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  • Inorganic Chemistry  (723)
  • LUNAR AND PLANETARY EXPLORATION  (717)
  • 1975-1979  (1,440)
  • 1975  (1,440)
  • 1
    Publication Date: 2005-02-24
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Res. in the Space Sci., Vol. 2, No. 1; 3 p
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  • 2
    Publication Date: 2006-01-12
    Description: Spacecraft- and Earth-based studies on the physical nature of the planets Mercury, Venus, and Mars are reported. Charts and graphs are presented on planetary surface properties, rotational parameters, atmospheric compositions, and astronomical characteristics.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA, Washington Found. of Space Biol. and Med., Vol. 1; p 133-196
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  • 3
    Publication Date: 2006-01-11
    Description: Results from the Lunakhod 2 experiment on the surface property variations and relief structure of lunar craters are presented. Tectonic fractures, iron composition of lunar rocks, magnetic measurements, lunar sky brightness, and corpuscular radiation of the lunar body were studied.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Mod. Achievements of Cosmonautics (NASA-TT-F-16221); p 39-50
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  • 4
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    Publication Date: 2006-01-11
    Description: A study of surface properties of the Lemonnier Crater by Lunakhod 2 is summarized. Special efforts were made to determine the variations of physical-chemical properties of the lunar surface as a function of the selenological-morphological structure in the transition zone of a mare region to the highlands. Studies were also made of the local magnetic situation, physical-mechanical properties of the soil, and the optical properties of the surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Mod. Achievements of Cosmonautics (NASA-TT-F-16221); p 5-19
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  • 5
    Publication Date: 2011-08-16
    Description: Material is ejected from impact craters in ballastic trajectories; it impacts first near the crater rim and then at progressively greater ranges. Ejecta from craters smaller than approximately 1 km are laid predominantly on top of the surrounding surface. With increasing crater size, more and more surrounding surface will be penetrated by secondary cratering action, and these preexisting materials will be mixed with primary crater ejecta. Ejecta from large craters, and especially basin-forming events, not only excavate preexisting local materials, but also are capable of moving large amounts of material away from the crater. Thus mixing and lateral transport give rise to continuous deposits that contain materials from within and outside the primary crater. As a consequence, ejecta of basins and large highland craters have eroded and mixed highland materials throughout geologic time and deposited them in depressions inside and between older crater structures.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 6
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    Publication Date: 2011-08-16
    Description: The solar system is considered along with the significance of meteorites as samples of the universe, the origin of planets, and earth's-eye view of the moon, previews of the lunar surface, aspects of impact cratering, lunar igneous processes, the mapping of the moon, the exploration of the moon in connection with the Apollo lunar landings, and the scientific payoff from the lunar samples. Studies of Mars, Venus, and the planets beyond are discussed, taking into account the Mariner Mars program, the Mariner orbiting mission, missions to Venus, the Mariner flight to Mercury, and the Pioneer missions. Attention is also given to the origin of the moon, implications of the moon's thermal history, similarities and differences in planetary evolution, and the role of internal energy in planetary development.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 7
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    Publication Date: 2011-08-16
    Description: The paper summarizes the physical and petrographic characteristics of the finer-grained fractions (less than 1 cm) of lunar regolith soil in Apollo and Luna samples. Lunar soils are poorly sorted and consist mostly of lithic and mineral debris derived by impact comminution of the underlying bedrock and glass particles formed by impact melting. Agglutinates constitute an important soil component and are key factors in the genetic history of lunar soil. Some models concerning the development of lunar regolith based on soil studies are examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Reviews of Geophysics and Space Physics; 13; Aug. 197
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  • 8
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    Publication Date: 2011-08-16
    Description: Models for the origin of the contrasts in the ultraviolet images of Venus are examined in an attempt to determine the physical differences between light and dark regions fundamental to a clear understanding of the apparent cloud motions. To evaluate the meaning of the wavelength dependence of the contrasts, an improved determination of the spherical albedo curve for Venus in the 0.225-1.06 micron range is made by fitting appropriate theoretical models to the observations of monochromatic magnitudes as a function of phase angle. It is shown that, because of differences between the spectral dependences of spherical albedo and contrasts, at least one major absorber other than the one causing the contrasts is almost certainly required. Several classes of models are compatible with present observational evidence. The contrasts and the absorption associated with them may in fact be occurring below, within or above the main visible cloud layer, and thus an unambiguous interpretation of the apparent cloud motions is not possible.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 9
    Publication Date: 2011-08-16
    Description: The polarization of reflected sunlight is computed for model atmospheres of Venus as a function of location on the apparent planetary disk. The calculations are for both homogeneous and layered models, as required to investigate the vertical distribution of particles. The results are compared with available observations. It is shown that the Rayleigh scattering observed in the polarization of Venus originates primarily from within the visible clouds, rather than from above the clouds. The visible 'clouds' are actually a very diffuse hazy region, and this visible-cloud layer extends at least up to the level where the pressure is of the order of 10 mb. The results indicate that the atmosphere behaves more nearly as the so-called 'homogeneous model' than as the 'reflecting-layer model'. However, there is some indication in the data that the turbidity increases with depth into the atmosphere. This conclusion receives stronger support from a comparison of particle number densities obtained from the polarization data with the number densities obtained from other observations which refer on the average to higher and lower levels in the atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of the Atmospheric Sciences; 32; June 197
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  • 10
    Publication Date: 2011-08-16
    Description: The atmosphere is assumed to be driven by a polar symmetric temperature field. The surface pressure gradient exhibits a latitudinal dependence opposite that of the depth-averaged temperature. The magnitude of the gradient is dependent upon the depth of the boundary layer, which depends upon the eddy viscosity, the boundary conditions imposed at the surface, and upon the temperature lapse rate. Using a temperature model for Mars based on Mariner 9 infrared spectral data with a 30% increase in the depth-averaged temperature from the winter pole to the subsolar point, the increase in surface pressure from the subsolar point to the winter pole was calculated as a function of eddy viscosity with no-slip conditions imposed at the surface. The meridional cellular flow rate is correlated with the eddy viscosity, causing a complete overturning of the atmosphere in tens of days for an eddy viscosity of .1 billion sq cm/sec and in hundreds of days for 1 million sq cm/sec. The implication of this overturning in the dust storm observed during the early part of the Mariner 9 mission is discussed briefly.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of the Atmospheric Sciences; 32; Jan. 197
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  • 11
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    Publication Date: 2011-08-16
    Description: The xenon anomalies trapped in meteorites and the moon may have first been trapped in circumstellar grains formed in or outside of postexplosive stars. In that case, the initial solar nebula need not have contained most of their radioactive progenitors, and this would necessitate major revision of the history of solar system formation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 12
    Publication Date: 2011-08-16
    Description: An estimate of the second zonal coefficient of the spherical-harmonic representation of the lunar gravitational field has been obtained from an analysis of particular orbital-element variations of the Explorer 35 and Explorer 49 spacecraft. Data from these spacecraft were used because the orbital configurations resulted in variations of the longitude of periapse and node which were, to first order, dependent only on the even zonal harmonics. The data time span for each satellite was extremely long: 2138 days for Explorer 35 and 230 days for Explorer 49. The value of the harmonic coefficient is determined and used to obtain a value of the lunar moment of inertia.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 2; Aug. 197
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  • 13
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 39; Aug. 197
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  • 14
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    Publication Date: 2011-08-16
