presence in the Limpopo belt of subordinate, but significant quantities (about 5% each) of two rock suites likely to have formed on a shallow marine platform of significant size (Eriksson and Kidd, in prep.). These suites consist of thick sections dominantly consisting of either carbonate and calc-silicate, or of pure metaquartzites, often fuchsite bearing, whose lithic characters are unlike those expected for metacherts but are very like those expected for platform arenites. Isotopic ages suggest these sediments are probably older than 3.3 Ga and younger than 3.5 Ga. Studies lead to the conclusions that (1) continental fragments large enough to provide a substrate for significant platform arenite and carbonate sedimentation existed by 3.3 to 3.5 Ga ago; (2) Wilson cycle tectonics seems to adequately explain most major features of the Archean gneissic terranes; and (3) Tibetan-Himalayan style collisional tectonics 2.6 Ga and older accounts for the large scale relationships between the Limpopo belt and the adjacent Archean greenstone granitoid terrane cratons. By inference, other more fragmentary Archean gneissic terranes may have once been part of such collisional zones.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 48-49
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  • 31
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    Anorthositic oceanic crust in the Archean Earth (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Ultrapure minerals separated from eclogite inclusions in kimberlites were analyzed for Sm, Nd, Sr, and oxygen isotopes and for major and trace elements. Clinopyroxene (cpx) and garnet (gnt) are the only primary mineral phases in these rocks, and mineral phases and their alteration products. The WR sub calc. is the reconstructed bulk composition excluding all the contamination influences. Two groups of eclogites: are distinguished: (1) type A Noritic-anorthositic eclogites; and (2) type B Ti-ferrogabbroic eclogites. The oxygen isotopes are primary mantle-derived features of these rocks and are not caused by posteruption processes, as they were measured on unaltered, clean mineral separates and show a correlation with REE pattern and Sr and Nd isotopes. It is suggested that the variation of the oxygen isotopes are caused by crustal-level fluid-rock interaction at relatively low temperature. It is shown that oxygen isotopes variation in MORB basalts caused by the hydrothermal system are in the same range as the observed oxygen isotope variation in eclogites. A model to explain the new set of data is proposed. It is thought that some of these eclogites might be emplaced into the upper lithosphere or lower crust at the time corresponding to their internal isochron age. The calculated WR composition was used to estimate model ages for these rocks.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 40-41
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  • 32
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    Noble gases and the early history of the Earth: Inappropriate paradigms and assumptions inhibit research and communication (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The development of models as tracers of nobel gases through the Earth's evolution is discussed. A new set of paradigms embodying present knowledge was developed. Several important areas for future research are: (1) measurement of the elemental and isotopic compositions of the five noble gases in a large number of terrestrial materials, thus better defining the composition and distribution of terrestrial noble gases; (2) determinations of relative diffusive behavior, chemical behavior, and the distribution between solid and melt of noble gases under mantle conditions are urgently needed; (3) disequilibrium behavior in the nebula needs investigation, and the behavior of plasmas and possible cryotrapping on cold nebular solids are considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 37-38
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  • 33
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    Constraints on the development of the early continental crust from isotopic data (1985)
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    Publication Date: 2011-08-19
    Description: Aspects of the origin and development of the early (AE) continential crust are addressed by radiogenic isotope and trace element studies. The most important ones are: (1) at what time did the earliest continental crust form; (2) what was its composition; (3) by what processes did it grow and by what processes was it destroyed; (4) what were the rates of production and destruction as a function of time during this time period? Nd is isotopic data on the oldest terrestrial rocks indicate that the mantle at this time had already suffered substantial depletion in incompatible elements due to earlier continent forming events. Isotopic data on young volcanic rocks derived from the depleted mantle show no evidence of this early history. The observed isotopic patterns of Nd, Sr, Hf and Pb through time together with the presently observed age spectrum of crustal rocks are considered. These patterns can be modelled by a transport model in which the continental growth and destruction rates are allowed to vary as a function of time. It is suggest that the mass of the continents at 3.8 AE ago was about 25% of the current continental mass. However, due to the very high recycling rates obtained in the early Archean only a few percent of this crust has been preserved up to the present.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 39
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  • 34
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    Submarine hydrothermal environments as sites for the origin and evolution of life (1985)
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    Publication Date: 2011-08-19
    Description: That life formed and evolved in hydrothermal environments is proposed. This hypothesis is plausible in terms of the tectonic, paleontological, and degassing history of the Earth. Submarine hydrothermal vents are the only contemporary geological environment which may truly be called primeval and which today continue to be a major source of gases and dissolved elements to the ocean. The microbial assemblages in present day hydrothermal systems therefore could be living analogues of the earliest microbial communities to develop on Earth. The evidence for the hypothesis is reviewed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 34-36
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  • 35
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    The degassing history of the Earth: Noble gas studies of Archaean cherts and zero age glassy submarine basalts (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Recent noble gas studies suggests the Earth's atmosphere outgassed from the Earth's upper mantle synchronous with sea floor spreading, ocean ridge hydrothermal activity and the formation of continents by partial melting in subduction zones. The evidence for formation of the atmosphere by outgassing of the mantle is the presence of radionuclides H3.-4, Ar-040 and 136 Xe-136 in the atmosphere that were produced from K-40, U and Th in the mantle. How these radionuclides were formed is reviewed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 28-30
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  • 36
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    The 3.5 b.y. old Onverwacht Group: A remnant of ancient oceanic crust (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The interaction between seawater and submarine volcanic rock has had important consequences for the chemistry of the ocean during the Phanerozoic. Most extant terranes have been regionally metamorphosed to the amphibolite and granulite facies, so that their precursor lithologies and structures are not readily determinable. However, the 3.5 b.y. old supracrustal rocks of the Barberton Mountain Land, South Africa, have not been subjected to high grade regional metamorphism, and therefore there was reason to hope that a laboratory investigation might reveal the extent to which these rocks had been exposed to subseafloor hydrothermal activity. Hart and de Wit describe bulk geochemical evidence from the entire suite as well as field evidence which support the concept of hydrothermal activity in the Barberton Mountain Land. Mineralogical and textural features which unequivocally mark it as a submarine sequence emplaced in a midocean ridge/fracture zone or back arc/fracture zone environment are briefly discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 31-33
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  • 37
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    Considerations of large scale impact and the early Earth (1985)
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    Publication Date: 2011-08-19
    Description: Bodies which have preserved portions of their earliest crust indicate that large scale impact cratering was an important process in early surface and upper crustal evolution. Large impact basins form the basic topographic, tectonic, and stratigraphic framework of the Moon and impact was responsible for the characteristics of the second order gravity field and upper crustal seismic properties. The Earth's crustal evolution during the first 800 my of its history is conjectural. The lack of a very early crust may indicate that thermal and mechanical instabilities resulting from intense mantle convection and/or bombardment inhibited crustal preservation. Whatever the case, the potential effects of large scale impact have to be considered in models of early Earth evolution. Preliminary models of the evolution of a large terrestrial impact basin was derived and discussed in detail.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 23-24
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  • 38
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    The problem of the Earth's CO2 content and the iron core (1985)
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    Publication Date: 2011-08-19
