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  • LUNAR AND PLANETARY EXPLORATION  (3,679)
  • 2015-2019
  • 1975-1979  (3,679)
  • 1945-1949
  • 1
    Publication Date: 2011-08-24
    Description: Two unique meteorites were identified by means of a mineralogical examination of the smaller-sized Yamato achondrites. Yamato-74130 is the most iron-rich ureilite with Na, Cr-rich augite instead of pigeonite. Yamato-74160 was extensively recrystallized, but the composition and proportion of olivine, orthopyroxene, augite, and plagioclase is consistent with LL7 chondrites. ALHA77005 is a unique achondrite with olivine, possibly three pyroxene assemblages, and maskelynite. These meteorites provide evidence that there may be other 'thermalized' asteroids than the howardite parent body. Detailed petrologic descriptions of the unique achondrites, recrystallized diogenite Yamato-74013, and the rapidly cooled eucrite Yamato-74450 with pyroxene phenocrysts are given. It is inferred from the bulk chemistry and the mineralogical reexamination of Yamato-75028 that it is composed of the H5-type clasts and chondrule-rich H(L)3-like matrix with the H5 fragments. A close relationship in the collisional evolution of some asteroids with these materials is inferred.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: National Institute of Polar Research, Memoirs (ISSN 0386-0744); 15, 1; 54-76
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  • 2
    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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  • 3
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    In:  CASI
    Publication Date: 2006-06-26
    Description: The high closing speed of 57km/s between the spacecraft and Halley poses special problems in the design of the required meteoroid protection. A double wall structure with a total thickness equal to 0.1 to 1 times the diameter of the largest meteoroid encountered is sufficient to stop that meteoroid. However, the unusually high number of meteoroid impacts on the Halley probe will cause significant erosion of the outer wall so that failure of the second wall is more likely to occur from a small meteoroid passing through a previously created hole in the outer wall and then penetrating the second wall. Calculations of the shielding required based on this failure mode, show that a double wall structure must actually have a total thickness 1.2 to 7.3 times the diameter of the largest meteoroid encountered, depending on the size distribution of the meteoroids.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: ESA Comet Halley Micrometeoroid Hazard Workshop; p 73-76
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  • 4
    Publication Date: 2006-01-16
    Description: Winograd's algorithm for computing the discrete Fourier transform is extended considerably for certain large transform lengths. This is accomplished by performing the cyclic convolution, required by Winograd's method, by a fast transform over certain complex integer fields. This algorithm requires fewer multiplications than either the standard fast Fourier transform or Winograd's more conventional algorithms.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Deep Space Network; p 134-140
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  • 5
    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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  • 6
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    Publication Date: 2006-01-16
    Description: Design principles of spaced, multiwall meteoroid protection are investigated in the light of experimental data generated during the Apollo Program. The outer wall or shield is shown to be the most important element in the meteoroid-spacecraft interaction. The condition of the debris is primarily a function of the shock pressure, the melting points of the meteoroid and the shield, and the length of the meteoroid and thickness of the shield. Spacing between the walls is effective up to approximately 100 times the length of the meteoroid. The required thickness of the second wall is shown to be proportional to the meteoroid mass, velocity, and density, and to the spacing between the walls, taken with exponents dependent upon the condition of the debris. The effects of placing additional elements (insulation or honeycomb cells) between the two walls are discussed, and the efficiency of various protective configurations is presented. An analysis of the meteoroid protection proposed for the Comet Halley probe is included as an appendix.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: ESA Comet Halley Micrometeoroid Hazard Workshop; p 85-92
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  • 7
    Publication Date: 2006-01-12
    Description: The beneficiation of lunar plagioclase and ilmenite ores to feedstock grade permits a rapid growth of the space manufacturing economy by maximizing the production rate of metals and oxygen. A beneficiation scheme based on electrostatic and magnetic separation is preferred over conventional schemes, but such a scheme cannot be completely modeled because beneficiation processes are empirical and because some properties of lunar minerals have not been measured. To meet anticipated shipping and processing needs, the peak lunar mining rate will exceed 1000 tons/hr by the fifth year of operation. Such capabilities will be best obtained by automated mining vehicles and conveyor systems rather than trucks. It may be possible to extract about 40 kg of volatiles (60 percent H2O) by thermally processing the less than 20 micron ilmenite concentrate extracted from 130 tons of ilmenite ore. A thermodynamic analysis of an extraction process is presented.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Resources and Space Settlements; p 275-288
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  • 8
    Publication Date: 2006-01-12
    Description: Although bulk lunar soil is not a suitable feedstock for extracting metals, certain minerals such as anorthite and ilmenite can be separated and concentrated. These minerals can be considered as potential ores of aluminum, silicon, titanium, andiron. A separation and metal extraction plant could also extract large amounts of oxygen and perhaps hydrogen from these minerals. Anorthie containing 19 percent aluminum and 20 percent silicon can be concentrated from some highland soils where it is present in amounts up to 60 percent. Ilmenite containing 32 percent titanium and 37 percent iron can be concentrated from some mare soils where it is present in amounts up to 10 percent. The ideal mining site would be located at the boundary between a high-titanium mare and a high-aluminum highlands. Such area may exist around the rims of some eastern maria, particularly Tranquilitatis. A location on Earth with raw materials as described above would be considered an economically valuable ore deposit if conventional terrestrial resources were not available.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Ames Res. Center Space Resources and Space Settlements; p 243-255
