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  • LUNAR AND PLANETARY EXPLORATION  (3,082)
  • 1985-1989  (3,082)
  • 1950-1954
Collection
Keywords
Years
Year
  • 101
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    The ionosphere of Neptune (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Limited knowledge of ionospheric processes of the outer planets and practically no information on the upper atmosphere of Neptune result in a range of possible ionospheres for Neptune. Various cases are investigated in order to establish a theoretical framework of the ionospheric structure against which the radio occultation measurements can be evaluated. The peak electron densities could range from 1000/cu cm to 10 to the 6th/cu cm depending on ion loss processes and particle ionization processes. The scale height could also range from 300 km to 2000 km depending on the exospheric temperature. Although various assumptions must be made, it is predicted that an auroral ionosphere with large electron densities and a large scale height will be observed by the ingress radio occultation measurement, and that a compressed ionosphere with small electron densities will be seen during the egress measurement.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 945-947
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  • 102
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    Moist convection on Neptune (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A study of methane moist convection on Neptune examines the stability conditions which initiate moist convection of methane clouds. Temperature lapse rates that are unstable to moist convection are subadiabatic by a factor of two or more, while adiabatic and superadiabatic lapse rates are stable. In the observed Neptune temperature structure, vertical velocities greater than 40 m/s are required to lift moist air above the stable region and initiate moist convection. Alternatively, moist convection could be initiated by air that is slightly drier than its surroundings. Moist convective clouds achieve altitudes up to 100 mb, thereby exceeding the temperature minimum and depositing methane in the Neptune stratosphere. At least 2000 such clouds penetrate the Neptune stratosphere/hour.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 929-932
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  • 103
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    Evidence for the abundance of water on Mars now and in the past (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper discusses evidence for the abundance of water on Mars early in its history, based on the analysis of the Viking 1 and 2 images and the Martian-atmosphere water measurements. It is argued that integrated networks of small valleys in the ancient cratered terrain of Mars may indicate that the planet once possessed a warmer climate. It is pointed out that most Martian outflow channels originate from the regions of collapsed and disrupted terrain, suggesting that they were formed by a catastrophic release of groundwater. The question of the fate of Martian water is discussed, and arguments are presented suggesting that the Martian crust may retain significant porosity to a depth of 10 km and may possess a total pore volume sufficient to store a global layer of water 0.5-1.5 km deep.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth in Space (ISSN 1040-3124); 1; 3-5
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  • 104
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    Non-linear three dimensional spectral model of the Venusian thermosphere with super-rotation. I - Formulation and numerical technique. II - Temperature, composition and winds (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A three-dimensional spectral model for the Venusion thermosphere is presented which uses spherical harmonics to represent the horizontal variations in longitude and latitude and which uses Fourier harmonics to represent the LT variations due to atmospheric rotation. A differencing scheme with tridiagonal block elimination is used to perform the height integration. Quadratic nonlinearities are taken into account. In the second part, numerical results obtained with the model are shown to reproduce the observed broad daytime maxima in CO2 and CO and the significantly larger values at dawn than at dusk. It is found that the diurnal variations in He are most sensitive to thermospheric superrotation, and that, given a globally uniform atmosphere as input, larger heating rates yield a larger temperature contrast between day and night.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science (ISSN 0032-0633); 37; 701-705
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  • 105
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    Radiative transfer modeling of Saturn's outer B ring (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The present investigation of Voyager images of the Saturn outer B ring's light-scattering behavior gives attention to the four radial regions formed by brighter and darker areas within and outside the 'spokes'. The B-ring particles are found to have a strongly backscattering phase function and a large-particle scattering albedo of 0.54 in the dark regions and 0.58 in the bright ones; these albedos are interpretable as due to multiple scattering among very pure ice grains covering the ring particle surfaces. It is shown that dark micrometeoroid impacts into the B ring would have darkened the particles to their current spherical albedo in as little as 100 to 200 million years.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 80; 104-135
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  • 106
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    Urey prize lecture - Water on Mars (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Taking the heat-transport physics of ice-covered lakes in the Dry Valleys of Antarctica as a model, it is presently suggested that liquid water lakes could have persisted for significant periods under protective ice covers in the Valles Marineris depressions of Mars. Calculations of ground ice thermodynamic stability in a Martian setting indicate that they may exist close to the surface at high latitudes, but are able to persist near the equator only at substantial depths. Such Martian landforms as terrain-softening are attributable to the creep of the Martian regolith under the influence of ground-ice deformation; FEM modeling of the flow process implies terrain-softening to be a near-surface phenomenon.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 79; 229-288
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  • 107
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    Neon isotope studies of Fayetteville and Kapoeta meteorites and clues to ancient solar activity (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Under the assumption that the solar-flare bombardment of the irradiated grains of gas-rich meteorites occurred about 4.5 b.y. ago on the parent body regoliths at 3 A.U., an estimate of the solar cosmic ray-produced Ne-21 is made by studying etched pyroxene minera separates from both light and dark portions of the gas-rich meteorites Fayetteville and Kapoeta. Excesses of solar cosmic ray Ne-21 were observed in dark portions of these meteorites, after accounting for their galactic cosmic ray Ne-21 production and solar flare Ne-21. In order to produce the estimated solar cosmic ray Ne-21 in the present samples, highly enhanced solar cosmic ray proton fluxes from the ancient sun are required.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 53; 1461-146
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  • 108
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    Spectral properties of condensed phases of disulfur monoxide, polysulfur oxide, and irradiated sulfur (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The spectral reflectances of S2O, as well as the polysulfur oxide (PSO) condensate dissociation products of SO2 and condensates of elemental sulfur irradiated with UV light and X-rays, have been ascertained in the 200-1700 nm range with a view to the relevance of these compounds to the interpretation of planetary data. While S2O is a dark red solid, PSO is a pale yellow one that absorbs strongly in the UV but exhibits no bands in either the visible or near IR. Elemental S produces strong bands in the UV, and while it is normally white at room temperature, UV irradiation causes it to turn yellow. X-ray irradiation of S turns it orange.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 79; 47-55
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  • 109
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    Unusual olivine and pyroxene composition in interplanetary dust and unequilibrated ordinary chondrites (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The presence, in both a number of interplanetary dust particles (IDPs) and in meteorite matrices, of olivine and orthopyroxene grains, low in FeO but containing up to 5 wt pct MnO, is reported. The majority of olivines and pyroxenes in meteorites contain less than 0.5 wt pct MnO. The presence of these low-iron, manganese-enriched (LIME) olivines and pyroxenes in IDPs and meteorites may indicate a link between the origin and history of IDPs and the matrix material of primitive meteorites. The origin of the LIME silicates could be explained by condensation from a gas of solar composition. Forsterite is the first major silicate phase to condense from a solar nebula gas, and Mn, which is not stable as a metal under solar nebula conditions, would condense at about 1100 K as Mn2SiO4 in solid solution with forsterite.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 339; 126-128
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  • 110
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    Beyond earth's boundaries (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Four candidate missions for exploring the solar system and establishing human settlements beyond earth orbit are described. Human expeditions to Phobos and Mars, the establishment of a lunar observatory, and the creation of lunar outpost for use in Mars exploration are examined. Near-term programs are discussed, including studies of earth-to-orbit transportation, life science research, robotic precursor missions, and the Space Station.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Policy (ISSN 0265-9646); 5; 138-146
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  • 111
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    Photochemical stability of CO2 in the Martian atmosphere - Reevaluation of the eddy diffusion coefficient and the role of water vapor (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Theoretical models of CO2 photodissociation in the atmosphere of Mars are developed and analyzed, with a focus on the conditions prevailing during the Mariner 6/7 experiments. The aeronomy of Martian CO2 is reviewed; the atomic O distribution in the upper atmosphere is characterized; the construction of the basic model is described; and simulation results are presented in extensive tables and graphs and discussed in detail. The vertical eddy-diffusion coefficient corresponding to the estimated upper-atmosphere O density (1-2 percent at 135 km) is found to be about 5 x 10 to the 7th sq cm/sec, and HO(x) is found to play a significant role in catalyzing the recombination of CO and O to form CO2. The reasons why the model overpredicts the production of HO(x) and hence of CO2 are explored.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geomagnetism and Geoelectricity (ISSN 0022-1392); 41; 3, 19
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  • 112
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    Aqueous alteration on the hydrous asteroids - Results of EQ3/6 computer simulations (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The two models of carbonaceous chondrite precursor material presently formulated to study the process of aqueous alteration in hydrous asteroids are based, in the first case, on the anhydrous mineralogy of CM chondrites, while the second is based on that of the CV chondrites. It is noted that the alteration mineralogy of the CM chondrites and their parent asteroids may be produced by starting with the anhydrous mineralogy of the same CM chondrites, at temperatures in the 1-25 C range, with a wide variety of rock/fluid ratios. The mineralogy of the important CI chondrites is reproducible through the alteration of either CM or CV anhydrous material, at temperatures in the 50-150 C.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 78; 411-425
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  • 113
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    On the shape and albedo variegation of asteroids - Results from Fourier analysis of synthetic and observed asteroid lightcurves (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Fourier analyses have been conducted of those asteroids in the Lagerkvist et al. (1987) lightcurves with substantially complete phase coverage and point density, and for which a unique period has been identified. Fourier coefficients are thereby obtained for 188 lightcurves of 91 asteroids, as well as for 868 synthetic lightcurves from a set of models different in shape and albedo markings; by comparing model and asteroid lightcurve coefficients, the possible shape and albedo variations for 18 asteroids are derived. An attempt is made to define the general distribution of shapes of all asteroid samples analyzed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 78; 311-322
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  • 114
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    Gravity field of the Saturnian system from Pioneer and Voyager tracking data (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Doppler-tracking data and star-satellite imaging from the Voyager 1 and 2 spacecraft are used along with Pioneer 11 Doppler tracking data to study the gravity field of the Saturnian system. The present analysis has yielded improved values for the masses of Rhea, Titan, and Iapetus, and Saturn. The results are consistent with the findings of Null et al. (1981) and Nicholson and Porco (1988) for the Saturn zonal harmonic coefficients J2, J4, and J6. The ratio of the mass of the sun to the mass of the Saturnian system is found to be 3497.898 + or - 0.018
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal (ISSN 0004-6256); 97; 1485-149
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  • 115
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    The resources of Mars for human settlement (1989)