    Description: The near absence of metallic iron and the presence of magnetite and FeS in the C-1 chondrites imply that metallic iron was a minor phase present during the accretion process that formed the C-1 chondrites. If the C-1 chondrites provided the bulk of the initial planetary growth materials, the carbon reduction model is favored. The above estimates suggest that some 1240 to 227 times as much CO2 may have been produced during the formation of the core than can be accounted for in the crust and mantle. This discrepancy taken to the extreme suggests either that: (1) the Earth has lost more than 99 percent of its initial CO2 during early differentiation (this is highly unlikely) or: (2) the Earth has acquired some 90 percent of its present mass by the accretion of debris from previously reduced and differentiated but subsequently disrupted planetary bodies whereby the associated CO2 would not be captured, or: (3) the C-1 chondrites represent only a trivial fraction of the initial accretion materials present in the nebular cloud or: (4) condensed iron and anhydrous silicate phases were preferentially accreted during the initial formation of the planetary bodies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 20-22
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  • 39
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    The problem of water on Mars (1985)
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    Publication Date: 2011-08-19
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 40
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    Electrolytic currents in Europa (1985)
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    Publication Date: 2011-08-19
    Description: The transverse electric (TE) and transverse magnetic (TM) currents at the Europan surface are calculated. The study was performed because of the proximity of Europa to Jupiter, which has a strong magnetic field, and the presence of a conductor (water ice) in copious quantities on the Europan surface. The moon is assumed to have a silica interior, an ice layer and, in places, an intermediate liquid layer. Account is taken of surface eddy currents, the maximum current density in the surface and a saline liquid layer, and the TM magnitudes with different liquid layer thicknesses. The effects of random appearances of vertical cracks in the ice are also considered. The calculations indicate that the surface currents could be higher on Europa than on Io, but may be too weak to produce heating effects sufficient to prevent refreezing of a crack.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 63; 39-44
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  • 41
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    On the proposed triggering of Jovian radio emissions (1985)
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    Publication Date: 2011-08-19
    Description: Calvert (1985) has proposed that a solar type III radio bursts can trigger the onset of certain Jovian hectometer wavelength emissions. It is shown, using the data obtained by the Voyager Planetary Radio Astronomy experiment, that this triggering hypothesis is not supported statistically. Furthermore, the causality of this proposed triggering is questioned because much of the Jovian hectometer emission is due to a quasi-continuous radio source rotating, in lighthouse fashion, with Jupiter. Thus, an observed 'onset' of emission is simply a function of the observer's position in local time around Jupiter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 12; 621-624
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  • 42
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    Lunar sample 14425 - Corrected analysis (1985)
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    Publication Date: 2011-08-19
    Description: A polished section of lunar sample 14425, an 8 mm glass bead, was studied using a scanning electron microscope and energy-dispersive X-ray analyzer. The silicon, aluminum, iron, magnesium, calcium, sodium, potassium, titanium, and chromium contents of the glass were determined. Two types of glass are visible in the polished section. One is clear and almost devoid of metallic spherules, while the other is cloudy and contains numerous metallic spherules, some less than one micron in size. Both glass types are homogeneous and identical in composition. This composition closely matches that of some Apollo 14 breccias or glass found in the breccias. The apparent similarity in composition between lunar sample 14425 and the high-magnesium microtektites found in a previous study was probably due to charging effects during analyses in which the sample was uncoated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 220; 1410
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  • 43
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    Magnetic field properties of Jupiter's tail at distances from 80 to 7500 Jovian radii (1985)
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    Publication Date: 2011-08-19
    Description: The results of a detailed study of the magnetic field data on the near and distant Jovian magnetotail from both Voyager 1 and 2 are presented. The spacecraft trajectories and the data are reviewed, and four distant tail encounters are examined and compared with the corresponding Voyager 1 interplanetary data sets. A power spectral analysis of both the near and distant tail intervals is given, and some of the differences between the tail encounters and the power spectra of these control data sets are discussed. Two solar wind or magnetosheath data sets obtained when Voyager 2 was not in the distant tail are analyzed. These more 'normal' solar wind conditions are contrasted with those reflected in both the Voyager 2 distant tail encounters and the conditions monitored by Voyager 1 farther downstream.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 8223-823
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  • 44
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    Bending waves and the structure of Saturn's rings (1985)
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    Publication Date: 2011-08-19
    Description: The surface mass density profiles at four locations within Saturn's rings are calculated using Voyager spacecraft images of spiral bending waves. The identification of a feature in Saturn's outer B ring as Mimas's 4:2 bending waves is confirmed, and these 4:2 waves are analyzed to determine the surface density in Saturn's B ring. A fourth set of bending waves, the Mimas 7:4, located in the inner A ring, is identified and analyzed. Mimas's 5:3 and 8:5 bending waves, observed in the middle and outer A ring respectively, are reanalyzed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 62; 433-447
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  • 45
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    Bolometric albedos of Titan, Uranus, and Neptune (1985)
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    Publication Date: 2011-08-19
    Description: The energy budgets of Titan, Uranus, and Neptune are reevaluated using new observational data on energy input as well as unpublished data on energy output. The bolometric geometric albedo of each object was determined, and preliminary determinations of the phase functions were used to compute the Bond albedos and effective temperatures. The values for the latter are 83 + or - 2 K for Titan, 57 + or - 2 K for Uranus, and 47 + or - 2 K for Neptune. The effective temperature of Titan is greater than the observed brightness temperatures in the thermal infrared region of the spectrum, indicating that the emissivity is less than unity for this part of the spectrum. An internal luminosity of (3.9 + or 1.1) x 10 to the 15th W is found for Neptune, and an upper limit of (0.6 + or - 1.4) x 10 to the 15th W is found for Uranus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 62; 425-432
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  • 46
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    Radial diffusion in magnetodiscs (1985)
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    Publication Date: 2011-08-19
    Description: The orbits of charged particles in magnetodiscs are considered. The bounce motion is assumed adiabatic except for transits of a small equatorial region of weak magnetic field strength and high field curvature. Previous theory and modeling have shown that particles scatter randomly in pitch angle with each passage through the equator. A peaked distribution thus diffuses in pitch angle on the time scale of many bounces. It is argued in this paper that spatial diffusion is a further consequence when the magnetodisc has a longitudinal asymmetry. A general expression for DLL, the diffusion of equatorial crossing radii, is derived. DLL is evaluated explicitly for ions in Jupiter's 20-35 radii magnetodisc, assumed to be represented by Connerney et al.'s (1982) Voyager model plus a small image dipole asymmetry. Rates are energy, species, and space dependent but can average as much as a few tenths of a planetary radius per bounce period.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 7587-759
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  • 47
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    Venus nightside ionospheric troughs - Implications for evidence of lightning and volcanism (1985)
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    Publication Date: 2011-08-19
    Description: The inferred presence of lightning has been a potentially very important result from the in situ exploration of the environment of Venus by the Pioneer Venus Orbiter (PVO). The evidence for lightning has been derived from impulsive low-frequency plasma wave events recorded by the Orbiter electric field detector. The present paper is concerned with an alternative interpretation of the plasma results. It is shown that prominent examples of the plasma waves which have previously been specifically attributed to lightning are associated with distinct nightside ionization troughs. It is suspected that many of the plasma wave disturbances are not due to lightning but rather result from energetic and dynamic processes to be expected in the vicinity of the magnetic field and plasma configurations involved.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 7415-742
