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  • LUNAR AND PLANETARY EXPLORATION  (715)
  • 1985-1989  (715)
  • 1980-1984
  • 1985  (715)
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  • 1985-1989  (715)
  • 1980-1984
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  • 101
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    On the Latitudinal Distribution of Debris in the Northern Hemisphere of Mars (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-08
    Beschreibung: Examination of Mariner 9 images showed evidence of debris mantling on Mars. The evidence included craters that appeared to be filled with debris and an apparent lack of small craters. Based on such data, it was suggested that a circumpolar debris mantle exists poleward of about 30N and 30S latitudes. The presence of a debris layer has important implications for the modulation over time of atmospheric pressure by the cap-regolith-atmosphere system. Preliminary efforts in providing constraints on the thickness and distribution of debris are discussed. The initial approach is to examine crater size-frequency data for selected regions on Mars, later expanding the study to include an inventory of aeolian features and other direct indicators of debris deposition. The crater size-frequency distributions for ten regions between latitudes 20N and 80N and covering a range of longitudes were discovered. Crater data were derived from Viking Orbiter images with resolutions of between 26 and 75 meters/pixel.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 297-299
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  • 102
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    Investigations of Planetary Ring Phenomena (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-30
    Beschreibung: The structure of Jupiter's rings was studied in an effort to understand the processes that generate the rings. The faint material in the Saturn system was investigated leading to the discovery of a new ring and a way to interpret the wavy features surrounding Encke's division in terms of perturbing moonlets. The interaction of faint rings and magnetospheres helped identify some of the charged particle absorbers seen by Pioneer 11 in the neighborhood of the F ring. Angular momentum drain might account for the slow rotations of intermediate sized asteroids. Much of the Jovian ring structure can be understood in terms of debris loss from satellites, rapid orbital evolution, resonance, and charged dust dynamics.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 35-37
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  • 103
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    Patterns of Fracture and Tidal Stresses Due to Nonsynchronous Rotation: Implications for Fracturing on Europa (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-30
    Beschreibung: Global lineaments on Europa were interpreted as fractures in an icy crust. A variety of lineament types were identified, which appear to form a systematic pattern on the surface. For a synchronously rotating body, the patterns of fractures observed could be produced by a combination of stresses due to orbital recession, orbital eccentricity, and internal contraction. However, it was recently suggested that the forced eccentricity of Europa's orbit may result in nonsynchronous rotation. The hypothesis that fractures in a thin icy crust may have formed in response to stresses resulting from nonsynchronous rotation is studied.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 24-26
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  • 104
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    Geomorphic Classification of Lava Flows on Io (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-30
    Beschreibung: The lava flows on Io are classified into the following categories: broad, filamental, digitate, intercalated, sheet, and contained. Each classification is described according to flow distribution, geomorphology, color, thickness, and source.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 15-19
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  • 105
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    Ripple Ring Basins on Ganymede and Callisto (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-09-27
    Beschreibung: The unusual morphology of the Valhalla multiple or ripple-ring basin in Callisto was totally unexpected in light of the morphologies of large impact structures on the terrestrial planets. Two other ripple-ring basins (RRB's), Asgard and a smaller structure near the crater Adlinda are also described. Several additional RRB's were found on Callisto, an example of which is shown. A previously unrecognized RRB on Ganymede was also found. An image and geologic sketch map of this RRB are shown. Morphometric and positional data for all known RRB's are given.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 206-208
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  • 106
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    The Control Network of Mars: October 1984 (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: Strips of Viking mapping pictures are being added to the planetwide control networks of Mars. These high resolution strips run from the Viking 1 lander site east to Airy-O, north along the 0 deg meridian to 60 deg latitude, southwest through the Viking 1 lander site to the equator, and along the equator encircling the planet. Everywhere along these strips, old points are incorporated in the measurements, thus assuring that the strips and planetwide net make a single large data set. The control points are much denser in the areas covered by the strips than in those regions not covered by strips and their coordinates of the control points is estimated to be less than 3 km and the error in longitude of a few points near Airy-O is less than 40 m. The horizontal coordinates of the control points on Mars have been updated with a single-block planetwide analytical triangulation. The standard error of measurement was 18.06 micron m. The longitude of the Viking 1 lander site was 47 deg.962 and the latitude 22 deg. 480. The latitude of Airy-O was -5 deg. 152.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 558
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  • 107
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    A Unified Lunar Control Network (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: A unified network program can tie independent regional networks into a single consistent planetwide control network. The Apollo 15, 16, and 17 ALSEP stations were identified on Apollo panorama photography and their locations transferred to Apollo mapping frames. Two primary control networks were computed based on the Apollo mapping pictures. Although these systems were computed relative to the center-of-mass, it was necessary to translate their origins to best-fit the ALSEP locations. The DMAAC/A15 system was translated 299 + or - 165 m and the NOS/USGS system was translated 2033 + or - 575 m. Many control networks have been computed based on pictures of the Moon taken through telescopes; these cover the Earth-facing region. Points common to the Apollo networks and to a telescopic network (Meyer, 1980) were selected. Using these points in the overlapping region of the two networks, best-fit translation, rotation, and scale parameters are computed to adjust the telescopic net to the Apollo net. As a start, ten well distributed points have been selected and parameters determined to adjust the telescopic network to the translated DMAAC/A15 system and the NOS/USGS system. The goodness of fit has not yet been examined.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 556-557
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  • 108
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    Viking Lander Mosaics of Mars (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: The Viking Lander 1 and 2 cameras acquired many high-resolution pictures of the Chryse Planitia and Utopia Planitia landing sites. Based on computer-processed data of a selected number of these pictures, eight high-resolution mosaics were published by the U.S. Geological Survey as part of the Atlas of Mars, Miscellaneous Investigation Series. The mosaics are composites of the best picture elements (pixels) of all the Lander pictures used. Each complete mosaic extends 342.5 deg in azimuth, from approximately 5 deg above the horizon to 60 deg below, and incorporates approximately 15 million pixels. Each mosaic is shown in a set of five sheets. One sheet contains the full panorama from one camera taken in either morning or evening. The other four sheets show sectors of the panorama at an enlarged scale; when joined together they make a panorama approximately 2' X 9'.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 552-553
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  • 109
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    Voyager Cartography (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: The Jovian and Saturnian satellites are being mapped at several scales from Voyager 1 and 2 data. The maps include specially formatted color mosaics, controlled photomosaics, and airbrush maps. More than 500 Voyager images of the Jovian and Saturnian satellites were radiometrically processed in preparation for cartographic processing. Of these images, 235 were geometrically transformed to map projections for base mosaic compilations. Special techniques for producing hybrid photomosaic/airbrush maps of Callisto are under investigation. The techniques involve making controlled computer mosaics of all available images with highest resolution images superimposed on lowest resolution images. The mosaics are then improved by airbrushing: seams and artifacts are removed, and image details enhanced that had been lost by saturation in some images. A controlled mosaic of the northern hemisphere of Rhea is complete, as is all processing for a similar mosaic of the equatorial region. Current plans and status of the various series are shown in a table.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 554-555
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  • 110
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    Mars Planimetric Mapping (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: The 1:5,000,000 scale shaded relief maps of Mars originally compiled from Mariner 9 pictures are being upgraded by adding details visible on Viking Orbiter images. This work is done by modifying the original airbrush drawings; no attempt is made to reposition features according to the latest control nets. Thirteen of these maps have been published to date, two are in compilation, and two are in press. A hard cover atlas containing reduced scale versions of all Mars cartographic products will be published upon completion of the revisions of the 1:5,000,000 scale maps, the 1:2,000,000 scale photomosaics, and Mars color albedo mapping tasks. This atlas will supersede the existing Atlas of Mars prepared by Batson and others.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 548-549
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  • 111
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    Geology of the Ganymede Quadrangle Jg7 (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: The western half of Ganymede quadrangle Jg7 is covered by Voyager 2 images with resolution of .5 to 5 km/pixel. The imaged area includes dark terrain in the north underlying the southeastern part of Galileo Regio, and light terrain in the south underlying the southeastern extension of Uruk Sulcus. Several slivers and wedges of dark terrain occur within the light areas. Numerous craters are present, as well as three large palimsests (crater scars with little topographic expression) in the dark terrain and a basin in the light terrain. The boundary between dark and light materials on the south side of Galileo Regio is locally marked by a scarp that faces the light terrain. The scarp truncates several craters. The truncation and rotation of structures suggest that light material grew at the expense of dark material, and that the destruction, except for minor pivoting, was essentially in situ. The composition and structural properties of the palimsests and craters are examined.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 546-547
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  • 112
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    The Galilean Satellite Geological Mapping Program, 1984 (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: About 40 investigators from various universities, research institutes, and government offices in the United States, England, Germany, and Italy are compiling maps of the Galilean satellites. All maps are at a scale of 1:5 million except for three of the Io maps, where high resolution pictures permit compilation of selected areas at larger scales. Guidelines for mapping Ganymede are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 544-545
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  • 113
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    Tectonics of the Valhalla Structure on Callisto (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: The surficial morphology of Callisto is dominated by large concentric patterns of ridges, scarps, and furrows. The largest one, Valhalla, shows a smooth central area 350 km in radius, surrounded by concentric sinuous ridges which extend as far as 600km from the center. Beyond the ridged area, scarps and furrows are observed as far as 2000 km. The global azimuthal distribution of the scarps and furrows of the outer ring (beyond 700 km from the center) was analyzed. It is proposed that the local geometry and the global distribution of scarps and furrows around Valhalla are the results of the reactivation of an old pattern by the Valhalla event. The coincidence of these local directions of a preexisting pattern (NW-SE and NE-SW) with the directions of the grids observed on most bodies observed so far in the solar system would indicate that this local pattern is a part of a global calistean grid.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 535-539
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  • 114
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    Mars Geologic Mapping: a Review and New Concepts (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: The final version of the 1.15 m scale geologic map of the western equatorial region of Mars based on Viking pictures has been completed in open file format. Geologic maps of the north and south polar regions were completed in provisional form. A map of the eastern equatorial region is in compilation. Evidences of erosion, water flooding, volcanic activity, and primary and satellite craters in these areas are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 541-543
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  • 115
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    Importance of the Tectonic Motions on Ganymede (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: Voyager close up views of Ganymede reveal some provinces of old, cratered, dark terrains that are broken into polygons and cut through by light stripes of grooved terrains. The groove terrain unit and its relationships with the other units was studied at various scales because these features seem to relate at least to two main scales of processes. Minor displacements concerning only local features, i.e., large scale processes and major displacements concerning usually the major evolution of the surface, i.e., small scale processes. It appears that tectonic processes, at least in the studied areas, if playing a role in the formation of local or regional features, are very limited. The conclusions reached agree with those of Thomas et al. who show that post grooves basins reveal the presence of a primitive grid that is not disturbed by the grooved terrains.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 531-534
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  • 116
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    Tectonics of the Galileo Regio on Ganymede (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: The surface of Ganymede consists of dark cratered terrain, and groved terrain. The dark cratered terrains form polygonal units, the largest of which is Galileo Regio, the surface of which is transected by furrows, smooth floored valleys bounded by relatively sharp parallel ridges. The most apparent of them are grouped together and form an apparently arcuate system of subparallel furrows which was mapped using Voyager pictures and plotted on a map using a stereographic projection. With this kind of projection, the main furrow system is not arcuate, but rectilinear. Observations strongly suggest that the Galileo Regio furrow systems are not of impact origin and appear to be irrelevant to discussions about the basins' morphology or evolution of planetary lithosphere determined from multiring structures.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 528-530
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  • 117
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    Global Tectonics on Ganymede (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: Three large basin surroundings on Ganymede located on grooved terrains, which are supposed to be intensely tectonized areas were studied. All rectilinear morphological elements such as ridges, block edges; and parts of scarps were mapped. The geometric properties (grid pattern) characteristics were determined and a history for the formation of the Ganymede basins studied is proposed. Results indicate that the grooved terrains are very surficial layers, and that their formation does not significantly affect, disturb or rotate the basement. This is in agreement with the conclusion obtained from completely different data (crosscutting relationships between groove sets and their basements).