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    Publication Date: 2011-08-19
    Description: Spacecraft exploration of Marshas shown that the essential resources necessary for life support are present on the Martian surface. The key life-support compounds O2, N2, and H2O are available on Mars. The soil could be used as radiation shielding and could provide many useful industrial and construction materials. Compounds with high chemical energy, such as rocket fuels, can be manufactured in-situ on Mars. Solar power, and possibly wind power, are available and practical on Mars. Preliminary engineering studies indicate that fairly autonomous processes can be designed to extract and stockpile Martian consumables.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: British Interplanetary Society, Journal (ISSN 0007-084X); 42; 147-160
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  • 116
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    Deuterium content of the Venus atmosphere (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The abundance of deuterium in the atmosphere of Venus is an important clue to the role of water in the planet's history, because ordinary and deuterated water escape the atmosphere at different rates. The high-resolution mode of the IUE was used to measure hydrogen Lyman-alpha emission from Venus, but only an upper limit on deuterium Lyman-alpha emission was found, from which was inferred a D/H ratio of less than 0.002-0.005. This is smaller by a factor of 3-8 than the D/H ratio derived from measurements by the Pioneer Venus Large Probe, and may indicate either a stratification of D/H ratio with altitude or a smaller overall ratio than previously thought.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 338; 567
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  • 117
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    Evidence for pigmentary hematite on Mars based on optical, magnetic, and Moessbauer studies of superparamagnetic (nanocrystalline) hematite (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Samples containing variable amounts of superparamagnetic hematite (sp-Hm) were prepared by a method in which the sp-Hm particles were dispersed throughout larger particles of silica gel, and the optical and magnetic properties of these samples were compared with those of larger-diameter hematite (bulk-Hm). It is shown that the optical properties of sp-Hm are different from those of bulk-Hm. Implications of the results for mineralogical interpretations of spectral data for the Martian surface and its terrestrial analogues are discussed. It is concluded that features resulting from ferric iron in the Martian spectral data and the results of the Viking magnetic properties experiment are both consistent with hematite present as both sp-Hm and bulk-Hm; the hematite particles most likely occur in pigmentary form, i.e., as particles dispersed throughout the volume of a spectrally neutral material.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 2760-277
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  • 118
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    On the wavelength dependence of apparent emissivity of asteroid microwave emissions - Ceres and Vesta (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Observations of Ceres and Vesta demonstrate the need for modifying the physical parameters of the standard model procedure in treating single-wavelength observations. It is suggested that simultaneous IR and cm-wavelength data should be used in order to determine such properties as the surface dielectric characteristics, layer depth, and radio emissivity. If using the standard model, an emissivity of 0.8 should be adopted for wavelengths of longer than 1 cm.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 101; 122-125
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  • 119
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    VLF emission bursts in the terrestrial and Venusian nightside troughs (1989)
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    Publication Date: 2011-08-19
    Description: It is shown here that the 100-Hz emission bursts in the Venusian nightside ionosphere are remarkably similar to those of the terrestrial VLF saucer emissions in terms of their spatial and temporal characteristics and the properties of their magnetoplasma environment. It is proposed that the generation mechanism for such VLF sources should be considered as a viable alternative to lightning as a source of Venusian ionospheric whistler-mode emissions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 341; 219-221
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  • 120
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    Age of Allan Hills 82102, a meteorite found inside the ice (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The terrestrial age of a meteorite that was recovered from below the surface of Antarctic ice is reported, and it is argued that this represents a measurement of the age of the ice itself. The cosmogenic radionuclides Be-10, C-14, Al-26, Cl-36, and Mn-53 are measured in the meteorite and Be-10 and Cl-36 in the ice. A terrestrial age of 11,000 yr is obtained for the meteorite, which suggests that the snow accumulation area where it fell was only a few tens of km away.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 340; 550-552
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  • 121
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    Surface discharges on natural dielectrics in the solar system (1989)
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    Publication Date: 2011-08-19
    Description: In a variety of environments, notably those defined by the magnetospheres of the giant planets, natural dielectrics are exposed to large fluxes of charged particles. Laboratory simulations of these potentially discharge-inducing charging phenomena have been conducted to ascertain whether discharges can occur on natural dielectrics. Charging beam intensities ranged from 10 to the 10th to 10 to the 12th particles/sq cm per sec, with exposure times of 1-10 min; the lowest intensity is comparable to that expected on the surface of Io. Discharges were recorded during all exposures.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 245; 622-624
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  • 122
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    Voyager 2 approaches Neptune (1989)
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    Publication Date: 2011-08-19
    Description: What is to be expected when Voyager 2 visits Neptune is discussed. Equipment tuning which has been done in preparation for the event is reviewed. The agenda of measurements to be performed on Neptune's atmosphere, magnetic and radiation fields, ring material, and satellites Nereid and Triton is described.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary Report (ISSN 0736-3680); 9; 19-21
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  • 123
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    Jupiter - First stop on Voyager's grand tour (1989)
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    Publication Date: 2011-08-19
    Description: The findings concerning Jupiter that were made by the Voyager missions are briefly reviewed. The ring and three new moons around Jupiter, the live volcanoes on Io, and atmospheric phenomena on Jupiter which were observed by Voyager 1 are described. The discoveries regarding Callisto and Europa made by Voyager 2 are briefly summarized.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary Report (ISSN 0736-3680); 9; 8-11
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  • 124
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    Neptune may have polar rings (1989)
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    Publication Date: 2011-08-19
    Description: Perturbations from Neptune's highly inclined satellite Triton can maintain rings passing nearly over Neptune's poles. These hypothetical polar rings are nearly perpendicular to Triton's orbit as well, and lie within several degrees of the plane of Voyager II's trajectory through the Neptunian system. Polar rings can coexist with equatorial rings at different radii. A randomly oriented torus of debris around Neptune has a probability of several percent to settle into a polar ring. Voyager II stands a significant chance of encountering a polar ring.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 949-952
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  • 125
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    Predictions of lightning activity at Neptune (1989)
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    Publication Date: 2011-08-19
    Description: Spacecraft observations of the seven innermost planets suggest that lightning is present on all planets with dense atmospheres. Thus lightning may be expected to occur on Neptune as well. Based on the level of lightning activity observed on Jupiter and on the assumption that the lightning energy dissipation rate is a constant fraction of the dissipation rate of the convective energy, the lightning rate on Neptune is estimated to be 1/19 that observed on Jupiter. It is predicted that approximately 60 events should be recorded by the Voyager imager during its search of the nightside of Neptune.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters (ISSN 0094-8276); 16; 937-939
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  • 126
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    Test of a geometric model for the modification stage of simple impact crater development (1989)
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    Publication Date: 2011-08-19
    Description: This paper presents a geometric model describing the geometry of the transient cavity of an impact crater and the subsequent collapse of its walls to form a crater filled by an interior breccia lens. The model is tested by comparing the volume of slump material calculated from known dimensional parameters with the volume of the breccia lens estimated on the basis of observational data. Results obtained from the model were found to be consistent with observational data, particularly in view of the highly sensitive nature of the model to input parameters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics (ISSN 0026-1114); 24; 83-88
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  • 127
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    Pluto's atmosphere - Models based on refraction, inversion, and vapor-pressure equilibrium (1989)
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    Publication Date: 2011-08-19
    Description: Viking spacecraft radio-occultation measurements indicate that, irrespective of substantial differences, the polar ice cap regions on Mars have inversions similar to those of Pluto, and may also share vapor pressure equilibrium characteristics at the surface. This temperature-inversion phenomenon occurs in a near-surface boundary layer; surface pressure-temperature may correspond to the vapor-pressure equilibrium with CH4 ice, or the temperature may be slightly higher to match the value derived from IRAS data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 80; 439-443
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  • 128
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    Radio emission from the magnetic equator of Uranus (1989)
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    Publication Date: 2011-08-19
    Description: The major observational characteristics of the smooth, narrow bandwidth component of Uranus' radio emissions are well described by sources radiating near the local electron gyrofrequency, confined to the magnetic equatorial plane and encircling the planet at radial distances of approximately 2 to 3 R(U). The most intense emission appears to be generated in association with the epsilon ring at 2.0 R(U) radial distance. A cold electron density of less than or equal to 4/cu cm are inferred in this region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 2399-240
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  • 129
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    Croconic acid - An absorber in the Venus clouds? (1989)
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    Publication Date: 2011-08-19
    Description: The absorbing species responsible for the UV cloud features and pale yellow hue of the Venus clouds is presently suggested to be the carbon monoxide-polymer croconic acid, which strongly absorbs in the blue and near-UV. Laboratory absorption-coefficient measurements of a dilute solution of croconic acid in sulfuric acid are used as the bases of cloud-scattering models; the Venus planetary albedo's observed behavior in the blue and near-UV are noted to be qualitatively reproduced. Attention is given to a plausible croconic acid-production mechanism for the Venus cloudtop region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 77; 382-390
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  • 130
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    Phobos and Deimos control networks (1989)
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    Publication Date: 2011-08-19
    Description: Viking Orbiter images of Phobos and Deimos have been measured to establish global control networks for 98 surface features of the former and 53 of the latter; photogrammetric triangulation has yielded body-fixed coordinates of these control-points, as well as mean triaxial radii of 13.3 x 11.1 x 9.3 km for Phobos and 7.5 x 6.2 x 5.4 for Deimos. Expressions are also obtained for the inertial orientations of these bodies' spin axes and prime meridians. While these expressions should be accurate to a few tenths of a deg for the 1971-1980 period, their accuracy will degrade with time as the orbit accuracy degrades.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 77; 275-286
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    Dynamic crystallization of chondrule melts of porphyritic olivine composition - Textures experimental and natural (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A full range of textures characteristic for porphyritic olivine chondrules was reproduced in melts of the same composition, crystallized under dynamic crystallization conditions (under controlled cooling), as determined by electron microprobe analyses. The primary differences between the natural and experimentally produced porphyritic olivine textures were the nature and the extent of matrix crystallization, which reflected the subsolidus or low-temperature cooling history. The most confining limits on the chondrule-forming process were found to be the presence of crystalline precursors for the chondrule melts and the upper temperature limit of melting.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 53; 461-470