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  • 48
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    Atmospheric temperature profiles of Uranus and Neptune (1985)
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    Publication Date: 2011-08-19
    Description: Far-infrared spectrophotometry of Uranus and Neptune in the 30-55 micron spectral range is presented. The measurements in the present six independent spectral bands allow the derivation of atmospheric temperature profiles for these planets. Both planets are found to have tropopause temperatures near 53 K, with Neptune having a stronger stratospheric temperature inversion than Uranus. Effective temperatures of 57.7 + or - 1.8 K and 58.2 + or - 1.9 K are obtained for Uranus and Neptune, respectively, confirming the large internal heat source in Neptune.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal, Part 2 - Letters to the Editor (ISSN 0004-637X); 292; L83-L86
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  • 49
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    The moons of Uranus, Neptune and Pluto (1985)
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    Publication Date: 2011-08-19
    Description: Voyager 2, launched in August 1977, will fly by Uranus in January, 1986, passing within 29,000 km of that planet's innermost moon, Miranda. It will subsequently encounter Neptune in August 1989, flying within 10,000 km of its inner satellite, Triton; images made of this moon by a high resolution camera are expected to reveal surface features as small as a few hundred meters in diameter. The composition of the Uranian moons will br inferred from their near-IR reflectance spectra and mean densities. While the spacecraft will not fly by Pluto, it is expected that the lessons learned from the Voyager encounters with Neptune and Uranus will expand current understanding of Pluto and its moon, Charon.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Scientific American (ISSN 0036-8733); 253; 38-47
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  • 50
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    Wavy edges suggest moonlet in Encke's gap (1985)
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    Publication Date: 2011-08-19
    Description: Voyager images have revealed radial undulations of the inner and outer edges of the 325 km wide Encke gap in Saturn's A ring. These waves are present at some, but not all, longitudes. Their locations and wavelengths provide strong indirect evidence for the presence of at least one dominant moonlet of about 10 km radius orbiting near the center of the gap. Implications for 'shepherding' theory are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 292; 276-290
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  • 51
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    The atmosphere of Saturn - An analysis of the Voyager radio occultation measurements (1985)
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    Publication Date: 2011-08-19
    Description: The Voyager 1 and 2 probes' radio links were used to study both the northern and southern latitudes of Saturn during occultation by that planet, yielding electron number density profiles for the ionosphere, and gas refractivity, number density, pressure, temperature, and ammonia abundance data for the troposphere and stratosphere. From the vertical pressure profiles obtained at different latitudes, it is possible to determine the size and shape of Saturn's isobaric surfaces.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal (ISSN 0004-6256); 90; 1136-114
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  • 52
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    Some morphologic systematics of complex impact structures (1985)
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    Publication Date: 2011-08-19
    Description: Current measurements of the horizontal dimensions of complex meteorite structures are summarized. The measurements were used in a least squares analysis of correlations among the dimensions of the crater rings and central peaks of compact meteorites. Some geometric similarities between terrestrial complex impact structures and the large multiring basin of the planets are demonstrated, and the possible physical constraints on ring formation are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 20; 49-68
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  • 53
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    Response of earth and Venus ionospheres to corotating solar wind stream of 3 July 1979 (1985)
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    Publication Date: 2011-08-19
    Description: Corotating solar wind stream interactions are examined for the earth and Venus in light of data from the plasma detectors aboard ISEE-3, the Pioneer Venus Orbiter (PVO), and Helios-A, as well as in situ ion composition measurements taken by the mass spectrometers aboard the PVO and Atmosphere Explorer-E spacecraft. During May-July 1979, a sequence of distinct, recurrent coronal regions developed at the sun; their analysis indicates a corresponding sequence of corotating streams. Although the planetary environments are distinctly different, it is noted that pronounced and analogous ionospheric responses to the stream passage were observed at both the earth and Venus. The response to the intercepted stream is consistent with independent investigations showing the importance of the variability of the solar wind momentum flux in the solar wind-ionosphere interaction at both planets.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth, Moon and Planets (ISSN 0167-9295); 32; 275-290
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  • 54
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    Terrestrial impactors at geological boundary events - Comets or asteroids? (1985)
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    Publication Date: 2011-08-19
    Description: In the present evaluation of evidence presented to date for a 26-28 million year periodicity in the extinction record and the age of large, well dated terrestrial impact craters, it is noted that no simple, one-to-one relationship emerges between major asteroid and/or comet impacts, siderophile anomalies, and biological extinction events. While impacts may indeed be the major extinction-triggering event in some or even most cases, either other major events, or secondary effects of the impacts, may be the actual extinction-causing mechanism. Long term obscuration of insolation, planetary cooling, or lethal atmospheric pollution may vary among extinctions, depending on the actual state of the planet and its biota during the geological period in question. The source of 28 million year-period asteroidal impactors, moreover, remains unknown and thereby casts doubt on the entire periodicity scenario.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 314; 517
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    Sizing up the planets (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Visual, scaled comparisons are made among prominent volcanic, tectonic, crater and impact basin features photographed on various planets and moons in the solar system. The volcanic formation Olympus Mons, on Mars, is 27 km tall, while Io volcanic plumes reach 200-300 km altitude. Valles Marineris, a tectonic fault on Mars, is several thousand kilometers long, and the Ithasa Chasma on the Saturnian moon Tethys extends two-thirds the circumference of the moon. Craters on the Saturnian moons Tethys and Mimas are large enough to suggest a collision by objects which almost shattered the planetoids. Large meteorite impacts may leave large impact basins or merely ripples, such as found on Callisto, whose icy surface could not support high mountains formed by giant body impacts.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Sky and Telescope (ISSN 0037-6604); 69; 404
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  • 56
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    What color is the solar system? (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Estimates are made of the true visual colors of various planets and moons in the solar system. Account is taken of the components of perceived color, i.e., hue, saturation and lightness. Earth is a blue planet while most of the others, including Mars, are yellow and differ only in their lightness. Widely disseminated Voyager images of Jupiter have been computer-enhanced to highlight details. A reflectance spectrum established by the International Commission on Illumination provides reference lines which are measured and compared with reference colors which would be seen on earth in normal daylight. Uranus is actually a light aqua color due to its absorption of 6190 A light and reflectance of 5000 A blue green light.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Sky and Telescope (ISSN 0037-6604); 69; 399-402
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  • 57
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    Venus gravity - A harmonic analysis and geophysical implications (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An improved theoretical model of Venusian global gravity has been obtained by fitting a tenth degree spherical harmonic series to 78 orbital arcs of Doppler tracking data from the Pioneer Venus Orbiter. Maps of the free-air anomaly and its formal error are presented. Isostatic anomaly and 'Geoid' maps are also presented, and their geophysical implications are discussed in details. Comparison with equivalent resolution topographic models reveals a strong correlation between long wavelength gravity and the topography of Venus. Analysis of the second degree harmonics showed two aspects of the orientation of the inertial axes of Venus: (1) a significant (about three degrees) departure of the axis of greatest inertia from the rotational axis; and (2) a near alignment of the axis of least inertia with the location of the subterrestrial point at the time of the next inferior conjunction with earth (December 16, 2101). A series of contour maps of the Venusian free-air anomalies is provided.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; C739-C75