    Description: The geochemistry of the bulk moon is considered, taking into account the large-scale chemical view of the lunar surface which has been obtained with the aid of three remote sensing experiments utilizing X-ray fluorescence, a gamma-ray spectrometer, and visible and near infrared reflectance measurements. Attention is also given to the regolith, the mare basins, and the lunar highlands and crust.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Reviews of Geophysics and Space Physics; 13; July 197
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  • 15
    Publication Date: 2011-08-16
    Description: The magnitudes of 92 surface mass points at designated locations were estimated from the radio tracking data of the Mariner Mars 1971 (M9) orbiter. This result is the first mass point model of a global field. The derived surface mass distribution correlates positively with the visible topography. The Hellas basin contains a mass deficiency, in contrast to some of the lunar basins which contain mass excesses. The Mars gravity field represented by the four parameters of an optimally located mass point (superimposed on an oblate spheroid) has third- and fourth-degree harmonics comparable to those of the complete model.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; July 10
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  • 16
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    Publication Date: 2011-08-16
    Description: Using Euler potentials, we construct a class of axisymmetric magnetic field models that exhibit the general features of the dayside Jovian field as observed by Pioneers 10 and 11. The particular model used for illustration contains a distended, disk-like field along the equator, a blunt, earth-like magnetosphere boundary, and the possibility of multiple trapping regions along a field line. The self-consistent ring current is calculated, together with representative drift periods for energetic particles.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 2; July 197
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  • 17
    Publication Date: 2011-08-16
    Description: An updated analysis and interpretation are presented of the magnetic field observations obtained during the Mariner 10 encounter with the planet Mercury on March 29, 1974. The combination of data relating to position of the detached bow shock wave and magnetopause and the geometry and magnitude of the magnetic field within the magnetosphere-like region surrounding Mercury lead to the conclusion that an internal planetary field exists with dipole moment approximately 5.1 times 10 to the 22nd G per cu cm. The dipole axis has a polarity sense similar to that of earth and is tilted 7 deg from the normal to Mercury's orbital plane. The magnetic field observations reveal a significant distortion of the modest Hermean field by the solar wind flow and the formation of a magnetic tail and neutral sheet which begins close to the planet on the night side. Presently, an active dynamo mechanism in the planetary interior appears to be favored in the interpretation of the field origin.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; July 1
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  • 18
    Publication Date: 2011-08-16
    Description: Observations from spacecraft have revealed naturally occurring radio emission emanating from two regions near earth. The characteristics of these two sources suggest a correlation with areas of known electron precipitation. The possibility of a similar production mechanism for observed nonthermal radio emissions from other planetary magnetospheres permits the polar magnetic field strengths of Jupiter and Saturn to be predicted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 189; July 25
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  • 19
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    Publication Date: 2011-08-16
    Description: Radio emissions from the direction of Saturn are analyzed which were observed by IMP-6 at 15 frequencies between 375 and 2200 kHz from April 1971 to October 1972. The radio bursts are identified in the IMP-6 data by a phase analysis of the spin-modulated signal from the spacecraft's dipole antenna, and approximately 12 storms are isolated whose occurrence corresponded to times when the spacecraft had an unobstructed view in the direction of Saturn. The spectral character of the radiation is found to be analogous to that of Jupiter, and a power-spectral analysis of the storm occurrence times indicates a weak periodicity for some of the observing frequencies. The Saturnian emission most similar to Jupiter's decametric emission is found to be strongest at 1100 kHz with a bandwidth of about 1000 kHz. A secondary spectral peak may exist at 400 kHz, which is similar to that observed for Earth and Jupiter. The detection of this nonthermal radio emission is shown to be the first direct evidence for the existence of a Saturnian magnetic field containing energetic particles.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; 198; June 1
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  • 20
    Publication Date: 2011-08-16
    Description: By using the Mariner 5 temperature profile and a homogeneous cloud model, and assuming that CO2 and cloud particles are the only opacity sources, the wavelength dependence of the Venus cloud opacity is inferred from the infrared spectrum of the planet between 450 and 1250 per cm. Volume extinction coefficients varying from 0.000005 to 0.000015 per cm, depending on the wavelength, are determined at the tropopause level of 6110 km. By using all available data, a cloud mass mixing ratio of approximately 0.000005 and a particle concentration of about 900 particles per cu cm at this level are also inferred. The derived cloud opacity compares favorably with that expected for a haze of droplets of a 75% aqueous solution of sulfuric acid.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 25; May 1975
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  • 21
    Publication Date: 2011-08-16
    Description: A 640 element phase-steerable dipole array has been used to make highly sensitive observations of the planet Jupiter during the 1973 apparition. The satellite Io is found to have very little influence at the low flux levels, whereas the definition of sources A and B appears to be relatively flux independent. A two-dimensional analysis of the data in the Jupiter-Io plane has revealed considerable source B activity at low intensities which is not influenced by Io.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 25; May 1975
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  • 22
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    Publication Date: 2011-08-16
    Description: The minor planet 44 Nysa has a unique combination of photopolarimetric parameters, with the most nearly neutral UBV colors, the shallowest negative polarization branch, and by far the highest polarimetric albedo yet obtained for any asteroid. Its surface apparently consists of a low-opacity, iron-free silicate strongly suggestive of enstatite achondrites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; 198; May 15
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  • 23
    Publication Date: 2011-08-16
    Description: Observations made by Mariner 10 during its third encounter with Mercury (Mercury III) are presented which confirm the tentative conclusion drawn from the first encounter (Mercury I) that Mercury has a modest intrinsic magnetic field. Some comparison between Mercury I and III data and trajectories is attempted, and the superior affirmative nature of Mercury III is pointed out. Definitive bow shock and magnetopause detections of solar wind deflection were made during both passes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 255; May 15
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  • 24
    Publication Date: 2011-08-16
    Description: Data from the Pioneer 10 radio occultation measurements are utilized to study the vertical electron number density distribution in the Jovian ionosphere. The immersion measurements were made at 26 North latitude in the late afternoon local time. The solar zenith angle in this region was 81 deg. Emersion measurements were made at 58 North latitude near the morning terminator where the solar zenith angle was 95 deg. The detectable portion of the Jovian ionosphere consists of a number of layers distributed over an altitude range of more than 3000 km. The maximum density appears to be on the order of 30,000 electrons per cu cm. Assuming that H(+) is the principal ion in the upper portion of the ionosphere yields a topside plasma temperature of 900 plus or minus 400 K.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomy and Astrophysics; 39; 1, Fe; Feb. 197
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  • 25
    Publication Date: 2011-08-16
    Description: Aspects of base surge transport are considered along with questions regarding the applicability of base surge transport to lunar sedimentation, the ballistic transport of crater and basin ejecta, Copernicus crater ballistics, and the effects of ejecta impact on preexisting lunar ground. An ejecta emplacement model is discussed and attention is given to the structure of the surface of continuous deposits of craters and basins, the thickness of crater and basin deposits, and the characteristics of impact melts.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Reviews of Geophysics and Space Physics; 13; May 1975
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  • 26
    Publication Date: 2011-08-16
    Description: Grooved and hilly terrains occur at the antipode of major basins on the moon (Imbrium, Orientale) and Mercury (Caloris). Such terrains may represent extensive landslides and surface disruption produced by impact-generated P-waves and antipodal convergence of surface waves. Order-of-magnitude calculations for an Imbrium-size impact on the moon indicate P-wave-induced surface displacements of 10 m at the basin antipode that would arrive prior to secondary ejecta. Comparable surface waves would arrive subsequent to secondary ejecta impacts beyond 1000 km and would increase in magnitude as they converge at the antipode. Other seismically induced surface features include: subdued, furrowed crater walls produced by landslides and concomitant secondary impacts; emplacement and leveling of light plains units owing to seismically induced 'fluidization' of slide material; and perhaps the production and enhancement of deep-seated fractures that led to the concentration of farside lunar maria in the Apollo-Ingenii region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 12; Feb. 197