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 525-527
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  • 118
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    Correction and Geological Analysis of Lunar 3.8 Cm Radar Data (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: Earth based radar observations of the Moon have been taken at many wavelengths during the last ten years -- at 3.8, 70 cm, and most recently, 7.5 cm. Radar returns have been collected in both polarized and depolarized form so that is possible to derive both topographic and local surface roughness from the data. Until recently, work with 3.8 cm radar data had consisted of qualitative correlation of photographic and thermal IR data with individual depolarized radar data frames (local surface roughness) at different wavelengths. These studies provided results which demonstrated that the relationships between surface roughness (measured by either thermal emission or radar reflectivity) at different wavelengths can be used as an index of a crater's state of degradation (age). However, systematic studies of craters, or other local terrain features, as well as regional or global studies of major terrains (involving a number of data frames), cannot be done until individual frames are calibrated, geometric distortion is removed, and corrected frames are mosaicked.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 456-457
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  • 119
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    Mapping and Geological Analysis of Mercury and Venus Radar Ranging Data (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-09
    Beschreibung: Although many radar profiles and images of the areas within 20 deg of Mercury's equator had been obtained from 1971, at both Goldstone and Arecibo radar facilities, surprisingly little geological analysis had been done with these data until recently. Topographic profiles and radar roughness reflectivity images which can be derived from these data will be crucial in completing the geological mapping of Mercury now underway at the U.S. Geological Survey. Earth based radar observations of Mercury and the other terrestrial planets as well are a potentially very valuable tool in the determination of the physical nature of their surfaces. Processing of available radar data must be completed to establish any systematic relationship between raar reflectivities and roughness, density, dielectric constant, and other related geological parameters.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 453-455
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  • 120
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    Unsupervised Classification of Global Radar Units on Venus (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: Characterization of the Venusian surface in terms of its radar properties was accomplished by application of an unsupervised, linear discriminant algorithm to two Pioneer-Venus (PV) Orbiter radar data sets: the RMS-slope (surface roughness) and reflectivity. Both databases were spatially filtered to the same effective resolution of 100 km prior to classification. A recent supervised classification study using these data was based on presupposed morphologic significance of selected data ranges. The knowledge of both Venusian geology and the geologic significance of the radar data is so limited that the data warrant a more unsupervised approach; for this study a linear discriminant classifier was chosen. This approach is purely statistical, thereby removing any observer bias. Statistical significance of the resulting clusters was evaluated by an ancillary program in which an F test utilizing the Mahalanobis' distance.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 450-452
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  • 121
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    Mercury radar altimetry: A preliminary analysis (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: Range-Doppler radar observations were made of the planet Mercury over the six year period 1978-1983. Approximately 30 continuous altitude profiles were obtained, each spanning between 20 and 90 degrees of longitude. The profiles are located in the equatorial zone of Mercury between 5 deg S and 12 deg N latitude. Approximately 40% of the total coverage is in the unimaged hemisphere.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 448-449
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  • 122
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    Progress in Planetary Radarclinometry (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: Efforts have continued to improve radarclinometry in spite of the fact that the theory and algorithms still predate the development of the radiometrically calibrated radar upon which they must depend in order to achieve metric precision. Such efforts help to insure the availability of the technique for data returned by the Venus Radar Mapper. Even now, compensation for layover and production of synthesized stereo enhance geologic interpretability of radar images. The theory of radarclinometry utilizes a knowledge of the relation between pixel DN value and terrain surface orientation to produce a topographic map. The process may be conceived in terms of a surface integral which develops away from a topographic profile as available ground truth. Alternatively, in consideration of the unavailability of ground truth in extraterrestrial applications, radarclinometry may develop as a line integral developing from a single point, providing reasonable assumptions about the mathematical nature of local curvature.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 445-447
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  • 123
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    Quantitative Analyses of Planetary Reflectance Spectra (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: The development of a set of quantitative models to analyze planetary reflectance spectra as a function of microscopic and macroscopic mineral mixtures, particle size, and illumination geometry is considered. The approach has been to simplify more sophisticated algorithms to include the smallest number of parameters possible, consistent with being able to use them to produce useful results. This means that they should be able to model the data to within the accuracy obtainable by laboratory, telescopic, and space instrumentation (roughly 1%). The algorithms are ideally given in terms of parameters that are directly measureable (such as spectral reflectance or particle size).
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 429-431
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  • 124
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    Basalts of Mars: Constraints on Volatile Evolution (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: The mineralogy of relatively unweathered rocks on Mars place important constraints on models of planetary oxidation state, volcanism and associated outgassing, accretion and associated volatile inventory, and geochemical changes over time. Reflectance spectra (300 to 2500 nm) provide direct mineralogic information about the surface materials. Spectra measured using Earth-based telescopes were analyzed by a multiple high-order derivative spectroscopy technique. Nine areas, measured during the 1978 opposition, were analyzed by the technique. Each contained suites of well-defined absorption bands. These bands can be interpreted in terms of constituent mineralogy by the technique of Adams. Among the features extracted from the spectra were bands attributed to iron oxides. Other bands can be attributed to silicates within chemically unweathered rocks/fines. Absorption features suggest the presence of Mg-olivine and plagioclase feldspar.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 387-388
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  • 125
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    Iron Oxides of Mars: Evidence for Contemporary Weathering (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: Reflectance spectra of Mars were analyzed using a multiple high order derivative spectroscopy technique. Among the results of the analysis was the presence of suites of bands in each of the spectra that can be attributed to Fe(3e) phases. Several of the spectra contained bands that are very close to the band positions in the laboratory spectra of goethite, an hexagonal hydrated ferric oxide. Spectra of other areas showed absorption bands that were within 3% of the positions for hematite, and hexagonal close packed unhydrated Fe203. Remaining areas showed bands that are intermediate in position to the goethite and hematite bands, suggesting that there may be mixtures of goethite and hematite, and/or intermediate (partially dehydrated goethite) phases present in those areas. Both bright areas and dark areas showed suites of goethite bands and hematite bands, and there does not therefore appear to be a correlation with albedo. The areas that showed the goethite bands are, however, within zones of ongoing or historically frequent dust cloud activity, and the areas with the hematite bands were outside of the zones of frequent dust cloud activity. This suggests the possiblility that the more hydrated phase may occur within a mobile dust component.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 393-394
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    The Search for Igneous Materials at the Viking Landing Sites (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: The use of Viking Lander 6 channel (0.4 to 1.1 microns) images to identify igneous materials is discussed. Movies of synthetic image cubes demonstrate that there are a number of contrast reversals between soils and certain rocks. Typically, large, angular rocks are brighter than the surrounding soils in the shortest wavelengths, and much darker than the soils at longest wavelengths. These results, which seem difficult to explain solely on the basis of photometric effects related to local lighting and viewing, are consistent with the presence of Fe+2 bearing silicates at the rock surfaces, producing relatively moderate absorptions in the blue and green parts of the spectrum, but more significant absorptions near about 1.0 micrometer (e.g., Fe+2 bearing pyroxenes). The soils, on the other hand, have signatures consistent with strong Fe+3 related absorptions at shorter wavelengths (e.g., Fe+3 bearing oxides or hydroxides).