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    Isotope analysis of crystalline impact melt rocks from Apollo 16 stations 11 and 13, North Ray Crater (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The North Ray Crater Target Rock Consortium was formed to study a large number of rake samples collected at Apollo 16 stations 11 and 13 with comparative chemical, mineralogical, and chronological techniques in order to provide a larger data base for the discussion of lunar highland evolution in the vicinity of the Apollo 16 landing region. The present investigation is concerned with Rb-Sr and Sm-Nd isotopic analyses of a number of whole-rock samples of feldspathic microporhyritic (FM) impact melt, a sample type especially abundant among the North Ray crater (station 11) sample collection. Aspects of sample mineralogy and analytical procedures are discussed, taking into account FM impact melt rocks 6715 and 63538, intergranular impact melt rock 67775, subophitic impact melt rock 67747, subophitic impact melt rock 67559, and studies based on the utilization of electron microscopy and mass spectroscopy.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; C431-C44
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  • 59
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    The depths of the mare basalt source region (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Chemical data for the parental magmas of the nine known VLT Array I pyroclastic glasses show statistically significant trends due to olivine (approximately Fo83) control during their formation by partial melting. The compositional scatter is largely due to compositional variations in the source regions on the + or - 1 percent level. This compositional scatter is small when one considers that the scale of the source region is up to 1000 km, but is sufficient to make positive identification of the residual phase(s) in the source regions difficult. Nevertheless, when the effects of the scatter are properly modeled, it is relatively clear that olivine is the residual phase in the source region. Hence these data and additional constraints indicate that the source regions are at shallow depths in the moon.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; C396-C40
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  • 60
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    Fault type predictions from stress distributions on planetary surfaces - Importance of fault initiation depth (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The prediction of fault type on planetary surfaces from model stresses calculated at depth is discussed. These fault-type predictions yield different faults than those predicted using the surface criteria commonly employed in geophysical models. For elastic-plate flexure models of mascon loading on the moon, stresses calculated at the surface predict the occurrence of strike-slip faulting at the radial distance where grabens are found. Normal faults bounding lunar grabens and thrust faults responsible for wrinkle ridges are analyzed. It is found that the former initiate at the mechanical discontinuity that separates the breccia of the megaregolith from in situ fractured rock and that the latter initiate at the mechanical discontinuity between basalt layers and the underlying basin floor. The difference between elastic constants for the outer few kilometers of brecciated megaregolith and the underlying lunar lithosphere are evaluated. Superposing nonisotropic stresses resulting from the weight of overburden to the depth of the relevant mechanical discontinuity yield stresses that predict wrinkle ridges in the basin centers and grabens outside the basin margin, and eliminate the predicted zone of strike-slip faults.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 3065-307
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  • 61
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    Spectral and other physicochemical properties of submicron powders of hematite (alpha-Fe2O3), maghemite (gamma-Fe2O3), magnetite (Fe3O4), goethite (alpha-FeOOH), and lepidocrocite (gamma-FeOOH) (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The spectral properties (0.35-2.20 microns) of submicron powders of hematite, maghemite, magnetite, goethite, and lepidocrocite are determined. Other physicochemical data are obtained for the powders in order to determine if deviations from stoichiometry occur due to their small particle size, to determine their state of chemical and phase purity, and to determine the physical characteristics of the individual powders. The physicochemical data obtained include mean particle diameter, discrete particle shape, chemical composition, crystallographic phase, magnetic parameters, and Moessbauer parameters. The positions of the spectral features for the hematite, maghemite, and magnetite powders are independent of temperature over the interval between about +20 and -110 C. For the goethite and lepidocrocite powders, a small shift of about 0.02 micron to shorter wavelengths is observed for some of the features after cooling to about -110 C. The spectral properties of the iron oxides and oxyhydroxides are important not only for understanding the basic physics and chemistry of the compounds but also for applications such as the remote sensing of the earth and Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 3126-314
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  • 62
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    Thickness of ice on perennially frozen lakes (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A simple energy-balance model for the perenially frozen lakes of Antarctica's southern Victoria Land is presented which, using the measured ablation rate of 30 cm/yr, can explain the observed ice thickness. Some speculations are presented on the ice cover that could have existed on possible former lakes in the equatorial regions of Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 313; 561
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  • 63
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    A model for diagenesis in proto-planetary bodies (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A model is proposed which eases the thermal constraints imposed by earlier models of low-temperature aqueous alteration in primitive extraterrestrial materials in which formation of an aqueous medium promoting these alterations required complete melting of the water-ice. It is argued that low-temperature alterations in a protoplanetary body such as the formation of hydrated silicates will occur because of the presence of an interfacial water layer.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 313; 293
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  • 64
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    Global map of eolian features on Mars (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A variety of common eolian features on Mars have been identified from a survey of Mariner 9 and Viking orbiter images, and their regional and global distributions and orientations are discussed. Ten features have been mapped including: light and dark streaks, splotches, barchan and transverse dunes, crescentric and anomalous dunes, yardangs, wind grooves, and deflation pits. The north polar region shows a complex wind regime. Dunes and other ephemeral features reveal winds from the northwest and northeast. In the middle and low northern latitudes, northeasterly winds are the most effective winds. Southeast winds are the effective winds in most southern latitudes. Erosional features in bedrock indicate long-term and perhaps ancient wind trends, whereas depositional features may record relatively more recent winds. Deflation pits in the mantled terrain may contain the best record of both ancient and present-day winds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 2038-205
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  • 65
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    Impact cratering history of the Saturnian satellites (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The impact flux history of the Saturn system has been modelled, and absolute ages estimated. The model assumes that the general history of impact flux was similar to that of the inner solar system and that the dominant source of material in the postaccretionary phases was external to the Saturn system. Population I and II craters represent the synheavy and postheavy bombardment periods, respectively. Observed crater densities are representative of the actual ages and do not appear to be saturation-equilibrium surfaces. It is concluded that some of the satellites have geologic histories which extend to about 3.5 b.y. Significant endogenic resurfacing has occurred on several satellite surfaces, which indicates that thermal conditions and material compositions are more complicated than might have been anticipated prior to Voyager encounters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 2029-203
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  • 66
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    Magnetic field in the wake of Venus and the formation of ionospheric holes (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Magnetic field structures are analyzed for both the ionospheric hole region and the magnetosheath/ionosphere interaction region of the nightside of Venus, in search of possible coupling between these two regimes. A magnetic coordinate system based on the directions of the solar wind and the interplanetary magnetic field is found to order the data reasonably well, allowing consistent superposition of observational data from individual passes of the Pioneer Venus orbiter. The results indicate that the magnetosheath plasma flow in the wake region plays an important role in forming the ionospheric holes through deformation of the nightside ionopause. The results are combined in a model of the three-dimensional magnetic field structure around the ionosphere of Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 1385-139