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  • 27
    Publication Date: 2011-08-16
    Description: A neon atmosphere and ionosphere is proposed for Io, based on Pioneer 10 observations of the peak electron number density, height of the peak above the surface, and the topside plasma scale height. Calculations of mass, momentum and energy equations for a neon atmosphere yield results that are in reasonable agreement with the observations. A nitrogen atmosphere and a neon-argon-helium atmosphere are also considered. Calculations of the electron number density of a neon ionosphere also yield reasonable agreement with observations. It is noted that Io has about the same mass and radius as the moon, and that Apollo mass spectrometer measurements indicated an abundance of neon in the lunar atmosphere. The presence of other elements, such as hydrogen, helium, and sodium, in Io's atmosphere is also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 2; Feb. 197
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  • 28
    Publication Date: 2011-08-16
    Description: Measurements were made of the rotational profiles of specific bands of the CO fourth-positive group (4PG). The CO 4PG bands were excited by electron impact dissociative excitation of CO2. The results are applicable to analysis of the Mariner observations of the CO 4PG in the dayglow of Mars. The results indicate that dissociative excitation of CO2 by electron impact leads to CO(A 1Pi) fragments with a rotational distribution that is highly nonthermal. The parent CO2 temperature was about 300 K in the experiment, while the fragment CO(A 1Pi) showed emission band profiles consistent with a rotational temperature greater than about 1500 K. Laboratory measurement of the reduced transmission of the hot bands by thermal CO appears to be the most direct way of determining the column density responsible for the CO(v',0) absorption of Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; Jan. 1
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  • 29
    Publication Date: 2011-08-16
    Description: Our analysis of the Venera 8 measurements yields equatorial morning terminator horizontal and vertical winds that are similar in a number of respects to the winds we obtained from our analysis of the Venera 7 measurements. The lower boundary of the horizontal retrograde '4-day' wind is defined by a 50-60% decrease in wind speed in the vicinity of 44 km, and there exists a retrograde wind 'plateau' of 15- to 40-m/s winds extending from 40 km down to the vicinity of 18 km, where the winds decrease rapidly to the order of 0.1 m/s near the surface. Updrafts of 2-5 m/s exist in the vicinity of 20-30 km and are apparently associated with a slightly superadiabatic lapse rate.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; Jan. 1
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  • 30
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    Publication Date: 2011-08-16
    Description: The return of Mars surface samples by the orbital rendezvous mode would require smaller, lighter vehicles than the direct return mode and would limit the exposure of the earth return systems to possible contamination by Martian biota. The reference mission considered would use a single Titan IIIE/Centaur launch vehicle, carry a 1 kg sample, and be launched in late 1981. The spacecraft would consist of an orbiter, a Mars lander, a Mars ascent vehicle, an earth return vehicle, and an earth entry capsule. The Mars ascent vehicle is the only all-new vehicle required, the others being derived from Viking and other programs. A key consideration is the feasibility of automatic rendezvous and sample transfer between the ascent vehicle and orbiter in Mars orbit. The maneuvers required and the maneuver algorithm developed in a NASA feasibility study are described in detail. The possibility of international cooperation on a Mars orbital rendezvous mission is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronautics and Aeronautics; 13; Jan. 197
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  • 31
    Publication Date: 2011-08-16
    Description: Isovaline is present in the Murchison meteorite as a racemic mixture (about equal concentrations of the R and S enantiomers). Since isovaline does not have a hydrogen atom on its asymmetric alpha-carbon atom, the racemic mixture could not have formed by commonly accepted mechanisms of racemization. Thus, isovaline in the meteorite most probably was synthesized as a racemic mixture and is not the result of the racemization of either the R or S enantiomer. Other chiral amino acids in the meteorite are present as racemic mixtures, and were probably synthesized in a similar manner by abiotic, extraterrestrial processes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 39; Nov. 197
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  • 32
    Publication Date: 2011-08-16
    Description: A significant new finding from analysis of Pioneer 11 observations in the magnetosphere of Jupiter is that there is net streaming of both electrons E above 40 keV and E above 560 keV and protons in the range from .61 to 3.41 MeV away from the planet along high-latitude field lines. This result is compatible with the recent suggestion of Nishida that energetic particles undergo trans-L shell diffusion at low altitudes without significant change of energy. This provides a plausible explanation for the remarkable pitch angle distributions near the equator in the range of L values from 12 to 25; the presence of particles of about 1 MeV energy at the outer edge of the magnetosphere; and hence, via conventional inward diffusion processes, the presence of those having magnetic moments of several hundred MeV per gauss in the inner magnetosphere. The recirculation of energetic particles emerges as an important dynamical feature of the Jovian magnetosphere.-
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 2; Oct. 197
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  • 33
    Publication Date: 2011-08-16
    Description: Mature surface fines have an equilibrium specific surface area of about 0.6 sq m/g the equivalent mean particle size being about 3 microns. The adsorption behavior of inert gases (reversible isotherms) indicates that the particles are also nonporous in the size range of pores from 10 to 3000 A. Apparently, in mature soils there is a balance in the forces which cause fining, attrition, pore filling, and growth of lunar dust grains. Immature, lightly irradiated soils usually have coarser grains which reduce in size as aging proceeds. The specific surface area, determined by nitrogen or krypton sorption at 77 K, is a valuable index of soil maturity.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 27; 3, Oc; Oct. 197
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  • 34
    Publication Date: 2011-08-16
    Description: Although our knowledge of lunar regolith stratification is incomplete, several categories of thick and thin strata have been identified. Relatively thick units average 2 to 3 cm in thickness, and appear surficially to be massive. On more detailed examination, these units can be uniformly fine-grained, can show internal trends, or can show internal variations which apparently are random. Other thick units contain soil clasts apparently reworked from underlying units. Thin laminae average approximately 1 mm in thickness; lenticular distribution and composition of some thin laminae indicates that they are fillets shed from adjacent rock fragments. Other dark fine-grained well-sorted thin laminae appear to be surficial zones reworked by micrometeorites. Interpretations of stratigraphic succession can be strengthened by the occurrence of characteristic coarse rock fragments and the orientation of large spatter agglutinates, which are commonly found in their original depositional orientation.
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  • 35
    Publication Date: 2011-08-16
    Description: This investigation uses results obtained in an earlier Monte Carlo study by Oberbeck et al. (1973) to shed light on the consequences of mare-regolith origin by impact comminution of primarily local basaltic rocks by evaluating regolith growth and mixing as a function of time. The study demonstrates that regolith growth is self-regulated and has the same trend and nearly the same terminal growth rates whatever the history of bombardment: rapid initial accumulation followed by diminishing rates of growth. Mixing and all other processes investigated are growth regulated. Mixing increases as growth slows, but never to the extent that the regolith is homogenized. Because the average regolith is never homogenized, products of growth-regulated processes are preserved in the stratigraphy. This model indicates that deeper levels contain thinner depositional units, lesser quantities of meteoritic and exotic components, and more debris derived from shallow levels in the mare basalts than material in near-surface layers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 36
    Publication Date: 2011-08-16
    Description: The process of breccia formation by viscous sintering in the absence of pressure, advanced by Simonds (1973), is examined in detail. The limitations on the standard model for such sintering are considered. The competing process of crystallization is analyzed kinetically in terms of time-temperature-transformation curves corresponding to various degrees of crystallinity. The analysis is applied to Lunar Composition 15418 to illustrate the approach. The results indicate that close constraints can be placed on the thermal histories of lunar breccias, particularly breccias with modest degrees of crystallinity, from microstructural observations and kinetic measurements.
