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  • Inorganic Chemistry  (6,921)
  • LUNAR AND PLANETARY EXPLORATION  (6,295)
  • 1985-1989  (6,497)
  • 1980-1984  (6,719)
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  • 1
    Publication Date: 2019-01-25
    Description: Interpretation of planetary observations and proper modeling of planetary atmospheres are critically upon accurate laboratory data for the chemical and physical properties of the constitutes of the atmospheres. It is important that these data are taken over the appropriate range of parameters such as temperature, pressure, and composition. Availability of accurate, laboratory data for vapor pressures and equilibrium constants of condensed species at low temperatures is essential for photochemical and cloud models of the atmospheres of the outer planets. In the absence of such data, modelers have no choice but to assume values based on an educated guess. In those cases where higher temperature data are available, a standard procedure is to extrapolate these points to the lower temperatures using the Clausius-Clapeyron equation. Last summer the vapor pressures of acetylene (C2H2) hydrogen cyanide (HCN), and cyanoacetylene (HC3N) was measured using two different methods. At the higher temperatures 1 torr and 10 torr capacitance manometers were used. To measure very low pressures, a technique was used which is based on the infrared absorption of thin film (TFIR). This summer the vapor pressure of acetylene was measured the TFIR method. The vapor pressure of hydrogen sulfide (H2S) was measured using capacitance manometers. Results for H2O agree with literature data over the common range of temperature. At the lower temperatures the data lie slightly below the values predicted by extrapolation of the Clausius-Clapeyron equation. Thin film infrared (TFIR) data for acetylene lie significantly below the values predicted by extrapolation. It is hoped to bridge the gap between the low end of the CM data and the upper end of the TFIR data in the future using a new spinning rotor gauge.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Maryland Univ., The 1989 NASA-ASEE Summer Faculty Fellowship Program in Aeronautics and Research; p 16-17
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  • 2
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    Publication Date: 2019-01-25
    Description: It is timely to consider the possible tectonic regimes on Venus both in terms of what is known about Venus and in terms of deformation mechanisms operative on the earth. Plate tectonic phenomena dominate tectonics on the earth. Horizontal displacements are associated with the creation of new crust at ridges and destruction of crust at trenches. The presence of plate tectonics on Venus is debated, but there is certainly no evidence for the trenches associated with subduction on the earth. An essential question is what kind of tectonics can be expected if there is no plate tectonics on Venus. Mars and the Moon are reference examples. Volcanic constructs appear to play a dominant role on Mars but their role on Venus is not clear. On single plate planets and satellites, tectonic structures are often associated with thermal stresses. Cooling of a planet leads to thermal contraction and surface compressive features. Delamination has been propsed for Venus by several authors. Delamination is associated with the subduction of the mantle lithosphere and possibly the lower crust but not the upper crust. The surface manifestations of delamination are unclear. There is some evidence that delamination is occurring beneath the Transverse Ranges in California. Delamination will certainly lead to lithospheric thinning and is likely to lead to uplift and crustal thinning.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 49
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  • 3
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    Publication Date: 2019-01-25
    Description: The putative paradigm that planets of the same size and mass have the same tectonic style led to the adaptation of the mechanisms of terrestrial plate tectonics as the a priori model of the way Venus should behave. Data acquired over the last decade by Pioneer Venus, Venera, and ground-based radar have modified this view sharply and have illuminated the lack of detailed understanding of the plate tectonic mechanism. For reference, terrestrial mechanisms are briefly reviewed. Venusian lithospheric divergence, hotspot model, and horizontal deformation theories are proposed and examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 33-34
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  • 4
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    Publication Date: 2019-01-25
    Description: The Archean Era of the Earth is not a direct analog of the present tectonics of Venus. In this regard, it is useful to review the state of the Archean Earth. Most significantly, the temperature of the adiabatic interior of the Earth was 200 to 300 C hotter than the current temperature. Preservation biases limit what can be learned from the Archean record. Archean oceanic crust, most of the planetary surface at any one time, has been nearly all subducted. More speculatively, the core of the Earth has probably cooled more slowly than the mantle. Thus the temperature contrast above the core-mantle boundary and the vigor of mantle plumes has increased with time on the Earth. The most obvious difference between Venus and the present Earth is the high surface temperature and hence a low effective viscosity of the lithosphere. In addition, the temperature contrast between the adiabatic interior and the surface, which drives convection, is less on Venus than on the Earth. It appears that the hot lithosphere enhanced tectonics on the early Venus significantly enough that its interior cooled faster than the Earth's. The best evidence for a cool interior of Venus comes from long wavelength gravity anomalies. The low interior temperatures retard seafloor spreading on Venus. The high surface temperatures on Venus enhance crustal deformation. That is, the lower crust may become ductile enough to permit significant flow between the upper crust and the mantle. There is thus some analogy to modern and ancient areas of high heat flow on the Earth. Archean crustal blocks typically remained stable for long intervals and thus overall are not good analogies to the deformation style on Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 46
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  • 5
    Publication Date: 2019-01-25
    Description: The relations between the identification of dominant lunar landforms, craters, and radar images at three resolutions are investigated. Although the percentage of craters that can be identified is found to increase with diameter or relief for any given resolution, it is noted that craters have not been identified at all diameters and relief. It is shown that the relation between the percentage of identified craters and their dimensions depends on the size-frequency distributions of both diameters and relief, and that crater identification depends strongly on the resolution of the radar image.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 32
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  • 6
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    Publication Date: 2019-01-25
    Description: Venus is more similar to Earth than to any other planet. It has elevated regions associated with marginal fold and thrust belts, fracture zones that extend tens of thousands of kilometers, crustal swells and shields that are hundreds of kilometers in diameter and 1 to 2 km high, and sublinear accumulations of volcanic cones and domes that stretch for thousands of kilometers across the plains. The Venusian surface is, however, distinctly different from Earth's in that: (1) its elevated terrains cannot be distinguished from its low plains on a hypsometric curve; (2) trenches have not been found plainsward of the marginal belts; (3) fracture zones bear no resemblance to mid-oceanic ridges; and (4) some features, such as the ridge-belt zone near 210 deg E, seem to have no terrestrial analog. Various theories about tectonism on Venus and Earth of other authors are reviewed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 29
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  • 7
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    Publication Date: 2019-01-25
    Description: It is shown how crater size-density counts may be used to help constrain the history of the Venus atmosphere, based on the predictions of simple but reasonable models for crater production, surface erosion, and the effects of atmospheric drag and breakup on incident meteors in the Venus atmosphere. In particular, if the atmosphere is young, the old (uneroded) surfaces will have crater densities upward of 0.0001/sq km and a ratio of small (4 km) craters to large (128 km) craters near 1000. If the atmosphere is old and the breakup mechanism is dominant, absolute crater densities on Venus surfaces will be diminished by several orders of magnitude relative to the young atmosphere case. If atmospheric drag is dominant, the absolute crater density will be lowered by perhaps an order of magnitude relative to the young atmosphere case, and the ratio of small to large craters will be reduced to a value near 10 to the 1.5 power. Once a large fraction of Venus surface has been imaged at kilometer resolution, as the Venus Orbiting Imaging Radar project promises to do, it could be possible to make an early determination of the age of the Venus atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 26
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  • 8
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    Publication Date: 2019-01-25
    Description: The brightness of surface features on side looking radar images of Venus is determined by many factors: the angles of incidence and reflection, polarization, surface geometry and composition, and so forth. The contribution from surface properties themselves can only be deduced by combining several types of measurement. For instance, without additional information, it is impossible to distinguish the effects of changes in surface roughness from those in dielectric constant. In common with the Moon and Mars, the surface of Venus appears to scatter radar waves in two ways: small-scale surface inhomogeneities, i.e., those smaller than the incident wavelength, depolarize and scatter the energy over a wide range of angles. The Pioneer Venus radar mapper experiment made three overlapping sets of measurements of the equatorial region of Venus from 15 deg S latitude to 45 deg N; the backscatter cross section at a range of incidence angles, the shape and intensity of radar echoes from the nadir, and the microwave brightness temperature of the surface. These techniques developed during the analysis of Pioneer Venus data will be used during the Magellan mission to extract measurements of surface slopes and dielectric constants over all areas covered by the SAR and altimeter antennae, with a resolution of about 10 km. A knowledge of the mechanisms that govern surface scattering will also be useful in the analysis of higher resolution side looking radar images, particularly in distinguishing the effects of changing roughness from those caused by a long range surface tilt or changing dielectric constant.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 12
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  • 9
    Publication Date: 2019-01-25
    Description: The high sensitivity of imaging radars to slope at moderate to low incidence angles enhances the perception of linear topography on images. It reveals broad spatial patterns that are essential to landform mapping and interpretation. As radar responses are strongly directional, the ability to discriminate linear features on images varies with their orientation. Landforms that appear prominent on images where they are transverse to the illumination may be obscure to indistinguishable on images where they are parallel to it. Landform detection is also influenced by the spatial resolution in radar images. Seasat radar images of the Gran Desierto Dunes complex, Sonora, Mexico; the Appalachian Valley and Ridge Province; and accreted terranes in eastern interior Alaska were processed to simulate both Venera 15 and 16 images (1000 to 3000 km resolution) and image data expected from the Magellan mission (120 to 300 m resolution. The Gran Desierto Dunes are not discernable in the Venera simulation, whereas the higher resolution Magellan simulation shows dominant dune patterns produced from differential erosion of the rocks. The Magellan simulation also shows that fluvial processes have dominated erosion and exposure of the folds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 11
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  • 10
    Publication Date: 2019-01-25
    Description: Observations of small terrestrial craters by Seasat synthetic aperture radar (SAR) at high resolution (approx. 25 m) and of comparatively large Venusian craters by Venera 15/16 images at low resolution (1000 to 2000 m) and shorter wavelength show similarities in the radar responses to crater morphology. At low incidence angles, the responses are dominated by large scale slope effects on the order of meters; consequently it is difficult to locate the precise position of crater rims on the images. Abrupt contrasts in radar response to changing slope (hence incidence angle) across a crater produce sharp tonal boundaries normal to the illumination. Crater morphology that is radially symmetrical appears on images to have bilateral symmetry parallel to the illumination vector. Craters are compressed in the distal sector and drawn out in the proximal sector. At higher incidence angles obtained with the viewing geometry of SIR-A, crater morphology appears less compressed on the images. At any radar incidence angle, the distortion of a crater outline is minimal across the medial sector, in a direction normal to the illumination. Radar bright halos surround some craters imaged by SIR-A and Venera 15 and 16. The brightness probably denotes the radar response to small scale surface roughness of the surrounding ejecta blankets. Similarities in the radar responses of small terrestrial impact craters and volcanic craters of comparable dimensions emphasize the difficulties in discriminating an impact origin from a volcanic origin in the images. Similar difficulties will probably apply in discriminating the origin of small Venusian craters, if they exist. Because of orbital considerations, the nominal incidence angel of Magellan radar at the center of the imaging swath will vary from about 45 deg at 10 deg N latitude to about 16 deg at the north pole and at 70 deg S latitude. Impact craters and comparable volcanic landforms will show bilateral symmetry parallel to the illumination vector and will appear increasingly compressed toward higher latitudes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 10
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  • 11
    Publication Date: 2019-01-25
    Description: The ensemble of 41 backscatter images of Venus acquired by the S Band (12.6 cm) Goldstone radar system covers approx. 35 million km and includes the equatorial portion of Guinevere Planitia, Navka Planitia, Heng-O Chasma, and Tinatin Planitia, and parts of Devana Chasma and Phoebe Regio. The images and associated altimetry data combine relatively high spatial resolution (1 to 10 km) with small incidence angles (less than 10 deg) for regions not covered by either Venera Orbiter or Arecibo radar data. Systematic analyses of the Goldstone data show that: (1) Volcanic plains dominate, including groups of small volcanic constructs, radar bright flows on a NW-SE arm of Phoebe Regio and on Ushas Mons and circular volcano-tectonic depressions; (2) Some of the regions imaged by Goldstone have high radar cross sections, including the flows on Ushas Mons and the NW-SE arm of Phoebe Regio, and several other unnamed hills, ridged terrains, and plains areas; (3) A 1000 km diameter multiringed structure is observed and appears to have a morphology not observed in Venera data (The northern section corresponds to Heng-O Chasma); (4) A 150 km wide, 2 km deep, 1400 km long rift valley with upturned flanks is located on the western flank of Phoebe Regio and extends into Devana Chasma; (5) A number of structures can be discerned in the Goldstone data, mainly trending NW-SE and NE-SW, directions similar to those discerned in Pioneer-Venus topography throughout the equatorial region; and (6) The abundance of circular and impact features is similar to the plains global average defined from Venera and Arecibo data, implying that the terrain imaged by Goldstone has typical crater retention ages, measured in hundreds of millions of years. The rate of resurfacing is less than or equal to 4 km/Ga.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 1