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 385-386
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    Geologic Interpretation of Remote Sensing Data for the Martian Volcano, Ascraeus Mons (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: Results of an investigation to relate remotely determined physical properties on Ascraeus Mons to the geologic history of the volcano are summarized. Products include a 1:2,000,000-scale photogeologic map of Ascraeus Mons and its environs; a 1:250,000-scale corrected thermal-inertia map of the summit caldera complex; four corrected thermal-inertia profiles across the volcano from high-resolution thermal data; fourteen low-resolution thermal sequences providing corrected thermal inertias for the volcano throughout half a Martian year; and a calibrated three-color photograph of the volcano. These data were combined with published spectral-reflectance, radar, and atmospheric water-vapor data relating to Acraeus Mons. Photogeologic mapping indicates that the sequence of events at Acraeus Mons is more complex than previously described. The plains surrounding the volcano include numerous flows, some of which can be traced to the flank of the volcano and some to different locations along the Tharsis Ridge. Surface morphology in the summit area is very distinct for features 100 m in scale, but the surface relief and tonal contrast steadily decrease toward the base of the shield, indicating modification by deposition or erosion.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 383-384
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    Multispectral Analysis of the Kasei Vallis-lanae Planum Region of Mars (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: The surficial geology of the Kasei Vallis - Lunae Planum region of Mars was investigated using the three color Viking Orbiter 1 data. Spatial resolution is 820m and Ls = 100 deg, a season of low atmospheric and and surface dustiness. This region was chosen for high quality color and thermal inertia data as well as for the diversity of volcanic plains and fluvial landform. The data was reformatted to Mercator projection and calibrated to normal reflectance using in flight calibration parameters and observed photometric properties. Color properties from this image are displayed in two forms: the Red Albedo vs. Violet Albedo two dimensional histogram, and representative 3 point spectra. Virtually the full range of regolith color properties known from prior research is represented, plus some new characteristics. Interpretations of the data are presented which address general composition and formation processes of channel and intracrater deposits.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 381-382
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    Distribution and Properties of Large Symmetric Knobs on Mars (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: Knobby terrain on Mars exists in a variety of forms from small closely spaced hills to widely separated large massifs. Fractional areal distributions of knobby terrain range from over 49% of the sampled area in regions of chaotic terrain to less than 5% along the cratered highland boundary in Amenthes and Aeolis. All symmetric knobs with long dimensions greater than or equal to 10 km were identified, mapped, and classified by shape. The spatial and dimensional distributions and shape characteristics of these features are discussed. The most common shape is elliptical: 79% of the knobs fall into this category, 11% were circular or round, 6% were triangular or wedge-shaped and the remaining 4% other shapes. All types show a roughly similar trend of rapidly decreasing number with increasing size, such that overall less than 10% of the knobs are larger than 20 km in long dimension. Circular knobs show the steepest fall-off in numbers with increasing diameter. Triangular knobs have a broader maximum with more than 65% falling in the 10 to 14 km range.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 355-357
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    Martian Fretted Terrain Morphometry Interpreted Using Principal Components Analysis (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-09
    Beschreibung: Martian fretted terrain is an extensive area of complex topography characterized by smooth, flat-floor valleys and mesas separated by abrupt escarpments along the boundary of heavily cratered uplands. The Deuteronilus-Protonilus region of the fretted terrain between latitude 35 degrees N and 50 degrees N and between 305 degrees W and 350 degrees W longitude was selected for quantitative landform study with the use of principal components analysis (PCA). The morphometry of upland mesa remnants and debris aprons was digitized with respect to latitude, longitude, and distance from the cratered terrain boundary (CTB). The PCA demonstrates that there are definable spatial variations in morphology with respect to longitude and latitude which suggest that the degradation along the CTB proceeded toward the southwest. The PCA also showed that there are organized relationships within the fretted landforms irrespective of their location. Finally, PCA indicated that an orientation of the degraded mesas exists which may be controlled by structure.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 352-354
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    Investigations of the Mars Cratered Terrain: Smooth Plains Boundary in the Eastern Equatorial Region (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-08
    Beschreibung: As part of an ongoing study to place geologic constraints on, and to interpret the origin of the ancient cratered terrain - smooth plains boundary on Mars, structural features in the eastern hemisphere were mapped, looking at wide-scale variations in aereal percentage of crater vocer and distinctive landforms. Maps and a digitized data set for graben, scarps, ridges and elongate plateaus in the eastern hemisphere were completed for 30 deg N to 30 deg. In the equatorial region, results indicate a marked change from the N oriented ridges north of the boundary to the NW orientations of those in the inter and intracrater plains south of the boundary. The WNW orientation of the boundary itself is matched by similar orientations of graben and scraps in the southern terrain. In order to determine whether outlying plateaus and isolated knobby hills found north of the boundary are formed from material of the ancient cratered terrain, the Viking 2 approach color data were used to discriminate surface materials in the eastern hemisphere. In the southern half of the Amenthes quadrange (MC-14), several correlations exist among surficial spectral reflectance and observed geologic units. Old terrain on the eastern rim of the Isidis basin is much redder than the smooth volcanic plains on either side of the rim, even though the plains unit east of the rim is located several kilometers higher than the plains on the floor of Isidis. Based on statistics derived from the color data, the plains within Isidis were found to differ from those north of the boundary zone.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Geol. and Geophys. Program, 1984; p 350-351
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    Permafrost and Subsurface Ice in the Solar System (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-08
    Beschreibung: The properties and behavior of planetary permafrost are discussed with reference to the ability of such surfaces to sustain loads characteristics of spacecraft landing and planetary bases. In most occurrences, water ice is in close proximity to, or in contact with, finely divided silicate mineral matter. When ice contacts silicate mineral surfaces, a liquid-like, transition zone is created. Its thickness ranges from several hundred Angstron units at temperatures near 0 degrees C to about three Angstrom units at -150 degrees C. When soluble substances are present, the resulting brine enlarges the interfacial zone. When clays are involved, although the interfacial zone may be small, its extent is large. The unfrozen, interfacial water may amount to 100% or more weight at a temperature of -5 degrees C. The presence of this interfacial unfrozen water acts to confer plasticity to permafrost, enabling it to exhibit creep at all imposed levels of stress. Nucleation processes and load-bearing capacity are examined.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 338-343
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    Mapping Structures Characteristic of the Highland Boundary Scarp on Mars (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-08
    Beschreibung: In an effort to shed some light on the processes which have produced the highlands/lowlands boundary scrap on Mars, the global distributions of knobby terrain, detached and separated blocks and mesas, and craters larger than 10 km diameter were mapped. These data were represented as fractional areal percentages of the sample box, which is 2.5 deg high (latitude) along north-south profiles every 5 deg in longitude. The fractional area of crater interiors provides a way of quantitatively characterizing the boundary between cratered highlands and relatively uncratered plains. In the vicinity of the nomimal scarp there is generally good agreement between the dropoff in fractional area of craters and a drop-off in topography. Contoured versions of the fractional area of crater interiors, even at the low resolution imposed by the sample box, show good agreement with the geologic mapping. The most northerly occurrence of detached plateaus and knobby terrain were located in order to test the plausibility of the hypothesis that much of the present day highland boundary scrap is due to southward migration of a former boundary.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 347-349
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    Origin of Martian Polygonal Terrain: Preliminary Results (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-08
    Beschreibung: The morphological characteristics of Martian polygonal terrain, and of the fractures defining the polygons were reviewed. The age relationships between the fractures defining the polygons and the material making up the polygonal terrain of Adamas Labyrinthus will be determined. This involves detailed mapping, with the relative ages of Key map units and the fractures determined by superposition and crater counts. The common occurrence of circular fracture patterns within the polygonal terrain is consistent with differential compaction over crater rims, and is easily accounted for by the tensile stresses that would be reasonably expected to occur in such places.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 332-334
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    Radiation-dominated Snowmelt on Mars (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-08
    Beschreibung: A set of microclimatic conditions conducive to the generation of liquid water is being sought to see whether their requirements are any less stringent than those suggested by the global-climatic models. In particular, the melting of snow and ice in the equatorial zone (where the valley networks are preferentially situated) is investigated with a model that includes detailed infrared radiation transfer between the atmosphere and the snow, penetration of sunlight into the snow, sensible heat transfer to the atmosphere, and water vapor diffusion within the surface boundary layer. IR fluxes are calculated by using pressure and temperature dependent forms for the band absorptances of CO2 and H2O in the spectral range 50 to 2000/cm.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 335-336
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  • 136
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    Fluvial Drainage Basins and Valley Networks: Eastern Margaritifer Sinus, Mars (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-08
    Beschreibung: The fluvial drainage of the eastern Margaritifer Sinus (MC-19NE, SE) and northeastern Argyre (MC-26NE) Quadrangles is dominated by two major longitudinal valley networks, the Parana/Loire system on the east, and the Samara Himera system to the west. It is believed that both of these drainages are through-going to the northwest and debouch into Margaritifer Chaos (general location: 12S, 22.5W). The Parana/Loire drainage is bounded on the east in part by an ancient multi-ringed impact basin. The Parana multi-digitate network drains northwest into a depositional basin, and impact basin floor, characterized by positive relief chaos. It is believed that Loire Vallis heads in the basin; thus Parana and Loire Valles may be treated as one system. Samara Valles heads in the northeastern Argyre Quadrangle and extends as a major truck valley to the northwest. Samara Valles cuts through the hills forming one of the concentric rings of the Ladon impact basin and joins the Himera drainage to trend in a more northerly direction to Margaritifer Chaos. The downstream portion of Himera is considered to be part of the Samara
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 316-318
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    The Origin of Regional Dust Deposits on Mars (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-08