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  • 37
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    Publication Date: 2011-08-16
    Description: The Viking mission is discussed which will search for evidence of life on Mars by performing extended and closeup reconnaissance of the planet's surface. Previous unsuccessful Soviet attempts to land scientific payloads on Mars are summarized, and choices of landing sites for the two Viking landers are discussed. The onboard computers in both the orbiter and the two landers are described with emphasis on their 18,000-word memories and reprograming capabilities. The mission profiles and lander programs are outlined in detail, and lander experiments are discussed which will involve surface imaging, meteorological and seismometric measurements, soil sampling, lower atmosphere analysis, and searches for possible Martian microorganisms.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Sky and Telescope; 50; July 197
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  • 38
    Publication Date: 2011-08-16
    Description: The second Mercury encounter has resulted in the acquisition of about 360 pictures of the south polar regions which provide a reliable cartographic and geologic tie between the two sides of the planet photographed on the first encounter. Stereoscopic coverage of large areas of the southern hemisphere was obtained by combining Mercury 1 and 2 pictures taken at different viewing angles. The south polar regions consist of heavily cratered terrain and intercrater plains interspersed with patches of smooth plains. No large areas of smooth plains similar to those surrounding Caloris occur in the south polar regions. No new types of terrain have been recognized, but lobate scarps are common. The second largest basin seen by Mariner 10 has been confirmed on the new photography. At high solar elevations the surface displays an abundance of rays and rayed craters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; June 10
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  • 39
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    Publication Date: 2011-08-16
    Description: If a molten, or partially molten, lunar core exists at present, constraints would be placed on the viscosity of the solid mantle and the distribution of radioactive heat sources. Models in which the heat sources have been concentrated near the surface would rapidly solidify if the effective viscosity did not exceed 10 to the 22nd power sq cm/sec. Retention of most of the heat sources throughout the mantle would permit present day solid convection to occur without cooling the core.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 12; Mar. 197
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  • 40
    Publication Date: 2011-08-16
    Description: Plasma electron count observations made during the first and third encounters of Mariner 10 with Mercury (i.e., during Mercury I and III) are reported. They provide detailed information on the magnetosphere of Mercury, especially those from Mercury III. A low-flux region was observed about closest approach (CA) of Mercury III, whereas no such region was detected by the lower-latitude Mercury I; a hot plasma sheet was measured on the outgoing (and near-equator) trajectory of Mercury I, while only cool plasma sheets were observed in the magnetosphere by Mercury III. Findings are similar, on a reduced scale, to models of the earth's magnetosphere and magnetosheath.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 255; May 15
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  • 41
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    Publication Date: 2011-08-16
    Description: The present state of knowledge concerning the planet Venus is examined. It is pointed out that Venus, even with our present data, remains enigmatic and contradictory. A summary is given of seven major areas in which further studies are needed. The rewards of such studies would be related to an emergence of basic principles and processes which shape the origin and evolution of planets in general. Present plans for exploring Venus include earth-based radar observations, the Pioneer Venus entry probes, and Orbiter missions. NASA missions after Pioneer depend upon the results of a scientific analysis of the data which will be available at that time. Attention is given to buoyant stations in the Venus atmosphere, survivable landers, and the observation of the Venus surface with the aid of orbiting imaging radar.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronautics and Aeronautics; 13; May 1975
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  • 42
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    Publication Date: 2011-08-16
    Description: A lunar olivine basalt sample is analyzed which exhibits unorthodox alternating field (AF) demagnetization behavior characterized by nonreproducible remanent magnetization values upon demagnetization at a given peak AF. It is shown that the direction of the remanence following AF demagnetization is roughly confined to a particular plane and that this behavior is an intrinsic property of certain magnetic carriers present in the sample. The viscous acquisition coefficient is found to be about 1-1/2 times greater than the absolute value of the decay coefficient. It is suggested that the behavior of this sample is due to the presence of a few planar, multidomain grains which represent a local mineral fabric, do not demagnetize, and may interfere with the determination of a meaningful time variation of lunar magnetic paleointensity.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 25; 3, Ap; Apr. 197
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  • 43
    Publication Date: 2011-08-16
    Description: The concentration of meteoroids of mass about 0.01 microgram in interplanetary space, in the asteroid belt, and near Jupiter has been measured. The data confirm the Pioneer 10 observation that the asteroid belt is not highly populated with small meteoroids, suggest that the high concentration of small particles around Jupiter is the result of gravitational focusing, and provide an indication of the mass distribution of meteoroids in interplanetary space.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 188; May 2
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  • 44
    Publication Date: 2011-08-16
    Description: For 2 weeks continuous imaging, photometry, and polarimetry observations were made of Jupiter and the Galilean satellites in red and blue light from Pioneer 11. Measurements of Jupiter's north and south polar regions were possible because the spacecraft trajectory was highly inclined to the planet's equatorial plane. One of the highest resolution images obtained is presented here along with a comparison of a sample of our photometric and polarimetric data with a simple model. The data seem consistent with increased molecular scattering at high latitudes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 188; May 2
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  • 45
    Publication Date: 2011-08-16
    Description: The report presented takes into account data from the low energy telescope which were obtained during the passage of Pioneer 11 through the Jovian magnetosphere. The detector system used measures the proton flux in the range from 0.2 to 21.2 MeV in seven energy intervals and the electron flux in the range from 0.1 to 2 MeV in four intervals. The significance of the effects measured in the inner core region of the magnetosphere is discussed and attention is given to the effects of Jovian moons on the particle flux in the planetary environment.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 188; May 2
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  • 46
    Publication Date: 2011-08-16
    Description: Pioneer 11 observations of the interaction of Jupiter's magnetosphere with the distant solar wind have confirmed the earlier Pioneer 10 observations of the great size and extreme variability of the outer magnetosphere. The nature of the plasma transitions across Jupiter's bow shock and magnetopause as observed on Pioneer 10 have also been confirmed on Pioneer 11. However, the northward direction of the Pioneer 11 outbound trajectory and the distance of the final magnetopause crossing (80 Jupiter radii) now suggest that Jupiter's magnetosphere is extremely broad with a half-thickness (normal to the ecliptic plane in the noon meridian) which is comparable to or greater than the sunward distance to the nose.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 188; May 2
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  • 47
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    Publication Date: 2011-08-16
    Description: Radionuclide concentration data for six samples from two cores of the Keyes chondrite are presented. The weighted average potassium content for samples was about 675 ppm, somewhat lower than the 800-900 ppm typically found in L chondrites. Spectra were analyzed for U and Th, with upper limits established at approximately 100 and 200 ppb, respectively.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; Apr. 10
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  • 48
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    Publication Date: 2011-08-16
    Description: The present work investigates the consequences implied by various rheological models of the early earth for the orbital history of the moon subsequent to its formation. Models of the earth that yield small tidal angles, such as low-viscosity models, imply that the moon never orbited in the earth's equatorial plane, thereby ruling out an equatorial origin for the moon. A high-viscosity model is shown to permit the moon to originate in the equatorial plane and still account for the present-day characteristics of the moon's orbit.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; Apr. 10
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  • 49
    Publication Date: 2011-08-16
    Description: Man-made alloy spheres simulating the compositions of particles found in the lunar soil and weighting approximately 10 mg are shown to be equivalent, insofar as remanence intensity and demagnetization stability are concerned, to more than about 10 billion submicrometer spherical iron particles. The large particles not only contain large stable magnetic remanence, but when the polished surfaces of these particles are etched and carefully studied, they provide useful petrogenetic information, imply the mechanism of magnetization, the time-temperature history, and outline the format for possible paleointensity analysis. The intensity and stability of the remanence in these large spheres is related to the microstructure developed during rapid cooling.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 2; Mar. 197
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  • 50
    Publication Date: 2011-08-16