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  • 12
    Publication Date: 2018-12-01
    Description: The diverse roles of robotic precursors are examined in the context of recent NASA studies on a long-term program to establish a human outpost on Mars. The scenario in which these precursors must function and the requirements they must satisfy are discussed, and a tentative set of missions is developed which satisfy this scenario and the set of requirements. The missions and an example of vehicle implementation are described, and how these missions assist in technology demonstrations and building an appropriate infrastructure is addressed. The experience to be gained in the areas of mission operations and management as a result of executing the missions is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: IAF PAPER 89-496
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  • 13
    Publication Date: 2018-12-01
    Description: Sample Experiment denotes the set of all operations that include collection, analysis, packaging, and environmental control of atmospheric and geologic samples of Mars. Various functions may be distributed among surface roving vehicles, stationary landers, and spacecraft but the Sample Experiment remains an integrated mission activity that extends from Mars landing through delivery of the sample payload to the recieving facility on Earth. Technological challenges not faced in previous planetary missions include development of robotic systems to manipulate and characterize samples and to reliably seal them in containers with minimal contamination or degradation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AIAA PAPER 89-0423
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  • 14
    Publication Date: 2018-12-01
    Description: To gain a detailed understanding of the character of the planet Mars, it is necessary to send vehicle to the surface and return selected samples for intensive study in earth laboratories. Toward that end, studies have been underway for several years to determine the technically feasible means for exploring the surface and returning selected samples. This paper describes several MRSR mission concepts that have emerged from the most recent studies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AIAA PAPER 89-0417
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  • 15
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    Publication Date: 2018-12-01
    Description: The results of the prephase A study of the Mars Rover Sample Return system are presented. Four mission scenarios are studied, two in the B-configuration, and two D-configuration missions. They incorporated variations in delivery-to-Mars mode, earth-return mode (propulsive or aerocapture), landing site latitude, and rover size and capability in order to identify system drivers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AIAA PAPER 89-0418
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  • 16
    Publication Date: 2013-08-31
    Description: A new catalog of the Apollo 15 coarse fines particles is presented. Powell's macroscopic descriptions, resulting from his 1972 particle by particle binocular examination of all of the Apollo 15 4 to 10 mm fines samples, are retained. His groupings are also retained, but petrographic, chemical, and other data from later analyses are incorporated into this catalog to better characterize individual particles and describe the groups. A large number of particles have no characterization beyond that done by Powell. Complete descriptions of the particles and all known references are provided. The catalog is intended for anyone interested in the rock types collected by Dave Scott and Jim Irwin in the Hadley-Appenine region, and particularly for researchers requiring sample allocations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: PSB-PUBL-81 , NASA-TM-101934 , NAS 1.15:101934 , JSC-24035
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  • 17
    Publication Date: 2013-08-31
    Description: The discovery of the existence of cosmoids, a class of meteoroid in near hyperbolic orbits, was made in a reevaluation of the Sisyphus Experiment on Pioneer 10 and 11. This experiment measured the spontaneous jetting of cosmoids and showed that the dispersion and increase in brightness occurs in microseconds and lasts only briefly. Cosmoid jetting caused multiple telescope thresholds to be exceeded simultaneously which explains the earlier inabilty to compute trajectories from the measured times in the fields of view. A new calculation correlated the Sisyphus individual event measurements with the zodiacal light. That the meteoroid population is dominated by cosmoids is demonstrated. Reported telescopic small comets, measured by a similar optical technique, appear consistent with the Sisyphus results. Characteristic jetting times measured by Sisyphus also show that the volatile cosmoids could not survive in short period orbits.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NAS 1.26:185997 , NASA-CR-185997
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  • 18
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    In:  CASI
    Publication Date: 2013-08-31
    Description: This review assesses the potential aeolian regime on Venus as derived from spacecraft observations, laboratory simulations, and theoretical considerations. The two requirements for aeolian processes (a supply of small, loose particles and winds of sufficient strength to move them) appear to be met on Venus. Venera 9, 10, 13, and 14 images show particles considered to be sand and silt size on the surface. In addition, dust spurts (grains 5 to 50 microns in diameter) observed via lander images and inferred from the Pioneer-Venus nephalometer experiments suggest that the particles are loose and subject to movement. Although data on near surface winds are limited, measurements of 0.3 to 1.2 m/sec from the Venera lander and Pioneer-Venus probes appear to be well within the range required for sand and dust entrainment. Aeolian activity involves the interaction of the atmosphere, lithosphere, and loose particles. Thus, there is the potential for various physical and chemical weathering processes that can effect not only rates of erosion, but changes in the composition of all three components. The Venus Simulator is an apparatus used to simulate weathering under venusian conditions at full pressure (to 112 bars) and temperature (to 800 K). In one series of tests, the physical modifications of windblown particles and rock targets were assessed and it was shown that particles become abraded even when moved by gentle winds. However, little abrasion occurs on the target faces. Thus, compositional signatures for target rocks may be more indicative of the windblown particles than of the bedrock. From these and other considerations, aeolian modifications of the venusian surface may be expected to occur as weathering, erosion, transportation, and deposition of surficial materials. Depending upon global and local wind regimes, there may be distinctive sources and sinks of windblown materials. Radar imaging, especially as potentially supplied via the Magellan mission, may enable the identification of such areas on Venus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 21-22
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  • 19
    Publication Date: 2013-08-31
    Description: The geomorphic expression of Mid-Ocean-Ridge (MOR) volcanism in a subaerial setting occurs uniquely on Earth in Iceland, and the most recent MOR eruptive activity has been concentrated in the Northeastern Volcanic Zone in an area known as Krafla. Within the Krafla region are many of the key morphologic elements of MOR-related basaltic volcanism, as well as volcanic explosion craters, subglacial lava shields, tectonic fissure swarms known as gjar, and basaltic-andesite flows with well developed ogives (pressure-ridges). The objective was to quantify the degree to which the basic volcanic and structural features can be mapped from directional SAR imagery as a function of the look azimuth. To accomplish this, the current expression of volcanic and tectonic constructs was independently mapped within the Krafla region on the E, W, and N-looking SAR images, as well as from SPOT Panchromatic imagery acquired in 1987. The initial observations of the E, W, and N images indicates that fresh a'a lava surfaces are extremely radar bright (rough at 3 cm to meter scales) independent of look direction; this suggests that these flows do not have strong flow direction related structures at meter and cm scales, which is consistent with typical Icelandic a'a lava surfaces in general. The basic impression from a preliminary analysis of the effects of look azimuth biasing on interpretation of the geology of an active MOR volcanic zone is that up to 30 percent of the diagnostic features can be missed at any given look direction, but that having two orthogonal look direction images is probably sufficient to prevent gross misinterpretation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 17-18
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  • 20
    Publication Date: 2013-08-31
    Description: Ridge belts, first identified in the Venera 15/16 images are distinguished as linear regions of concentrated, parallel to anastomosing, ridges. They are tens to several hundreds of km wide, hundreds to over one thousand km long, and composed of individual ridges 5 to 20 km wide and up to 200 km long. The ridges appear symmetrical in the radar images and are either directly adjacent to each other or separated by mottled plains. Cross-strike lineaments, visible as dark or bright lines, are common within the ridge belts, and some truncate individual ridges. In places the ridge belt may be offset by these lineaments, but such offset is rarely consistent across the ridge belt. Once the mode of formation of these ridge belts is understood, their distribution and orientation will help to constrain the homogeneity and orientation of the stresses over the period of ridge belt formation. The look direction for the Venera system was to the west, so ridges appear as pairs of bright and dark lineaments, with the bright line to the east of the dark. The term ridge was used in a general sense to refer to a linear rise. The use of this term is restricted to rises which have a sharp transition from bright to dark at the crest, and are 5 to 15 km wide. These ridges are either continuous or discontinuous. The continuous ridges are over 30 km long and form coherent ridge belts, while the discontinuous ridges are less than 30 km long and do not form a coherent ridge belt. The continuous ridges were divided into 3 components: (1) Anastomosing ridges, in which the individual ridges are sinuous and often meet and cross at small angles, are the most common component; (2) The parallel ridge component also consists of well defined ridges, often with plains separating the individual ridges, but the ridges are more linear and rarely intersect one another; and (3) Parallel ridged plains are composed of indistinct ridges, some of which do not have a distinctive bright-dark pattern. The nature of deformation within the ridge belts is complex and not fully understood at present. Some belts show distinct signs of compression, while others have symmetrical patterns expected in extensional environments. Thus the ridge belts may have formed by more than one style of deformation; some may be extensional, while others are compressional. All the ridge belts are being systematically mapped, especially for symmetrical relationships.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping and Workshop; p 13-14
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  • 21
    Publication Date: 2013-08-31
    Description: Tessera terrain consists of complexly deformed regions characterized by sets of ridges and valleys that intersect at angles ranging from orthogonal to oblique, and were first viewed in Venera 15/16 SAR data. Tesserae cover more area (approx. 15 percent of the area north of 30 deg N) than any of the other tectonic units mapped from the Venera data and are strongly concentrated in the region between longitudes 0 deg E and 150 deg E. Tessera terrain is concentrated between a proposed center of crustal extension and divergence in Aphrodite and a region of intense deformation, crustal convergence, and orogenesis in western Ishtar Terra. Thus, the tectonic processes responsible for tesserae are an important part of Venus tectonics. As part of an effort to understand the formation and evolution of this unusual terrain type, the basic characteristics of the tesserae were compared to the predictions made by a number of tectonic models. The basic characteristics of tessera terrain are described and the models and some of their basic predictions are briefly discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 4-5
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  • 22
    Publication Date: 2013-08-31
    Description: The development of construction materials such as concrete from lunar soils without the use of water requires a different methodology than that used for conventional terrestrial concrete. A unique approach is attempted that utilizes factors such as initial vacuum and then cyclic loading to enhance the mechanical properties of dry materials similar to those available on the moon. The application of such factors is expected to allow reorientation, and coming together, of particles of the materials toward the maximum theoretical density. If such a density can provide deformation and strength properties for even a limited type of construction, the approach can have significant application potential, although other factors such as heat and chemicals may be needed for specific construction objectives.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA Space Engineering Research Center for Utilization of Local Planetary Resources; 3 p
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  • 23
    Publication Date: 2013-08-31
    Description: Extraterrestrial materials, processes, and products were identified which are associated with the production of propellants in space, including the most complete possible conversion of the feedstocks for propellant production into useful products with the minimum feasible expenditure of energy. Laboratory research was identified and begun on several processes that promise very large increases in the mass of useful products at the cost of only modest increases in energy consumption. Processes for manufacturing propellants then become processes for making propellants plus metals and refractories. It is the overall yield of useful materials per unit expended energy that matters, not simply the yield of propellants. Three tasks have been undertaken to date: (1) Literature search and compilation of a dBase 3 data base on space materials processing; (2) Gaseous carbonyl extraction and purification of ferrous metals; and (3) Characterization of lunar ilmenite and its simulants.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA Space Engineering Research Center for Utilization of Local Planetary Resources; 2 p
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  • 24
    Publication Date: 2013-08-31
    Description: A concept for a space station to be placed in low lunar orbit in support of the eventual establishment of a permanent moon base is proposed. This space station would have several functions: (1) a complete support facility for the maintenance of the permanent moon base and its population; (2) an orbital docking area to facilitate the ferrying of materials and personnel to and from Earth; (3) a zero gravity factory using lunar raw materials to grow superior GaAs crystals for use in semiconductors and mass produce inexpensive fiber glass; and (4) a space garden for the benefit of the air food cycles. The mission scenario, design requirements, and technology needs and developments are included as part of the proposal.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-186223 , NAS 1.26:186223
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  • 25
    Publication Date: 2013-08-31
    Description: The outer layers of the Venusian lithosphere appear to dissipate heat from the interior through mantle-driven thermal anomalies (hot spots, swells). As a result, Venus exhibits diverse forms of thin-skin tectonism and magmatic transfer to and extrusion from countless numbers of volcanic centers (e.g., shields, paterae, domes) and volcano-tectonic complexes (e.g., coronae, arachnoids). What is known about the distribution and morphologies of major Venusian shields is summarized, and the evidence for possible structural control of major accumulations as long as 5000 km of small volcanic domes is described.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 39-40