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  • 132
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    Orbital evolution of circumplanetary dust by resonant charge variations (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Vast ethereal rings composed of micron-sized particles have been detected about the three giant planets so far visited by Voyager. An orbital evolution mechanism for gravitationally dominated circumplanetary dust is identified here that may temporarily overwhelm other processes. Evolution rates that agree with numerical integrations are derived, and it is suggested how this process could affect the location of the faint rings evident today.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 337; 340-343
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  • 133
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    Evidence from the Semarkona ordinary chondrite for Al-26 heating of small planets (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The first observation of radiogenic Mg-26 in nonrefractory meteoritic material, a plagioclase-bearing, olivine-pyroxene clast chondrule in the Semarkona ordinary chondrite, is reported. The inferred initial abundance of Al-26 is sufficient to produce incipient melting in well-insulated bodies of chondritic composition. It is concluded that planetary accretion and diffentiation must have begun on a timescale comparable to the half-life of Al-26 and that, even if widespread melting did not occur, Al-26 heating played a significant role in thermal metamorphism on small planets.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 337; 238-241
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  • 134
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    To the moon on gossamer wings (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The development of the Lunar Get-Away Special (GAS) canister to search for water on the moon is discussed. The possibility of detecting water on the moon with a gamma-ray spectrometer in a close polar orbit is reviewed. The Lunar GAS configuration, payloads, and subsystems, and a mission scenario are described. The Lunar GAS has a total mass of 150 kg and would require only 33 kg of xenon gas propellant to reach lunar orbit after a launch by the Space Shuttle.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Aerospace America (ISSN 0740-722X); 27; 40-42
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  • 135
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    Geochemical implications of the formation of the moon by a single giant impact (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The origin of the moon by a single massive impact of a body slightly larger than Mars with the earth can explain the angular momentum, orbital characteristics and unique nature of the earth-moon system. The density and chemical differences between the earth and the moon are accounted for by deriving the moon from the mantle of the impactor. A cosmochemically plausible impactor can be formed in the region of the inner Solar System, lending support to the impact hypothesis.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 338; 29-34
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  • 136
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    Impact cratering: A geologic process (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The mechanisms involved in the formation of impact craters are examined theoretically, reviewing the results of recent investigations. Topics addressed include crater morphology, stress waves in solids, the contact and compression stage, the excavation stage, and ejecta deposits. Consideration is given to the scaling of crater dimensions, the crater modification stage, multiring basins, cratered landscapes, atmospheric interactions, and the implications of impact cratering for planetary evolution. Extensive diagrams, graphs, tables, and images of typical craters are provided.
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  • 137
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    Standing hydromagnetic waves in the Io plasma torus - Voyager 1 observations (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: An attempt to analyze Voyager 1 magnetic field data for the existence of any ultralow-frequency hydromagnetic waves in the Io plasma torus is presented. The coincidence between the increase in wave activity and the entry into the Io plasma torus is in support of treating the torus as a low Alfven velocity region and thus as a hydromagnetic waveguide. A first theoretical treatment of hydromagnetic wave propagation within the torus suggests that decoupling of toroidal and poloidal type oscillations can occur under the condition of axisymmetry of the wave field. Numerical calculations of the fundamental mode toroidal and first harmonic poloidal eigenperiods for a model Jovian magnetosphere give values quite in agreement with the observed periods. Observations of nearly axisymmetric, decoupled toroidal and poloidal mode eigenoscillations of the Io plasma torus suggest a large-scale source mechanism for the detected magnetic field fluctuations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 15063-15
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  • 138
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    Plasma pressure in the environment of Jupiter, inferred from Voyager 1 magnetometer observations (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A model combining the internal magnetic field with a self-consistent model of the Jovian magnetodisc was fitted to the Voyager 1 Jovian magnetic field data by means of a generalized inverse technique. The model parameters included the internal field spherical harmonic coefficients as well as with parameters describing the plasma distribution in the magnetosphere. Assuming that the pressure in the middle and outer magnetosphere is related to the unit flux tube volume V through PV exp gamma = const, the model fit yielded a value of 0.88 for gamma. If the hot (30 keV) plasma is transported adiabatically inward under the interchange instability triggered by centrifugal force of the heavy torus ions, losses are not sufficient to account for such a low value of gamma beyond L = 10. Closer to the planet, as the outer edge of the Io plasma torus is approached, PV exp gamma is found to decrease inward, as expected from the particle measurements, which identified an inner boundary of the particle fluxes in that region. With the present stage of the development of magnetodisc models, secular variations of the internal field still remain difficult to estimate.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 94; 15055-15
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  • 139
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    The puzzling case of asteroid 8 Flora solved (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: This paper reports the results obtained in an international campaign devoted to the observations of the asteroid 8 Flora, a possible target of the Vesta mission. Using the lightcurves obtained during three oppositions (1980, 1983, 1984), a synodic rotational period of 12.87 hours was determined. This period, applied to the lightcurves of 8 Flora already published, satisfactorily explains these observations. Applying the AM-method described by Zappala et al. (1983), the pole position was calculated. The slope parameter G, determined during the 1969 and 1983 apparitions, differs by about 0.10. Considering that in those years the ecliptic longitudes of the asteroid were about 115 degrees apart, this fact probably indicates the presence of variations in the structure and chemical compositions of the surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 223; 1-2,
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  • 140
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    Interstellar SiC in the Murchison and Murray meteorites - Isotopic composition of Ne, Xe, Si, C, and N (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Detailed ion-probe data are reported on Murchison and Murray C2 chondrites, along with noble-gas data on Murchison, with the purpose of characterizing the number and isotopic composition of independent SiC components and to link them to their stellar sources. Results show that coarse-grained and fine-grained SiC (totaling about 6-9 ppm of the two meteorites) contains record concentrations of two exotic components: Ne-E(H) (nearly monoisotopic Ne-22) and Se-S (enriched in isotopes 128, 130, and 132), respectively. The Ne-21 content was found to exceed up to 40-fold the content expected from the recent cosmic-ray irradiation, implying a presolar cosmic-ray exposure age of about 39 Ma. This age is much shorter that the predicted 500 Ma lifetime of refractory interstellar grains and implies either a selective interstellar destruction process for SiC, enhanced supernova activity in the protosolar neighborhood, or late outgassing of greater than 90 percent of the SiC.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 53; 3273-329
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  • 141
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    Voyager radio science observations of Neptune and Triton (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Voyager 2 undertook radio science investigations of the Neptune and Triton masses and densities, as well as of their atmospheric and ionospheric vertical structures, the atmospheric composition and low-order gravitational harmonics of Neptune, and ring material characteristics. Upon probing the atmosphere of Neptune to a pressure level of about 500,000 Pa, the effects of a methane cloud region and of ammonia absorption below the cloud have become apparent. The tenuous neutral atmosphere of Triton produced distinct signatures in the occultation data; it is inferred that the Triton atmosphere is controlled by water-pressure equilibrium with surface ices.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 246; 1466-147
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  • 142
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    Photometry from Voyager 2 - Initial results from the Neptunian atmosphere, satellites, and rings (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Voyager 2 has performed photopolarimetric measurements for the planet, several of its satellites, and its ring system. The Great Dark Spot is noted to appear as a low-albedo region, while the bright companion appear to lie at a higher altitude than the Great Dark Spot. Triton's linear phase coefficients are consistent with a solid-surface object having high reflectivity; its rotational phase curve indicates two major compositional units at its surface. The deficiency of material in Neptune's ring system by comparison with that of Uranus may indicate the absence of a recent moon-shattering event.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 246; 1450-145
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  • 143
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    An analysis of the moon's surface using reflected illumination from the earth during a waning crescent lunar phase (1989)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: There have been many articles written concerning the lunar after-glow, the spectacular reflection from the moon's surface, and the possible observation of luminescence on the dark side of the moon. The researcher, using a 600 mm cassegrain telescope lense and Kodak 400 ASA T-Max film, photographed the crescent moon whose dark side was clearly visible by the reflected light from earth. The film was digitized to a Perkin-Elmer 1010M microdensitometer for enhancement and enlargement. The resulting pictures indicate a completely different land pattern formation than observed during a full moon. An attempt is made to analyze the observed structures and to compare them to the pictures observed during the normal full moon. There are boundaries on the digitized dark section of the moon that can be identified with structures seen during the normal full moon. But, these variations do change considerably under enhancement.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Alabama A & M Univ., NASA-HBCU Space Science and Engineering Research Forum Proceedings; p 276-28
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  • 144
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    Extraction of volatiles and metals from extraterrestrial ores (1989)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: Extraterrestrial materials, processes, and products were identified which are associated with the production of propellants in space, including the most complete possible conversion of the feedstocks for propellant production into useful products with the minimum feasible expenditure of energy. Laboratory research was identified and begun on several processes that promise very large increases in the mass of useful products at the cost of only modest increases in energy consumption. Processes for manufacturing propellants then become processes for making propellants plus metals and refractories. It is the overall yield of useful materials per unit expended energy that matters, not simply the yield of propellants. Three tasks have been undertaken to date: (1) Literature search and compilation of a dBase 3 data base on space materials processing; (2) Gaseous carbonyl extraction and purification of ferrous metals; and (3) Characterization of lunar ilmenite and its simulants.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA Space Engineering Research Center for Utilization of Local Planetary Resources; 2 p
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  • 145
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    Development of construction materials like concrete from lunar soils without water (1989)
    In:  CASI
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    Publication Date: 2013-08-31