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  • 9
    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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  • 10
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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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  • 11
    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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  • 12
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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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  • 13
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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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  • 14
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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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  • 15
    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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  • 16
    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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  • 17
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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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  • 18
    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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  • 19
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 39; Aug. 197
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  • 20
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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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  • 21
    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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  • 22
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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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  • 23
    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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  • 24
    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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  • 25
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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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  • 26
    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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  • 27
    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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  • 28
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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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  • 29
    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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  • 30
    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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  • 31
    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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  • 32
    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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  • 33
    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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  • 34
    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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  • 35
    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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  • 36
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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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  • 37
    Publication Date: 2011-08-17
    Description: In 6 of the 7 instances where posteclipse brightening of Io has been reported by observers using blue filters, a major solar flare occurred within 10 degrees of the sub-Jovian longitude in the 100-day interval prior to observation. In none of the 18 instances where no posteclipse brightening was observed did such a flare occur. It is proposed that a phenomenon associated with a major solar flare causes an increase in the trapped particle flux at Io's orbit by an order of magnitude. The posteclipse brightening may be caused by thermoluminescence of Io's surface material upon emergence. Alternatively, it is possible that the increase in trapped particle flux would warm the surface, creating a temporary atmosphere which would precipitate during eclipse cooling and vaporize in the period of warming after reemergence.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 33; Jan. 197
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  • 38
    Publication Date: 2011-08-17
    Description: Radio tracking data associated with the February 1977 encounters between the Martian satellite Phobos and the Viking Orbiter I spacecraft have been analyzed to determine the gravitational constant of Phobos. A linear error analysis was conducted to determine the selection of data and the parameter solution set which would yield the best estimate of the gravitational constant. This error analysis indicated that the optimal data set was a data arc beginning just prior to the closest encounter and spanning three consecutive spacecraft orbits; data near periapsis were deleted. The most feasible parameter solution set consisted of the Phobos gravitational constant and the spacecraft initial conditions. The result of the data analysis was an estimate of (7.3 plus or minus 0.7) x 10 to the -4th cu km/sq sec for the gravitational constant of Phobos.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 4; Dec. 197
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  • 39
    Publication Date: 2011-08-17