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  • 26
    Publication Date: 2013-08-31
    Description: Lakshmi Planum, a broad smooth plain located in western Ishtar Terra and containing two large oval depressions (Colette and Sacajawea), has been interpreted as a highland plain of volcanic origin. Lakshmi is situated 3 to 5 km above the mean planetary radius and is surrounded on all sides by bands of mountains interpreted to be of compressional tectonic origin. Four primary characteristics distinguish Lakshmi from other volcanic regions known on the planet, such as Beta Regio: (1) high altitude, (2) plateau-like nature, (3) the presence of very large, low volcanic constructs with distinctive central calderas, and (4) its compressional tectonic surroundings. Building on the previous work of Pronin, the objective is to establish the detailed nature of the volcanic deposits on Lakshmi, interpret eruption styles and conditions, sketch out an eruption history, and determine the relationship between volcanism and the tectonic environment of the region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 37-38
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  • 27
    Publication Date: 2013-08-31
    Description: Clotho Tessera, adjacent to southeast Lakshmi Planum, may provide additional evidence for lateral crustal motions, and a model for the origin of small tessera fragments. Clotho Tessera and Lakshmi Planum are so noticeably different, and in such close proximity, it is difficult to derive a reasonable model of their formation in situ. Squeezing of material out from beneath Lakshmi has been suggested as an origin for Moira Tessera, which is also adjacent to Lakshmi and 1400 km west of Clotho. However, a logical model of juxtaposition of the two different terrains, originally from points once distant, can be made for Clotho and Lakshmi (and perhaps other small tesserae as well). It is suggested that Clotho Tessera was once part of Fortuna Tessera, but was cut off by a transcurrent fault zone (the DLZ) striking perpendicular to the Sigrun rift and carried westward where it collided with Lakshmi Planum (forming Danu Montes). A gravity anomaly along the southern border of Lakshmi, in the area of Danu Montes, was interpreted as indicating subduction there, providing additional supporting evidence for the collision hypothesis. Diffusion of the DLZ with proximity to Sigrun Fossae may be due to either higher ductility near the postulated Sigrun rift, or to burial by flows away from the rift nearer to Valkyrie Fossae. Other possible examples of migrating tesserae occur elsewhere: small pieces of Ananke Tessera can be fit back together as though they had rifted apart, and the spreading apart of Ananke and Virilis Tesserae has been suggested because of their symmetric locations about the axis of an inferred spreading zone. Other tessera fragments appear to have been isolated by rifting, with little, if any, significant lateral motion (e.g., Meni and Tellus Tesserae, and Thethus and Fortuna Tesserae). The migrating terrain model for Clotho Tessera supports Sukhanov's interpretation of tesseral fragments as rafts of lighter crustal material.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 27-28
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  • 28
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2013-08-31
    Description: A central question for any planet is the age of its surface. Based on comparative planetological arguments, Venus should be as young and active as the Earth (Wood and Francis). The detection of probable impact craters in the Venera radar images provides a tool for estimating the age of the surface of Venus. Assuming somewhat different crater production rates, Bazilevskiy et al. derived an age of 1 + or - 0.5 billion years, and Schaber et al. and Wood and Francis estimated an age of 200 to 400 million years. The known impact craters are not randomly distributed, however, thus some area must be older and others younger than this average age. Ages were derived for major geologic units on Venus using the Soviet catalog of impact craters (Bazilevskiy et al.), and the most accessible geologic unit map (Bazilevskiy). The crater counts are presented for (diameters greater than 20 km), areas, and crater densities for the 7 terrain units and coronae. The procedure for examining the distribution of craters is superior to the purely statistical approaches of Bazilevskiy et al. and Plaut and Arvidson because the bins are larger (average size 16 x 10(6) sq km) and geologically significant. Crater densities define three distinct groups: relatively heavily cratered (Lakshmi, mountain belts), moderately cratered (smooth and rolling plains, ridge belts, and tesserae), and essentially uncratered (coronae and domed uplands). Following Schaber et al., Grieve's terrestrial cratering rate of 5.4 + or - 2.7 craters greater than 20 km/10(9) yrs/10(6) sq km was used to calculate ages for the geologic units on Venus. To improve statistics, the data was aggregated into the three crater density groups, deriving the ages. For convenience, the three similar age groups are given informal time stratigraphic unit names, from youngest to oldest: Ulfrunian, Sednaian, Lakshmian.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 54-55
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  • 29
    Publication Date: 2013-08-31
    Description: Previous analyses have recognized several styles and orientations of compressional deformation, crustal convergence, and crustal thickening in Eastern Ishtar Terra. An east to west sense of crustal convergence through small scale folding, thrusting, and buckling is reflected in the high topography and ridge-and-valley morphology of Maxwell Montes and the adjacent portion of Fortuna Tessera. This east to west convergence was accompanied by up to 1000 km of lateral motion and large scale strike-slip faulting within two converging shear zones which has resulted in the present morphology of Maxwell Montes. A more northeast to southwest sense of convergence through large scale buckling and imbrication is reflected in large, northwest-trending scarps along the entire northern boundary of Ishtar Terra, with up to 2 km of relief present at many of the scarps. It was previously suggested that both styles of compression have occurred at the expense of pre-existing tessera regions which have then been overprinted by the latest convergence event. The difference in style is attributed mostly to differences in the properties of the crust converging with the tessera blocks. If one, presumably thick, tessera block converges with another tessera region, then the widespread, distributed style of deformation occurs, as observed in western Fortuna Tessera. However, if relatively thin crust (such as suggested for the North Polar Plains converges with thicker tessera regions, then localized deformation occurs, as reflected in the scarps along Northern Ishtar Terra. The purpose is to identify the types of features observed in Eastern Ishtar Terra. Their potential temporal and spatial relationships, is described, possible origins for them is suggested, and how the interpretation of some of these features has led to the multiple-style tectonic evolution model described is shown.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 50-51
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  • 30
    Publication Date: 2013-08-31
    Description: The Tellus Regio area of Venus represents a subset of a narrow latitude band where Pioneer Venus Orbiter (PVO) altimetry data, line-of-sight (LOS) gravity data, and Venera 15/16 radar images have all been obtained with good resolution. Tellus Regio also has a wide variety of surface morphologic features, elevations ranging up to 2.5 km, and a relatively low LOS gravity anomaly. This area was therefore chosen in order to examine the theoretical stress distributions resulting from various models of compensation of the observed topography. These surface stress distributions are then compared with the surface morphology revealed in the Venera 15/16 radar images. Conclusions drawn from these comparisons will enable constraints to be put on various tectonic parameters relevant to Tellus Regio. The stress distribution is calculated as a function of the topography, the equipotential anomaly, and the assumed model parameters. The topography data is obtained from the PVO altimetry. The equipotential anomaly is estimated from the PVO LOS gravity data. The PVO LOS gravity represents the spacecraft accelerations due to mass anomalies within the planet. These accelerations are measured at various altitudes and angles to the local vertical and therefore do not lend themselves to a straightforward conversion. A minimum variance estimator of the LOS gravity data is calculated, taking into account the various spacecraft altitudes and LOS angles and using the measured PVO topography as an a priori constraint. This results in an estimated equivalent surface mass distribution, from which the equipotential anomaly is determined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 52-53
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  • 31
    Publication Date: 2013-08-31
    Description: Future missions to Mars will require a communications system to link activities on the Martian surface with each other and with mission controllers on Earth. A conceptual design is presented for an aerosynchronous communications satellite to provide these links. The satellite provides the capability for voice, data/command, and video transmissions. The mission scenario assumed for the design is described, and a description of a single aerosynchronous satellite is explained. A viable spacecraft design is then presented. Communication band selection and channel allocation are discussed. The communications system conceptual design is presented along with the trades used in sizing each of the required antennas. Also, the analyses used to develop the supporting subsystem designs are described as is the communications impact on each subsystem design.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: L-16580 , NAS 1.60:2942 , NASA-TP-2942
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  • 32
    Publication Date: 2013-08-31
    Description: The encounter of the spacecraft Voyager 2 with Neptune and its large satellite Triton in August 1989 will provide a crucial test of ideas regarding the origin and chemical composition of the outer solar system. In this pre-encounter publication, the possibility is quantified that Titron is a captured moon which, like Pluto and Charon, originally condensed as a major planetesimal within the gas ring that was shed by the contracting protosolar cloud at Neptune's orbit. Ideas of supersonic convective turbulence are used to compute the gas pressure, temperature and rat of catalytic synthesis of CH4, CO2, and C(s) within the protosolar cloud, assuming that all C is initially present as CO. The calculations lead to a unique composition for Triton, Pluto, Charon: each body consists of, by mass, 18 1/2 percent solid CO2 ice, 4 percent graphite, 1/2 percent CH4 ice, 29 percent methanated water ice and 48 percent of anhydrous rock. This mix has a density consistent with that of the Pluto-Charon system and yields a predicted mean density for Triton of 2.20 + or - 0.5 g/cu cm, for satellite radius equal to 1,750 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL-PUBL-89-37 , NAS 1.26:186298 , NASA-CR-186298
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  • 33
    Publication Date: 2013-08-31
    Description: The average surface age of a planet is a major indicator of the level of its geologic activity and thus of the dynamics of its interior. Radar images obtained by Venera 15/16 from the northern quarter of the Venus (lat 30 to 90 degs) reveal about 150 features that resemble impact craters, and they were so interpreted by Soviet investigators B. A. Ivanov, A. T. Basilevsky, and their colleagues. These features range in diameter from about 10 to 145 km. Their areal density is remarkably similar to the density of impact structures found on the American and European continental shields. The basic difference between the Soviet and American estimates of the average surface age of Venus's northern quarter is due to which crater-production rate is used for the Venusian environment. Cratering rates based on the lunar and terrestrial cratering records, as well as statistical calculations based on observed and predicted Venus-crossing asteroids and comets, have been used in both the Soviet and American calculations. The single largest uncertainty in estimating the actual cratering rates near Venus involves the shielding effect of the atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 41-42
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  • 34
    Publication Date: 2013-08-31
    Description: The surface characteristics and morphology of the equatorial region of Venus were first described by Masursky et al. who showed this part of the planet to be characterized by two topographic provinces, rolling plains and highlands, and more recently by Schaber who described and interpreted tectonic zones in the highlands. Using Pioneer Venus (PV) radar image data (15 deg S to 45 deg N), Senske and Head examined the distribution, characteristics, and deposits of individual volcanic features in the equatorial region, and in addition classified major equatorial physiographic and tectonic units on the basis of morphology, topographic signature, and radar properties derived from the PV data. Included in this classification are: plains (undivided), inter-highland tectonic zones, tectonically segmented linear highlands, upland rises, tectonic junctions, dark halo plains, and upland plateaus. In addition to the physiographic units, features interpreted as coronae and volcanic mountains have also been mapped. The latter four of the physiographic units along with features interpreted to be coronae.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 43-44
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  • 35
    Publication Date: 2013-08-31
    Description: A major component of the 1988 Mojave Field Experiment involved the simultaneous acquisition of quad-polarization multifrequency airborne Synthetic Aperture Radar (SAR) imaging radar data and ground measurements thought to be relevant to the radar scattering behavior of a variety of desert surfaces. In preparation for the Magellan mission to Venus, the experiment was designed to explore the ability of SAR to distinguish types of geological surfaces, and the effects of varying incidence angles on the appearance of such surfaces. The airborne SAR system acquired images at approx. 10 m resolution, at 3 incidence angles (30, 40, 50 degs) and at 3 wavelengths (P:68 cm, L:24 cm, C:5.6 cm). The polarimetric capabilities of the instrument allow the simulation of any combination of transmit and receive polarizations during data reduction. Calibrated trihedral corner reflectors were deployed within each scene to permit absolute radiometric calibration of the image data. Initial analyses of this comprehensive radar data set is reported, with emphasis on implications for interpretation of Magellan data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 35-36
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  • 36
    Publication Date: 2013-08-31
    Description: Simple impact craters are known to occur on all of the terrestrial planets and the morphologic expression of their ejecta blankets is a reliable indicator of their relative ages on the Moon, Mars, Mercury, and most recently for Venus. It will be crucial for the interpretation of the geology of Venus to develop a reliable means of distinguishing smaller impact landforms from volcanic collapse and explosion craters, and further to use the observed SAR characteristics of crater ejecta blankets (CEB) as a means of relative age estimation. With these concepts in mind, a study was initiated of the quantitative SAR textural characteristics of the ejecta blanket preserved at Meteor Crater, Arizona, the well studied 1.2 km diameter simple crater that formed approx. 49,000 years ago from the impact of an octahedrite bolide. While Meteor Crater was formed as the result of an impact into wind and water lain sediments and has undergone recognizable water and wind related erosion, it nonetheless represents the only well studied simple impact crater on Earth with a reasonably preserved CEB. Whether the scattering behavior of the CEB can provide an independent perspective on its preservation state and style of erosion is explored. Finally, airborne laser altimeter profiles of the microtopography of the Meteor Crater CEB were used to further quantify the subradar pizel scale topographic slopes and RMS height variations for comparisons with the scattering mechanisms computed from SAR polarimetry. A preliminary assessment was summarized of the L-band radar scattering mechanisms within the Meteor Crater CEB as derived from a NASA/JPL DC-8 SAR Polarimetry dataset acquired in 1988, and the dominant scattering behavior was compared with microtopographic data (laser altimeter profiles and 1:10,000 scale topographic maps).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 19-20