    Description: The development of construction materials such as concrete from lunar soils without the use of water requires a different methodology than that used for conventional terrestrial concrete. A unique approach is attempted that utilizes factors such as initial vacuum and then cyclic loading to enhance the mechanical properties of dry materials similar to those available on the moon. The application of such factors is expected to allow reorientation, and coming together, of particles of the materials toward the maximum theoretical density. If such a density can provide deformation and strength properties for even a limited type of construction, the approach can have significant application potential, although other factors such as heat and chemicals may be needed for specific construction objectives.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA Space Engineering Research Center for Utilization of Local Planetary Resources; 3 p
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  • 146
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    Discrete electromagnetic emissions in planetary magnetospheres (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The present state of knowledge and observations of discrete electromagnetic emissions detected in the magnetospheres of earth and the outer planets are reviewed. The history of ground observations and satellite observations is included. Active experiments studying wave propagation, wave-wave and wave-particle interactions, and the generation and triggering of discrete emissions are addressed. The various theories proposed to explain the phenomena are examined, and computer simulations of wave-particle interactions and the generation and triggering of discrete emissions are reviewed. Related phenomena observed at frequencies above both the electron cyclotron frequency and the plasma frequency are considered. Areas of future investigation are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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    Voyager Last Picture Show (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This video presentation blends animation, actual photos, and data of the Voyager-Neptune encounter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL-AVC-017-90 , NASA-CR-195796 , NONP-NASA-VT-94-15914
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  • 148
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    Galileo: The Jovian Laboratory (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This video presentation gives a pre-launch description of the Galileo Mission.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL-AVC-007-90 , NASA-CR-196043 , NONP-NASA-VT-94-15912
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  • 149
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    Voyager: National Air and Space Museum (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A recap of the travels of the Voyager spacecraft to the outer planets is presented. (This video was originally made for a talk at the National Air and Space Museum.)
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL-AVC-017-90 , NASA-CR-195905 , NONP-NASA-VT-94-15913
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    Antarctic carbonaceous chondrites - New opportunities for research (1989)
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    Publication Date: 2019-06-28
    Description: An account is given of the types of carbonaceous meteorites available in the Antarctic collections of the U.S. and Japan. In the case of the collection for Victoria Land and Queen Maud Land, all known classes for meteorites except C1 are present; available pairing data, though limited, are indicative of the presence of many different falls. Thus far, attention has been focused on the largest meteorites. Most samples, however, are small.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: ; : Problems in the ae
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    The diverse roles of unmanned precursors in supporting manned missions to Mars (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The diverse roles of robotic precursors are examined in the context of recent NASA studies on a long-term program to establish a human outpost on Mars. The scenario in which these precursors must function and the requirements they must satisfy are discussed, and a tentative set of missions is developed which satisfy this scenario and the set of requirements. The missions and an example of vehicle implementation are described, and how these missions assist in technology demonstrations and building an appropriate infrastructure is addressed. The experience to be gained in the areas of mission operations and management as a result of executing the missions is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: IAF PAPER 89-496
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  • 152
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    The role of climate studies in the future exploration of Mars (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Three major reasons for the continued study of the weather and climate of Mars are: (1) the engineering support of future unmanned and manned missions, including operations on the Martian surface, (2) the comparative study of the climates of earth and Mars, and (3) the perspective provided by understanding what Mars is really like now and how it got that way. Together, the suite of national and international missions to Mars currently in progress and in the advanced planning stages could provide a credible data base for addressing many outstanding climatic questions, as well as greatly improving current engineering models of the Mars atmosphere and surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AAS PAPER 87-199
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  • 153
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    Mars Rover Sample Return mission study (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The Mars Rover/Sample Return mission is examined as a precursor to a manned mission to Mars. The value of precursor missions is noted, using the Apollo lunar program as an example. The scientific objectives of the Mars Rover/Sample Return mission are listed and the basic mission plans are described. Consideration is given to the options for mission design, launch configurations, rover construction, and entry and lander design. Also, the potential for international cooperation on the Mars Rover/Sample Return mission is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AAS PAPER 87-195
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  • 154
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    Measurements of the D/H ratio in planetary atmospheres by ground based infrared spectroscopy (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A systematic study of deuterium in the solar system using the molecules CH3D and HDO as tracers is carried out. For the outer solar system, ground-based spectra of Saturn, Uranus, Neptune and Titan in the region of CH3D absorptions near, 1.6 microns are obtained. The analyses of these spectra required extensive high-resolution laboratory studies of both CH4 and CH3D. For the terrestrial planets, the spectrum of Mars in the region of HDO absorption near 3.7 microns, is recorded. A similar study of Venus is underway. The values of D/H derived from these investigations are used to constrain models for the origin and evolution of the various atmospheres.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: ESA, Infrared Spectroscopy in Astronomy,; p 41-47
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  • 155
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    Conceptual design of a synchronous Mars telecommunications satellite (1989)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Future missions to Mars will require a communications system to link activities on the Martian surface with each other and with mission controllers on Earth. A conceptual design is presented for an aerosynchronous communications satellite to provide these links. The satellite provides the capability for voice, data/command, and video transmissions. The mission scenario assumed for the design is described, and a description of a single aerosynchronous satellite is explained. A viable spacecraft design is then presented. Communication band selection and channel allocation are discussed. The communications system conceptual design is presented along with the trades used in sizing each of the required antennas. Also, the analyses used to develop the supporting subsystem designs are described as is the communications impact on each subsystem design.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TP-2942 , L-16580 , NAS 1.60:2942
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  • 156
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    Crustal deformation: Earth vs Venus (1989)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: It is timely to consider the possible tectonic regimes on Venus both in terms of what is known about Venus and in terms of deformation mechanisms operative on the earth. Plate tectonic phenomena dominate tectonics on the earth. Horizontal displacements are associated with the creation of new crust at ridges and destruction of crust at trenches. The presence of plate tectonics on Venus is debated, but there is certainly no evidence for the trenches associated with subduction on the earth. An essential question is what kind of tectonics can be expected if there is no plate tectonics on Venus. Mars and the Moon are reference examples. Volcanic constructs appear to play a dominant role on Mars but their role on Venus is not clear. On single plate planets and satellites, tectonic structures are often associated with thermal stresses. Cooling of a planet leads to thermal contraction and surface compressive features. Delamination has been propsed for Venus by several authors. Delamination is associated with the subduction of the mantle lithosphere and possibly the lower crust but not the upper crust. The surface manifestations of delamination are unclear. There is some evidence that delamination is occurring beneath the Transverse Ranges in California. Delamination will certainly lead to lithospheric thinning and is likely to lead to uplift and crustal thinning.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 49
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    Venus: Mantle convection, hotspots, and tectonics (1989)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The putative paradigm that planets of the same size and mass have the same tectonic style led to the adaptation of the mechanisms of terrestrial plate tectonics as the a priori model of the way Venus should behave. Data acquired over the last decade by Pioneer Venus, Venera, and ground-based radar have modified this view sharply and have illuminated the lack of detailed understanding of the plate tectonic mechanism. For reference, terrestrial mechanisms are briefly reviewed. Venusian lithospheric divergence, hotspot model, and horizontal deformation theories are proposed and examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 33-34
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  • 158
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    Crater identification and resolution of lunar radar images (1989)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The relations between the identification of dominant lunar landforms, craters, and radar images at three resolutions are investigated. Although the percentage of craters that can be identified is found to increase with diameter or relief for any given resolution, it is noted that craters have not been identified at all diameters and relief. It is shown that the relation between the percentage of identified craters and their dimensions depends on the size-frequency distributions of both diameters and relief, and that crater identification depends strongly on the resolution of the radar image.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 32
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  • 159
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    Venus and the Archean Earth: Thermal considerations (1989)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The Archean Era of the Earth is not a direct analog of the present tectonics of Venus. In this regard, it is useful to review the state of the Archean Earth. Most significantly, the temperature of the adiabatic interior of the Earth was 200 to 300 C hotter than the current temperature. Preservation biases limit what can be learned from the Archean record. Archean oceanic crust, most of the planetary surface at any one time, has been nearly all subducted. More speculatively, the core of the Earth has probably cooled more slowly than the mantle. Thus the temperature contrast above the core-mantle boundary and the vigor of mantle plumes has increased with time on the Earth. The most obvious difference between Venus and the present Earth is the high surface temperature and hence a low effective viscosity of the lithosphere. In addition, the temperature contrast between the adiabatic interior and the surface, which drives convection, is less on Venus than on the Earth. It appears that the hot lithosphere enhanced tectonics on the early Venus significantly enough that its interior cooled faster than the Earth's. The best evidence for a cool interior of Venus comes from long wavelength gravity anomalies. The low interior temperatures retard seafloor spreading on Venus. The high surface temperatures on Venus enhance crustal deformation. That is, the lower crust may become ductile enough to permit significant flow between the upper crust and the mantle. There is thus some analogy to modern and ancient areas of high heat flow on the Earth. Archean crustal blocks typically remained stable for long intervals and thus overall are not good analogies to the deformation style on Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 46
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    Tectonism on Venus: A review (1989)
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    Publication Date: 2019-01-25
    Description: Venus is more similar to Earth than to any other planet. It has elevated regions associated with marginal fold and thrust belts, fracture zones that extend tens of thousands of kilometers, crustal swells and shields that are hundreds of kilometers in diameter and 1 to 2 km high, and sublinear accumulations of volcanic cones and domes that stretch for thousands of kilometers across the plains. The Venusian surface is, however, distinctly different from Earth's in that: (1) its elevated terrains cannot be distinguished from its low plains on a hypsometric curve; (2) trenches have not been found plainsward of the marginal belts; (3) fracture zones bear no resemblance to mid-oceanic ridges; and (4) some features, such as the ridge-belt zone near 210 deg E, seem to have no terrestrial analog. Various theories about tectonism on Venus and Earth of other authors are reviewed.