    Description: The ratio for the equivalent widths for the unsaturated H2 quadrupole transitions observed in the Jovian planets is calculated and compared with a large number of observations. The comparison indicates that equilibrium hydrogen may be present in Jupiter and Saturn, while Uranus and Neptune exhibit ratios not in accord with equilibrium hydrogen. Observations which can differentiate among the possible states of H2 are proposed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 33; Jan. 197
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  • 40
    Publication Date: 2011-08-17
    Description: The paper reports JHK colors observed for ten asteroids and synthesized JHK colors for seven meteorite groups, samples of iron and nickel metal, pyroxene, olivine, feldspar, a lunar anorthite and some terrestrial mineral samples. Pronounced differences are apparent between the chondritic and achondritic meteorite classes; the chondritic classes show less subdued trends in J-H color which reflect their metamorphic grade. We find small but significant differences between the JHK colors of the predominant C and S classes of asteroids. All JHK colors of asteroids observed here fall within the limited domain defined by the various chondritic and iron-rich meteorites but are strikingly different from those of most achondritic meteorites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 13; Mar. 31
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  • 41
    Publication Date: 2011-08-17
    Description: The spectral radiance and color of the Martian sky and soil and the spectral reflectance of soil features are estimated from six-channel (0.4-1.0 micron) spectral data obtained with the Viking lander cameras. Images taken near local noon from the two landers reveal a sky that is brighter near the horizon than the soil but with a similar spectral radiance shape and color. The scenes are predominantly moderate yellowish brown in color with only subtle variations except for some dark grey rocks. Most spectral reflectance estimates are similar: they rise rapidly with increasing wavelength between 0.4 and 0.8 micron and with only a few exceptions exhibit a pronounced minimum centered about 0.93 micron. These characteristics are consistent with an abundance of Fe(3+)-rich weathering products, notably nontronite. However, the delineation of the number and abundances of total mineral phases requires further analyses and laboratory comparisons. Reflectance estimates for rocks have not been repeatable, probably because most rocks have irregular pitted surfaces that introduce significant shadowing components.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Sept. 30
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  • 42
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    Publication Date: 2011-08-17
    Description: Observations of hydroxyl (OH) emission from meteors were made during the late summers of 1975 and 1976 from altitudes of 10,600 and 14,200 feet (3.2 km and 4.45 km). The observations were made with OH meteor photometers developed at the NASA-Langley Research Center. Two of the meteors were Perseids, and one was an Alpha Capricornid. The Perseid meteors produced a peak irradiance at a distance of 100 km from the meteors of about 0.00005 erg/sq cm per sec in the OH emission region. The zero-magnitude Alpha Capricornid meteor produced a spectral irradiance at 3100 A of 23 hundred-millionths erg/sq cm per A per sec. This may be indicative of significant amounts of H2O in these meteors.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 217
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  • 43
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    Publication Date: 2011-08-17
    Description: It has been suggested that NH3 and other reducing gases were present in the earth's primitive atmosphere, enhancing the global greenhouse effect; data obtained through isotopic archeothermometry support this hypothesis. Computations have been applied to the evolution of surface temperatures on Mars, considering various bolometric albedos and compositions. The results are of interest in the study of Martian sinuous channels which may have been created by aqueous fluvial errosion, and imply that clement conditions may have previously occurred on Mars, and may occur in the future.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 269; Sept. 15
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  • 44
    Publication Date: 2011-08-17
    Description: Mineralogical and chemical characteristics of the Happy Canyon meteorite, found in 1971 near Wayside, Texas, show it to be a new type of enstatite achondrite occupying the gap between the recrystallized enstatite chondrites and the igneous, crystalline, unbrecciated enstatite chondrites. Although the bulk composition of the specimen is consistent with that of an E6 enstatite chondrite, it has a crystal cumulate texture. There are minor amounts of metal and troilite which have survived extensive weathering. The Happy Canyon meteorite may represent an E6 composition which has melted and reprecipitated at a slightly higher oxidation state, possibly in the core of a small parent body.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 12; June 30
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  • 45
    Publication Date: 2011-08-17
    Description: Photoionization of the upper atmosphere of Titan by sunlight is expected to produce a substantial ionospheric layer. One-dimensional forms of the mass, momentum, and energy conservation equations for ions and electrons have been solved along with electron number densities of about 1000/cu cm, using various model atmospheres. The significant ions in a CH4-H2 atmosphere are H(+), H3(+), CH5(+), CH3(+), and C2H5(+). Electron temperatures may be as high as 1000 K, depending on the abundance of hydrogen in the high atmosphere. Interaction of the solar wind with the ionosphere is also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 31; May 1977
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  • 46
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    Publication Date: 2011-08-17
    Description: A description is given of the observation of five brief occultations of the star SAO 158687 which occurred both before and after its occultation by Uranus on March 10, 1977. The events were observed with a three-channel occultation photometer, attached to a 91-cm telescope. The observations indicate that at least five rings encircle the planet Uranus. Possible reasons for the narrowness of the Uranus rings are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 267; May 26