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  • 37
    Publication Date: 2013-08-31
    Description: Approximately 22,000 small dome-like hills were recognized on the northern 20 percent of the surface of Venus imaged by Verera 15/16. These features were described as generally circular in planimetric outline, with a range in basal diameter from the effective resolution of the Venera images (1 to 2 km) up to 20 km. The General Characteristics, Dome Distribution and Terrain Unit and Geologic Feature Associations are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 2-3
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  • 38
    Publication Date: 2013-08-31
    Description: The Parallel Architectures for Planetary Exploration Requirements (PAPER) project is essentially research oriented towards technology insertion issues for NASA's unmanned planetary probes. It was initiated to complement and augment the long-term efforts for space exploration with particular reference to NASA/LaRC's (NASA Langley Research Center) research needs for planetary exploration missions of the mid and late 1990s. The requirements for space missions as given in the somewhat dated Advanced Information Processing Systems (AIPS) requirements document are contrasted with the new requirements from JPL/Caltech involving sensor data capture and scene analysis. It is shown that more stringent requirements have arisen as a result of technological advancements. Two possible architectures, the AIPS Proof of Concept (POC) configuration and the MAX Fault-tolerant dataflow multiprocessor, were evaluated. The main observation was that the AIPS design is biased towards fault tolerance and may not be an ideal architecture for planetary and deep space probes due to high cost and complexity. The MAX concepts appears to be a promising candidate, except that more detailed information is required. The feasibility for adding neural computation capability to this architecture needs to be studied. Key impact issues for architectural design of computing systems meant for planetary missions were also identified.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-185370 , NAS 1.26:185370
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  • 39
    Publication Date: 2013-08-31
    Description: A heat-pipe mechanism is proposed for the transport of heat through the lithosphere of Venus. This mechanism allows the crust and lithosphere on Venus to be greater than 150 km. thick. A thick basaltic crust on Venus is expected to transform eclogite at a depth of 60 to 80 km; the dense eclogite would contribute to lithospheric delamination that returns the crust to the interior of the planet completing the heat-pipe cycle. Topography and the associated gravity anomalies can be explained by Airy compensation of the thick crust. The principal observation that is contrary to this hypothesis is the mean age of the surface that is inferred from crater statistics; the minimum mean age is about 130 Myr and this implies an upper limit of 2 cubic kilometers per year for the surface volcanic flux. If the heat-pipe mechanism was applicable on the Earth in the Archean it would provide the thick lithosphere implied by isotopic data from diamonds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NAS 1.26:184791 , NASA-CR-184791
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  • 40
    Publication Date: 2013-08-31
    Description: The Soviet Space Program proposes large-scale investigations of Mars as one of the most important trends for the next 10 to 15 years. The objectives include global studies of the surface of Mars, its atmosphere, and the return of soil samples to Earth. The first stage of the program is to be implemented in the mid-90s. It includes measurements from an orbiter and a balloon in the atmosphere and on the surface from a rover as well. This can be done using the high energy upper stage of the launch vehicle. The payload mass could amount to about 1500 to 1700 kg. The capabilities of the Mars Mission in 1994 are discussed. As presently planned, Mars will be studied concurrently with the following facilities: an orbiter with instruments for remote sensing from a polar orbit; a balloon deployed in the Martian atmosphere; a rover on the surface; a network of smaller stations on the surface; a subsatellite; and a device to return a container with photo films of the Martian surface taken with a super high resolution. If the exploration of Mars with the MARS-94 spacecraft begins late in 1994 the American Mars-Observer will still be functioning in the near-Mars orbit. Thus, joint operation of the two satellites becomes possible providing coordinated exploration, the creation of joint data banks, joint data interpretation, and the development of a joint engineering model of Mars for its further exploration. There is an opportunity for experiments and instrumentation on the Soviet missions that address questions of interest to exobiology. American scientists are invited to participate in the upcoming Soviet missions, and lend expertise to further understanding of the relationship between the physical and chemical evolution of the solar system and the appearance of life.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Ames Research Center, Exobiology and Future Mars Missions; p 43
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  • 41
    Publication Date: 2013-08-31
    Description: A core handling device for use on Mars is being designed. To provide a context for the design study, it was assumed that a Mars Rover/Sample Return (MRSR) Mission would have the following characteristics: a year or more in length; visits by the rover to 50 or more sites; 100 or more meter-long cores being drilled by the rover; and the capability of returning about 5 kg of Mars regolith to Earth. These characteristics lead to the belief that in order to bring back a variegated set of samples that can address the range of scientific objetives for a MRSR mission to Mars there needs to be considerable analysis done on board the rover. Furthermore, the discrepancy between the amount of sample gathered and the amount to be returned suggests that there needs to be some method of choosing the optimal set of samples. This type of analysis will require pristine material-unaltered by the drilling process. Since the core drill thermally and mechanically alters the outer diameter (about 10 pct) of the core sample, this outer area cannot be used. The primary function of the core handling device is to extract subsamples from the core and to position these subsamples, and the core itself if needed, with respect to the various analytical instruments that can be used to perform these analyses.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Ames Research Center, Exobiology and Future Mars Missions; p 29
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  • 42
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2013-08-31
    Description: A Mars Rover/Sample Return (MRSR) mission is currently being studied for the late 1990's. The objectives of the mission are to better understand the origin and evolution of Mars, to search for evidence of former life, and to improve the knowledge of the Martian environment in preparation for subsequent human exploration. Having formed in a different part of the Solar System from Earth, Mars will provide clues that will better enable the discrimination between conflicting theories of Solar System formations. Mars is also a natural laboratory on which a wide range of geologic and meteorological processes have operated under conditions very different from those on Earth. Samples are needed so that the full range of analytical techniques available here on Earth can be applied to the study of these issues. The rover provides the mobility needed to access different materials, and can be equipped with an analytical capability so that the planet can be sampled intelligently. The rover will also provide the means of exploring the planet on a human scale and performing a wide range of in situ measurements at different locations. Different mission scenarios are currently being studied with the goal of achieveing sample return before the end of the century.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Ames Research Center, Exobiology and Future Mars Missions; p 11
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  • 43
    Publication Date: 2013-08-31
    Description: Technologies necessary for the creation of a cis-Lunar infrastructure, namely: (1) automation and robotics; (2) life support systems; (3) fluid management; (4) propulsion; and (5) rotating technologies, are explored. The technological focal point is on the development of automated and robotic systems for the implementation of a Lunar Oasis produced by Automation and Robotics (LOAR). Under direction from the NASA Office of Exploration, automation and robotics were extensively utilized as an initiating stage in the return to the Moon. A pair of autonomous rovers, modular in design and built from interchangeable and specialized components, is proposed. Utilizing a buddy system, these rovers will be able to support each other and to enhance their individual capabilities. One rover primarily explores and maps while the second rover tests the feasibility of various materials-processing techniques. The automated missions emphasize availability and potential uses of Lunar resources, and the deployment and operations of the LOAR program. An experimental bio-volume is put into place as the precursor to a Lunar environmentally controlled life support system. The bio-volume will determine the reproduction, growth and production characteristics of various life forms housed on the Lunar surface. Physicochemical regenerative technologies and stored resources will be used to buffer biological disturbances of the bio-volume environment. The in situ Lunar resources will be both tested and used within this bio-volume. Second phase development on the Lunar surface calls for manned operations. Repairs and re-configuration of the initial framework will ensue. An autonomously-initiated manned Lunar oasis can become an essential component of the United States space program.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NAS 1.26:186220 , NASA-CR-186220
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  • 44
    Publication Date: 2013-08-31
    Description: A basic procedure for robotically constructing a manned Mars base is outlined. The research procedure was divided into three areas: environment, robotics, and habitat. The base as designed will consist of these components: two power plants, communication facilities, a habitat complex, and a hangar, a garage, recreation and manufacturing facilities. The power plants will be self-contained nuclear fission reactors placed approx. 1 km from the base for safety considerations. The base communication system will use a combination of orbiting satellites and surface relay stations. This system is necessary for robotic contact with Phobos and any future communication requirements. The habitat complex will consist of six self-contained modules: core, biosphere, science, living quarters, galley/storage, and a sick bay which will be brought from Phobos. The complex will be set into an excavated hole and covered with approximately 0.5 m of sandbags to provide radiation protection for the astronauts. The recreation, hangar, garage, and manufacturing facilities will each be transformed from the four one-way landers. The complete complex will be built by autonomous, artificially intelligent robots. Robots incorporated into the design are as follows: Large Modular Construction Robots with detachable arms capable of large scale construction activities; Small Maneuverable Robotic Servicers capable of performing delicate tasks normally requiring a suited astronaut; and a trailer vehicle with modular type attachments to complete specific tasks; and finally, Mobile Autonomous Rechargeable Transporters capable of transferring air and water from the manufacturing facility to the habitat complex.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NAS 1.26:186224 , NASA-CR-186224
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  • 45
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    Unknown
    In:  CASI
    Publication Date: 2013-08-31
    Description: The Venera 15/16 spacecraft revealed a number of features of unknown origin including coronae, elongate to circular structures with a complex interior surrounded by an annulus of concentric ridges. Eighteen coronae were identified in Venera 15/16 data of Venus; an additional thirteen possible coronae are found in Pioneer Venus and Arecibo data. Coronae, with maximum widths of 160 to over 650 km, are found primarily in two clusters in the Northern Hemisphere located to the east and west of Ishtar Terra. Another possible cluster is located in Themis Regio in the Southern Hemisphere. The majority of coronae are at least partially raised less than 1.5 km above the surrounding region, and over half are partially surrounded by a peripheral trough. A sequence of events for coronae has been determined through mapping. Prior to corona formation, regional compression or extension creates bands of lineaments along which coronae tend to later form. During the early stages of corona formation, relatively raised topography is produced by uplift and volcanic construction. The evolution of coronae and their general characteristics have been compared to two models of corona origin: hotspots and sinking mantle diapirs. In the hotspot or rising mantle diapir model, heating and melting at depth create uplift at the surface. Uplift is accompanied by central extension, facilitating volcanism. Gravitational relaxation of the uplifted region follows producing the compressional features within the annulus and the peripheral trough. Both models can predict the major characteristics and evolutionary sequence of coronae. The sinking diapir model does predict an early-time low and central compression as well as broadening and shallowing of the peripheral trough with time, all of which are not observed at current data resolution. In addition, the sinking mantle diapir mode predicts more simultaneous formation of the high topography, annulus and trough unlike the hotspot or rising mantle diapir mode. High resolution Magellan data will be used to distinguish between the two models of corona origin.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 47-48
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  • 46
    Publication Date: 2013-08-31
    Description: Linear mountain belts in Ishtar Terra were recognized from Pioneer-Venus topography, and later Arecibo images showed banded terrain interpreted to represent folds. Subsequent analyses showed that the mountains represented orogenic belts, and that each had somewhat different features and characteristics. Orogenic belts are regions of focused shortening and compressional deformation and thus provide evidence for the nature of such deformation, processes of crustal thickening (brittle, ductile), and processes of crustal loss. Such information is important in understanding the nature of convergent zones on Venus (underthrusting, imbrication, subduction), the implications for rates of crustal recycling, and the nature of environments of melting and petrogenesis. The basic elements of four convergent zones and orogenic belts in western Ishtar Terra are identified and examined, and then assess the architecture of these zones (the manner in which the elements are arrayed), and their relationships. The basic nomenclature of the convergent zones is shown.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 24-25
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  • 47
    Publication Date: 2013-08-31