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    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 29
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    Deducing the age of the dense Venus atmosphere (1989)
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    Publication Date: 2019-01-25
    Description: It is shown how crater size-density counts may be used to help constrain the history of the Venus atmosphere, based on the predictions of simple but reasonable models for crater production, surface erosion, and the effects of atmospheric drag and breakup on incident meteors in the Venus atmosphere. In particular, if the atmosphere is young, the old (uneroded) surfaces will have crater densities upward of 0.0001/sq km and a ratio of small (4 km) craters to large (128 km) craters near 1000. If the atmosphere is old and the breakup mechanism is dominant, absolute crater densities on Venus surfaces will be diminished by several orders of magnitude relative to the young atmosphere case. If atmospheric drag is dominant, the absolute crater density will be lowered by perhaps an order of magnitude relative to the young atmosphere case, and the ratio of small to large craters will be reduced to a value near 10 to the 1.5 power. Once a large fraction of Venus surface has been imaged at kilometer resolution, as the Venus Orbiting Imaging Radar project promises to do, it could be possible to make an early determination of the age of the Venus atmosphere.
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    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 26
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    Contrasting landform perception with varied radar illumination geometries and at simulated resolutions of Venera and Magellan (1989)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The high sensitivity of imaging radars to slope at moderate to low incidence angles enhances the perception of linear topography on images. It reveals broad spatial patterns that are essential to landform mapping and interpretation. As radar responses are strongly directional, the ability to discriminate linear features on images varies with their orientation. Landforms that appear prominent on images where they are transverse to the illumination may be obscure to indistinguishable on images where they are parallel to it. Landform detection is also influenced by the spatial resolution in radar images. Seasat radar images of the Gran Desierto Dunes complex, Sonora, Mexico; the Appalachian Valley and Ridge Province; and accreted terranes in eastern interior Alaska were processed to simulate both Venera 15 and 16 images (1000 to 3000 km resolution) and image data expected from the Magellan mission (120 to 300 m resolution. The Gran Desierto Dunes are not discernable in the Venera simulation, whereas the higher resolution Magellan simulation shows dominant dune patterns produced from differential erosion of the rocks. The Magellan simulation also shows that fluvial processes have dominated erosion and exposure of the folds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 11
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    Venus surface properties deduced from radar and radiometry (1989)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The brightness of surface features on side looking radar images of Venus is determined by many factors: the angles of incidence and reflection, polarization, surface geometry and composition, and so forth. The contribution from surface properties themselves can only be deduced by combining several types of measurement. For instance, without additional information, it is impossible to distinguish the effects of changes in surface roughness from those in dielectric constant. In common with the Moon and Mars, the surface of Venus appears to scatter radar waves in two ways: small-scale surface inhomogeneities, i.e., those smaller than the incident wavelength, depolarize and scatter the energy over a wide range of angles. The Pioneer Venus radar mapper experiment made three overlapping sets of measurements of the equatorial region of Venus from 15 deg S latitude to 45 deg N; the backscatter cross section at a range of incidence angles, the shape and intensity of radar echoes from the nadir, and the microwave brightness temperature of the surface. These techniques developed during the analysis of Pioneer Venus data will be used during the Magellan mission to extract measurements of surface slopes and dielectric constants over all areas covered by the SAR and altimeter antennae, with a resolution of about 10 km. A knowledge of the mechanisms that govern surface scattering will also be useful in the analysis of higher resolution side looking radar images, particularly in distinguishing the effects of changing roughness from those caused by a long range surface tilt or changing dielectric constant.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 12
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    Potential for observing and discriminating impact craters and comparable volcanic landforms on Magellan radar images (1989)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: Observations of small terrestrial craters by Seasat synthetic aperture radar (SAR) at high resolution (approx. 25 m) and of comparatively large Venusian craters by Venera 15/16 images at low resolution (1000 to 2000 m) and shorter wavelength show similarities in the radar responses to crater morphology. At low incidence angles, the responses are dominated by large scale slope effects on the order of meters; consequently it is difficult to locate the precise position of crater rims on the images. Abrupt contrasts in radar response to changing slope (hence incidence angle) across a crater produce sharp tonal boundaries normal to the illumination. Crater morphology that is radially symmetrical appears on images to have bilateral symmetry parallel to the illumination vector. Craters are compressed in the distal sector and drawn out in the proximal sector. At higher incidence angles obtained with the viewing geometry of SIR-A, crater morphology appears less compressed on the images. At any radar incidence angle, the distortion of a crater outline is minimal across the medial sector, in a direction normal to the illumination. Radar bright halos surround some craters imaged by SIR-A and Venera 15 and 16. The brightness probably denotes the radar response to small scale surface roughness of the surrounding ejecta blankets. Similarities in the radar responses of small terrestrial impact craters and volcanic craters of comparable dimensions emphasize the difficulties in discriminating an impact origin from a volcanic origin in the images. Similar difficulties will probably apply in discriminating the origin of small Venusian craters, if they exist. Because of orbital considerations, the nominal incidence angel of Magellan radar at the center of the imaging swath will vary from about 45 deg at 10 deg N latitude to about 16 deg at the north pole and at 70 deg S latitude. Impact craters and comparable volcanic landforms will show bilateral symmetry parallel to the illumination vector and will appear increasingly compressed toward higher latitudes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 10
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  • 165
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    Geology of Southern Guinevere Planitia, Venus, based on analyses of Goldstone radar data (1989)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: The ensemble of 41 backscatter images of Venus acquired by the S Band (12.6 cm) Goldstone radar system covers approx. 35 million km and includes the equatorial portion of Guinevere Planitia, Navka Planitia, Heng-O Chasma, and Tinatin Planitia, and parts of Devana Chasma and Phoebe Regio. The images and associated altimetry data combine relatively high spatial resolution (1 to 10 km) with small incidence angles (less than 10 deg) for regions not covered by either Venera Orbiter or Arecibo radar data. Systematic analyses of the Goldstone data show that: (1) Volcanic plains dominate, including groups of small volcanic constructs, radar bright flows on a NW-SE arm of Phoebe Regio and on Ushas Mons and circular volcano-tectonic depressions; (2) Some of the regions imaged by Goldstone have high radar cross sections, including the flows on Ushas Mons and the NW-SE arm of Phoebe Regio, and several other unnamed hills, ridged terrains, and plains areas; (3) A 1000 km diameter multiringed structure is observed and appears to have a morphology not observed in Venera data (The northern section corresponds to Heng-O Chasma); (4) A 150 km wide, 2 km deep, 1400 km long rift valley with upturned flanks is located on the western flank of Phoebe Regio and extends into Devana Chasma; (5) A number of structures can be discerned in the Goldstone data, mainly trending NW-SE and NE-SW, directions similar to those discerned in Pioneer-Venus topography throughout the equatorial region; and (6) The abundance of circular and impact features is similar to the plains global average defined from Venera and Arecibo data, implying that the terrain imaged by Goldstone has typical crater retention ages, measured in hundreds of millions of years. The rate of resurfacing is less than or equal to 4 km/Ga.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 1
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  • 166
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    Low temperature measurement of the vapor pressures of planetary molecules (1989)
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    Publication Date: 2019-01-25
    Description: Interpretation of planetary observations and proper modeling of planetary atmospheres are critically upon accurate laboratory data for the chemical and physical properties of the constitutes of the atmospheres. It is important that these data are taken over the appropriate range of parameters such as temperature, pressure, and composition. Availability of accurate, laboratory data for vapor pressures and equilibrium constants of condensed species at low temperatures is essential for photochemical and cloud models of the atmospheres of the outer planets. In the absence of such data, modelers have no choice but to assume values based on an educated guess. In those cases where higher temperature data are available, a standard procedure is to extrapolate these points to the lower temperatures using the Clausius-Clapeyron equation. Last summer the vapor pressures of acetylene (C2H2) hydrogen cyanide (HCN), and cyanoacetylene (HC3N) was measured using two different methods. At the higher temperatures 1 torr and 10 torr capacitance manometers were used. To measure very low pressures, a technique was used which is based on the infrared absorption of thin film (TFIR). This summer the vapor pressure of acetylene was measured the TFIR method. The vapor pressure of hydrogen sulfide (H2S) was measured using capacitance manometers. Results for H2O agree with literature data over the common range of temperature. At the lower temperatures the data lie slightly below the values predicted by extrapolation of the Clausius-Clapeyron equation. Thin film infrared (TFIR) data for acetylene lie significantly below the values predicted by extrapolation. It is hoped to bridge the gap between the low end of the CM data and the upper end of the TFIR data in the future using a new spinning rotor gauge.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 16-17