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  • 67
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    Large-amplitude MHD waves upstream of the Jovian bow shock Reinterpretation (1985)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of large amplitude magnetohydrodynamic (MHD) waves upstream of the Jovian bow shock were previously interpreted as arising from a resonant electromagnetic ion beam instability. That interpretation was based on the conclusion that the observed fluctuations were predominantly right elliptically polarized in the solar wind rest frame. Because it was noted that the fluctuations are, in fact, left elliptically polarized, a reanalysis of the observations was necessary. Several mechanisms for producing left hand polarized MHD waves in the observed frequency range were investigated. Instabilities excited by protons appear unlikely to account for the observations. A resonant instability excited by relativistic electrons escaping from the Jovian magnetosphere is a likely source of free energy consistent with the observations. Evidence for the existence of such a population of electrons was found in both the Low Energy Charged Particle experiments and Cosmic Ray experiments on Voyager 2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 90; 302-310
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  • 68
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    Rift systems on Venus: An assessment of mechanical and thermal models (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The formation and distribution of major tectonic features on Venus are closely linked to the dominant mechanism of lithospheric heat loss. Among the most spectacular and extensive of the major tectonic features on Venus are the Chasmata, deep linear valleys generally interpreted to be the products of lithospheric extension and rifting. Systems of chasmata and related features can be traced along several tectonic zones up to 20,000 km in linear extent. Mechanical and thermal models for terrestrial continental-rifting are applied to the rift systems of Venus. The models are tested against known topographic and tectonic characteristics of Venus chasmata as well as independent information on the physical properties of the Venus crust and lithosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Papers Presented to the Conference on Heat and Detachment in Crustal Extension on Continents and Planets; p 138 - 141
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    Extensional tectonics of the Saturnian Satellites (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The saturnian satellites were imaged by the Voyager spacecraft at sufficient resolutions to reveal landforms that indicate histories of extensional tectonics for several of these bodies. The relationships among landforms on various satellites imply that extensional tectonism is a consequence of several different energy sources. Case histories of several satellites are discussed to illustrate the interaction of various phenomena associated with extensional tectonism.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Papers Presented to the Conference on Heat and Detachment in Crustal Extension on Continents and Planets; p 91-92
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    Hot-spot tectonics on Io (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The thesis is that extensional tectonics and low-angle detachment faults probably occur on Io in association with the hot spots. These processes may occur on a much shorter timescale on Ion than on Earth, so that Io could be a natural laboratory for the study of thermotectonics. Furthermore, studies of heat and detachment in crustal extension on Earth and the other terresrial planets (especially Venus and Mars) may provide analogs to processes on Io. The geology of Io is dominated by volcanism and hot spots, most likely the result of tidal heating. Hot spots cover 1 to 2% of Io's surface, radiating at temperatures typically from 200 to 400 K, and occasionally up to 700K. Heat loss from the largest hot spots on Io, such as Loki Patera, is about 300 times the heat loss from Yellowstone, so a tremendous quantity of energy is available for volcanic and tectonic work. Active volcanism on Io results in a resurfacing rate as high as 10 cm per year, yet many structural features are apparent on the surface. Therefore, the tectonics must be highly active.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Papers Presented to the Conference on Heat and Detachment in Crustal Extension on Continents and Planets; p 76-80
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    Lithospheric strength of Ganymede: Clues to early thermal profiles from extensional tectonic features (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: While it is generally agreed that the strength of a planet's lithosphere is controlled by a combination of brittle sliding and ductile flow laws, predicting the geometry and initial characteristics of faults due to failure from stresses imposed on the lithospheric strength envelope has not been thoroughly explored. Researchers used lithospheric strength envelopes to analyze the extensional features found on Ganymede. This application provides a quantitative means of estimating early thermal profiles on Ganymede, thereby constraining its early thermal evolution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Papers Presented to the Conference on Heat and Detachment in Crustal Extension on Continents and Planets; p 45-49
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  • 72
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    Tectonic determinations of lithospheric thickness on Ganymede and Callisto (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The concept of the Maxwell time of a viscoelastic material (4.5) is used in conjunction with calculated thermal profiles to evaluate the significance of tectonic estimates of lithospheric thickness. Thermal lithospheric thicknesses provide fundamental constraints on planetary thermal histories that complement the constraints provided by dateable surface deposits of endogenic origin. Lithospheric constraints are of particular value on the icy satellites where our understanding of both rheology and surface ages is considerably poorer than it is for the terrestrial planets. Certain extensional tectonic features can and have been used to estimate lithospheric thicknesses on Ganymede and Callisto. These estimates, however, refer to the depth of the elastic lithosphere defined by the zone of brittle failure. The relation between the elastic lithosphere and the thermal lithosphere (generally defined by the zone of conductive heat transport) is not straightforward, because the depth of brittle failure depends not only on the thermal profile, but also on rheology and strain rate (or the characteristic time over which stresses build towards failure). Characteristic time considerations are not trivial in this context because stresses generating brittle failure on the icy satellites may be produced by impacts, with characteristic times of seconds to days, or by geologic processes with time scales of hundreds of millions of years.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Papers Presented to the Conference on Heat and Detachment in Crustal Extension on Continents and Planets; p 34-37
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  • 73
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    Rifting on Venus: Implications for lithospheric structure (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Lithospheric strength envelopes on Venus are reviewed and their implications for large scale rifting are discussed. Their relationship to crustal thicnesses and thermal gradients are explored. Also considered are the implications of a theory for rift formation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. Papers Presented to the Conference on Heat and Detachment in Crustal Extension on Continents and Planets; p 2
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    Planetary perspective. Report of Working Group Number 4 (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The study of global megageomorphology from a planetary perspective requires that, philosophically, we view the Earth as a planet like any other; one among a number of bodies of varied size and composition which, together with the Sun, form the Solar System. A first step in the study of the Earth from the planetary perspective is the development of global distribution maps of surface factors as landforms, tectonics, and of key processes operating on Earth. Data of other types, such as gravity and magnetism, should also be included and, so far as possible, multiple data sets should be developed. The compilation of maps would serve as a catalyst for research and a basis for interpretation. They could be used scientifically to document changes such as glacial variations and their relationships to climate, volcanic eruptions and their effects, and coastal alterations. Slow and rapid changes should be studied together with the relationships between scale and the rapidity of change. A study of the relationship of geomorphology (i.e., surficial processes) to lithology and structure is needed. The planetary perspective can also help in the identification and investigation of exotic features such as suspect terrains.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Global Mega-Geomorphology; p 109-110