    Description: The electrical conductivity and water soluble Na, K, Ca, and Mg of aqueous solutions of terrestrial soils and finely divided igneous and metamorphic rocks were determined. Soils from dry terrestrial basins with a history of water accumulation as well as soils from the topographic lows of valleys accumulated water soluble cations, particularly Na and Ca. These soils as a group can be distinguished from the rocks or a second group of soils (leached upland soils and soils from sites other than the topographic lows of valleys) by significant differences in their mean electrical conductivity and water-soluble Na + Ca content. Similar measurements on multiple samples from the surface of Mars, collected by an automated long-range roving vehicle along a highlands-to-basin transect at sites with morphological features resembling dry riverlike channels, are suggested to determine the fluvial history of the planet.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 24; Mar. 197
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  • 51
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    Publication Date: 2011-08-16
    Description: Current knowledge of the atmosphere of Uranus is reviewed and specific objectives are suggested for satellite missions to Uranus. The anomalous composition of Uranus makes determinations of its atmospheric composition particularly valuable for testing theories of solar system evolution. The weakness of its atmospheric heating makes the determination of its atmospheric structure and dynamics particularly valuable for testing theories of atmospheric behavior. The large axial inclination of Uranus implies an anomalous latitudinal variation of temperature and dynamics different from that of the other planets.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 24; Mar. 197
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  • 52
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 253; Feb. 27
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  • 53
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    Publication Date: 2011-08-16
    Description: The relative abundances and origins of the xenon isotopes found in carbonaceous meteorites are discussed. It is proposed that carbonaceous-chondrite-fission (CCF) xenon is not caused by fission, but is the direct result of a modified r-process nucleosynthesis which produces a peak at Z = 54 and N = 82. The xenon produced in this way would have been trapped in dust grains which were subsequently incorporated in the solar system with minimal degassing.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 253; Feb. 6
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  • 54
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; 195; Jan. 1
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  • 55
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    Publication Date: 2011-08-16
    Description: Studies with the combined gas chromatograph-mass spectrometer were conducted to characterize further the amino acids found in extracts of the Murchison meteorite. With the exception of beta-aminoisobutyric acid, all of the amino acids which were found in previous studies of the Murchison meteorite and the Murray meteorite have been identified. The results obtained lend further support to the hypothesis that amino acids are present in the Murchison meteorite as the result of an extraterrestrial abiotic synthesis.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 56
    Publication Date: 2011-08-16
    Description: A Mars surface sample return mission using Mars direct entry and Mars parking orbit return is described. The mission is designed for a minimum energy requirement and is relatively simple in comparison to the alternative Mars orbital rendezvous mode. The design calls for minimal science, and uses a single Titan IIIE/Centaur launch vehicle. The primary science areas included are biology, biochemistry, geochemistry, and petrology, for detecting life, age dating, and determining chemical compositions and rock types. The total minimum sample requirement would be 30 g. Sampling conditions and recommended measurements are discussed. Maximum use of hardware and experience from the Mariner, Pioneer, and Viking missions is contemplated. The profile for a 1979 conjunction-class mission would include a total time of 1025 days, including one year in Mars parking orbit after sampling. The lander structure, components, and recovery alternatives are explained.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronautics and Aeronautics; 13; Jan. 197
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  • 57
    Publication Date: 2011-08-17
    Description: Contrary to popular belief, very large meteorites can be sufficiently slowed by aerodynamic drag to survive impact with the earth's surface provided that they enter the atmosphere at very low angles. This is a stringent requirement and survival probabilities for large, unguided objects are low; but they are not zero. Based on high-velocity impact experiments and published tabulations of the parameters of shallow angle entry trajectories, we estimate the probability of survival for an iron meteorite approximately the size and shape of the legendary Chinguetti meteorite (100 x 40 x 20-40 m) to be between 0.1 and 1 percent. Together with a limiting estimate of the flux of such bodies encountering the earth, this leads to an expected survival rate of one per (0.1-1.0) billion years on the earth's land surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Smithsonian Contributions to the Earth Sciences; 14, 1; 1975
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  • 58
    Publication Date: 2011-08-16
    Description: Pb-204, Bi, Tl, and Zn in samples from the Apollo 17 site exhibit relationships not found in samples from other sites. Pb-204, Tl, and Zn in residues remaining after dilute acid leaching are correlated with one another. Orange soil 74220, which is enriched in Pb-204, Tl, and Zn, is included in these relationships. In addition, the submicron metallic phase generally associated with agglutinate formation is correlated with all three of these elements; this relationship has already been reported for Pb-204 in other samples. Thus, orange soil and agglutinates appear to be involved in concentrating heavy volatile metals. A process other than mixing is required to account for this. As a consequence of the isolation of the landing site by the surrounding massifs, local supply and recycling of volatile trace elements in soils may account for some of the interelement relations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 27; 2, Se; Sept
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  • 59
    Publication Date: 2011-08-16
    Description: A plausible surface history of Mercury is presented which is suggested by Mariner 10 television pictures. Five periods are postulated which are delineated by successive variations in the modification of the surface by external and internal processes: accretion and differentiation, terminal heavy bombardment, formation of the Caloris basin, flooding of that basin and other areas, and light cratering accumulated on the smooth plains. Each period is described in detail; the overall history is compared with the surface histories of Venus, Mars, and the moon; and the implications of this history for earth are discussed. It is tentatively concluded that: Mercury is a differentiated planet most likely composed of a large iron core enclosed by a relatively thin silicate layer; heavy surface bombardment occurred about four billion years ago, which probably affected all the inner planets, and was followed by a period of volcanic activity; no surface modifications caused by tectonic, volcanic, or atmospheric processes took place after the volcanic period.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; June 10
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  • 60
    Publication Date: 2011-08-16
    Description: A complete atlas of the 5 nu-1 absorption band of NH3 is presented together with measurements of the total band intensity, line intensities, and self-broadening coefficients. The spectrum, which is displayed in the interval from 6418 to 6550 A, was obtained photoelectrically at a pressure of 0.061 atm, and many more lines were seen in this spectrum than in a previous one obtained at a pressure of 0.39 atm. The band intensity is used to derive the NH3 abundance in the atmospheres of Jupiter and Saturn, and the abundances in a single vertical path are found to be about 10 m amagat for Jupiter and 2 m amagat for Saturn. These results are shown to be in agreement with previous results obtained from higher resolution photographic spectra.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 25; May 1975
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  • 61
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    Publication Date: 2011-08-16
    Description: The possibility is considered that tektites are lunar volcanic ejecta, and lunar regions are examined from which tektites could be ejected with the necessary velocities and trajectories to reach the earth. The examined regions include areas around the Lunar Transient Phenomena sites near Censorinus, Messier, Messier A, and Taruntius, the area of Mare Foecunditatis near Secchi X, areas near Cauchy and Capella, and the eastern part of Mare Tranquillitatis. Evidence of acidic volcanic activity in these regions is described in detail, including possible calderas, mudflows, and endogenous domes. It is suggested that the moon is still gently degassing and that more violent eruptions of material may still occur on rare occasions. Remotely-sensed evidence of recent lunar internal activity is noted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 12; Mar. 197
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  • 62
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    Publication Date: 2011-08-16
    Description: Exploratory calculations using accretionary theory are made to demonstrate plausible sizes of second-largest, third-largest, etc., bodies at the close of planet formation in heliocentric orbits near the planets, assuming asteroid-like size distributions at the start of the calculation. Many satellite-sized bodies are found to be available for capture, cratering, or collisional fragmentation. In the case of earth-sized planets, the models suggest second-largest bodies of 500 to 3000 km radius, and tens of bodies larger than 100 km radius. Many of these interact with the planet before suffering any fragmentation events with each other. Collision of a large body with earth could eject iron-deficient crust and upper mantle material, forming a cloud of refractory, volatile-poor dust that could form the moon. Other satellite systems may have been affected by major capture or collision events of chance character.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 63
    Publication Date: 2011-08-16