    Description: Venera 15/16 radar data for an area in NW Ishtar Terra, Venus, show an area with moderate radar return and a smooth textured surface which embays low lying areas of the surrounding mountainous terrain. Although this unit may be an extension of the lava plains of Lakshmi Planum to the southeast, detailed study suggests a separate volcanic center in NW Ishtar Terra. Lakshmi Planum, on the Ishtar Terra highland, exhibits major volcanic and tectonic features. On the Venera radar image radar brightness is influenced by slope and roughness; radar-facing slopes (east-facing) and rough surfaces (approx. 8 cm average relief) are bright, while west-facing slopes and smooth surfaces are dark. A series of semi-circular features, apparently topographic depressions, do not conform in orientation to major structural trends in this region of NW Ishtar Terra. The large depression in NW Ishtar Terra is similar to the calderas of Colette and Sacajawea Paterae, as all three structures are large irregular depressions. NW Ishtar Terra appears to be the site of a volcanic center with a complex caldera structure, possibly more than one eruptive vent, and associated lobed flows at lower elevations. The morphologic similarity between this volcanic center and those of Colette and Sacajawea suggests that centralized eruptions have been the dominant form of volcanism in Ishtar. The location of this volcanic center at the intersection of two major compressional mountain belts and the large size of the calders (with an inferred larg/deep magma source) support a crustal thickening/melting rather than a hot-spot origin for these magmas.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 15-16
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  • 48
    Publication Date: 2013-08-31
    Description: Thermochemical reactions between sulfur-bearing gases in the atmosphere of Venus and calcium-, iron-, magnesium-, and sulfur-bearing minerals on the surface of Venus are an integral part of a hypothesized cycle of thermochemical and photochemical reactions responsible for the maintenance of the global sulfuric acid cloud cover on Venus. SO2 is continually removed from the Venus atmosphere by reaction with calcium bearing minerals on the planet's surface. The rate of volcanism required to balance SO2 depletion by reactions with calcium bearing minerals on the Venus surface can therefore be deduced from a knowledge of the relevant gas-solid reaction rates combined with reasonable assumptions about the sulfur content of the erupted material (gas + magma). A laboratory program was carried out to measure the rates of reaction between SO2 and possible crustal minerals on Venus. The reaction of CaCO3(calcite) + SO2 yields CaSO4 (anhydrite) + CO was studied. Brief results are given.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 8-9
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  • 49
    Publication Date: 2013-08-31
    Description: The modes of lithospheric heat transfer and the tectonic styles may differ between Earth and Venus, depending on how the high surface temperature (700 K = 430 C), dense and opaque atmosphere (approx. 10 MPa = 100 bars), lack of water oceans, and the other known ways in which Venus differs from Earth, influence basic lithospheric processes, thermal gradient, upper mantle temperature, thermal and chemical evolution, and convection. A fundamental question is whether the lithosphere of Venus is horizontally stable, like the other terrestrial planets, or is mobile like that on Earth. The variety of characteristics, their integrated relationships, and their predictable behavior throughout Western Aphrodite Terra are similar to those features known to occur in association with the terrestrial seafloor at spreading centers and divergent plate boundaries. It is concluded that Western Aphrodite Terra represents the site of crustal spreading centers and divergent plate boundaries. The extent of similar characteristics and processes elsewhere on Venus outside of the 13,000 km long Western and Eastern Aphrodite Terra rise is unknown at the present, but their presence in other areas of the equatorial highlands, suggested from recent analysis, may be tested with forthcoming Magellan data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Abstracts for the Venus Geoscience Tutorial and Venus Geologic Mapping Workshop; p 6-7
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  • 50
    Publication Date: 2013-08-31
    Description: The precipitation of 30 mbar of Martian atmosphere CO2 as carbonates in lakes is suggested to be the source of thick sequences of layered deposits found in the Valles Marineris. Support is adduced for this scenario from processes occurring in the perennially frozen dry valley lakes of Antarctica, where the lake water is supersaturated with atmospheric gases. Atmospheric CO2 would have accumulated in such Martian lakes as temperature fell, and the presence of an insulating ice cover would have allowed liquid water to exist.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Exobiology and Future Mars Missions; p 44-4
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  • 51
    Publication Date: 2013-08-31
    Description: Thin cherty sedimentary layers within the volcanic portions of the 3,500 to 3,300 Ma-old Onverwacht and Fig Tree Groups, Barberton Greenstone belt, South Africa, and Warrawoona Group, eastern Pilbara Block, Western Australia, contain an abundant record of early Archean life. Five principal types of organic and probably biogenic remains and or structures can be identifed: stromatolites, stromatolite detritus, carbonaceous laminite or flat stromalite, carbonaceous detrital particles, and microfossils. Early Archean stromatolites were reported from both the Barberton and eastern Pilbara greenstone belts. Systematic studies are lacking, but two main morphological types of stromatolites appear to be represented by these occurrences. Morphology of the stromalites is described. Preserved early Archean stromatolites and carbonaceous matter appear to reflect communities of photosynthetic cyanobacteria inhabiting shallow, probably marine environments developed over the surfaces of low-relief, rapidly subsiding, simatic volcanic platforms. The overall environmental and tectonic conditions were those that probably prevailed at Earth's surface since the simatic crust and oceans formed sometime before 3,800 Ma. Recent studies also suggest that these early Archean sequences contain layers of debris formed by large-body impacts on early Earth. If so, then these early bacterial communities had developed strategies for coping with the disruptive effects of possibly globe-encircling high-temperature impact vapor clouds, dust blankets, and impact-generated tsunamis. It is probable that these early Archean biogenic materials represent organic communities that evolved long before the beginning of the preserved geological record and were well adapted to the rigors of life on a young, volcanically active Earth during late bombardment. These conditions may have had parallels on Mars during its early evolution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Ames Research Center, Exobiology and Future Mars Missions; p 40-41
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  • 52
    facet.materialart.
    Unknown
    In:  CASI
    Publication Date: 2013-08-31
    Description: The valley systems in Mars' ancient cratered terrain provide strong evidence for a warmer and wetter climate very early in planetary history. The valley systems in some instances debouch into closed depressions that could have acted as local ponding basins for the flow. A survey of the Martian equatorial region shows that numerous local depressions at the confluence of valley systems exist. These depressions (approximately 100 km) typically are characterized by many valleys flowing into them and few or none flowing out. If ponding did take place, these basin would have contained lakes for some period during Mars' early warmer epoch. Although the collection basins are numerous, location of ones that have not suffered significant subsequent geologic modification is difficult. Some morphologic features suggest that volcanic lavas may have filled them subsequent to any early fluvial activity. Two detailed maps of valley systems and local ponding basins in USGC 1:2,000,000 subquadrangles were completed and a third is in progress. The completed regions are in Mare Tyrrhenum (MC-22 SW) and Margarifter Sinus (MC-19 SE), and the region in progress is in Iapygia (MC-21 NW). On the maps, the valley systems and interpreted margins of ponding basins are indicated. The depressions are of interest for two reasons. First, the depressions were surely the sites in which the materials eroded from the valleys were deposited. Such sediments could preserve important information about the physical conditions at the time of deposition. Second, the sediments could preserve evidence of water-atmosphere interactions during the early period of the Martian climate. Atmospheric carbon dioxide would dissolve in water, and solid carbonate minerals would tend to precipitate out to form carbonate sedimentary deposits. Formation of carbonates in this manner might account for some of the CO2 lost from the early more dense atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Ames Research Center, Exobiology and Future Mars Missions; p 26
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  • 53
    Publication Date: 2013-08-31
    Description: A number of questions concerning the surface mineralogy and the history of water on Mars remain unresolved using the Viking analyses and Earth-based telescopic data. Identification and quantitation of iron-bearing clays on Mars would elucidate these outstanding issues. Near infrared correlation analysis, a method typically applied to qualitative and quantitative analysis of individual constituents of multicomponent mixtures, is adapted here to selection of distinctive features of a small, highly homologous series of Fe/Ca-exchanged montmorillonites and several kalinites. Independently determined measures of surface iron, relative humidity and stored electronic energy were used as constituent data for linear regression of the constituent vs. reflectance data throughout the spectral region 0.68 to 2.5 micrometers. High correlations were found in appropriate regions for all three constituents, though that with stored energy is still considered tenuous. Quantitation was improved using 1st and 2nd derivative spectra. High resolution data over a broad spectral range would be required to quantitatively identify iron-bearing clays by remotely sensed reflectance.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Ames Research Center, Exobiology and Future Mars Missions; p 12
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  • 54
    Publication Date: 2013-08-31
    Description: Particles in the mass range from 10 to the minus 7th power to 10 to the minus 3rd power grams contribute 80 percent of the total mass influx of meteoritic material in the 10 to the minus 13th power to 10 to the 6th power gram mass range at Earth (Hughes, 1978). On Earth atmospheric entry, all but the smallest particles in the 10 to the minus 7th power to 10 to the minus 3rd power gram mass range, about 60 to 1200 micrometers in diameter, are heated sufficiently to melt and vaporize. Mars, because of its lower escape velocity and larger atmospheric scale height, is a much more favorable site for unmelted survival of micrometeorites on atmospheric deceleration. Researchers calculate that a significant fraction of particles throughout the 60 to 1200 micrometer diameter range will survive atmospheric entry unmelted. Thus returned Mars soils may offer a resource for sampling micrometeorites in a size range uncollectable in unaltered form at Earth. The addition of meteoritic material to the Mars soils should perturb their chemical composition, as has been detected using the soils on the Moon (Anders, et al., 1973). Using measured mass influx at Earth and estimates of the Mars/Earth flux ratio, researchers estimate a mass influx at Mars of between 2,700 and 202,000 metric tons per year.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Lyndon B.; NASA, Lyndon B. John
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  • 55
    Publication Date: 2013-08-31
    Description: A zonally symmetric, linear radiative-dynamical model is compared with observations of the upper tropospheres and stratospheres of the outer planets. Seasonal variation is included in the model. Friction is parameterized by linear drag (Rayleigh friction). Gas opacities are accounted for but aerosols are omitted. Horizontal temperature gradients are small on all the planets. Seasonal effects are strongest on Saturn and Neptune but are weak even in these cases, because the latitudinal gradient of radiative heating is weak. Seasonal effects on Uranus are extremely weak because the radiative time constant is longer that the orbital period. One free parameter in the model is the frictional time constant. Comparison with observed temperature perturbations over zonal currents in the troposphere shows that the frictional time constant is on the same order as the radiative time constant for all these objects. Vertical motions predicted by the model are extremely weak. They are much smaller than one scale height per orbital period, except in the immediate neighborhood of tropospheric and zonal currents.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-184826 , NAS 1.26:184826
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  • 56
    Publication Date: 2013-08-31
    Description: The Cassini Orbiter and Titan Probe model payloads include a number of infrared and microwave instruments. This document describes: (1) the fundamental scientific objectives for Saturn and Titan which can be addressed by infrared and microwave instrumentation, (2) the instrument requirements and the accompanying instruments, and (3) the synergism resulting from the comprehensive coverage of the total infrared and microwave spectrum by the complement of individual instruments. The baseline consists of four instruments on the orbiter and two on the Titan probe. The orbiter infrared instruments are: (1) a microwave spectrometer and radiometer; (2) a far to mid-infrared spectrometer; (3) a pressure modulation gas correlation spectrometer, and (4) a near-infrared grating spectrometer. The two Titan probe infrared instruments are: (1) a near-infrared instrument, and (2) a tunable diode laser infrared absorption spectrometer and nephelometer.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NAS 1.61:1213 , REPT-89B0006 , NASA-RP-1213
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  • 57
    Publication Date: 2018-12-01
    Description: The Cassini Mission, a NASA/ESA cooperative project which includes a deployment of probe into the atmosphere of Titan, is described, with particular attention given to the shock radiometer experiment planned for the Titan probe for the analysis of Titan's atmosphere. Results from a shock layer analysis are presented, demonstrating that the mole fractions of the major species (N2, CH4, and, possibly Ar) in the Titan atmosphere can be successfully determined by the Titan-probe radiometer, by measuring the intensity of the CN(violet) radiation emitted in the shock layer during the high velocity portion of the probe entry between 200 and 400 km altitude. It is shown that the sensitivity of the CN(violet) radiation makes it possible to determine the mole fractions of N2, CH4, and Ar to about 0.015, 0.003, and 0.01, respectively, i.e., much better than the present uncertainties in the composition of Titan atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AIAA PAPER 89-1770
    Format: text
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  • 58
    Publication Date: 2016-03-09
    Description: A preliminary control network for the Saturnian satellite Phoebe was determined based upon 6 distinct albedo features mapped on 16 Voyager 2 images. Using an existing map and an analytical triangulation program which minimized the measurement error, the north pole of Phoebe was calculated to be alpha sub 0 = 355.0 deg + or - 9.6 deg, delta sub 0 = 68.7 deg + or - 7.9 deg, where alpha sub 0, delta sub 0 are standard equatorial coordinates with equinox J2000 at epoch J2000. The prime meridian of Phoebe was computed to be W = 304.7 deg + 930.833872d, where d is the interval in days from JD 2451545.0 TDB.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-185716 , N-2934-NASA , NAS 1.26:185716
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  • 59
    Publication Date: 2016-03-09
    Description: Antarctica has been a prolific source of meteorites since meteorite concentrations were discovered in 1969. The Antarctic Search For Meteorites (ANSMET) project has been active over much of the Trans-Antarctic Mountain Range. The first ANSMET expedition (a joint U.S.-Japanese effort) discovered what turned out to be a significant concentration of meteorites at the Allan Hills in Victoria Land. Later reconnaissance in this region resulted in the discovery of meteorite concentrations on icefields to the west of the Allan Hills, at Reckling Moraine, and Elephant Moraine. Antarctic meteorite location maps (reduced versions) of the Allan Hills main, near western, middle western, and far western icefields and the Elephant Moraine icefield are presented. Other Antarctic meteorite location maps for the specimens found by the ANSMET project are being prepared.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: LPI-TR-89-02 , NASA-CR-181510 , NAS 1.26:181510
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  • 60
    facet.materialart.