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    The problem of scale in planetary geomorphology (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: Recent planetary exploration has shown that specific landforms exhibit a significant range in size between planets. Similar features on Earth and Mars offer some of the best examples of this scale difference. The difference in heights of volcanic features between the two planets has been cited often; the Martian volcano Olympus Mons stands approximately 26 km high, but Mauna Loa rises only 11 km above the Pacific Ocean floor. Polygonally fractured ground in the northern plains of Mars has diameters up to 20 km across; the largest terrestrial polygons are only 500 m in diameter. Mars also has landslides, aeolian features, and apparent rift valleys larger than any known on Earth. No single factor can explain the variations in landform size between planets. Controls on variation on Earth, related to climate, lithology, or elevation, have seldom been considered in detail. The size differences between features on Earth and other planets seem to be caused by a complex group of interacting relationships. The major planetary parameters that may affect landform size are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Global Mega-Geomorphology; p 76-78
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    Mega-geomorphology: Mars vis a vis Earth (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The areas of chaotic terrain, the giant chasma of the Valles Marineris region, the complex linear and circular depressions of Labyrinthus Noctis on Mars all suggest the possibility of large scale collapse of parts of the martian crust within equatorial and sub equatorial latitudes. It seems generally accepted that the above features are fossil, being perhaps, more than a billion years old. It is possible that parts of Earth's crust experienced similar episodes of large scale collapse sometime early in the evolution of the planet.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Goddard Space Flight Center Global Mega-Geomorphology; p 18-20
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    Mars: Seasonally variable radar reflectivity (1985)
    In:  CASI
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    Publication Date: 2016-06-07
    Description: The 1971/1973 Mars data set acquired by the Goldstone Solar System Radar was analyzed. It was established that the seasonal variations in radar reflectivity thought to occur in only one locality on the planet (the Solis Lacus radar anomaly) occur, in fact, over the entire subequatorial belt observed by the Goldstone radar. Since liquid water appears to be the most likely cause of the reflectivity excursions, a permanent, year-round presence of subsurface water (frozen or thawed) in the Martian tropics can be inferred.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst. 16th Lunar and Planetary Sci. Conf.; p 74-77
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    Seasonal and Secular Variation of the Solis Lacus Albedo Feature: Relation to the Martian Dust-transport Cycle (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: As documented over the course of thirty-six Martian years, dramatic seasonal and secular variations occur in albedo features in the Solis Planum region of Mars. The most striking of these is the classical dark albedo features, Solis Lacus. Solis Lacus is generally most distinct during southern spring and summer. Mariner 9 and Viking Orbiter images reveal that Solis Lacus contains and is surrounded by a conspicuous pattern of bright and dark wind streaks. A seasonal dust-transport cycle is proposed to explain these observations. During later southern spring or early summer, dust is eroded from the surface and transported from the region by local dust storms which may become a global dust storm. Removal of dust over a wide area results in the dark Solis Lacus feature. During the cessation stage of global dust-storm activity (typically mid- to late-southern summer), enhanced deposition in the lee of obstacles forms the prominent patterns of bright streaks observed within and around Solis Lacus. As the year progresses (southern fall and winter), sedimentation from the atmospheric dust load occurs over the entire region, decreasing the contrast of the albedo features to their surroundings. Dust-storm activity the following year renews the cycle by again removing dust from the region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 290-292
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    Observed Changes at Viking Lander 1 (1985)
    In:  CASI
    Details
    Publication Date: 2014-10-08
    Description: A local dust storm raged in Chryse Planitia, Mars, in June 1981. The changes wrought in the vicinity of the lander (Mutch Memorial Station) by this storm sometime near Sol 1742 were partly described previously. Here, changes related to the storm are itemized, evidence for wind directions during the peak of the storm are cited, and two observations unrelated to the storm are noted. The observations suggest that the eroding winds of the Sol 1742 storm were more easterly (N. 35 deg to 90 deg E.) than those (N. 5 deg to 11 deg E.) that formed the large wind tails; and fragments in erosional residues are 0.7 cm and larger, but smaller ones may be present. Some fragments 0.4 to 0.5 cm and smaller were somehow removed, at least locally; wind speeds of the 1742 local storm were probably greater than those of a previous local dust storm (25 to 30 m/s) that occurred during the same season on Sol 423 because the earlier storm did not alter the surface; the major, if not entire, amount of erosion by the storm occurred between Sols 1728 and 1757; and erosion chiefly occurred where the surface configuration and material properties were altered by the lander and its sampler.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 285-289
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    Emplacement of Long Lava Flows on Mauna Loa (hawaii) and Alba (mars) (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: Spacecraft images revealed that extremely long lava flows (more than 200 km long) exist on the surface of Mars and Io. Compared to terrestial volcanic eruptions, the occurrence of these long flows is very unusual, and may hint at a different style of either magma production or eruption. Attempts to model the emplacement of the long flows on other planets, using a Bingham rheological model, were only partially successful. The objective is to conduct field measurements on long lava flows in Hawaii (where individual flows such as those of 1859 and 1881 exceed 40 km in length) in order to document and interpret their flow characteristics. In this way, a better understanding of the formation of long lava flows is sought as well as a determination of whether the Mauna Loa flows are terrestrial analogs to the long flows seen on Mars and Io.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 248-250
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    Estimates of Lava Eruption Rates at Alba Patera, Mars (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The Martian volcanic complex Alba Patera exhibits a suite of well-defined, long and relatively narrow lava flows qualitatively resembling those found in Hawaii. Even without any information on the duration of the Martian flows, eruption rates (total volume discharge/duration of the extrusion) estimates are implied by the physical dimensions of the flows and the likely conjecture that Stephan-Boltzmann radiation is the dominating thermal loss mechanism. The ten flows in this analysis emanate radially from the central vent and were recently measured in length, plan areas, and average thicknesses by shadow measurement techniques. The dimensions of interest are shown. Although perhaps morphologically congruent to certain Hawaiian flows, the dramatically expanded physical dimensions of the Martian flows argues for some markedly distinct differences in lava flow composition for eruption characteristics.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 245-247
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    Thickness of Ridged Plains Materials in Hesperia Planum, Mars (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The thickness distribution of plains-forming materials in Hesperia Planum is determined by the diameter of partially buried craters. As with all Martian thickness studies, the distribution of measured thicknesses is sparse due to a low number of suitable partially buried craters. The resulting isopach of plains materials has a low level of confidence but is sufficient for generalized thickness trends. The mean of the thickness estimates is 360 + or - 120 m. The isopach of plains-forming materials exhibits an uneven thickness distribution. Average thickness, determined by grid sampling over the region, is 216 + or - 153 m. Local lenses exceed 500 m. A fifth order trend surface provides a partial match (coefficient of correlation = 0.657) to the isopach.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 242-244
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    Volcanic Debris Flows in the Elysium Region of Mars (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: Photogeologic studies of the Elysium volcanic province appear to provide a specific example of the importance of volcanic-ice interaction to produce the channels of Hrad and Granicus Valles. In addition, these studies shows that the channels lie on the surface of a large sedimentary deposit which is interpreted as an accumulation of volcanic debris flows or lahars. In spite of some similarities with Martian outflow channels, this latter difference may distinguish the Elysium channels from other types of Martian channels. Geologic relations are described which demonstrate that the debris flows formed amidst other volcanic activity in the Elysium region thereby suggesting that the magmatism was important to the generation of the mobilizing liquid. The lahars resulted from the melting of ground ice and liquefaction of subsurface materials. The intersection of this fluid reservoir with the regional fracture system lead to the rapid expulsion of a muddy slurry down the steep western slope of the province.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 239-241