    Description: Measurements of Rb-Sr systematics, K-Ar gas retention ages, and the isotopic compositions of He, Ne, and Ar have been performed for lunar troctolite 76535. Other investigators have presented evidence that this important rock formed as a cumulate at depth, which would make it an important link in the early chronology of the moon. Rb-Sr data do not define an isochron. Total Ar-40/K ages of whole rock and plagioclase range from 4.40-4.54 b.y. The trapped Ne and Ar in 76535 cannot be uniquely characterized as either 'planetary derived' or solar wind derived, but appear to have characteristics of both. The data suggest that 76535 formed 4.3-4.6 b.y. ago, and the accumulation process and/or subsequent annealing may have incorporated excess noble gases. Separation of radiogenic parents and daughters with incomplete isotopic equilibration may also have occurred during cooling or during a subsequent 'event'.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 26; 1, Ma; May 1975
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  • 64
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    Publication Date: 2011-08-16
    Description: Ratio picture techniques which enhance color or polarization contrasts are proposed for Uranus imagery on the MJU79 mission. Currently available low-resolution pictures of Uranus are assessed, and specific objectives of the fly-by are described, including exploratory imaging, measurement of fundamental properties (rotation period, rotation axis orientation, diameter), and examination of atmospheric properties. An attempt is made to predict the aspect of Uranus from current knowledge about its atmosphere. It is proposed that the imaging system should emphasize photo-polarimetric observations between 5500 and 10,000 A if the planet alone is to be imaged, or it should be a high-resolution system based on the MJS one if the satellites will also be imaged. Performance of a possible high-resolution system at Uranus is assessed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 24; Mar. 197
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  • 65
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    Publication Date: 2011-08-16
    Description: Correlation between the Cayley Formation and the magnetic anomaly at the Apollo 16 site in the northern plains of the crater Van de Graaf is discounted. The planar fill in the north end of Van de Graaf is described as dissimilar from Cayley-like plains, and orbital magnetic data collected by Apollo sub-satellites is shown not to substantiate the correlation of Cayley-like plains with any particular magnetic signature. The magnetic anomaly near Van de Graaf is explained as most likely being due to a subsurface source.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 253; Feb. 20
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  • 66
    Publication Date: 2011-08-16
    Description: The secular variation of the thermal structure of the Martian atmosphere during the dissipation phase of the 1971 dust storm is examined, using temperatures obtained by the infrared spectroscopy investigation on Mariner 9. For the latitude range -20 to -30 deg, the mean temperature at the 2-mbar level is found to decrease from approximately 220 K in mid-December 1971 to about 190 K by June 1972 while for the 0.3-mbar level a decrease from 203 K to 160 K is observed. Over the same period, the amplitude of the diurnal temperature wave also decreased. Assuming a simplified radiative heating model, the dust optical depth is found to decrease approximately exponentially with an e-folding time of about 60 days at both the 0.3- and 2-mbar levels. Stokes-Cunningham settling alone cannot account for this behavior. Sedimentation models which include both gravitational settling and vertical mixing are developed in an effort to explain the time evolution of the dust.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 24; Jan. 197
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  • 67
    Publication Date: 2011-08-16
    Description: Various theories have been published that consider the material of the Cayley Formation (a lunar smooth plain) to be ejecta of distant multiringed basins. Results presented in this paper indicate that the material cannot be solely basin ejecta. If smooth-plains are a result of formation of these basins or other distant large craters, then the plains materials are mainly ejecta of secondary craters of these basins or craters with only minor contributions of primary-crater or basin ejecta. Primary-crater ejecta can be a significant fraction of a deposit emplaced by an impact crater only if the primary crater is nearby. Other proposed mechanisms for emplacement of smooth-plains formations are discussed, and implications regarding the origin of material in the continuous aprons surrounding large lunar craters is considered. It is emphasized that the importance of secondary-impact cratering in the highlands has in general been underestimated and that this process must have been important in the evolution of the lunar surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 12; Jan. 197
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  • 68
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    Publication Date: 2011-08-16
    Description: The preliminary results of an analysis of quick-look data obtained from a high field magnetometer placed on Pioneer 11 are presented. It is found that within three planetary radii of Jupiter, the planetary magnetic field is too complex to be represented by a simple offset tilted dipole (OTD), as was suggested by Pioneer 10 data, and that higher harmonic multipoles are required. Reconciliation is achieved with earlier independently derived estimates obtained from ground-based observations of radio emissions, since the movement and tilt of the Pioneer 10 model yielded a field configuration and intensity that were inconsistent with those estimates.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 253; Jan. 31
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  • 69
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 12; Jan. 197
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  • 70
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; Jan. 1
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  • 71
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 24; 3, Ja; Jan. 197
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  • 72
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    Publication Date: 2011-08-16
    Description: Observations of the linear polarization properties of Jupiter's decimetric radioemission showed the planet's total intensity to increase between late summer 1973 and July 1974. Measurements were made with the NASA 64-m parabolic antenna operating at a wavelength of 13.1 cm. Data were plotted as a function of the longitude of the central meridian. Both data sets showed similar periodic intensity variation with longitude. However, the 1974 data points were consistently above the corresponding 1973 values. The flux density difference was attributed to the increase in the planet's decimetric radio emission. Measured at wavelengths of 21 cm and 11 to 13 cm the average peak flux densities were plotted as a function of the epoch of each observation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 253; Jan. 10
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  • 73
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    Publication Date: 2011-08-16
    Description: Morphologic as well as morphometric changes occur in the character of fresh lunar craters at a diameter range of about 10-20 km. The continuous size/morphology sequence advocated by Smith and Sanchez (1973) is sustained by their data only for craters between 10-20 km and about 100 km in diameter. The cumulative-morphology index, and the frequency-of-occurrence of wall terraces, central peaks, flat floors, and 'swirl texture' (Smith and Sanchez, 1973) support the existence of a morphologic transition at a crater diameter of 10-20 km, rather than a continuous gradation in shape within craters between 4 and 150 km in diameter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Modern Geology; 5; Nov. 197
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  • 74
    Publication Date: 2011-08-16
    Description: We have made a detailed examination of the mineralogy, textures, and assemblages of six calcium-aluminum-rich inclusions (CAI) in the Allende meteorite. They can be classified into four types - hibonite-bearing, fassaite- and olivine-bearing, feldspathoid-bearing and fassaite-bearing CAI that are hibonite and olivine free. Examples of each type appear to have crystallized from a liquid rather than by agglomeration of solid nebular condensates. Some lines of evidence for a liquid origin are the presence of spherical and ovoid shapes and rims containing minerals that are more refractory than minerals inside the inclusion. Thermodynamic calculations and comparisons with liquidus phase diagrams indicate that the CAI could have been produced by direct condensation to metastable subcooled liquids that subsequently crystallized or by remelting of an equilibrium high-temperature condensate by impact. The diopside rims in some hibonite-bearing CAI and the paucity of metal in fassaite-olivine-bearing CAI are more consistent with direct condensation of a liquid.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 39; Dec. 197
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  • 75
    Publication Date: 2011-08-16
    Description: A similitude parameter is derived which is based on theoretical considerations of erosion due to sand in saltation. This parameter has been used to correlate wind tunnel experiments of particle flow over model craters. The characteristics of the flow field in the vicinity and downstream of a crater are discussed and it is shown that erosion is initiated in areas lying under a pair of trailing vortices. The erosion rate parameter is used to calculate erosion rates on Mars, reported in Part 2, to be published later.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 26; Nov. 197
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  • 76
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    In:  Other Sources
    Publication Date: 2011-08-16
    Description: A coherent magnetochemical picture of lunar samples is presented which was determined from a synthesis of available magnetic-property data and corresponding chemical and petrographic data for soils and rock samples collected at the Apollo landing sites. The magnetic properties of the samples are correlated with Al/Si ratio as well as with telescope spectral reflectivity curves, and magnetochemical diagrams based on composition-sensitive magnetic parameters describing the Fe metal and Fe(2+) contents are used to classify the samples. It is shown that the relative metal-fraction size distribution and magnetic stability for different rock types and soils of varying Al/Si values are reflected in a plot of the ratio of saturation isothermal remanence to saturation magnetization vs the ratio of remanent coercive force to coercive force. It is concluded that all the Apollo landing sites have distinct telescope curves correlated with petrology, chemistry, Al/Si values, and magnetic properties. The established correlations suggest the possibility of estimating the magnetic properties of the regolith from remote-sensing observations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 77