    Beschreibung: Recently, additional evidence was derived from the Viking Infrared Thermal Mapper observations that allows a more complete model for the formation of Low Thermal inertia-high Albedo regions to be proposed. The first observation is that dust appears to be currently accumulating in the low thermal inertia regions. Following each global dust storm a thin layer of dust is deposited globally, as evidenced by an increase in surface albedo seen from orbit and from the Viking Lander sites. During the period following the storm, the bright dust fallout is subsequently removed from low albedo regions, as indicated by the post-storm darkening of these surfaces and by an increase in the atmospheric dust content over dark regions relative to the bright, low thermal inertia regions. Thus, the fine dust storm material is removed from dark regions but not from the bright regions, resulting in a net accumulation within the bright, low thermal inertia regions. Once deposition has begun, the covering of exposed rocks and sand and the accumulation of fine material on the surface make removal of material increasingly difficult, thereby enhancing the likelihood that material will accumulate within the low thermal inertia regions.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA Washington Repts. of Planetary Geol. and Geophys. Program; p 295-296
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    Transformation of Polar Ice Sublimate Residue into Martian Circumpolar Sand (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-08
    Beschreibung: The experimental demonstration that a credible Martian sand may be formed from dust-bearing ice provides a new set of possible explanations for some of the observed Martian aeolian landforms. It is hypothesized that a light-weight fluffy rind is formed on the polar caps. This could provide material easily entrainable by Martian winds, which generally blow equatorward from the poles. These winds would peel the fluffy rind from the surface of the sublimating summer polar caps and from the equatorward slopes of the polar troughs. These pieces of material would then be rolled into lumps (of high sailarea/mass ratio) by the wind. They would become pigmented as they saltate across the surface, perhaps gathering carbonaceous meteoritic dust or other impurities on their surfaces, or through chemical reactions with the ice-free environment away from their point of origin. Once they became trapped in topographic wind shadows, they would form dune structures because they are hydraulically equivalent to sand particles.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 300-302
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    Eolian Erosion on Mars: Three Scales (1985)
    In:  CASI
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    Publikationsdatum: 2014-10-08
    Beschreibung: Formation and erosion of deposits on Mars with vertical scales of 100 to 1,000 meters and horizontal scales of 100 km may have occurred at rates very different from present ones. Evidence for the rates on small scales comes from observations of dust storms and photometry of wind streaks. These observations cover scales less than 1 cm vertically and time scales less than 10 years. Intermediate scale features such as yardangs and sand dunes are more difficult to evaluate, but for dunes, plausible rates of transport may be calculated. Net eolian action in some areas may be so low that in order to study the large features one needs to select those likely to have been modified more rapidly and that exhibit distinctive contrasts with surrounding areas. Best suited for such study are relatively soft deposits overlying more resistant substrates. Viking Orbiter images of four of the largest such areas were examined to test how the erosional features correlate with patterns attributable to winds, properties of deposits, or non-eolian erosion, and for constraints on erosion and transport rates.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 293-294
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    Polar Cap Formation on Ganymede (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: Since thermal migration is not an effective mechanism for water transport in the polar regions at the Galilean satellites, some other process must be responsible for the formation of Ganymede's polar caps. It is proposed that Ganymede's polar caps are the optical manifestation of a process that began with the distribution of an ice sheet over the surface of Ganymede. The combined processes of impact gardening and thermal migration led, in regions at latitudes less than 40 to 45 deg., to the burial of some fraction of this ice, the migration of some to the polar caps margins, and a depletion of free ice in the optical surface. At higher latitudes, no process was effective in removing ice from the optical surface, so the remanants of the sheet are visible today.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 33-34
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    Sulfur Oxygen Processes on Io (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: The presence of allotropic sulfur as a possible major constituent of Io's surface and the properties of sulfur in combination with various sulfur-oxygen compounds believed to be present on Io's surface and in its atmosphere are studied by a series of laboratory experiments.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 20-22
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    Hot Spots on Io: Correlation of Infrared Emission and Visible Reflectance (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: The Voyager 1 infrared spectrometer (IRIS) data and two recently compiled data sets (Voyager imaging mosaics and measurements of Io's thermal emission from the NASA Infrared Telescope Facility) are correlated. These data were used to refine the correlation between dark spot optical properties (albedo and color) and thermal emission, to examine this correspondence on a satellite-wide scale, and to identify additional hot spots not included in the IRIS inventory. The results suggest the hot spots are liquid sulfur lava lakes, for the following reasons: (1) the melting point of sulfur is 390 K, and the model hot spot temperatures range from approximately 200 to 450 K; (2) the albedos and color of the dark spots, measured from the global mosaics, are consistent with laboratory measurements for liquid sulfur; (3) high resolution images of the dark features show morphologies suggestive of lava lakes; and (4) this hypothesis provides a simple and direct explanation for why dark spots are hot on Io.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 3-5
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    Stability of the Galilean Satellites in Deep Orbital Resonance (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: The Galilean satellites are locked in the Laplace resonance, which is responsible for forcing their significant orbital eccentricites. The eccentricites in turn result in tidal energy dissipation within the satellites that is responsible for the great thermal activity on Io, including both volcanism observed by Voyager and heat flux measured from Earth. The resonance results from the nearly 2:1 commensurability of orbital periods (or equivalently of mean motions) taken by pairs. These geometrical relations enhance the mutual gravitational effects. Yoder pointed out that tides raised on Io tend to drive the system out of resonance (toward greater nu and correspondingly smaller eccentricities) while tides raised on Jupiter tend to drive the system towards deeper resonance (smaller nu and larger forced eccentricities). The possible behavior of the system in deep resonance is investigated.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 9-11
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    Io: Generation of Silicate Magma by Shear Melting at the Base of a Basaltic Lithosphere (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: Tidal theory and observational evidence indicates that about 1 w/sq. m. of energy is released at the surface of Io. In order to place limits on how much tidal energy can be dissipated within a rigid lithosphere, depth-temperature profiles were calculated for different lithosphere thickness assuming that the tidal energy was dissipated uniformly throughout the lithosphere. Thus a thick lithosphere implies that a significant fraction of the tidal energy is dissipated below the depth where solidus temperatures are reached. One possibility is that Io has a crust consisting of a low melting temperature fraction such as basalt, overlying a mantle of a high melting temperature fraction such as peridotite. Thus, if the lithosphere of Io is thicker than 30 km, as appears probable, then high rates of silicate volcanism are implied and a significant fraction of the tidal energy must be dissipated by viscous deformation rather than rigid flexure.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 6-8
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    Small Solar System Bodies (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: The feasibility of using ranging data to a spacecraft lander on a synchronously rotating satellite to determine the satellite's orbit, the planet's orbit, the lander coordinates, and the principal term of forced physical librations was studied. Classifications of asteroids into their proper elements and families are also presented. Measurements and reduction of positions on comets and the minor planets with less common orbits was the focus for the astrometry program.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 72-73
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    Study and Estimation of Planet-crossing Asteroid Populations: Discoveries and Analysis (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: The populations of the various classes of planet-crossing asteroids, based on the results of the systematic Planet-Crossing Asteroid Survey (PCAS) search program are evaluated. Knowledge of the populations is crucial to the stimation of lunar and terrestrial planet cratering rates from asteroidal and cometary sources needed to establish the chronology of other surface features on those bodies. A secondary objective is to identify the sources of these crater-forming objects and their relative importance in producing the observed planet-crossing asteroid population. Some key PCAS asteroid discoveries relevant to the population problem and the progress in using the available search data to update and refine earlier estimates of the planet-crossing asteroid population are described.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 69-71
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    Relative Time-scale for Channeling Events Within Chaotic Terrains, Margaritifer Sinus, Mars (1985)
    In:  CASI
    Details
    Publikationsdatum: 2014-10-08
    Beschreibung: A relative time scale for ordering channel and chaos forming events was constructed for areas within the Margaritifer Sinus region of Mars. Transection and superposition relationships of channels, chaotic terrain, and the surfaces surrounding them were used to create the relative time scale; crater density studies were not used. Channels and chaos in contact with one another were treated as systems. These systems were in turn treated both separately (in order to understand internal relationships) and as members of the suite of Martian erosional forms (in order to produce a combined, master time scale). Channeling events associated with chaotic terrain development occurred over an extended geomorphic period. The channels can be divided into three convenient groups: those that pre-date intercrater plains development post-plains, pre-chasma systems; and those associated with the development of the Vallis Marineris chasmata. No correlations with cyclic climatic changes, major geologic events in other regions on Mars, or triggering phenomena (for example, specific impact events) were found.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program; p 325
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    Surfaces of Asteroids and Cometary Nuclei (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: The types of landforms and processes that may exist on cometary nuclei and asteroidal surfaces are investigated. Acknowledging that some asteroids may be cometary nuclei in disguise, asteroids are treated in this report as a simpler case than comets, owing to their more limited response to the state environment. Larger bodies (D 100 km) will not be discussed, even though they are recognized to be extremely important. This limitation permits only processes depending on exogenic phenomena to be considered (excluding processes such as volcanism on Vesta, for example), thus focusing discussion on the more unique aspects of these bodies, namely, their size and number.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 83-85
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  • 149
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    Convex-profile Inversion of Asteroid Lightcurves (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: A lightcurve inversion method that yields a two-dimensional convex profile is introduced. The number of parameters that characterize the profile is limited only by the number of Fourier harmonics used to represent the parent lightcurve. The implementation of the method is outlined by a recursive quadratic programming algorithm, and its application to photoelectric lightcurves and radar measurements is discussed. Special properties of the lightcurves of geometrically scattering ellipsoids are pointed out, and those properties are used to test the inversion method and obtained a criterion for judging whether any lightcurve could actually be due to such an object. Convex profiles for several asteroids are shown, and the method's validity is discussed from a physical as well as purely statistical point of view.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 80-82