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    Galileo Probe Spacecraft Mission to Jupiter (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This video contains Galileo probe animation, mission diagrams, and testing and manufacturing footage.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AAV-1283 , NASA-TM-109646 , NONP-NASA-VT-93-190444
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    Voyager 2: Neptune Encounter (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Computer graphics, actual images, and stock footage of the Voyager 2's Neptune encounter are narrated with music.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL-AVC-099-89 , NASA-TM-109423 , NONP-NASA-VT-93-190220
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    Galileo Jupiter Probe Ready to Go (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: This video presents close cloud views of Jupiter, probe deployment, descent, chute opening, trajectories, and views of assembly at Hughes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-109648 , NONP-NASA-VT-93-190446
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    NASA Report to Education, Volume 7 (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Segments of this video include the STS-34 Mission, Pegesus tests, and Voyager's Neptune.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: LERC-3043 , NASA-TM-109435 , NONP-NASA-VT-93-190232
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    Voyager: Neptune Encounter Highlights (1989)
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    Publication Date: 2019-06-28
    Description: Voyager encounter data are presented in computer animation (CA) and real (R) animation. The highlights include a view of 2 full rotations of Neptune. It shows spacecraft trajectory 'diving' over Neptune and intercepting Triton's orbit, depicting radiation and occulation zones. Also shown are a renegade orbit of Triton and Voyager's encounter with Neptune's Magnetopause. A model of the spacecraft's complex maneuvers during close encounters of Neptune and Triton is presented. A view from Earth of Neptune's occulation experiment is is shown as well as a recreation of Voyager's final pass. There is detail of Voyager's Image Compensation technique which produces Voyager images. Eighteen images were produced on June 22 - 23, 1989, from 57 million miles away. A 68 day sequence which provides a stroboscopic view - colorization approximates what is seen by the human eye. Real time images recorded live from Voyager on 8/24/89 are presented. Photoclinometry produced the topography of Triton. Three images are used to create a sequence of Neptune's rings. The globe of Neptune and 2 views of the south pole are shown as well as Neptune rotating. The rotation of a scooter is frozen in images showing differential motion. There is a view of rotation of the Great Dark Spot about its own axis. Photoclinometry provides a 3-dimensional perspective using a color mosaic of Triton images. The globe is used to indicate the orientation of Neptune's crescent. The east and west plumes on Triton are shown.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL-AVC-151-89 , NASA-TM-109421 , NONP-NASA-VT-93-190218
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    Voyager Encounter Highlights (1989)
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    Publication Date: 2019-06-28
    Description: The following are presented: computer animation of trajectories for both Voyagers 1 and 2; view of Jupiter during one orbit of Ganymede; computer animation of Voyager 2's encounter with Jupiter and its satellites; time lapse of the planet's rotation and its satellites; stroboscopic sequence of selected frames; cloud motion; Jupiter's Great Red Spot (4/25 - 5/24, 1979) through a violet filter; and the Great Red Spot through a blue filter by Voyager 1. The dynamics of Jupiter's clouds are shown - the whole planet is shown first, then two closer looks are repeated several times. Also included are pans of stills of Jupiter's satellites and a computer simulation tour of Saturn system from POV just behind Voyager, made of 116 images of Saturn through a green filter and of 516 images taken by Voyager 1 (9/12 - 9/14, 1980). Frames are enhanced to show the motion of features in Saturn's rings. Pans of stills of Saturn's satellites are shown. There is computer animation of the planet's system, rings, and Sigma Sagittari. Images on January 14, 1986 are through an orange filter. Uranus's satellites are shown as is computer animation of an August 1989 encounter.
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    Type: NASA-TM-109420 , NONP-NASA-VT-93-190217
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    Antarctic Meteorite Location Map Series (1989)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: Antarctica has been a prolific source of meteorites since meteorite concentrations were discovered in 1969. The Antarctic Search For Meteorites (ANSMET) project has been active over much of the Trans-Antarctic Mountain Range. The first ANSMET expedition (a joint U.S.-Japanese effort) discovered what turned out to be a significant concentration of meteorites at the Allan Hills in Victoria Land. Later reconnaissance in this region resulted in the discovery of meteorite concentrations on icefields to the west of the Allan Hills, at Reckling Moraine, and Elephant Moraine. Antarctic meteorite location maps (reduced versions) of the Allan Hills main, near western, middle western, and far western icefields and the Elephant Moraine icefield are presented. Other Antarctic meteorite location maps for the specimens found by the ANSMET project are being prepared.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-181510 , NAS 1.26:181510 , LPI-TR-89-02
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    A heat-pipe mechanism for volcanism and tectonics on Venus (1989)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A heat-pipe mechanism is proposed for the transport of heat through the lithosphere of Venus. This mechanism allows the crust and lithosphere on Venus to be greater than 150 km. thick. A thick basaltic crust on Venus is expected to transform eclogite at a depth of 60 to 80 km; the dense eclogite would contribute to lithospheric delamination that returns the crust to the interior of the planet completing the heat-pipe cycle. Topography and the associated gravity anomalies can be explained by Airy compensation of the thick crust. The principal observation that is contrary to this hypothesis is the mean age of the surface that is inferred from crater statistics; the minimum mean age is about 130 Myr and this implies an upper limit of 2 cubic kilometers per year for the surface volcanic flux. If the heat-pipe mechanism was applicable on the Earth in the Archean it would provide the thick lithosphere implied by isotopic data from diamonds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-184791 , NAS 1.26:184791
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    The environment at the lunar surface (1989)
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    Publication Date: 2019-06-28
    Description: The geologic nature of the lunar surface and the composition of the lunar atmosphere are discussed. General characteristics are presented such as the strength of the moon's gravitational field. The properties of seismic signals which occur deep within the moon at depths of 700 to 1100 km and are related to tidal forces inside the moon are examined. Tables are also provided of the composition of the lunar atmosphere at night, and of the micrometeorite fluxes on the moon. The magnetic field, radiation environment, composition of regolith, and crater morphologies are also discussed.
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    Prediction of the He distribution at the lunar surface (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Data on the contents of He and TiO2 and the maturity index, Is/FeO have been compiled, for all lunar soils for which measurements have been reported, in order to quantitatively asses the relationship between these parameters. The He content in lunar soils correlates approximately linearly with the product (Is/FeO)(TiO2 wt pct) over the range of measured values. The advantage of such a trend is the assistance it may provide in mapping the lunar surface for He and other solar-wind volatiles in a quantitative manner. A remote means of assessing Is/FeO in addition to TiO2 will be required.
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    Production of oxygen from lunar soil by molten salt electrolysis (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A simple approach to utilizing lunar resources proposes to dissolve lunar soil, without or with little beneficiation, in a suitable molten salt and to electrolyze the oxides to oxygen and a metal byproduct. The envisioned process and the required technological advances are discussed. Promising electrolysis conditions have been identified in a recent experimental program to manufacture silicon and aluminum from anorthite.
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    Properties of the moon, Mars, Martian satellites, and near-earth asteroids (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Environments and surface properties of the moon, Mars, Martian satellites, and near-earth asteroids are discussed. Topics include gravity, atmospheres, surface properties, surface compositions, seismicity, radiation environment, degradation, use of robotics, and environmental impacts. Gravity fields vary from large fractions of the earth's field such as 1/3 on Mars and 1/6 on the moon to smaller fractions of 0.0004 g on an asteroid 1 km in diameter. Spectral data and the analogy with meteor compositions suggest that near-earth asteroids may contain many resources such as water-rich carbonaceous materials and iron-rich metallic bodies. It is concluded that future mining and materials processing operations from extraterrestrial bodies require an investment now in both (1) missions to the moon, Mars, Phobos, Deimos, and near-earth asteroids and (2) earth-based laboratory research in materials and processing.
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    Present state and chemical evolution of the atmospheres of Titan, Triton, and Pluto (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: An evaluation is made of the current understanding of the atmospheres of Titan, Triton, and Pluto, as well as of theoretical models for their origin and evolution. All three atmospheres contain methane, while Titan, and probably Triton, have nitrogen. The primary driver in the evolution of the Titan atmosphere has been the irreversible photolysis of methane. If a surface reservoir of liquid methane exists to resupply the atmosphere, it is subject to enrichment in ethane due to the long-term photolysis of methane. The key issue in the origin and early evolution of Titan's atmosphere is the source of molecular nitrogen; two schemes for the conversion of ammonia to nitrogen have been considered.