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    Ridged Plains of Lunae Planum: Thickness Distribution Revised (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: New data are used to revise the isopach of plains-forming material in the Lunae Planum region. The distribution of data points in the region has not increased; consequently, the new map is still valid for generalized thickness trends only. The isopach map is based on a total of 65 points; 32 points represent thickness estimates at partially buried craters. The remaining 33 points define the limits of plains-forming materials (zero thickness). Suitable buried craters are randomly distributed and sparse near the western edge and northern portion of the area. The overall thickness trend is similar to the previously mapped distribution, but there is a significant reduction in thickness values.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 237-238
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    The Evolution of CO2 on Mars (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The consequences of the hypothesis that the evolution of CO2 is directly linked to the occurrence of at least transitory pockets of moisture were exposed. The current conditions preclude the existence of open bodies of liquid water and the formation of moisture in disequilibrium is not excluded by any known constraints. The water evaporation rate is inversely proportional to PCO2, and the existence of a limiting value (P*) for which liquid water can form in the Mars environment is postulated. The evolution of PCO2 is controlled largely by relatively rapid aqueous chemistry forming carbon-containing sedimentary rocks, perhaps during early history in open water, but more recently in transitory pockets of moisture in the soil. Once the total atmospheric pressure is reduced to near P*, the occurrence of transitory moisture is inhibited, and atmospheric CO2 is no longer depleted by an efficient mechanism. The role of the carbonate reservoir in the current overall carbon budget on Mars, according to this scheme, is illustrated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 232-234
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    Magmas as Selective Filters of Volatiles Between Planetary Mantles and Surfaces (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The composition of early planetary atmospheres and biospheres which is a knowledge of the relationship between mantle volatiles and volcanic gases was analyzed. In the case of Earth it appears that volcanic rocks and gases are relatively oxidized compared to the upper mantle. In the case of the C-O-H volatiles, (H2O, CO2, CO, CH4, H2) the volcanic gases are enriched in H2O and CO2 while the volatiles in the mantle may be dominated by H2O, H2 and possibly CH4. An experimental technique was perfected for phase equilibrium studies in the 5-30 kbar range which allows accurate control of volatile species activities in the fluid phase. The system was used to measure the relative solubilities of H2O, CO2, CO, CH4 and H2 in magmas at 10 kbar pressure. It is found that mantle magmas will selectively screen volatiles from planetary surfaces, forcing volcanic gases towards the neutral QFM oxidation state where H2O is the dominant species.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 229-231
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    High Pressure Cosmochemistry of Major Planetary Interiors: Laboratory Studies of the Water-rich Region of the System Ammonia-water (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The behavior of gas-ice mixtures in major planets at very high pressures was studied. Some relevant pressure-temperature-composition (P-T-X) regions of the hydrogen (H2)-helium (He)-water (H2O-ammonia (NH3)-methane (CH4) phase diagram were determined. The studies, and theoretical model, of the relevant phases, are needed to interpret the compositions of ice-gas systems at conditions of planetary interest. The compositions and structures of a multiphase, multicomponent system at very high pressures care characterized, and the goal is to characterize this system over a wide range of low and high temperatures. The NH3-H2O compositions that are relevant to planetary problems yet are easy to prepare were applied. The P-T surface of water was examined and the corresponding surface for NH3 was determined. The T-X diagram of ammonia-water at atmospheric pressure was studied and two water-rich phases were found, NH3-2H2O (ammonia dihydrate), which melts incongruently, and NH3.H2O (ammonia monohydrate), which is nonstoichiometric and melts at a higher temperature than the dihydrate. It is suggested that a P-T surface at approximately the monohydrate composition and the P-X surface at room temperature is determined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 212-213
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    Implications of Convection in the Moon and the Terrestrial Planets (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The early evolution of the Moon and its implications for the early evolution of the Earth was studied. The study is divided into two parts: (1) studies of core formation. Cosmochemical studies strongly favor a near-homogeneous accretion of the Earth. It is shown that core segregation probably occurred within the first 10,000 years of Earth history. It is found that dissipative heating may be a viable mechanism for core segregation if sufficiently large bodies of liquid iron can form; (2) early thermal evolution of the Earth and Moon. The energy associated with the accretion of the Earth and the segregation of the core is more than sufficient to melt the entire Earth. The increase in the mantle liquidus with depth (pressure) is the dominant effect influencing heat transfer through the magma ocean. It is found that a magma ocean with a depth of 100 km would have existed as the Earth accreted. It is concluded that this magma ocean zone refined the earth resulting in the simultaneous formation of the core and the atmosphere during accretion. The resulting mantle was a well-mixed solid with a near pyrolite composition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 211
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    Interaction of Martian Flow Ejecta Blankets with Pre-existing Impact Craters: Morphological Observations (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The evidence of interaction between impact flow ejecta blankets and pre-existing landforms such as craters, scarps, and wrinkle ridges may yield important clues as to the nature of the ejecta emplacement process. The morphology of flow ejecta blankets and the interactions of these blankets with pre-emplacement impact craters were characterized. About 80 small satellite craters on or in 3 well-expressed low ejecta parent impact craters were recognized. Interaction of the blanket with pre-existing structures was studied, and several types were described. These are: (1) infilling; (2) encroachment; (3) overflow; and (4) breaching. Examination of the overall morphology of three ejecta blankets reveals a range of thickness, from depths sufficient to completely bury craters in the 5 km diameter range in distal areas of the blankets, to very thin blankets which allow subtle pre-existing topography to be visible within a half the diameter of the parent crater. Radial and azimuthal symmetries appear to exist within the blankets over a range of morphologies. It also appears that there is a weak linear correlation between the diameter of craters with nearly 100% infilling and distance from the center of the parent crater.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program 1984; p 204-205
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    Capture of Planetesimals into a Circumterrestrial Swarm (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The lunar origin model considered in this report involves processing of protolunar material through a circumterrestrial swarm of particles. Once such a swarm has formed, it can gain mass by capturing infalling planetesimals and ejecta from giant impacts on the Earth, although the angular momentum supply from these sources remains a problem. The first stage of formation of a geocentric swarm by capture of planetesimals from initially heliocentric orbits is examined. The only plausible capture mechanism that is not dependent on very low approach velocities is the mutual collision of planetesimals passing within Earth's sphere of influence. The dissipation of energy in inelastic collisions or accretion events changes the value of the Jacobi parameter, allowing capture into bound geocentric orbits. This capture scenario was tested directly by many body numerical integration of planetesimal orbits in near Earth space.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 132-133
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    Orbital Resonances and Planetary Accretion in the Solar Nebula (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: Planetesimal orbital evolution in a resisting medium near an accreting protoplanet was studied to explore mechanisms for capture into Trojan and satellite orbits. Various mechanisms for capture into libration were proposed, e.g., increase in Jupiter/Sun mass ratio, change in Jovian orbital radius, and collisions of asteroids with interplanetary dust. Studies include effects of solar nebula gas drag on orbital evolution. In general, the gas deviates from Keplerian motion, causing secular decay of planetesimal orbits, as well as damping eccentricity. The motion of bodies near Jupiter under the effect of a resisting medium was numerically explored. The equations of motion were integrated using the formalism of the planar restricted three body problem, modified to include effects by gas drag and a growing Jupiter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 134-136
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    Models of Angular Momentum Input to a Circumterrestrial Swarm from Encounters with Heliocentric Planetesimals (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: Models of lunar origin in which the Moon accretes in orbit about the Earth from material approaching the Earth from heliocentric orbits must overcome a fundamental problem: the approach orbits of such material would be, in the simplest approximation, equally likely to be prograde or retrograde about the Earth, with the result that accretion of such material adds mass but not angular momentum to circumterrestrial satellites. Satellite orbits would then decay due to the resulting drag, ultimately impacting onto the Earth. One possibility for adding both material and angular momentum to Earth orbit is investigated: imbalance in the delivered angular momentum between pro and retrograde Earth passing orbits which arises from the three body dynamics of planetesimals approaching the Earth from heliocentric space. In order to study angular momentum delivery to circumterrestrial satellites, the near Earth velocities were numerically computed as a function of distance from the Earth for a large array of orbits systematically spanning heliocentric phase space.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 129-131