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  • 150
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    Asteroid Collisional Evolution Studies (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: Understanding asteroid collisional evolution is important for characterizing the physical state of asteroids today and for learning about the processes that acted in this region of the solar system early in its history. The collisional outcome algorithm in the numerical simulation of asteroid evolution was revised to reflect pressure-strengthening. Asteroid collisions are now treated as a distribution of oblique impacts rather than as only head-on collisions. The initial and evolved size distribution of a plausible asteroid population is compared with the observed size distribution. Asteroid accretion times and reconstruction of the primordial solar nebula suggest that there was significantly more mass in this part of the solar system when the asteroids were accreting.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 77-79
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  • 151
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    The Olivine Asteroids: Discovery, Mineralogy, and Relationship to Palasites (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: Telescopic observations have recently revealed the existence of a new class of asteroids whose surfaces show the spectral signature of abundant olivine. The mineralogy of a well-observed example (446 Aeternitas) is discussed and the implications for the origins of the olivine-rich meteorites and the thermal evolution of asteroids outlined.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 74-76
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  • 152
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    The Structure and Composition of Uranus and Neptune (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: Uranus and Neptune form a special class of planetary objects; intermediate in mass and composition between the giant Hydrogen-rich planets, Jupiter and Saturn, and the small, rocky terrestrial planets. Their structure and composition are not only of intrinsic importance, but also should provide information as to the nature of the protoplanetary nebula and the processes of planetary formation. A detailed set of theoretical models of these planets within the framework of two and three shell models was constructed. The ratio of ice to rock (1/r) is varied. The three shell model fits the data on the two planets best.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 58-60
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  • 153
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    Origin and Evolution of the Saturn System (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: As was the case for Jupiter, Saturn formed either as a result of a gas instability within the solar nebula or the accretion of a solid core that induced an instability within the surrounding solar nebula. In either case, the protoplanet's history can be divided into three major stages: early, quasi-hydrostatic evolution (stage 1); very rapid contraction (stage 2); and late, quasi-hydrostatic contraction (stage 3). During the early history of the Saturn system, giant impact events may have catastrophically disrupted most of the original satellites of Saturn. Such disruption, followed by reaccretion, may be responsible, in part, for the occurrence of Trojans and coorbital moons in the Saturn system, the apparent presence of a stochastic component in the trend of satellite density with radial distance, and the present population of ring particles. Saturn's excess luminosity and viscous dissipation are also discussed in relation to the satellite formation.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 53-54
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  • 154
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    Plasma Production by Meteoroid Impact (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-30
    Beschreibung: Material ejected from the surfaces of satellites in the outer solar system plays an important role in the magnetospheres of the outer planets, and may dominate the mass loading, as in the vicinity of the Jovian satellite Io. At least four potential ejection mechanisms can be identified - intrinsic geologic activity, thermal sublimation, sputtering, and micrometeoroid impact vaporization. On all the icy satellites, except possibly Enceladus, sputtering and impact vaporization are the only two potentially important sources of magnetospheric plasma. Sputtering was shown to be an important mass source at both Jupiter and Saturn. The impact mechanism as a plasma source is assessed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: NASA, Washington Repts. of Planetary Geol. and Geophys. Program, 1984; p 50-51
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  • 155
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    The Venus Balloon Project (1985)
    In:  CASI
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    Publikationsdatum: 2014-09-18
    Beschreibung: During the Soviet Vega Mission to Venus and Comet Halley, two instrumented balloons will be placed into the Venusian atmosphere in June 1985. These Soviet/French balloons will be used to study the structure and dynamics of the Venusian atmosphere by means of in situ measurements and earth-based VLBI determination of balloon position and velocity. The DSN 64-meter subnet will be part of an international network of antennas organized by the French to support this mission. The DSN is installing new L-band receiving systems for this task. All scientific data from the balloons will be analyzed by a joint Soviet/French/U.S. science team.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: The Telecommun. and Data Acquisition Rept.; p 195-201
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  • 156
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    Mare basalt genesis - Modeling trace elements and isotopic ratios (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Various types of mare basalt data have been synthesized, leading to the production of an internally consistent model of the mare basalt source region and mare basalt genesis. The model accounts for the mineralogical, major oxide, compatible siderophile trace element, incompatible trace element, and isotopic characteristics of most of the mare basalt units and of all the pyroclastic glass units for which reliable data are available. Initial tests of the model show that it also reproduces the mineralogy and incompatible trace element characteristics of the complementary highland anorthosite suite of rocks and, in a general way, those of the lunar granite suite of rocks.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; D19-D30
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  • 157
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    Very high potassium (VHK) basalt - Complications in mare basalt petrogenesis (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The first comprehensive report on the petrology and geochemistry of Apollo 14 VHK (Very High Potassium) basalts and their implications for lunar evolution is presented. The reported data are most consistent with the hypothesis that VHK basalts formed through the partial assimilation of granite by a normal low-Ti, high-Al mare basalt magma. Assimilation was preceded by the diffusion-controlled exchange of alkalis and Ba between basalt magma and the low-temperature melt fraction of the granite. Hypotheses involving volatile/nonvolatile fractionations or long-term enrichment of the source regions in K are inconsistent with the suprachondritic Ba/La ratios and low initial Sr-87/Sr-86 ratios of VHK basalt. An important implication of this conclusion is that granite should be a significant component of the lunar crust at the Apollo 14 site.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; D3-D18
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  • 158
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    Spectra of simulated lightning on Venus, Jupiter, and Titan (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Laser-induced plasmas in various gas mixtures were used to simulate lightning in other planetary atmospheres. This method of simulation has the advantage of producing short-duration, high-temperature plasmas free from electrode contamination. The laser-induced plasma discharges in air are shown to accurately simulate terrestrial lightning and can be expected to simulate lightning spectra in other planetary atmospheres. Spectra from 240 to 880 nm are presented for simulated lightning in the atmospheres of Venus, earth, Jupiter, and Titan. The spectra of lightning on the other giant planets are expected to be similar to that of Jupiter because the atmospheres of these planets are composed mainly of hydrogen and helium. The spectra of Venus and Titan show substantial amounts of radiation due to the presence of carbon atoms and ions and show CN Violet radiation. Although small amounts of CH4 and NH3 are present in the Jovian atmosphere, only emission from hydrogen and helium is observed. Most differences in the spectra can be understood in terms of the elemental ratios of the gas mixtures. Consequently, observations of the spectra of lightning on other planets should provide in situ estimates of the atmospheric and aerosol composition in the cloud layers in which lightning is occurring. In particular, the detection of inert gases such as helium should be possible and the relative abundance of these gases compared to major constituents might be determined.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 64; 221-232
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  • 159
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    Are Uranus' rings black because they are in the solar wind? (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: It is shown that the rings of Uranus are mostly immersed in the solar wind if Uranus lacks an intrinsic magnetic field. Except for geologically active moons like Io, the rings and moons of Jupiter and Saturn have either high albedos in a low radiation environment or low albedos in a high radiation environment. It is suggested that the moons of Uranus have a significantly lower albedo than those in the low radiation environment of Saturn, and that the rings of Uranus are black because the rings and moons of that planet are relatively depleted in their surface stores of ices. In this scenario, immersion of the Uranus rings in the solar wind provides a loss mechanism for ring ices. The black rings may thus imply the lack of an intrinsic Uranus magnetic field.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 12; 855-858
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  • 160
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    A search for nitrogen on Triton (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Improved spectrophotometry of Triton at 2.16 microns was obtained with the MMT infrared photometer at a resolution of 1.0 percent. The observations do not reveal an absorption feature due to liquid nitrogen. Three explanations are consistent with this finding: (1) there is liquid nitrogen on the surface but it is not distributed uniformly; (2) the feature varies with time, e.g., it is sometimes obscured by cloud cover; and (3) the feature might be relatively broad.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 64; 153-155
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  • 161
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    Mercury - Absence of crystalline Fe(2+) in the regolith (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: A composite visible and near-IR (0.53-1.02 micron) reflectance spectrum of terrain on Mercury including smooth plains and intercrater plains was produced (with a theoretical resolution of 17 A) from 59 high-SNR spectra of the planet taken on November 24, 1984 at the 1.0-m telescope of the CTIO. No evidence was found in the spectrum for the proposed orthopyroxene absorption centered near 0.9 micron observed in older spectra of this terrain; the surface material is highly reduced, with any Fe present in metallic form.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 64; 133-138
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  • 162
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    What have we learned from modeling giant planet interiors? (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Models of the giant planets are reviewed. The theoretical techniques used in computing the models are described, and the observational and experimental inputs are summarized. Special emphasis is placed on uncertainties in these input data. The models are then examined and the results of various authors presented. It is demonstrated that all the planets have heavy-element enhancements of between 10 and 40 earth masses, with a large fraction of this material residing in the core. It is also shown that the ratio of ice to rock in Uranus and Neptune is on the order of three. The implications of these results for theories of the origin of the solar system are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 163