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    Achondrites and igneous processes on asteroids (1989)
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    Publication Date: 2019-06-28
    Description: The possible roles of partial melting and fractional crystallization in the formation of eucrite and ureilite achondrites are discussed, summarizing the results of recent petrological investigations and theoretical modeling efforts. Typical data are presented graphically, and it is found that there is as yet no consensus on the correct model of achondrite evolution, and hence no agreement on the chemistry of the parent bodies. Assuming that the ureilites formed as adcumulates, their properties support a role for fractionation in relatively small bodies, even though the magmatic composition of the ureilite parent bodies is different from that of terrestrial cumulates.
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    Parallel Architectures for Planetary Exploration Requirements (PAPER) (1989)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: The Parallel Architectures for Planetary Exploration Requirements (PAPER) project is essentially research oriented towards technology insertion issues for NASA's unmanned planetary probes. It was initiated to complement and augment the long-term efforts for space exploration with particular reference to NASA/LaRC's (NASA Langley Research Center) research needs for planetary exploration missions of the mid and late 1990s. The requirements for space missions as given in the somewhat dated Advanced Information Processing Systems (AIPS) requirements document are contrasted with the new requirements from JPL/Caltech involving sensor data capture and scene analysis. It is shown that more stringent requirements have arisen as a result of technological advancements. Two possible architectures, the AIPS Proof of Concept (POC) configuration and the MAX Fault-tolerant dataflow multiprocessor, were evaluated. The main observation was that the AIPS design is biased towards fault tolerance and may not be an ideal architecture for planetary and deep space probes due to high cost and complexity. The MAX concepts appears to be a promising candidate, except that more detailed information is required. The feasibility for adding neural computation capability to this architecture needs to be studied. Key impact issues for architectural design of computing systems meant for planetary missions were also identified.
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    Type: NASA-CR-185370 , NAS 1.26:185370
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    Temperature and circulation in the stratospheres of the outer planets (1989)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A zonally symmetric, linear radiative-dynamical model is compared with observations of the upper tropospheres and stratospheres of the outer planets. Seasonal variation is included in the model. Friction is parameterized by linear drag (Rayleigh friction). Gas opacities are accounted for but aerosols are omitted. Horizontal temperature gradients are small on all the planets. Seasonal effects are strongest on Saturn and Neptune but are weak even in these cases, because the latitudinal gradient of radiative heating is weak. Seasonal effects on Uranus are extremely weak because the radiative time constant is longer that the orbital period. One free parameter in the model is the frictional time constant. Comparison with observed temperature perturbations over zonal currents in the troposphere shows that the frictional time constant is on the same order as the radiative time constant for all these objects. Vertical motions predicted by the model are extremely weak. They are much smaller than one scale height per orbital period, except in the immediate neighborhood of tropospheric and zonal currents.
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    Type: NASA-CR-184826 , NAS 1.26:184826
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    Trace gases in the atmosphere of Mars - An indicator of microbial life (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The detection of certain trace gases in the atmosphere of Mars would indicate the presence of microbial life on the surface. Candidate biogenic gases include CH4, NH3, N2O, and several reduced sulfur species. Chemical thermodynamic equilibrium and photochemical calculations preclude the presence of these gases in any measurable concentrations in the atmosphere of Mars in the absence of biogenic production. A search for these gases utilizing either high-resolution (spectral and spatial) spectroscopy from a Mars orbiter, such as the Mars Observer orbiter, and/or in situ measurements from a Mars lander or rover is proposed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AAS PAPER 87-247
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  • 184
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    Mars soil - A sterile regolith or a medium for plant growth? (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The mineralogical composition and the physical, chemical and mechanical properties of the Mars soil have been the subject of a number of studies. Though definitive mineralogical measurements are lacking, elemental-chemical analyses and simulation experiments have indicated that clays are major components of the soil and that iron is present as adsorbed ion and as amorphous mineral coating the clay particles (Banin, 1986). Whether this soil can support plant growth or food production, utilizing conventional or advanced cultivational technologies, is a question that has not been thoroughly analyzed, but may be of importance and usefulness for the future exploration of Mars. Assuming that the proposed model of Mars soil components is valid, and drawing additional information from the analyses of the SNC meteorites believed to be ejected Mars rocks - the present contribution analyzes and evaluates the suitability of the soil as a medium for plant growth, attempting to identify the most critical limiting factors for such an undertaking and the possible remedies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AAS PAPER 87-215
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  • 185
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    An aeronomy mission to investigate the entry and orbiter environment of Mars (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The need for an aeronomy mission to Mars as a precursor to a manned Mars mission is discussed. The upper atmosphere and radiation environment of Mars are reviewed, focusing on the implications of the Martian atmosphere for a manned mission. Plans for an aeronomy mission to Mars are described, including the Mars Aeronomy Observer and the Earth/Mars Aeronomy Orbiter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AAS PAPER 87-196
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  • 186
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    The Voyager 2 mission to Neptune (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Voyager 2 and its twin, Voyager 1, were launched in 1977. Both spacecraft investigated Jupiter's and Saturn's systems. Voyager 2 continued on to fly past Utranus in 1986 and Neptune in 1989, while Voyager 1 headed out of the solar system. The mission at Neptune presented many engineering and scientific challenges. Neptune is about 30 Astronomical Units (AU) from the sun and earth, resulting in extremely low lights levels (nearly 1000 times lower than at earth) and in communication distances of nearly 4.5 billion kilometers. To compensate for the long communication distances, several new techniques were developed. As at Uranus, an onboard backup computer compressed the imaging data. In addition, the data return was further improved by electronically arraying and expanding several receiving antennas. As a result, the data rates from Neptune were about the same as they were from Saturn, even though the distance was three times greater. Several changes were made in the onboard software to optimize Voyager's operations at the very low light levels at Neptune. Finally, to obtain the maximum information from the Neptune encounter, a trajectory was selected which passed within just 5000 kilometers of Neptune's atmosphere, but which also posed several possible environmental hazards.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: IAF PAPER 89-471
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  • 187
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    Venus volcanism: Rate estimates from laboratory studies of sulfur gas-solid reactions (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Thermochemical reactions between sulfur-bearing gases in the atmosphere of Venus and calcium-, iron-, magnesium-, and sulfur-bearing minerals on the surface of Venus are an integral part of a hypothesized cycle of thermochemical and photochemical reactions responsible for the maintenance of the global sulfuric acid cloud cover on Venus. SO2 is continually removed from the Venus atmosphere by reaction with calcium bearing minerals on the planet's surface. The rate of volcanism required to balance SO2 depletion by reactions with calcium bearing minerals on the Venus surface can therefore be deduced from a knowledge of the relevant gas-solid reaction rates combined with reasonable assumptions about the sulfur content of the erupted material (gas + magma). A laboratory program was carried out to measure the rates of reaction between SO2 and possible crustal minerals on Venus. The reaction of CaCO3(calcite) + SO2 yields CaSO4 (anhydrite) + CO was studied. Brief results are given.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 8-9
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  • 188
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    Neptune's Triton: A moon rich in dry ice and carbon (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The encounter of the spacecraft Voyager 2 with Neptune and its large satellite Triton in August 1989 will provide a crucial test of ideas regarding the origin and chemical composition of the outer solar system. In this pre-encounter publication, the possibility is quantified that Titron is a captured moon which, like Pluto and Charon, originally condensed as a major planetesimal within the gas ring that was shed by the contracting protosolar cloud at Neptune's orbit. Ideas of supersonic convective turbulence are used to compute the gas pressure, temperature and rat of catalytic synthesis of CH4, CO2, and C(s) within the protosolar cloud, assuming that all C is initially present as CO. The calculations lead to a unique composition for Triton, Pluto, Charon: each body consists of, by mass, 18 1/2 percent solid CO2 ice, 4 percent graphite, 1/2 percent CH4 ice, 29 percent methanated water ice and 48 percent of anhydrous rock. This mix has a density consistent with that of the Pluto-Charon system and yields a predicted mean density for Triton of 2.20 + or - 0.5 g/cu cm, for satellite radius equal to 1,750 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-186298 , NAS 1.26:186298 , JPL-PUBL-89-37
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  • 189
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    The Apollo 15 coarse fines (4-10 mm) (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A new catalog of the Apollo 15 coarse fines particles is presented. Powell's macroscopic descriptions, resulting from his 1972 particle by particle binocular examination of all of the Apollo 15 4 to 10 mm fines samples, are retained. His groupings are also retained, but petrographic, chemical, and other data from later analyses are incorporated into this catalog to better characterize individual particles and describe the groups. A large number of particles have no characterization beyond that done by Powell. Complete descriptions of the particles and all known references are provided. The catalog is intended for anyone interested in the rock types collected by Dave Scott and Jim Irwin in the Hadley-Appenine region, and particularly for researchers requiring sample allocations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-101934 , JSC-24035 , NAS 1.15:101934 , PSB-PUBL-81
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  • 190