    Unknown
    In:  Other Sources
    Publication Date: 2018-12-01
    Description: Voyager 2 and its twin, Voyager 1, were launched in 1977. Both spacecraft investigated Jupiter's and Saturn's systems. Voyager 2 continued on to fly past Utranus in 1986 and Neptune in 1989, while Voyager 1 headed out of the solar system. The mission at Neptune presented many engineering and scientific challenges. Neptune is about 30 Astronomical Units (AU) from the sun and earth, resulting in extremely low lights levels (nearly 1000 times lower than at earth) and in communication distances of nearly 4.5 billion kilometers. To compensate for the long communication distances, several new techniques were developed. As at Uranus, an onboard backup computer compressed the imaging data. In addition, the data return was further improved by electronically arraying and expanding several receiving antennas. As a result, the data rates from Neptune were about the same as they were from Saturn, even though the distance was three times greater. Several changes were made in the onboard software to optimize Voyager's operations at the very low light levels at Neptune. Finally, to obtain the maximum information from the Neptune encounter, a trajectory was selected which passed within just 5000 kilometers of Neptune's atmosphere, but which also posed several possible environmental hazards.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: IAF PAPER 89-471
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  • 61
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 568 (1989), S. 8-21 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Na(V3-xNbx)Nb6O14  -  A Novel Oxoniobate with [Nb6O12] and [M2O9] ClustersGoldcolored single crystals and black powders of Na(V3-xNbx)Nb6O14 have been prepared by heating a pellet containing a mixture of NaNbO3, NbO2, NbO, VO2 and NaF or Na2B4O7 (as mineralizers) at 900°C in a sealed gold capsule. The analytically determined Nb : V ratio is 5 : 1 and means that x is about 1.5. The compound crystallizes in P63/m with a = 603.4(1), c = 1807.9(5) pm and Z = 3.The crystal structure can be described in terms of common close packing of sheets of O and Na atoms together with Nb6 octahedra. Characteristic building groups of the new structure type are [Nb6O12] clusters, [M2O9] clusters and NbO5 bipyramids. V atoms are distributed only on the positions of the Nb atoms within the trigonal bipyramids or the [M2O9] clusters. The [Nb6O12] clusters show characteristicaly short distances dNb-Nb = 279.4 and 281.3 pm, respectively. In the [M2O9] units, which are built from two MO6 octahedra that share a common face, V or Nb atoms form M-M dumbbells with dM-M = 255.9 pm. The electronic structure is discussed using Extended Hückel calculations.
    Notes: Goldgelb glänzende Einkristalle und schwarze Pulver von Na(V3-xNbx)Nb6O14 wurden durch Tempern eines zu einer Pille gepreßten Gemenges aus NaNbO3, NbO2, NbO, VO2 und NaF oder Na2B4O7 (als Mineralisatoren) bei 900°C in einem geschlossenen Goldrohr dargestellt. Das analytisch ermittelte Verhältnis Nb : V ist ungefähr 5 : 1, so daß x bei etwa 1,5 liegt. Die Verbindung kristallisiert in P63/m mit a = 603,4(1), c = 1807,9(5) pm und Z = 3.Die Kristallstruktur baut sich aus gemeinsam dicht gepackten Schichten von O-Atomen, Na-Atomen und Nb6-Oktaedern auf. Charakteristische Baugruppen des neuen Strukturtyps sind [Nb6O12]- und [M2O9]-Cluster sowie NbO5-Bipyramiden. Die V-Atome verteilen sich nur auf die Positionen der Nb-Atome in den trigonalen Bipyramiden und den [M2O9]-Cluster. Innerhalb der [Nb6O12]-Cluster liegen charakteristisch kurze Abstände dNb-Nb = 279,4 bzw. 281,3 pm vor. In [M2O9]-Einheiten, zwei über Flächen verknüpften MO6-Oktaedern, bilden V- und Nb-Atome M-M-Hanteln mit dM-M = 255,9 pm. Die Bindungsverhältnisse werden unter Zuhilfenahme von Extended-Hückel-Rechnungen diskutiert.
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  • 62
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 568 (1989), S. 29-34 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Ba5AlIr2O11: A New Compound with Iridium(IV, V)The hitherto unknown compound Ba5AlIr2O11 was prepared and investigated by X-ray technique (space group D2h16-Pnma, a = 18.8360; b = 5.7887; c = 11.1030 Å; Z = 4). Iridium has an octahedral coordination in each case two octahedra are connected by a plane. These double octahedra form with corner connected AlO4 tetrahedra [Ir2AlO11]10- units. Ba5AlIr2O11 is not related to the perovskite type compounds.
    Notes: Die bisher unbekannte Verbindung Ba5AlIr2O11 wurde dargestellt und die Kristallstruktur bestimmt (Raumgruppe D2h16-Pnma, a = 18,8360; b = 5,7887; c = 11,1030 Å). Iridium ist oktaedrisch koordiniert, je zwei Oktaeder sind flächenverknüpft. Je ein Oktaederdoppel bildet mit eckenverknüpften AlO4-Tetraedern eine [Ir2AlO11]10--Baueinheit. Ba5AlIr2O11 gehört nicht zu den Perowskitvarianten.
    Additional Material: 3 Ill.
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  • 63
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Experiments about the Mixed Crystal Formation between Zincoxotantalates and -antimonates: ZnTa2-xSbxO6 and Zn4Ta2-xSbxO9In the area of substituted oxotantalates of zinc two new phases of the composition A: ZnTa1·8Sb0·2O6 and B: Zn4Ta1·2Sb0·8O9 were prepared and investigated by X-ray single crystal technique. A crystallizes with tetragonal symmetry (space group D4h14-P42/mnm, a = 4.7314; c = 9.2160 Å; Z = 2). B is monoclinic (space group C2h6-C2/c; a = 15.103; b = 8.839; c = 10.378 Å; β = 93.81°; Z = 8). A crystallizes with trirutile structure, although there is a small replacement of Ta5+ by Sb5+. B maintains the Zn4Ta2O9 structure. One of the point positions of the M5+ ions is occupied statistically by Ta5+/Sb5+ and Zn2+. B is a metastable compound.
    Notes: Im Bereich substituierter Oxotantalate des Zinks wurden zwei neue Phasen A: ZnTa1,8Sb0,2O6 und B: Zn4Ta1,2Sb0,8O9 an Einkristallen röntgenographisch untersucht. A kristallisiert tetragonal (Raumgruppe D4h14-P42/mnm, a = 4,7314; c = 9,2160 Å; Z = 2), B monoklin (Raumgruppe C2h6-C2/c, a = 15,103; b = 8,839; c = 10,378 Å; β = 93,81°; Z = 8). A kristallisiert trotz des geringen Ersatzes von Ta5+ gegen Sb5+ im Trirutiltyp. B behält die Struktur von Zn4Ta2O9 bei. Eine Position der oktaedrisch koordinierten M5+-Ionen ist mit Zn2+ statistisch besetzt. B ist metastabil.
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  • 64
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Pseudochalcogen Compounds. XVIII. Cyanamidolysis of Organophosphoryl-(phosphonyl-) chloridesCyanamidolytic reactions of organophosphoryl- and -phosphonyl chlorides are leading in dependence on the conditions of the reactions to metal-organo-cyanamidophosphates, M[(RO)2P(Y)NCN], and -cyanamidophosphonates, M[(RO)R'P(Y)NCN], M2[RP(Y)(NCN)2] respectively, as well as to the corresponding organo phosphoryl (phosphonyl) hydrogencyanamides, (RO)2P(Y)NHCN, (RO)R'P(Y)NHCN, RP(Y)(NHCN)2 and to Bis-(organophosphoryl)- and Bis-(organophosphonyl)-carbodiimides, (RO)2P(Y)-NCN-P(Y)(OR)2, (RO)R'P(Y)-NCN-P(Y)R' (OR). (Y: O, S). Conditions for synthesis as well as properties and structures of the new compounds are discussed on the basis of characteristic IR- and 31P-NMR-data.
    Notes: Cyanamidolysereaktionen an Organophosphoryl- und -phosphonyl-chloriden führen in Abhängigkeit von den gewählten Reaktionsbedingungen zu Metall-organo-cyanamidophosphaten, M[(RO)2P(Y)NCN], Metall-organo-cyanamidophosphonaten, M[(RO)R'P(Y)NCN], M2[RP(Y)(NCN)2] (Y: O, S), ferner zu den entsprechenden Organophosphoryl-(phosphonyl)-hydrogencyanamiden, (RO)2P(Y)NHCN, (RO)R'P(Y)NHCN, RP(Y)(NHCN)2 sowie zu Bis-(organophosphoryl)-carbodiimiden, (RO)2P(Y)—NCN—P(Y)(OR)2 und Bis-(organophosphonyl)-carbodiimiden, (RO)R'P(Y)-NCN-P(Y)R'(OR). Synthesebedingungen, Strukturen und Eigenschaften der neuen Verbindungen werden anhand der charakteristischen IR- und 31P-NMR-Daten diskutiert.
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  • 65
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 568 (1989), S. 73-84 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemical transport of vanadiummonophosphide with iodineWell shaped crystals of vanadiummonophosphide can be grown by CVT using iodine as transport agent (e. g. → 900°C). As a result of thermodynamical calculations the evaporation and deposition of VP should be expressed by the following exothermic equilibrium \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm VP}_{\rm s} + 7{\rm /}2{\rm I}_{2,{\rm g}} {\rm = VI}_{4,{\rm g}} {\rm + PI}_{3,{\rm g}} . $$\end{document} At higher temperatures and low concentrations of Iodine, combined with desorption of moisture from the walls of the silica ampules endothermic deposition of VP according to \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm VP}_{\rm s} {\rm } + {\rm }2{\rm HI}_{\rm g} {\rm = VI}_{2,{\rm g}} {\rm + }1/2{\rm P}_{2,{\rm g}} {\rm } + {\rm H}_{2,{\rm g}} {\rm .} $$\end{document} has been observed. Assuming ΔBH°298(VPs) = -61 [kcal/mol] a satisfying agreement between thermodynamical calculations and experimental results can be reached.
    Notes: VP wandert bei hinreichender Zugabe von Iod im Temperaturgefälle (z. B. 800 → 900°C) in die heißere Zone. Bestimmend ist das exotherme Gleichgewicht:\documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm VP}_{\rm s} + 7{\rm /}2{\rm I}_{2,{\rm g}} {\rm = VI}_{4,{\rm g}} {\rm + PI}_{3,{\rm g}} . $$\end{document} Bei niedrigen Transportmittelmengen und hohen Temperaturen (1125 → 1080°C) führt die Abgabe von H2O aus der Wand der Quarzglasampulle zu einer endothermen Transportreaktion: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm VP}_{\rm s} {\rm } + {\rm }2{\rm HI}_{\rm g} {\rm = VI}_{2,{\rm g}} {\rm + }1/2{\rm P}_{2,{\rm g}} {\rm } + {\rm H}_{2,{\rm g}} {\rm .} $$\end{document} Thermodynamische Rechnungen zum chemischen Transport von VP stimmen mit den Experimenten unter der Annahme von ΔBH°298(VPs) = -61 [kcal/mol] befriedigend überein.