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    Meteoritic constraints on processes in the solar nebula (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The origin of chondritic meteorites is discussed. The characteristics of the chondrite subtypes are shown, and the fine structure of chondrites is described in terms of the three principal categories of aggregated objects present in chondrites: chondrules, Ca,Al-rich inclusions (CAIs), and matrix. Four possibilities for the origin of these components are considered, leading to four important constraints on the chondrite-forming processes, based on mineralogy and astrophysics. It is concluded that the chondrules and CAIs were formed in the solar nebula at a radial distance of about 3 AU. Some type of transient high-energy event or process, operating in zones of dust enrichment, furnished the high temperatures needed to process the chondrules and CAIs. These objects cooled on a time scale of minutes, then on a similarly short time scale began to aggregate, together with dust, into chondritic masses having approximately the solar proportions of major condensable elements.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 164
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    Rings and moons - Clues to understanding the solar nebula (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Planetary satellites, ranging in size from ring particles to the Galilean moons of Jupiter, constitute a small but diverse compmonent of the solar system. In some respects, the satellite systems of the giant planets can be thought of as miniature solar systems. The chemical and physical properties of these systems can yield clues to the conditions under which they may have formed, and thus can constrain models of the circumplanetary nebulae and the solar nebula. Planetary rings contain a great deal of structure, most strikingly displayed in Voyager spacecraft images. Understanding the causes of this structure can yield important insights into the dynamics of the protoplanetary disk. Taken together, rings and moons offer clues as to the nature of the processes which led to the formation of the planets themselves.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 165
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    The coming revolution in planetology (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Current ideas about the moon appear to be mistaken on two fundamental points. First, at least within certain large classes of lunar craters, internal origin (i.e., some form of volcanism) predominates over impact; this result raises questions about the reality of the 'era of violent bombardment'. Second, the origin of tektites by meteoritic impact on the earth cannot be reconciled with physical principles and is to be abandoned. The only viable alternative is origin by lunar volcanism, which implies the following: continuance of (rare) explosive lunar volcanism to the present time; existence of silicic lunar volcanism and of small patches of silicic rock at the lunar surface; a body of rock in the lunar interior, probably at great depth, which is closely similar to the earth's mantle and which contains billions of tons of volatiles, probably including hydrogen; and origin of the moon from the earth after the formation of the earth's core.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: EOS (ISSN 0096-3941); 66; 89
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  • 166
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    Sulfur in achondritic meteorites (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The sulfur abundances of samples of nearly 50 achondrites were examined to enlarge the database on the sulfur contents of various categories of achondrites. The study covered eucrites, howardites, diogenites, shergottites, chassignites, nakhilites, aubrites and three unique specimens. The study was spurred by the possibility that the S abundances could help identify the meteorites as originating on Mars or Venus. The S abundances and distributions varied widely, but confirmed that the data were valid indicators of the brecciation and thermal metamorphic history of each meteorite.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Meteoritics (ISSN 0026-1114); 20; 503-511
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  • 167
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    Survival of interstellar matter in meteorities - Evidence from carbonaceous material (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An interstellar origin has been attributed to certain organic and apparently elemental forms of C which occurs in carbonaceous meteorites. Evidence for such an origin comes from anomalous isotopic composition either of the C itself or of elements, such as N, H, or the noble gasses, which are combined with or trapped within the carbonaceous material. Suggested sources for these anomalous compositions include atmospheres of red giant stars, novae and super-novae, and interstellar molecular clouds.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 168
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    Recent results on the Venus atmosphere from Pioneer Venus radio occultations (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Temperature structure of the Venus atmosphere was derived from radio occultation data collected by the Pioneer Venus spacecraft during seven occultation seasons in the 1978-1983 period. The measurements, which cover latitudes from both poles to the equator from 40 km to 85 km altitudes, show a latitudinal dependence. At latitudes below 45 deg, there is a smooth temperature transition from the troposphere to the mesosphere. Between 60 and 80 deg, in the 'collar cloud' region, a strong temperature inversion (up to 30 K) appears, which disappears again in the polar areas (80-90 deg), where the mesosphere becomes isothermal without inversion. This temperature behavior is related to the persistent circulation pattern, in which a zonal retrograde motion below 45 deg changes gradually to a circumpolar vortex at the 'collar cloud'. A considerable temporal variability was observed in the thermal structure above the tropopause, suggesting a weather-like variability in the persistent circulation pattern.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Advances in Space Research (ISSN 0273-1177); 5; 9, 19; 41-49
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  • 169
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    Formation of the giant planets and their satellite-ring systems - An overview (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The origin of the outer planets and their satellite systems is discussed within the framework of astrophysical theories of the origin of stars and the nature of viscous accretion disks. The nature of the outer planet systems is reviewed, and the gas-instability and core-instability models of the origin of the outer planets are described. Critical tests of the models are discussed, showing that the core-instability model is favored. The main phases of evolution that the giant planets underwent during and after their formation are outlined, and the source of their current excess luminosity is considered in detail. The origin of the regular and irregular satellites of the outer planets is discussed, focusing on their formation in viscous accretion disks or by collision, and the possibility of capture by planets.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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  • 170
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    The thermal structure of the dayside upper atmosphere of Venus above 125 km (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A one-dimensional model of the Venus thermosphere has been constructed which includes computation of the heating efficiency of solar ultraviolet radiation, heat loss by radiation to space of infrared-active species, thermal transport by molecular and eddy conduction, and viscous dissipation. By comparing model predictions with results obtained from the Pioneer Venus Orbiter spacecraft, the results indicate that energy transport parameterized by eddy heat conduction plays a dominant role in determining thermospheric temperature. It is suggested that there exists a feedback mechanism linking heating and thermospheric circulation such that eddy cooling maintains an asymptotic temperature of about 300 K for both solar-maximum and solar-minimum conditions. The variation in thermospheric temperature with solar zenith angle, atomic oxygen-mixing ratio, rate of vibrational excitation of CO2 by ground-state O atoms, and the assumed transfer of O(1D) electronic energy to CO2 vibrational energy are also studied.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 64; 205-220
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  • 171
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    Planetary mission operations - An overview (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: An overview of the missions operations systems (MOS) used to support NASA planetary missions is given. The principal factors governing the design characteristics of MOS are discussed, including: the communications requirements of spacecraft over long distance from the earth, the fragility of the scientific payloads, and the inability to carry out planetary missions more than a few times a decade. The uplink and downlink parts of the MOS of Galileo and Voyager spacecraft are illustrated as examples of successful MOS design. A black and white photograph of the operations control center of JPL is provided.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: (ISSN 0007-084X); 38; 435-438
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  • 172
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    Selecting and implementing scientific objectives (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The procedures used to select and implement scientific objectives for the Voyager 1 and 2 planetary encounters are described. Attention is given to the scientific tradeoffs and engineering considerations must be addressed at various stages in the mission planning process, including: the limitations of ground and spacecraft communications systems, ageing of instruments in flight, and instrument calibration over long distances. The contribution of planetary science workshops to the definition of scientific objectives for deep space missions is emphasized.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: (ISSN 0007-084X); 38; 439-443
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  • 173
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    The photochemistry of the atmospheres of the outer planets and their satellites (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: The thermal structure and composition of Uranus, Neptune, Saturn, Jupiter, Titan, and Io are described. Molecular hydrogen is the dominant constituent in the atmosphere of the outer planets. The hydrogen and helium, methane, ammonia and phosphine, and carbon monoxide photochemical reactions of the outer planets are studied. The importance of Jupiter's lightning as a source of organic matter is examined. The aerosol and haze layers of the stratosphere of Jupiter, Saturn, Neptune, and Uranus are observed. The photochemistry of Titan's atmosphere, which includes nitrogen, methane, carbon monoxide, and carbon dioxide reactions, is analyzed. The SO2 atmosphere on Io is discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
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    Advanced missions to primitive bodies (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Six interplanetary spacecraft, three earth orbital experiments, and one spacecraft orbiting Venus will observe comets Halley and Giacobini-Zinner in 1985-86. At comet Halley, attempts will be made to image the nucleus, remote sensing will be made by spectrometers in wavelength ranges from the IR to the UV, and in-situ observations will be made with neutral, ion and dust mass spectrometers. Plasma measurements will be made at both comets and at comet Halley the upstream solar wind flux will be simultaneously monitored by nearby spacecraft. In the post-Halley era, there are several missions being planned for the continued exploration of the solar system's most primitive bodies - comets and asteroids.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Astronomical Society of the Pacific, Publications (ISSN 0004-6280); 97; 871-876
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  • 175
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    Hidden carbon dioxide on Mars (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A recent proposal that much of the outgassed CO2 on Mars is tied up in the planet's crust in the form of carbonate mineral is discussed. According to this hypothesis, carbonate formation on Mars continued after open bodies of liquid water became unstable. A consequence of the hypothesis is that, in the absence of a recycling mechanism for CO2, the surface pressure on Mars will monotonically decrease until it reaches the minimum atmospheric overburden pressure required for liquid water to form. The theory explains Mars' low surface pressure, and also implies that the climate of Mars has evolved linearly over geologic time, rather than cyclically.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature (ISSN 0028-0836); 318; 599
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  • 176