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    CIS-lunar space infrastructure lunar technologies: Executive summary (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Technologies necessary for the creation of a cis-Lunar infrastructure, namely: (1) automation and robotics; (2) life support systems; (3) fluid management; (4) propulsion; and (5) rotating technologies, are explored. The technological focal point is on the development of automated and robotic systems for the implementation of a Lunar Oasis produced by Automation and Robotics (LOAR). Under direction from the NASA Office of Exploration, automation and robotics were extensively utilized as an initiating stage in the return to the Moon. A pair of autonomous rovers, modular in design and built from interchangeable and specialized components, is proposed. Utilizing a buddy system, these rovers will be able to support each other and to enhance their individual capabilities. One rover primarily explores and maps while the second rover tests the feasibility of various materials-processing techniques. The automated missions emphasize availability and potential uses of Lunar resources, and the deployment and operations of the LOAR program. An experimental bio-volume is put into place as the precursor to a Lunar environmentally controlled life support system. The bio-volume will determine the reproduction, growth and production characteristics of various life forms housed on the Lunar surface. Physicochemical regenerative technologies and stored resources will be used to buffer biological disturbances of the bio-volume environment. The in situ Lunar resources will be both tested and used within this bio-volume. Second phase development on the Lunar surface calls for manned operations. Repairs and re-configuration of the initial framework will ensue. An autonomously-initiated manned Lunar oasis can become an essential component of the United States space program.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-186220 , NAS 1.26:186220
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  • 191
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    M.I.N.G., Mars Investment for a New Generation: Robotic construction of a permanently manned Mars base (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A basic procedure for robotically constructing a manned Mars base is outlined. The research procedure was divided into three areas: environment, robotics, and habitat. The base as designed will consist of these components: two power plants, communication facilities, a habitat complex, and a hangar, a garage, recreation and manufacturing facilities. The power plants will be self-contained nuclear fission reactors placed approx. 1 km from the base for safety considerations. The base communication system will use a combination of orbiting satellites and surface relay stations. This system is necessary for robotic contact with Phobos and any future communication requirements. The habitat complex will consist of six self-contained modules: core, biosphere, science, living quarters, galley/storage, and a sick bay which will be brought from Phobos. The complex will be set into an excavated hole and covered with approximately 0.5 m of sandbags to provide radiation protection for the astronauts. The recreation, hangar, garage, and manufacturing facilities will each be transformed from the four one-way landers. The complete complex will be built by autonomous, artificially intelligent robots. Robots incorporated into the design are as follows: Large Modular Construction Robots with detachable arms capable of large scale construction activities; Small Maneuverable Robotic Servicers capable of performing delicate tasks normally requiring a suited astronaut; and a trailer vehicle with modular type attachments to complete specific tasks; and finally, Mobile Autonomous Rechargeable Transporters capable of transferring air and water from the manufacturing facility to the habitat complex.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-186224 , NAS 1.26:186224
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  • 192
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    Reexamination of data from the asteroid/meteoroid detector (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The discovery of the existence of cosmoids, a class of meteoroid in near hyperbolic orbits, was made in a reevaluation of the Sisyphus Experiment on Pioneer 10 and 11. This experiment measured the spontaneous jetting of cosmoids and showed that the dispersion and increase in brightness occurs in microseconds and lasts only briefly. Cosmoid jetting caused multiple telescope thresholds to be exceeded simultaneously which explains the earlier inabilty to compute trajectories from the measured times in the fields of view. A new calculation correlated the Sisyphus individual event measurements with the zodiacal light. That the meteoroid population is dominated by cosmoids is demonstrated. Reported telescopic small comets, measured by a similar optical technique, appear consistent with the Sisyphus results. Characteristic jetting times measured by Sisyphus also show that the volatile cosmoids could not survive in short period orbits.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-185997 , NAS 1.26:185997
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  • 193
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    Radar scattering mechanisms within the meteor crater ejecta blanket: Geologic implications and relevance to Venus (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: Simple impact craters are known to occur on all of the terrestrial planets and the morphologic expression of their ejecta blankets is a reliable indicator of their relative ages on the Moon, Mars, Mercury, and most recently for Venus. It will be crucial for the interpretation of the geology of Venus to develop a reliable means of distinguishing smaller impact landforms from volcanic collapse and explosion craters, and further to use the observed SAR characteristics of crater ejecta blankets (CEB) as a means of relative age estimation. With these concepts in mind, a study was initiated of the quantitative SAR textural characteristics of the ejecta blanket preserved at Meteor Crater, Arizona, the well studied 1.2 km diameter simple crater that formed approx. 49,000 years ago from the impact of an octahedrite bolide. While Meteor Crater was formed as the result of an impact into wind and water lain sediments and has undergone recognizable water and wind related erosion, it nonetheless represents the only well studied simple impact crater on Earth with a reasonably preserved CEB. Whether the scattering behavior of the CEB can provide an independent perspective on its preservation state and style of erosion is explored. Finally, airborne laser altimeter profiles of the microtopography of the Meteor Crater CEB were used to further quantify the subradar pizel scale topographic slopes and RMS height variations for comparisons with the scattering mechanisms computed from SAR polarimetry. A preliminary assessment was summarized of the L-band radar scattering mechanisms within the Meteor Crater CEB as derived from a NASA/JPL DC-8 SAR Polarimetry dataset acquired in 1988, and the dominant scattering behavior was compared with microtopographic data (laser altimeter profiles and 1:10,000 scale topographic maps).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 19-20
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  • 194
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    Phoebe: A preliminary control network and rotational elements (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A preliminary control network for the Saturnian satellite Phoebe was determined based upon 6 distinct albedo features mapped on 16 Voyager 2 images. Using an existing map and an analytical triangulation program which minimized the measurement error, the north pole of Phoebe was calculated to be alpha sub 0 = 355.0 deg + or - 9.6 deg, delta sub 0 = 68.7 deg + or - 7.9 deg, where alpha sub 0, delta sub 0 are standard equatorial coordinates with equinox J2000 at epoch J2000. The prime meridian of Phoebe was computed to be W = 304.7 deg + 930.833872d, where d is the interval in days from JD 2451545.0 TDB.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-185716 , NAS 1.26:185716 , N-2934-NASA
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  • 195
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    The 'sample experiment' on the Mars Rover/Sample Return mission (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Sample Experiment denotes the set of all operations that include collection, analysis, packaging, and environmental control of atmospheric and geologic samples of Mars. Various functions may be distributed among surface roving vehicles, stationary landers, and spacecraft but the Sample Experiment remains an integrated mission activity that extends from Mars landing through delivery of the sample payload to the recieving facility on Earth. Technological challenges not faced in previous planetary missions include development of robotic systems to manipulate and characterize samples and to reliably seal them in containers with minimal contamination or degradation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AIAA PAPER 89-0423
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  • 196
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    Mars Rover Sample Return mission (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: To gain a detailed understanding of the character of the planet Mars, it is necessary to send vehicle to the surface and return selected samples for intensive study in earth laboratories. Toward that end, studies have been underway for several years to determine the technically feasible means for exploring the surface and returning selected samples. This paper describes several MRSR mission concepts that have emerged from the most recent studies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AIAA PAPER 89-0417
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  • 197
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    Conceptual design of the Mars Rover Sample Return system (1989)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The results of the prephase A study of the Mars Rover Sample Return system are presented. Four mission scenarios are studied, two in the B-configuration, and two D-configuration missions. They incorporated variations in delivery-to-Mars mode, earth-return mode (propulsive or aerocapture), landing site latitude, and rover size and capability in order to identify system drivers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AIAA PAPER 89-0418
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  • 198
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    The Cassini mission: Infrared and microwave spectroscopic measurements (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: The Cassini Orbiter and Titan Probe model payloads include a number of infrared and microwave instruments. This document describes: (1) the fundamental scientific objectives for Saturn and Titan which can be addressed by infrared and microwave instrumentation, (2) the instrument requirements and the accompanying instruments, and (3) the synergism resulting from the comprehensive coverage of the total infrared and microwave spectrum by the complement of individual instruments. The baseline consists of four instruments on the orbiter and two on the Titan probe. The orbiter infrared instruments are: (1) a microwave spectrometer and radiometer; (2) a far to mid-infrared spectrometer; (3) a pressure modulation gas correlation spectrometer, and (4) a near-infrared grating spectrometer. The two Titan probe infrared instruments are: (1) a near-infrared instrument, and (2) a tunable diode laser infrared absorption spectrometer and nephelometer.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-RP-1213 , NAS 1.61:1213 , REPT-89B0006
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  • 199
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    A lunar space station (1989)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A concept for a space station to be placed in low lunar orbit in support of the eventual establishment of a permanent moon base is proposed. This space station would have several functions: (1) a complete support facility for the maintenance of the permanent moon base and its population; (2) an orbital docking area to facilitate the ferrying of materials and personnel to and from Earth; (3) a zero gravity factory using lunar raw materials to grow superior GaAs crystals for use in semiconductors and mass produce inexpensive fiber glass; and (4) a space garden for the benefit of the air food cycles. The mission scenario, design requirements, and technology needs and developments are included as part of the proposal.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-186223 , NAS 1.26:186223
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  • 200
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    Classification of IRAS asteroids (1989)
    In:  Other Sources
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    Publication Date: 2019-07-13
    Description: The results of analyses of IRAS-derived asteroid albedos are presented, and their application to asteroid classification is discussed. It is noted that, while most IRAS-derived albedos are reliable, a substantial fraction of albedos lack needed corrections (e.g., for flux overestimation), and a few may be erroneous. The three-parameter taxonomic system introduced by Tedesco et al. (1989) uses only albedos based on well-observed IRAS asteroids; in this system, eleven taxonomic classes are defined on the basis of asteroid spectrum and its albedo.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Asteroids II; Mar 08, 1988 - Mar 11, 1988; Tucson, AZ; United States
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