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  • 66
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 568 (1989), S. 95-105 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Chemical transport of the vanadium oxides V2O5, V3O7, and V6O13The suitability of water and some halogenating transport agents (NH4Cl, NH4Br, I2) for the chemical transport (temperature gradient 850/750 K) of V2O5, V3O7, and V6O13 has been investigated. Transport rates for V2O5 and V6O13 could be measured and reproduced. The best transport agent for V2O5 is NH4Cl or H2O. For V3O7 a combination of the transport agents I2/H2O give the best results and for V6O13 the combination of NH4Br/H2O was most appropriate.
    Notes: Die Eignung von Wasser und einigen halogenierenden Transportmitteln (NH4Cl, NH4Br, I2) zum chemischen Transport (Temperaturgefälle 850/750 K) von V2O5, V3O7 und V6O13 wurde untersucht. Für V2O5 und V6O13 konnten Transportraten reproduzierbar ermittelt werden. V2O5 ließ sich am besten durch einen Zusatz von NH4Cl oder von H2O transportieren. Für V3O7 ist die Transportmittelkombination I2/H2O und für V6O13 die Kombination NH4Br/H2O am besten geeignet.
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  • 67
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Chalcogenolates. 190. Esters of 2-Oxophenyldithioacetic Acid. 1. Preparation and CharacterizationThe dark red or yellowish brown colored title compounds C6H5—CO—CS—SR, where R = CH3, C2H5, C(CH3)3, CH2—C6H5, have been produced in one-pot synthesis by reaction of chloro acetophenone with sulfur in the presence of triethylamine followed by alkylation with the corresponding alkyl halide.The electron absorption, infrared, nuclear magnetic resonance, and mass spectra of the esters are given.
    Notes: Die dunkelrot bzw. gelbbraun gefärbten Titelverbindungen C6H5—CO—CS—SR mit R = CH3, C2H5, C(CH3)3 und CH2 — C6H5 wurden in Eintopfverfahren durch Umsetzung von Chloracetophenon mit Schwefel in Gegenwart von Triethylamin und anschließender Alkylierung mit dem entsprechenden Alkylhalogenid hergestellt.Die Elektronenabsorptions-, Infrarot-, Kernresonanz- und Massenspektren werden mitgeteilt.
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  • 68
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Thermal Behaviour of the Hydrogen Sulfates of Magnesium, Calcium, Strontium and BariumThe thermal behaviour of the solvent-free crystals of alkaline earth hydrogen sulfates has been investigated. The DTA and TG curves of MII(HSO4)2 indicate a decomposition following the equation Thermal treatment of Mg(HSO4)2 in static gas atmosphere yields α-MgSO4 which is transformed to α-MgSO4 at higher temperature. Contrary to that in dynamic gas atmosphere direct decomposition to α-MgSO4 can be observed. TpMg(HSO4)2 = 356°C, TpCa(HSO4)2 = 204°C, TpSr(HSO4)2 = 175°C, TpBa(HSO4)2 = 156°C. The strong difference between the peak temperatures of Mg(HSO4)2 and the other alkaline earth hydrogen sulfates may be explained not only through the higher covalency of the bondings in the Mg compound but, especially, through differences of their structures. Whereas the hydrogen sulfates of Ca, Sr, and Ba contain chains of edge-linked MIIO8 polyhedra, in Mg(HSO4)2 exist isolated MgO6 octahedra.
    Notes: Das thermische Verhalten der Kristalle der Erdalkalimetallhydrogensulfate wurde untersucht. Aus den DTA- und TG-Kurven folgt für die untersuchten Hydrogensulfate ein einstufiger Zerfall: Beim Aufheizen unter statischen Bedingungen wird aus Mg(HSO4)2 α-MgSO4 erhalten, das bei höherer Temperatur in α-MgSO4 übergeht, während unter dynamischen Bedingungen direkt α-MgSO4 erhalten wird. Die Zersetzungstemperaturen fallen mit zunehmendem Radius der Erdalkalimetallkationen: TpMg(HSO4)2 = 356°C, TpCa(HSO4)2 = 204°C, TpSr(HSO4)2 = 175°C, TpBa(HSO4)2 = 156°C. Der deutliche Unterschied in den Tp Werten zwischen Mg(HSO4)2 und den übrigen Erdalkalihydrogensulfaten ist neben dem stärker ausgeprägten Kovalenzbindungsanteil vor allem auf deren strukturelle Unterschiede zurückzuführen; Ba(HSO4)2, Sr(HSO4)2 und Ca(HSO4)2 bilden über gemeinsame Kanten verknüpfte MIIO8-Polyederketten, während in Mg(HSO4)2 isolierte MgO6-Oktaeder vorliegen.
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  • 69
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 569 (1989), S. 31-42 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: A New Lithosilicate: Rb5LiNiSi2O8 = Rb5[LiNiSi2O8]Nearly colourless crystals of Rb5LiNiSi2O8 resulted by heating intimate mixtures of RbO0.6, LiO0.5, and SiO2 (Rb : Li : Si = 3 : 1.2 : 1) in tightly closed Ni-tubes. The crystal structure was determined (four-circle-diffractometer-data, 1 733 of 1 740 I0 (h kl), R = 6.9%, Rw = 5.5%, parameters see text). The new “Lithosilicate” crystallizes monoclinic (Space group C2/c) with a = 860.0(2), b = 1 026.2(2), c = 1 376.1(3) pm, β = 101.28(2)° (Guinier-Simon-powder-data), Z = 4. The structure is built up by chains ∞1[O2/2SiO2LiO2SiO2NiO2/22] where Si4+ resp. Li+ are coordinated tetrahedrally, Ni2+ however quadratic planar. The Madelung Part of Lattice Energy, MAPLE, and Effective Coordination Numbers, ECoN, these calculated via Mean Fictive Ionic Radii, MEFIR, are given.
    Notes: Fast farblose Kristalle von Rb5LiNiSi2O8 entstanden beim Tempern inniger Gemenge von RbO0.6, LiO0.5 und SiO2 (Rb : Li : Si = 3 : 1.2 : 1) in fest verschlossenen Ni-Bömbchen. Die Kristallstruktur wurde aufgeklärt (Vierkreisdiffraktometerdaten, 1 733 von 1 740 I0(h kl), R = 6,9%, Rw = 5,5%, Parameter siehe Text). Das neue “Lithosilicat” kristallisiert monoklin (Raumgruppe C2/c) mit a = 860,0(2), b = 1026,2(2), c = 1376,1(3) pm, β = 101,28(2)° (Guinier-Simon-Pulverdaten), Z = 4. Die Struktur wird aus Ketten ∞1[O2/2SiO2LiO2SiO2NiO2/2]2 aufgebaut, in denen Si4+ bzw. Li+ tetraedrisch, Ni2+ jedoch quadratisch planar koordiniert ist. Der Madelunganteil der Gitterenergie, MAPLE, sowie Effektive Koordinationszahlen, ECoN, diese über Mittlere Fiktive Ionenradien, MEFIR, berechnet, werden angegeben.
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  • 70
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 569 (1989), S. 16-30 
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The First Binuclear Oxoferrate(II): „Cs2K4[O2FeOFeO2]“For the first time „Cs2K4[Fe2O5]“ was obtained by annealing intimate mixtures of Cs2O, K2O, and CsFeO2 (molar ratio Cs : K : CsFeO2 1.3 : 2.1 : 1) in a closed Fe-cylinder (74 d; 470°C) in the form of red single crystals. The structure determination (four-circle diffractometer, MoKα, 760 out of 857 Io(h kl); R = 5.8%, Rw = 4.6%) confirms the space group C2/m; a = 707.4, b = 1138.5, c = 699.7 pm, β = 91.76°, Z = 2. Essential part of the structure is the binuclear, planar [O(1)2Fe—O(2)—FeO(1)2]6- group which is for the first time observed with oxoferrates(II).Despite different space groups the crystal structure is related to that of Rb2Na4[Co2O5].
    Notes: „Cs2K4[Fe2O5]“ wurde erstmals durch Tempern inniger Gemenge von Cs2O, K2O und CsFeO2 (Einwaageverhältnis Cs:K:CsFeO2 1,3 : 2,1 : 1) in einem verschlossenen Fe-Zylinder (74 d; 470°C) in Form von granatroten Einkristallen erhalten. Die Strukturaufklärung (Vierkreisdiffraktometerdaten, MoKα, 760 von 857 Io(h kl); R = 5,8%, Rw = 4,6%) belegt die Raumgruppe C2/m; a = 707,4, b = 1138,5, c = 699,7 pm, β = 91,76°, Z = 2. Wesentlicher Teil der Kristallstruktur ist die zweikernige, planare Baugruppe [O(1)2Fe—O(2)—FeO(1)2]6-, die erstmals bei Oxoferraten(II) beobachtet wird.Die Struktur ist trotz unterschiedlicher Raumgruppen verwandt mit der von Rb2Na4[Co2O5].
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  • 71
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Contributions to the Chemistry of Phosphorus. 191. On the Reaction Behavior of Sodium Tetraphosphinoborate NaB(PH2)4Sodium tetraphosphinoborate rearranges to sodium heptaphosphinodiborate, Na[(PH2)3B—PH2—B(PH2)3] (1), at moderate temperatures in the presence of tetrahydrofuran. By reacting NaB(PH2)4 with BH3 ß THF sodium tetrakis(boranephosphino)borate, NaB(PH2BH3)4 (2), is formed, which has a remarkable thermal stability, but is not stable without solvent. With methyl iodide, the easily decomposible triphosphinoborane-methylphosphane, B(PH2)3PH2CH3 (3), has been obtained. The 31P- and 11B-NMR data of 1-3 are reported and discussed.
    Notes: Natriumtetraphosphinoborat lagert sich in Gegenwart von Tetrahydrofuran schon bei mäßigen Temperaturen in Natrium-heptaphosphinodiborat, Na[(PH2)3B—PH2—B(PH2)3] (1), um. Bei der Reaktion von NaB(PH2)4 mit BH3 · THF entsteht Natriumtetrakis(boranphosphino)borat, NaB(PH2BH3)4 (2), das eine bemerkenswerte thermische Stabilität aufweist, lösungsmittelfrei aber nicht beständig ist. Mit Methyliodid wird das leicht zersetzliche Triphosphinoboranmethylphosphan, B(PH2)3PH2CH3 (3), gebildet. Die 31P- und 11B-NMR-Daten von 1-3 werden mitgeteilt und diskutiert.
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  • 72
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Cyclic Diazastannylenes. XXVIII. Inorganic Polycyclic Compounds from the Reaction of Bis(amino)stannylene or Iminostannylene with SnCl2, SnBr2, and tert-Butoxitin(II) Chloride or BromideThe cyclic bis(amino)stannylene 1 may react with tert-butoxitin(II) chloride or bromide yielding a Lewis acid-base adduct 4 resp. 5, in which the two molecules are held together via N→Sn (233.8(3) pm) and O→Sn (215.1(2) pm) bonds. The resulting adduct 4 contains therefore two four membered rings sharing one common edge as found by X-ray structure determination. If 1 is allowed to react with SnCl2 or SnBr2, the salts Me2Si(NtBu)2Sn2Br+Sn2Br5- (7) are formed. Structure analysis reveals the cations in 6 and 7 to be very similar: SnCl+ and SnBr+ are coordinated by the “trihapto ligand” 1 in a way resulting a polycyclic SiN2Sn2X-arrangement. To a central Sn2N2 tetrahedron Si and halogen X are added occupying and bridging two opposite edges (mean values: N—Sn = 232(5) (6), N—Sn = 230(2) (7), Sn—C1 = 265(1), Sn- Br = 275(1) pm). The reaction intermediate (SnNtBu)2 adds to SnCl2 to form the crystalline polymer ( tBuN)2Sn3C12 (8). X-ray structure determination reveals the solid to be built up by one-dimensional chains of polycyclic Sn3(NtBu)2C13 sharing two chlorine atoms with neighbouring units. The unit Sn3(NtBu)2C13 can be visualized as an equilateral triangle of chlorine atoms, on which a smaller triangle of tin atoms is superimposed; the corners of the smaller triangle being located in the middle of the larger triangle's edges. The tin atoms are bipyramidally coordinated by two N- tBu-groups thus forming a nearly perfect Sn3N2s trigonal bipyramide (Sn—N = 222.7(3) pm). Two chlorine atoms of the triangle are connected to neighbouring units, the chlorine atoms thus attain an unusual nearly square-planar coordination sphere (Sn—Cl(mean) = 308(5) pm). The tertbutyl groups at the nitrogen atoms “screen” the inorganic part of the structure leading to a layer structure.