    Publication Date: 2011-08-16
    Description: A new nomenclature for Martian regions and topographic features uncovered by Mariner 9, as officially adopted by the International Astronomical Union, is described. About 180 craters generally of diameters greater than 100 km have been named, as well as 13 classes of topographic features designated catena, chasma, dorsum, fossa, labyrinthus, mensa, mons, patera, planitia, planum, tholus, vallis, and vastitas. In addition seven craters and the Kepler Dorsum are named on Phobos, and two craters on Deimos. Coordinates and maps of each named feature are displayed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 26; Sept
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  • 78
    Publication Date: 2011-08-16
    Description: Three-layer monotonic electrical conductivity models for the lunar interior to a depth of 600 km are used in conjunction with laboratory measurements of the electrical conductivity of olivine and pyroxene to estimate a temperature-depth profile. The temperatures calculated for depths of 400-600 km are consistent with attenuation of the seismic shear wave. The temperature calculated at a depth of 100-250 km yields a heat flow that is in good agreement with the directly measured lunar heat flow. The temperature, however, is sufficiently close to melting that mascon anisostasy would not be maintained. Thus a better conductor is required at this depth.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 258; Nov. 13
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  • 79
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    Publication Date: 2011-08-16
    Description: This paper reviews observations of the rings of Saturn at visual, infrared, and radio wavelengths. Critical assessments are made of attempts to derive the physical characteristics of the rings from these measurements. A discussion is also given of the origin and evolution of the rings.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 18; Oct. 197
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  • 80
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    Publication Date: 2011-08-16
    Description: Infrared observations of Saturn from 5 to 40 microns are described. There is intense limb brightening at 12.35 microns over the southern polar cap. The C ring is anomalously bright at 10 and 20 microns and has bluer (hotter) colors than the A and B rings. The ring spectra have been extrapolated beyond 40 microns and subtracted from low-resolution far-infrared measurements to show that the far-infrared spectrum of the disk of Saturn is qualitatively similar to that of Jupiter and that Saturn radiates 2.5 plus or minus 0.6 times the energy it absorbs from the sun.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 26; Sept
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  • 81
    Publication Date: 2011-08-16
    Description: Comparisons of calculated diurnal and eclipse temperatures of the lunar outermost layer are made with earth-based infrared and millimeter data. The thermophysical model upon which the calculations are based incorporates variable physical properties. The thermal conductivity is a function of both density (depth) and temperature; the specific heat is a function of temperature; the density is a function of depth; and the dielectric constant and loss tangent are functions of density (depth). Laboratory measurements and Apollo-sample results are incorporated in the property data. Calculational cases are based largely upon different density profiles. The model is consistent with the data, and the comparisons of theoretical and observational temperatures are very favorable. For such comparisons, further sophistication of the thermophysical model of the outermost layer is probably not justified.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 13; Aug. 197
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  • 82
    Publication Date: 2011-08-16
    Description: Lunar geology evidence is examined for clues to the origin and evolution of the moon and earth. Seven evolutionary episodes, the last covering three billion years to the present day, are constructed for the moon. Parallel episodes in the earth's evolution are masked by the dynamic continuing evolution of the earth over a 4.5 billion year span, in contrast to the moon's quiescence and inability to retain fluids. Comparisons are drawn between the geochemistry and tectonics of the lunar basaltic maria and the earth's ocean basins. Lunar maria rocks differ strikingly in chemical composition from meteoritic matter and solar material. Inundation of frontside lunar maria basins by vast oceans of dark basalt mark the last of the major internally generated evolutionary episodes, and is attributed to consequences of meltdown of the lunar mantle and crust by radioisotope decay from below. Data are drawn primarily from Apollo missions 11-17, supplemented by other sources.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geological Society; vol. 131
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  • 83
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    Publication Date: 2011-08-16
    Description: The results of absorption coefficient measurements of HCl in the region 1400 to 2200 A are reported and compared with those previously published. It is concluded that the present results represent the best compromise of all measurements and should be used for any calculations on the photodissociation rate of HCl in planetary atmospheres.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of the Atmospheric Sciences; 32; Dec. 197
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  • 84
    Publication Date: 2011-08-16
    Description: Using a recently developed furnace, ferromagnetic resonance (FMR) thermomagnetic studies up to 900 C were employed to measure the Curie points of the superparamagnetic (SP) and single domain (SD) particles in lunar soils and potential magnetic analogue materials. Based on measured Curie points of 775 C, the SP and SD particles in lunar soils 10084-853, 12070-29, 14161-46, and 67010-4 are essentially pure metallic Fe. Synthetic and terrestrial samples containing magnetite, titanomaghemites, and magnetite-like particles have measured Curie points below 600 C are thus not magnetic analogues of lunar soils.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 2; Oct. 197
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  • 85
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    Publication Date: 2011-08-16
    Description: A model He exosphere of Mercury is developed whose source derives from accretion of the small fraction of solar-wind He(++) that is captured by the magnetosphere and absorbed at the planetary surface. The model is based on a lunar analogy whereby the surface is saturated with He. Surface and radial density distributions are derived, and the dayside concentration is determined by requiring that the limb intensity at 584 A equals the observed intensity. To maintain the He exosphere, it is found that only a fraction of the solar-wind He(++) flux intercepted by the magnetosphere need be captured. This corresponds to a total accretion rate of 6.8 by 10 to the 22nd power He(++) ions per sec at the surface, which also represents the upper limit to the total outgassing rate of He from the interior.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 80; Sept. 1
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  • 86
    Publication Date: 2011-08-16
    Description: The abundances and distributions of carbon, nitrogen, and sulfur in lunar soils are reviewed. Carbon and nitrogen have a predominantly extra-lunar origin in lunar soils and breccias, while sulfur is mostly indigeneous to the moon. The lunar processes which effect the movement, distribution, and evolution of carbon, nitrogen, and sulfur, along with the volatile alkali elements sodium, potassium, and rubidium during regolith processes are discussed. Possible mechanisms which may result in the addition to or loss from the moon of these volatile elements are considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 87
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    Publication Date: 2011-08-16
    Description: Comminution, agglutination, and replenishment processes in a lunar soil are modeled by a system of time-dependent linear differential equations. In the model, a soil is subdivided into coarse-particle, fine-particle, and agglutinate fractions. The relative mass abundance of each component in a mature soil is found to be proportional to rates for the reworking processes. Evolution of the grain-size distribution from a fresh ejecta blanket to a mature soil is described quantitatively in terms of the changing proportions of the three soil constituents. If size data are available for an immature soil and a mature soil of the same system, rates for the various processes can be calculated under certain simplifying assumptions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 88
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 89
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    Publication Date: 2011-08-16
    Description: It is noted that previously calculated models of Jupiter, in which the H/He ratio is assumed to be solar, required the inclusion of considerable additional mass in the form of volatilized condensates in the atmosphere and excess mass in the central core. Several additional models are considered in this paper which take into account the stricter constraints imposed by Pioneer 10 measurements of Jupiter's gravitational moments. These measurements have indicated that the mass of the excess volatilized condensates (assumed to be water) relative to the core mass (assumed to be rock) exceeds the relevant solar ratio. The present models are tested for sensitivity to variations in the H/He ratio, in the softness of the equation of state for water, in the treatment of the internal adiabat, in departures from an internal adiabat, and in temperature at the one-bar level. The preliminary results indicate that the ratio of excess water to rock in Jupiter is considerably in excess of the solar value.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 25; Aug. 197
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  • 90
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    Publication Date: 2011-08-16
    Description: A theory is developed for the photoclinometric determination of topography when the photometric function of a planetary surface is not restricted beyond the expectation that it is a function of phase angle, angle of incidence, and angle of emergence. Several versions of such an operational theory are presented together with several approaches to the numerical analysis. Reasons for the differences in numerical techniques are discussed. A preliminary result is considered which has been produced for an early Mariner 9 frame wherein the dust-laden atmosphere seems to exhibit standing-wave patterns. It is shown that if the assumption of homologous departures from plane-parallel atmospheric configuration is valid, the photoclinometry implies that laminar flow lines in the optically observable dust layer undergo a near-sinusoidal rise and fall of about 40 to 50 meters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 25; Aug. 197