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    The Pioneer Venus extended mission (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A history of the Pioneer Venus Orbiter is given, as well as a presentation of the ongoing and future missions (through reentry in 1992). General characteristics of Venus including atmospheric and ionospheric data are reviewed. Development of the Pioneer program and studies including comet detection, gamma ray bursts, composition and structure of the atmosphere, ionosphere, clouds, and solar wind are discussed. Planned observations of Halley's Comet in 1986 and of past observations of the Comet Enke are examined in detail. Maps and diagrams illustrate the studies and observations of this extended mission. Specification of the spacecraft as well as details of its orbits are given.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Spaceflight (ISSN 0038-6340); 27; 445-450
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  • 177
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    Young thrust-fault scarps in the highlands - Evidence for an initially totally molten moon (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Attention is given to thermoelastic stress calculations implying that if only the outer few hundreds of km of a moon with a cool interior were initially molten, the lunar highlands should not have young compressional tectonic features. Extrapolations from Apollo panoramic images showing young thrust faults in the highlands suggest that about 2000 thrust fault scarps exist on the highlands, generally occurring in series or complexes of four or five scarps that are on average 5 km long. The ages of the scarps range from 60 + or - 30 to 680 + or - 250 my, with a possible factor bias of +2 to -4. The scarps are the youngest endogenic features on the moon, and indicate that the moon was initially molten.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 63; 421-441
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  • 178
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    Light scattering in a spherical, exponential atmosphere, with applications to Venus (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: In the present discussion of the problem presented by the reflection of light from an optically thick spherical atmosphere, in which the scatterers are distributed exponentially with a scale height that is small by comparison to the radius of the planet, exact formal solutions are obtained for the single scattered component. The results obtained are applied to the analysis of the Mariner 10 limb and terminator images of Venus, which show a detached haze layer as a planetwide feature that is similar in location, scale height, and thickness during both Pioneer Venus and Mariner 10 missions, by contrast to the dramatically altered lower haze. The possible nature of the limb hazes is discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 63; 354-373
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  • 179
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    Voyager at the seventh planet (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The success of the Voyager 1 flyby of Titan permitted configuring the Voyager 2 trajectory for flybys of Uranus and Neptune. Satellite instruments will gather data on the Uranian atmosphere, rings, satellites and magnetosphere (if there is one). The observational sequences were coded for transmission to Voyager 2 in November 1985. Earlier commands have stabilized the spacecraft to avoid image smearing during the approach and have reduced the time of firing of the thrusters for course changes. Imaging data compression will economize on the degraded communications link to Voyager 2 and lower the demands on the slowly failing radiothermoelectric power supply. The encounter will take place in February 1986 and, should failure of the command link occur, be accompanied by carrying out of a preprogrammed set of observational and operational sequences lasting through a 1989 Neptune flyby.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Spaceflight (ISSN 0038-6340); 27; 403-409
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  • 180
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    Mars sample-return options (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Attention is given to the comparative merits of two options for the return to earth of Mars round-trip sampling probe missions. The first option makes use of an onboard propulsion system to place the returning vehicle into a highly elliptical orbit around the earth. An orbital transfer vehicle (OTV) or OTV/orbital maneuvering vehicle combination retrieves the sample from the return vehicle. The second option uses aerocapture to place the return vehicle in earth orbit; this maneuver imposes no greater weight penalty for proceeding to a low orbit than remaining at one that is high. The second option delivers the sample to a Space Station-compatible orbit for pickup.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Aerospace America (ISSN 0740-722X); 23; 50-53
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  • 181
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    Can cometary bombardment disrupt synchronous rotation of planetary satellites? (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The distribution of craters on Jupiter's Galilean satellites Ganymede and Callisto and on Saturn's midsized airless moons is much more symmetric and uniform than theoretical analysis predicts. A number of explanations for this situation have been considered, taking into account also the possibility that impacts due to cometary bombardment might disrupt the synchronous rotation of the moons. The feasibility of such a disruption is explored in the present study. The results of this study are presented in a table. It is found that a disruption of the synchronous rotation of the considered moons by impacts is very unlikely.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 90; 11
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  • 182
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    Possible nightside source dominance in nonthermal radio emissions from Uranus (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Desch and Kaiser (1984) have formulated a radiometric Bode's law from which they have attempted to estimate the low frequency, nonthermal radio power of the magnetosphere of Uranus. It is shown here that, if Uranus possesses a magnetosphere, it is more likely that the radio emission is from the nightside as opposed to the dayside as assumed by Desch and Kaiser. A nightside source for the radio emissions would radically alter the predicted time for direct observations of the emissions.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Nature (ISSN 0028-0836); 318; 47
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  • 183
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    Low-frequency waves and associated energetic ions downstram of Saturn (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Examples of highly coherent, low-frequency waves that were observed by Voyager 2 in the IMF during several months following the Saturn encounter in 1981 are presented. It is shown that the detection of these events was due to a favorably oriented IMF. These events are discussed in terms of correlated ion and magnetic field data, and the evolution of their properties with incresing distance from Saturn is addressed. The spectral and eigenfunction characteristics of the observed waves are shown, and the mode of the waves and their possible excitation mechanisms are considered, including an instability analysis. The results are compared with those obtained in the foreshock regions of other planets, especially the earth.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 90; 10
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  • 184
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    Discovery of sodium in the atmosphere of Mercury (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The spectrum of Mercury at the Fraunhofer sodium D lines shows strong emission features that are attributed to resonant scattering of sunlight from sodium vapor in the atmosphere of the planet. The total column abundance of sodium was estimated to be 8.1 x 10 to the 11th atoms per square centimeter which corresponds to a surface density at the subsolar point of about 150,000 atoms per cubic centimeter. The most abundant atmospheric species found by the Mariner 10 mission to Mercury was helium, with a surface density of 4500 atoms per cubic centimeter. It now appears that sodium vapor is a major constituent of Mercury's atmosphere.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science (ISSN 0036-8075); 229; 651-653
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  • 185
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    Saturn radio emission and the solar wind - Voyager-2 studies (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Voyager 2 data from the Plasma Science experiment, the Magnetometer experiment and the Planetary Radio Astronomy experiment were used to analyze the relationship between parameters of the solar wind/interplanetary medium and the nonthermal Saturn radiation. Solar wind and interplanetary magnetic field properties were combined to form quantities known to be important in controlling terrestrial magnetospheric processes. The Voyager 2 data set used in this investigation consists of 237 days of Saturn preencounter measurements. However, due to the immersion of Saturn and the Voyager 2 spacecraft into the extended Jupiter magnetic tail, substantial periods of the time series were lacking solar wind data. To cope with this problem a superposed epoch method (CHREE analysis) was used. The results indicate the superiority of the quantities containing the solar wind density in stimulating the radio emission of Saturn - a result found earlier using Voyager 1 data - and the minor importance of quantities incorporating the interplanetary magnetic field.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Advances in Space Research (ISSN 0273-1177); 5; 4, 19
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  • 186
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    CO2 impact ionization-driven plasma instability observed by Pioneer Venus Orbiter at Periapsis (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Observations of enhanced ac electric field noise about Pioneer Venus periapsis are shown to be related to spacecraft-generated impact ionization of the ambient CO2. The frequency of the electric field noise is found to peak in the vicinity of the CO2(+) ion plasma frequency and to closely follow the form of the neutral CO2 density profile. When the electric field noise in all channels is normalized by the square root of the CO2 number density, the ratio is constant. Since the impact electron density measured by the Pioneer Venus Langmuir probe, is observed to scale directly with the neutral CO2, the growth of the electric field amplitude is found to be linear in time with a growth rate proportional to the CO2(+) ion plasma frequency. On the basis of these results the impact ionization-driven instability is shown to be the ion acoustic instability. Implications for the lack of observations by Pioneer Venus of reflected-O(+)-driven instabilities, as have been proposed for the space shuttle, are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 90; 6631-663
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  • 187
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    Collisional balance of the meteoritic complex (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The present study has the objective to reevaluate the size distribution of interplanetary meteoroids on the basis of the most recent data, and to analyze the probable nature of the sinks and sources of meteoritic material. The flux of interplanetary meteorites at 1 AU is discussed, taking into account general characteristics, lunar crater distribution, flux curves, spatial densities, and cross-sectional distribution and light scattering. Collisional effects are examined, giving attention to catastrophic collisions, collision rate, and destroyed mass and generated fragments. The effect of radiation pressure on small particles is considered along with the difference between the lunar and interplanetary flux models, collisional evolution at 1 AU, potential sources for large meteoroids, and observational evidence of losses of small micrometeoroids.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 62; 244-272
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  • 188
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    Venus topography - A harmonic analysis (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A model of Venusian global topography has been obtained by fitting an eighteenth-degree harmonic series to Pioneer Venus orbiter radar altimeter data. The mean radius is (6051.45 + or - 0.04) km. The corresponding mean density is (5244.8 + or 0.5) kg/cu m. The center of figure is displaced from the center of mass by (0.339 + or - 0.088) km towards (6.6 + or 10.1) deg N, (148. 8 + or - 7.7) deg. The figure of Venus is distinctly triaxial, but the orientation and magnitudes of the principal topographic axes correlate rather poorly with the gravitational principal axes. However, the higher-degree harmonics of topography and gravity are significantly correlated. The topographic variance spectrum of Venus is very similar in form to those of the moon, Mars, and especially earth. It is suggested that this spectral similarity simply reflects a statistical balance between constructional and degradational geomorphic proceses. Venus and earth are particularly similar (and differ from the moon and Mars) in that the larger bodies both exhibit a significant low degree deficit (relative to the extrapolated trend of the higher harmonics).