    Notes: Das cyclische Bis(amino)stannylen 1 reagiert mit tert-Butoxizinn(II)-chlorid oder -bromid zu einem Lewis-Säure-Base-Addukt 4 bzw. 5, in dem die beiden Moleküle über N→Sn- (233,8(3) pm) und O→Sn- (215,1(2) pm) Bindungen zusammengehalten werden, was zur Bildung zweier anellierter Vierringe führt (Röntgenstrukturanalyse von 4). Setzt man 1 hingegen mit SnCl2 oder SnBr2 um, so entstehen die “Salze” Me2Si(NtBu)2Sn2Br+Sn2Br5- (7). Gemäß Strukturanalysen sind die Kationen in 6 und 7 strukturell nahe verwandt: SnCl+ bzw. SnBr+ werden von dem “Trihaptoliganden” 1 so koordiniert, daß eine polycyclische SiN2Sn2X-Einheit mit einem N2Sn2-Tetraeder und kantenüberbrückenden Si und Halogen (X) entsteht (Mittelwerte : N—Sn = 232(2) (6), 230(2) (7), Sn—Cl = 265(1), Sn—Br = 275(1) pm). (tBuNSn)2, eine kurzlebige Zwischenstufe, addiert sich an SnCl2 unter Bildung eines kristallinen Polymers (tBuN)2Sn3Cl2 (8). Der Festkörper besteht nach Röntgenstrukturanalyse aus einer unendlichen Kette von (tBuN)2Sn3Cl3-Polycyclen, die sich mit benachbarten Einheiten jeweils zwei Chloratome teilen. (tBuN)2Sn3Cl3 bildet ein gleichseitiges Dreieck aus Chloratomen, auf dessen Kantenmitten ein zweites gleichseitigtes Dreieck aus Zinnatomen hineingestellt ist. Diese sind ihrerseits durch (NtBu)-Gruppen trigonal bipyramidal verknüpft. Die verbrückenden Chloratome besitzen eine ungewöhnliche planare, fast quadratische Koordination (Sn—Cl(Mittel) = 308(5) pm). Der mittlere Sn3N2-Polycyclus der Figur kann als nahezu perfekte trigonale Bipyramide beschrieben werden (Sn—N = 222,7(3) pm). Die tert-Butylgruppen an den Stickstoffatomen schirmen den anorganischen Teil der Struktur so ab, daß eine Schichtstruktur entsteht.
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  • 73
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Element-Element-Bonds. V. Synthesis, Molecular and Crystal Structure of Tetrakis-(Trimethylstannyl)distibaneLithium bis(trimethylsilyl)antimonide · 2 tetrahydrofuran reacts with benzyl chloride to form benzylbis(trimethylsilyl)stibane 1 which by treatment with chlorotrimethylstannane smoothly affords its trimethylstannyl derivative 2. Selective photochemical decomposition of 2 yields dark red tetrakis(trimethylstannyl)distibane 4; from benzene modification 4a is precipitated.Comparative X-ray structure determinations of 4a at +20 and -120°C as well as of homologous tetrakis(trimethylsilyl)distibane 3 at -120°C (+20°C: [2]) show the Sb…Sb contacts within the almost linear chains of Sb—Sb dumb-bells to be shortened at -120°C by 7 (4a) and 10 pm (3), respectively. On the contrary, the Sb—Sb bond is not lengthened accordingly as found for tetramethyldistibane previously [3, 4].Molecular parameters determined for 4a at +20°C {Sb—Sb 288; Sb—Sn 280 pm; Sb—Sb—Sn 91° and 96°; Sn—Sb—Sn 92°} are in agreement with corresponding values of a second modification 4b obtained by Dräger, Breunig and coworkers [5]. The crystal structures of 3 and 4b are isotypic (type B) and related to the homeotypic one of 4a (type A).
    Notes: Das aus Lithium-bis(trimethylsilyl)antimonid · 2 THF(1) THF: Tetrahydrofuran; DME: 1,2-Dimethoxyethan; TMS: Tetramethylsilan. und Benzylchlorid dargestellte Benzylbis(trimethylsilyl)stiban 1 setzt sich mit Chlortrimethylstannan zum Trimethylstannyl-Derivat 2 um. Dessen selektive Zersetzung am Tageslicht liefert das dunkelrote Tetrakis(trimethylstannyl)distiban 4.Vergleichende Röntgenstrukturanalysen bei +20 und -120°C zeigen sowohl für die aus Benzol kristallisierende Modifikation 4a als auch für das homologe Tetrakis(trimethylsilyl)distiban 3 (+20°C: [2]), daß die bei tiefer Temperatur innerhalb der fast linearen Ketten von Sb—Sb-Hanteln eintretende Verkürzung der Sb…Sb-Kontakte um 7 (4a) bzw. 10 pm (3) nicht wie beim Tetramethyldistiban [3, 4] zu einer Verlängerung der Sb—Sb-Bindung führt.Die von uns an 4a ermittelten Bindungsparameter {+20°C: Sb—Sb 288; Sb—Sn 280 pm; Sb—Sb—Sn 91°, 96° Sn—Sb—Sn 92°} stimmen gut mit den kürzlich von Dräger, Breunig u. Mitarb. [5] an einer zweiten Modifikation 4b erhaltenen Werten überein. Während die Kristallstrukturen von 3 und 4b isotyp sind (Typ B), ist die Kristallstruktur von 4a (Typ A) als hierzu homöotyp zu beschreiben.
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  • 74
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Reactions of N-Chloroacetoneimine with Molybdenum Pentachloride and Tungsten Hexachloride. Crystal Structure of Me2C=NH2[MoOCl4]WCl6 reacts with N-chloroacetoneimine under elimination of chlorine and formation of pentachloro-isopropylideneimino-tungsten(VI), Cl5W=N=CMe2, a brown-black crystal powder, which was characterized by i.r. spectroscopy. MoCl5 reacts in a similar way, although only a product mixture can be obtained. Partial hydrolysis of this mixture yields isopropylideneiminium-tetrachlorooxomolybdate(V), Me2C=NH2+[MoOCl4]-, of which the crystal structure was determined (2323 unique observed reflexions, R = 0.049). Space group P21/c, Z = 4, a = 878.6, b = 907.2, c = 1252.2 pm, β = 91.29°. The compound consists of Me2C=NH2+ ions with a planar arrangement of the skeletal atoms and a CN bond length of 126.7 pm and of dimeric, centrosymmetric anions [MoOCl4]22- having Mo atoms linked via asymmetric chloro bridges (MoCl distances 238.4 and 307.6 pm). The longer Mo—Cl contacts are located in the trans-positions of the terminal oxoligands (MoO distance 164 pm).
    Notes: WCl6 reagiert mit N-chloracetonimin unter Chlorabspaltung und Bildung von Pentachlor(isopropylidenimido)wolfram(VI), Cl5W=N=CMe2, einem schwarzbraunen Kristallpulver, das durch sein IR-Spektrum charakterisiert wird. ähnlich verläuft die Umsetzung mit MoCl5, wobei allerdings kein einheitliches Produkt isoliert werden kann. Durch partielle Hydrolyse entsteht aus diesen Produkten Isopropylideniminiumtetrachloro-oxomolybdat(V), Me2C=NH2+[MoOCl4], von dem wir eine Kristallstrukturanalyse angefertigt haben (2323 unabhängige beobachtete Reflexe, R = 4,9%). Raumgruppe P21/c, Z = 4, Gitterabmessungen: a = 878,6; b = 907,2; c = 1252,2 pm; β = 91,29°. Die Verbindung besteht aus Kationen Me2C=NH2+, deren Gerüstatome in einer Ebene liegen und die eine CN-Bindungslänge von 126,7 pm haben, sowie zentrosymmetrischen dimeren Anionen [MoOCl4]22-, deren Mo-Atome über asymmetrische Chlorobrücken mit Mo—Cl-Abständen von 238,4 pm und 307,6 pm verknüpft sind. Die langen Mo—Cl-Kontakte befinden sich in trans-Stellung zu den terminal gebundenen Oxoliganden (Abstand MoO = 164 pm).
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  • 75
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: [Cl3PNPCl3][MoNCl4], a Compound having Columns of Stacked AnionsThe title compound is formed by the reaction of [Cl3PNPCl3]Cl with MoNCl3 in CH2Cl2 and subsequent precipitation with CCl4 in from of orange-red crystals. According to the 31P-NMR spectrum, the compound exists as its isomer phosphaneiminate [Cl5Mo(NPCl2NPCl3)] in CD2Cl2/CH3CN solution. The crystal structure of [Cl3PNPCl3][MoNCl4] is isotypic with that of [Cl3PNPCl3][MoOCl4] and shows the same kind of two-dimensional disorder. X-ray diffraction patterns show planes of diffuse scattering as well as Bragg reflexions. The latter correspond to an averaged structure with a = 1590.0, b = 1141.6, c = 418.0 pm, space group Pba2, Z = 2. In the averaged structure (606 reflexions, R = 0.071) the atom sites have fractional occupation. The real structure consists of square-pyramidal [MoNCl4]- ions stacked to form columns with alternating MoN distances of 175 and 243 pm. The packing of the columns is disordered in that the [MoNCl4]- pyramids point either in the +c or -c direction. The [Cl3PNPCl3]+ ions are stacked in the c direction and show two types of disorder, namely a displacement parallel to c and a rotation by 120° about the P—P axis.
    Notes: Die Zielverbindung entsteht durch Umsetzung von [Cl3PNPCl3]Cl mit MoNCl3 in CH2Cl2 und anschließender Fällung mit CCl4 in Form orangeroter Kristalle. Nach dem 31P-NMR-Spektrum liegt die Verbindung in CD2Cl2/CH3CN-Lösung als strukturisomeres Phosphaniminat [Cl5Mo(NPCl2NPCl3)] vor. [Cl3PNPCl3][MoNCl4] kristallisiert isotyp zu [Cl3PNPCl3][MoOCl4] und zeigt die gleiche zweidimensionale Fehlordnung wie dieses. In den Röntgenbeugungsdiagrammen treten Ebenen von diffuser Streuung senkrecht zu c* neben Braggschen Reflexen auf. Aus den letzteren ergibt sich eine gemittelte Struktur einer Subzelle mit a = 1590,0, b = 1141,6, c = 418,0 pm, Raumgruppe Pba2, Z = 2. Aus der gemittelten Struktur (606 Reflexe, R = 7,1%) mit partiell besetzten Atomlagen läßt sich die tatsächliche Struktur und ihre Fehlordnung ableiten. Quadratische pyramidale [MoNCl4]--Ionen sind zu Strängen mit abwechselnden MoN-Abständen von 175 und 243 pm gestapelt. Die Stränge sind fehlgeordnet gepackt, indem die [MoNCl4]--Pyramiden entweder in die +c oder -c-Richtung weisen. Die [Cl3PNPCl3]+-Ionen sind zu Säulen parallel c gestapelt und auf zweierlei Art fehlgeordnet, nämlich durch Versetzung in Richtung c und durch Einnahme von dreierlei Positionen, die sich durch Drehung um 120° um die P—P-Verbindungslinie unterscheiden.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 76
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis of Ferrocenyltriethylstannanes and Electronic Properties of Substituted Ferrocenyl LigandsFerrocenyltriethylstannanes of the type RSnEt3 [R = Et3SnC5H4FeC5H4, C5H5FeC5H3(2-CH2NMe2), C5H5FeC5H3(2-CH2NC5H10), C5H5FeC5H3(2-CH2OMe), MeOCH2C5H4FeC5H4] were synthesized from Et3SnCl and the corresponding ferrocenyl lithium derivatives. The compounds were characterized by elementary analyses, 1H-, 13C-, 119Sn-n.m.r. and i.r. spectroscopic investigations. From the coupling constants 1J(119Sn—13CEt) the electronic influence of substituted ferrocenyl ligands was estimated.
    Notes: Ferrocenyltriethylstannane des Typs RSnEt3 [R = Et3SnC5H4FeC5H4, C5H5FeC5H3(2-CH2NMe2), C5H5FeC5H3(2-CH2NC5H10), C5H5FeC5H3(2-CH2OMe), MeOCH2C5H4FeC5H4] wurden aus Et3SnCl und den entsprechenden Ferrocenyllithium-Derivaten synthetisiert und mittels ihrer 1H-, 13C-, 119Sn-NMR- und IR-Spektren sowie elementaranalytisch charakterisiert. Aus den Kopplungskonstanten 1J(119Sn—13CEt) wurde der elektronische Einfluß der substituierten Ferrocenylreste abgeschätzt.
    Additional Material: 3 Ill.