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  • 91
    Publication Date: 2011-08-16
    Description: The atmospheric temperature-pressure profiles derived from the Pioneer 10-Pioneer 11 radio occultation experiment are mutually consistent but differ markedly from the results of other investigations. Current studies indicate that the occultation interpretation contains errors that were made very large by an inherent magnification effect, and that these errors have both geometrical and equipment sources. The apparent consistency between the Pioneer 10 and Pioneer 11 results must be considered fortuitous. Despite these difficulties, the occultation technique, when optimally instrumented and carefully interpreted, retains its potential for atmospheric profile measurements of high accuracy and resolution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 189; Sept. 12
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  • 92
    Publication Date: 2011-08-16
    Description: The decrease in the reflectivity of Venus in the near-UV can be explained if the clouds contain particles of elemental sulfur in addition to sulfuric acid. The low-resolution McDonald-Pittsburgh spectrum can be fitted by two sulfur-containing, multiple-scattering cloud models: (1) a mixed cloud consisting of one particle of elemental sulfur of radius 10 microns for every 670 particles of sulfuric acid of radius 1 micron, and (2) a layered cloud of optical thickness tau = 1.0 consisting of one-micron particles of sulfuric acid overlying a thick cloud of elemental sulfur particles of radius 3.6 microns. Some of the sulfur is incompletely polymerized. The source of the sulfur is photo-dissociation of COS, although some may also be recycled from the lower atmosphere. The sulfur plays a crucial role in the planetary meteorology of Venus since it is responsible for the bulk of the absorption of solar energy.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 93
    Publication Date: 2011-08-16
    Description: Summary of the evidence showing that the first optical depth of the Venus cloud layer is composed of a water solution of sulfuric acid, including earlier aircraft observations of Venus' reflectivity in the region from 1 to 4 microns obtained at a phase angle of 120 deg. Analyses of these aircraft results indicated that of all the proposed cloud candidates only a sulfuric acid solution with a concentration of 75% or more H2SO4 by weight was consistent with the observed 3-micron cloud feature. Aircraft observations of Venus are presented which were obtained in the same spectral region at a phase angle of 40 deg and in the region from 3 to 6 microns at a phase angle of 136 deg. Comparing the two sets of observations in the region from 1 to 4 microns, a striking phase effect is found: the reflectivity is much lower in the 3-micron region and there is a much more marked decline between 1.3 and 2.5 microns for the data obtained at the smaller phase angle. The observations made at the 40-deg phase angle are consistent with the theoretical behavior of a sulfuric acid cloud and imply that the sulfuric acid is present to at least many tens of optical depth below the cloud tops. Arguments concerning the concentration of the solution are reviewed, and it is concluded that the best current estimate is about 85% H2SO4 by weight.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 94
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    Publication Date: 2011-08-16
    Description: Ground-based observations and Venera 8 entry-probe measurements are used to infer the vertical distribution of cloud particles in the atmosphere of Venus. In the cloud-top region, from a few millibars to a few hundred millibars pressure, the mixing ratio of cloud particles to gas increases with depth. The visible clouds are diffuse with a scale height about one-half of the gaseous atmosphere. Although the presence of significant vertical structure could escape detection by available observations, the diffuse haze appears to extend over at least 20 km in altitude. The Venera 8 measurements suggest considerable vertical structure in the deep atmosphere. A unique solution for the cloud structure is not possible, but if it is assumed that the cloud optical properties are independent of height, then some characteristics of the relative cloud structure can be deduced. Under this assumption, the results show a maximum cloud density near 40 km, a nearly homogeneous particle mixing in the region from about 40 to 50 km, and a fairly sharp cloud bottom near 30 km. Relative maxima in the cloud density are also implied near 55 and 10 km, but with much greater uncertainty.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 95
    Publication Date: 2011-08-16
    Description: Results are reported for accurate multiple-scattering calculations to determine the solar-energy deposition profile in the atmosphere of Venus. It is found that most of the absorbed energy is deposited in the main cloud-layer region, located at altitudes above 35 km, and that the ground receives approximately 3% of the energy absorbed in toto by Venus. Using these results, vertical temperature profiles are computed under conditions of pure radiative equilibrium and radiative-convective equilibrium. Since the latter results satisfactorily match the temperature structure determined from various spacecraft observations, it is inferred that the greenhouse effect can account for the high surface temperature. Aerosols make an important contribution to the infrared opacity in these calculations. Preliminary three-dimensional calculations of the general circulation of the atmosphere are discussed which incorporate the results of the radiative calculations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 96
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    Publication Date: 2011-08-16
    Description: The physical structure of Jupiter is discussed on the basis of data obtained by Pioneers 10 and 11. It is argued that the elemental composition of Jupiter is similar to that of the sun, and it is shown that this argument is supported by measurements of the planet's density and H/He ratio. Jupiter's shape and gravitational field are described, and a model of the planet is proposed in which there are a small iron-silicate core at the center, a very thick liquid-hydrogen stratum divided into metallic (inner) and molecular (outer) layers, and a gaseous atmosphere. According to this model, the excess heat radiated by Jupiter is simply a remnant of the heat generated when the planet coalesced from the solar nebula. The appearance of the planetary disk is described together with the Jovian magnetic field, and the Great Red Spot is shown to be a cyclonic disturbance similar to a hurricane. Effects of the Galilean satellites on the magnetic field are considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Scientific American; 233; Sept
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  • 97
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    Publication Date: 2011-08-16
    Description: Models of the interior and thermal evolution of Mercury calculated by Siegfried and Solomon (1974) using Lewis' (1972) cosmochemical calculations to constrain the composition are tested for four necessary conditions for MHD dynamo generation. It is shown that dynamo generation requires at least a partially fluid interior, an energy source that drives a flow of core fluid relative to the rigidly rotating planet, a magnetic-field diffusion time in excess of the characteristic fluid-flow time scale, and a fluid flow of sufficient complexity to satisfy Cowling's (1934) theorem. It is concluded that a literal interpretation of Lewis' calculations implies that dynamo generation in Mercury is improbable. Generation would be possible only if the metallic core were contaminated with substantial amounts of radioactive material.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 256; Aug. 21
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  • 98
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    Publication Date: 2011-08-16
    Description: The evolution and physical structure of Mars are discussed primarily on the basis of Mariner 9 observations. The Martian atmosphere, density, and iron abundance are compared with those of earth, and it is noted that the planet was probably formed in less than 100,000 years. Stages in Martian differentiation are described together with the atmospheric composition, condensation and dust clouds, and surface winds. The surface is shown to have a wide diversity of geological landforms resulting from a variety of processes, including meteoroid bombardment, volcanic and tectonic activity, sapping, the action of running water, and wind action. Described landforms include impact craters, volcanic plains and domes, shield volcanoes, sinuous channels and gullies apparently formed by running water, and the enormous canyon system. Mechanisms for climatic change are considered, and questions are posed regarding the possibility of life on Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Scientific American; 233; Sept
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  • 99
    Publication Date: 2011-08-16
    Description: Reexamination of a photograph of Saturn taken on Nov. 15, 1966, when the earth was nearly in the ring plane, indicates that ring material may exist outside the visible rings, extending to more than 6 Saturnian radii. Although the suspected feature on the photograph appears to be real, the possibility of its being a developed pressure mark or a chance alignment of grains cannot be ruled out. The observed brightness in the blue light was estimated to be 19.5 plus or minus 0.5 per linear arcsecond, implying a normal optical thickness, .0000001 for ice-covered particles. For spacecraft passing through this region, the hazards are found to be minimal.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 100
    Publication Date: 2011-08-16
    Description: A program of lunar infrared radiometry which uses large-area scanning is described. Procedures for atmospheric-attenuation correction and data reduction to temperature by relative radiometry are outlined. The scan data of the waning moon taken during ten evenings in the 10- to 12-micron window are presented as isothermal contour maps of the lunar disk. More than 160 areas of anomalous thermal emission have been found in the lunar dark-side data. These are tabulated and are also shown on an accompanying map. An error analysis, derived from accuracy estimates of the independent parameters, is included.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Moon; 12; Apr. 197
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