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    A Circum-terrestrial Compositional Filter (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: A major question about the moon is its under abundance of iron. It is the purpose of this research to understand whether a metal-silicate fractionation of heliocentrically orbiting bodies can be achieved through collisional interactions with a circum-terrestrial swarm. Rates of diffusion are investigated and the mutual collisional destruction within the population is examined. The interactions of these differentiated planetesimals and their collisional products (both silicate mantle fragments and iron cores) with a swarm of Earth orbiting lunesimals (perhaps ejecta from the Earth) of km scale, totaling a mass of order 0.1 lunar mass, extending out 10 or 20 Earth radii are considered. It is found that such a small near Earth population of lunesimals can filter out silicate rich material, while passing iron cores, and form a moon composed partly of terrestrial material, but more substantially of the captured silicate rich portions of the planetesimals.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 127-128
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    Lunar Origin: Role of Giant Impacts (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The explanation that lunar origin involved giant impacts remains attractive. Large planetesimals are consistent with current accretion models, and may have been widely scattered in the early solar systems; their existence is a reasonably, assumption in Moon origin models. Isotopic data require the Moon's formation primarily from local material resembling Earth's upper mantle, not material from elsewhere in the solar system. Giant impacts are stochastic, class predictable events that would provide the required type of ejected Earth mantle material without requiring large moons to form near other planets (a problem with less stochastic processes). Such material may have mixed with incoming meteorites during lunar formation, affecting lunar chemistry.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 125-126
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    Response of Earth's Atmosphere to Increases in Solar Flux and Implications for Loss of Water from Venus (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: A one dimensional radiative convective model is used to compute temperature and water vapor profiles as functions of solar flux for earthlike atmosphere. The troposphere is assumed to be fully saturated with a moist adiabatic lapse rate, and changes in cloudiness are neglected. Predicted surface temperatures increase monotonically from -1 to 111 C as the solar flux is increased from 0.81 to 1.45 times its present value. The results imply that the surface temperature of a primitive water rich Venus should have been at least 80-100 C and may have been much higher, water vapor should have been a major atmospheric constituent at all altitudes, leading to the rapid hydrodynamic escape of hydrogen. The oxygen left behind by this process was presumably consumed by reactions with reduced minerals in the crust.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 121
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    Venus Chasmata: A Lithospheric Stretching Model (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: An outstanding problem for Venus is the characterization of its style of global tectonics, an issue intimately related to the dominant mechanism of lithospheric heat loss. Among the most spectacular and extensive of the major tectonic features on Venus are the chasmata, deep linear valleys generally interpreted to be the products of lithospheric extension and rifting. Systems of chasmata and related features can be traced along several tectonic zones up to 20,000 km in linear extent. A lithospheric stretching model was developed to explain the topographic characteristics of Venus chasmata and to constrain the physical properties of the Venus crust and lithosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 117-118
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    Paleohydrologic Implications of Valley Networks of Mars (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: Valley networks in the heavily cratered terrains of Mars represent an ancient epoch of hydrologic conditions greatly different from those of today. Available crater counts on the valley networks indicate formation during the high flux of impacting bodies charaterizing the early heavy bombardment phase of Martian history. Two populations of valleys are recognized in the equatorial regions of Mars: pristine and degraded. The latter probably formed at the very end of the heavy bombardment phase, extending into the post-heavy bombardment by formation in the intercrater plains. Pristine valleys generally form segments of larger networks with degraded components. This suggests that valley formation was a prolonged process coeval with the heavy bombardment period and extending just beyond that period in martian history. The pristine networks and pristine portions of compound networks on Mars show morphological attributes consistent with an origin by headward growth through spring sapping. On Earth spring sapping occurs where groundwater out-streamflow can be generated by insolation changes associated with orbital parameters or with geothermal effects, such as might be associated with impact or with the volcanic emplacement of the intercrater plains. Thus, it is appropriate to specify the most conservation deviation from modern hydrologic conditions on Mars that could account for the ancient epoch of valley formation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 313-315
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    Microdunes and Other Aeolian Bedforms on Venus: Wind Tunnel Simulations (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: The development of aeolian bedforms in the simulated Venusian environment has been experimentally studied in the Venus Wind tunnel. It is found that the development of specific bedforms, including ripples, dunes, and waves, as well as their geometry, are controlled by a combination of factors including particle size, wind speed, and atmospheric density. Microdunes are formed which are analogous to full-size terrestrial dunes and are characterized by the development of slip faces, internal cross-bedding, a low ratio of saltation path length to dune length, and a lack of particle-size sorting. They begin to develop at wind speeds just above saltation threshold and evolve into waves at higher velocities. At wind speeds of about 1.5 m/sec and higher, the bed is flat and featureless. This evolution is explained by a model based on the interaction of alternating zones of erosion and deposition and particle saltation distances.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 309
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    Potential Bedforms on Venus: Wind Tunnel Simulations (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: Wind tunnel studies involving mixtures of particle sizes (bimodal and multimodal distributions) indicate the microdunes and related ridge- and wave-like structures can occur over a wider range of conditions. The results indicate that the bedforms develop as a consequence of the effective sorting capability of the high-density Venusian atmosphere. Four mixtures of different particle-size distributions were investigated. The results of these experiments suggest that: (1) small-scale bedforms on Venus may be more common than previously anticipated from simulations involving only unimodal sands; (2) small particles are rapidly sorted on Venus if winds slightly above threshold are available; (3) coarse particles are transported in traction within the bedforms as well as rolled by saltating fines, suggesting that the capacity of wind on Venus to transport material is greater than anticipated from previous flux studies and (4) microdunes and related ridges and waves with coarse and fine layers can be produced during sorting.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 307-308
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    The Effect of Particle Density on Aeolian Transport (1985)
    In:  CASI
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    Publication Date: 2014-10-08
    Description: A set of experiments using a wide range of particle densities was performed in an open-circuit, terrestrial-atmospheric-pressure wind tunnel at Arizona State University. The results show that saltation flux equations derived for typical geologic material overpredict the flux of low-density particles. Walnut shells (approximately 1.1 g/cc) were used in the experiment and correspond to volcanic ash or ice. Less mass is transported by the wind in the case of low particle density because the style of transport is different. There is a direct, counter-intuitive relationship between particle density and transport height. Measurements of the vertical distribution of material show that the low-density walnut shells travel in a zone within 10 cm of the surface while high-density (approximately 4.5 g/cc) chromite particles travel as 50 cm. Furthermore, the overall saltation rate of the chromite is approximately four times greater than the walnut shells at the same freestream wind speed, even though the wind is much further above threshold for the walnut shells.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 303-304
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