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 90; 827-836
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  • 189
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    A model for GCR-particle fluxes in stony meteorites and production rates of cosmogenic nuclides (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: A model is presented for the differential fluxes of galactic-cosmic-ray (GCR) particles with energies above 1 MeV inside any spherical stony meteorite as a function of the meteorite's radius and the sample's depth. This model is based on the Reedy-Arnold equations for the energy-dependent fluxes of GCR particles in the moon and is an extension of flux parameters that were derived for several meteorites of various sizes. This flux is used to calculate the production rates of many cosmogenic nuclides as a function of radius and depth. The peak production rates for most nuclides made by the reactions and energetic GCR particles occur near the centers of meteorites with radii of 40 to 70 g/cm (2). Although the model has some limitations, it reproduces well the basic trends for the depth-dependent production of cosmogenic nuclides in stony meteorites of various radii. These production profiles agree fairly well with measurments of cosmogenic nuclides in meteorites. Some of these production profiles are different than those calculated by others. The chemical dependence of the production rates for several nuclides varies with size and depth.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; C722-C72
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  • 190
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    Lunar sample 14425 - Characterization and resemblance to high-magnesium microtektites (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Measurements by energy-dispersive X-ray analysis of the surface of lunar sample 14425, a large glass bead, yield a noritic composition enriched in aluminum and magnesium and, as compared with other norites, depleted in iron and especially calcium. The sample is close in composition to the most basic microtektites. Spherical inclusions of nickel-iron, flattened where they protrude, are found to be enriched in sulfur and phosphorus, at least at the surface. The inclusions form approximately 1 percent of the volume.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Science (ISSN 0036-8075); 227; 515
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  • 191
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    Chemical constraints on the evolution of Archean continental crust (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: One of the challenges of Archean geochronology is to find isotopic systems that preserve an indication of a rock's primary age in spite of the effects of later metamorphism. Zircon dating has been used widely with considerable success but not without difficulty, especially in polymetamorphic terrains. Zircons in such cases commonly are found to have lost radiogenic Pb, and despite fractionizing the zircons or abrading them to remove disturbed portions; it often is not possible to define a pattern of Pb loss from which the original age can confidently be inferred. The refinement of techniques to enable extremely small samples, or even single crystals, to be analyzed has contributed greatly to solving the problem but even those techniques cannot resolve the micron scale isotopic heterogeneities within single zircons in which much of their history is recorded. That can only be done by ion microprobe. Progress reports on studies of four Archean rocks, each of which illustrates the power and potential of ion microprobe analysis in solving problems of Archean geochronology are discussed.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 82-83
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    Thermal, dynamic and compositional aspects of the core-forming Earth (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Core formation is the most important and singular differentiation event in the history of a terrestrial planet. It almost certainly involved the downward migration of a partially or wholly molten iron alloy through a silicate and oxide mantle, and was contemporaneous with accretion. Several important, unresolved issues which have implications for mantle and core geochemistry, the thermal history of the Earth, and the origin of geomagnetism are addressed: whether the early Earth was molten; whether core formation involved low or high pressure geochemistry, or both; early Earth mantle homogenization; whether equilibration established between core forming material and the mantle through which it migrated; and how much iron is stranded and unable to reach the core.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 76-78
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  • 193
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    Chemical evolution of the Earth: Equilibrium or disequilibrium process? (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: To explain the apparent chemical incompatibility of the Earth's core and mantle or the disequilibrium process, various core forming mechanisms have been proposed, i.e., rapid disequilibrium sinking of molten iron, an oxidized core or protocore materials, and meteorite contamination of the upper mantle after separation from the core. Adopting concepts used in steady state thermodynamics, a method is devised for evaluating how elements should distribute stable in the Earth's interior for the present gradients of temperature, pressure, and gravitational acceleration. Thermochemical modeling gives useful insights into the nature of chemical evolution of the Earth without overly speculative assumptions. Further work must be done to reconcile siderophile elements, rare gases, and possible light elements in the outer core.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 68-70
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  • 194
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    Carbon and nitrogen in the deep Earth (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: High sensitivity mass spectrometric techniques were utilized to study the C-N isotope systematics in basic igneous rocks and mantle materials in an attempt to ultimately constrain the primordial isotopic compositions of these elements and their subsequent fate during the early history of the Earth. Preliminary results obtained for a selection of submarine basaltic glasses and diamonds are summarized concentrating on: (1) the problem of whether isotopes are significantly fractionated during igneous processes; and on (2) the effects of crustal recycling.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 59-61
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  • 195
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    Archean sedimentary systems and crustal evolution (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: Current knowledge of preserved Archean sedimentary rocks suggests that they accumulated in at least three major depositional settings. These are represented generally by sedimentary units: (1) in early Archean, pre-3.0 Ga old greenstone belts, (2) on late Archean sialic cratons, and (3) in late Archean, post-3.0 Ga old greenstone belts. Research suggests that the Archean was characterized by at least two distinctive and largely diachronous styles of crustal evolution. Thick, stable early Archean simatic platforms, perhaps analogous to modern oceanic islands formed over hot spots, underwent a single cycle of cratonization to form stable continental blocks in the early Archean. Later formed Archean continents show a two stage evolution. The initial stage is reflected in the existence of older sialic material, perhaps representing incompletely cratonized areas or microcontinents of as yet unknown origin. During the second stage, late Archean greenstone belts, perhaps analogous to modern magmatic arcs or back arc basins, developed upon or adjacent to these older sialic blocks. The formation of this generation of Archean continents was largely complete by the end of the Archean. These results suggest that Archean greenstone belts may represent a considerable range of sedimentological and tectonic settings.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 51-53
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  • 196
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    Conditions during formation of the Earth (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The formation of the Earth starts with gravitational instabilities in the gas of primitive solar nebula, which form giant gaseous protoplanets. The envelopes of these are thermally evaporated, but solids can gravitationally settle to the center of the protoplanets, and most of the core and mantle of the Earth were formed at that time (age about 10,000 years). The protoearth then survived a period of high temperatures in the surrounding gas (age about 10 to the 5th years). While and after the gas was thermally stabilized and removed from the solar system, the Earth grew by bombardment of planetesimals and its early atmosphere was established. A late major collision led to formation of the Moon and loss of the primordial atmosphere (age about 10 to the 8th years). The present atmosphere resulted from still later accretion. The presence of this atmosphere spreads out the mantle cooling and solidification over hundreds of millions of years.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 11-13
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    Was core formation violent enough to homogenize the early mantle? (1985)
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    Publikationsdatum: 2011-08-19
    Beschreibung: The dynamics of iron, its thermal state and its phase in the accreting Earth probably played a major role in the Earth's early thermal evolution. Plausible impact thermal histories make it possible that pure iron was molten in the accreting Earth after it was about 10% grown. Hence, iron eutectic alloys (FeS, FeO) certainly were. Additionally, the initial temperature of the core is an important constraint on the secular cooling of the early Earth and on the strength of the early geodynamo. Whether iron is solid or molten would influence geochemical equilibria in the upper and lower mantle; the mode of core formation, by spherical or near-spherical blobs, stalk-like instabilities, or something more catastrophic would influence the partitioning of siderophiles between silicate and iron phases. Early descent of iron (during accretion) favors partitioning according to low-pressure phase equilibria, whereas late descent favors higher pressure. The later core formation occurs, the greater the heat pulse, due to the strong dependence of gravitational potential energy on planetary radius. The heat may homogenize the mantle if core formation is global; otherwise, heterogeneity of iron differentiation may leave some of the pre-archean mantle unaffected. The larger the chunks of proto-core (and hence smaller surface/volume ratios) the greater the heterogeneity.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 17-19
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    Constraints on early atmosphere from planetary accretion processes (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: Evidence for composition and dynamics of release of the earliest volatiles was in lack of anything better being sought from the most ancient sediments known at the time, although they were recognized to be younger than three billion years. Origin of life on Earth was considered to require a lasting atmosphere with hydrogen and methane as major components. The new observations together with theoretical studies generated by the space program and by systematic exploration of the Earth's oceanic crust changed the climate of opinion in which the questions of the primordial atmosphere are discussed. Even though existing evidence does not permit conclusive choice of any specific scenario, the acceptance of specific model elements now forces the consideration of a series of consequences, some of which may be tested by observation.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Lunar and Planetary Inst. Workshop on the Early Earth: The Interval from Accretion to the Older Archean; p 4-7
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    On the diurnal variations in the temperature and composition - A three-dimensional model with superrotation (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An improved (Mayr et al., 1980) three-dimensional multiconstituent spectral model of the Venus thermosphere dynamics is presented, which describes the diurnal variations in the atmospheric composition (in terms of O, CO, and CO2 densities obtained by ONMS and OIMS, temperature, and wind fields on the basis of simplified theoretical interpretations of data obtained by the Pioneer Venus mission. The improved model accounts for nonlinear processes, includes higher order tidal elements, and describes the major gases in self-consistent form. Also presented is a self-consistent, nonlinear solution from a two-dimensional quasi-axisymmetric spectral model which describes the four-day superrotation in the lower atmosphere.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Advances in Space Research (ISSN 0273-1177); 5; 9, 19
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    The internal structures and the relative rotation rates of Uranus and Neptune (1985)
    In:  Other Sources
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    Publikationsdatum: 2011-08-19
    Beschreibung: An analysis of the difference between the interior structures of Uranus and Neptune is presented, based on models which fit the observed mass, radius, and gravitational moments for the assumed rotation periods of these planets. If Uranus and Neptune are assumed to be as similar in internal structure as they are in mass and radius, the rotation period for Neptune must be shorter than that for Uranus. It is suggested that the true rotation period is given by Neptune's oblateness, while the photometric period corresponds to the motion of Rossby waves in the upper atmosphere.
    Schlagwort(e): LUNAR AND PLANETARY EXPLORATION
    Materialart: Icarus (ISSN 0019-1035); 63; 266-271
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