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  • 47
    Publication Date: 2011-08-17
    Description: Two nightside encounters with Mercury's magnetosphere by Mariner 10 revealed bow shock and magnetosheath signatures in the plasma electron data that are entirely consistent with the geometry expected for an interaction between a planet-centered magnetic dipole and the solar wind. The geometrically determined distance between the planet's center and the solar wind stagnation point is 1.4 plus or minus 0.1 R sub M. Both diffuse and sharp shock crossings were observed on the two magnetosphere encounters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; May 1
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  • 48
    Publication Date: 2011-08-17
    Description: Twenty-two light curves of Hebe are analyzed along with results of UBV photometry and photometric astrometry. A mean synodic period of approximately 7 hr 16 min 28.7 sec is adopted, and it is found that the amplitude of Hebe appears to vary directly with phase. The asteroid's magnitudes and colors are plotted against phase, its pole orientation is estimated, and the sidereal period is determined to be about 7 hr 16 min 28.01 sec from photometric astrometry. A color curve is plotted which shows that Hebe has a reddened region on its surface near the secondary minimum and that the asteroid is nearly spherical. Opposition effects are compared and found to be closely similar for Hebe, Ceres, Lydia, Massalia, and Vesta.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal; 82; Mar. 197
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  • 49
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    Publication Date: 2011-08-17
    Description: Basic data are presented on the Del Rio, Nordheim, and Monahans ataxites found in Texas. Results are reported for bulk-chemistry analysis, metallographic observations, and electron-microprobe analysis of the Del Rio meteorite. It is shown that Del Rio is distinctly different from the other two ataxites in terms of nickel, phosphorous, and carbon content, and is composed of at least three coarse grains in different crystallographic orientations. All the kamacite in Del Rio is found to have transformation structures that are probable shock products, and minor inclusions of daubreelite, schreibersite, and troilite are observed. It is concluded that Del Rio was apparently mildly shocked prior to its fall.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 12; Mar. 31
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  • 50
    Publication Date: 2011-08-17
    Description: Effects of collisions and finite winds characteristic of a highly perturbed atmosphere on the thermal escape of terrestrial hydrogen and helium are investigated using a Monte Carlo approach. The limiting cases of vertical and horizontal winds are considered, and the relaxation layer between the collisionless exosphere and the collision-dominated thermosphere is modeled as a plane-parallel slab of given column density, depth, and atmospheric density. For both gases, the upwardly injected flux at the base of the relaxation layer is compared with the returning downward flux distribution at the same location; the technique is also applied to the atmosphere of Titan. The results show that inclusion of collisions in the escape model for terrestrial hydrogen with winds effectively throttles the escape process, that collisional throttling is negligible for helium when the exobase temperature is at least 5000 K, and that the escape of a planetary-atmosphere constituent depends on the ratio of its gravitational and kinetic energies as well as on the ratio of its mass to that of the background gas.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Mar. 1
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  • 51
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    Publication Date: 2011-08-17
    Description: Over one thousand occultations of each planet in the solar system have occurred during the period from mid-1973 through mid-1976 as seen from the lunar orbiting Radio Astronomy Explorer 2 (RAE 2) spacecraft. These occultations have been examined for evidence of planetary radio emissions in the 0.025-13.1 MHz band. Only Jupiter and the earth have given positive results. Lack of detection of emission from the other planets can mean that either they do not emit radio noise in this band or the flux level of their emissions and/or its occurrence rate are too low to be detected by RAE 2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Mar. 1
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  • 52
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    Publication Date: 2011-08-17
    Description: The infrared spectrometer and radiometer for the Mariner-Jupiter-Saturn mission is described. Results of Nimbus and Mariner 9 IR spectroscopy of earth and Mars are used as examples to demonstrate the power and diversity of the technique. Determinations of planetary surface compositions, surface temperatures, vertical temperature profiles, surface pressures, and atmospheric constituents are summarized. Applications to Jupiter and Saturn are briefly mentioned.
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  • 53
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 195; Mar. 11
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  • 54
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    Publication Date: 2011-08-17
    Description: The article presents a rebuttal of Young's (1975) view that the 140 m/sec horizontal wind at 45 km reported by Venera 8 is anomalous or spurious. Some errors are discussed and the largest contribution is attributed to descent probe measurements designed to find the true probe descent rate. Young's suggestion of error in in situ measurement of winds due to selection of a reference speed and to unrecognized oscillator drift is scrutinized. Evidence is seen for a wide band of variable high-grade retrograde horizontal winds girdling Venus at the equator. Mariner 10 evidence (UV photographs) is taken into account. The band of winds at 45 km is seen to extend well beyond the top of the visible cloud, and an upper turbulent region is attributed to vertical convection currents carried along by high-speed horizontal winds.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 30; Feb. 197
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  • 55
    Publication Date: 2011-08-17
    Description: Viking 2 entry data on the structure of Mars' atmosphere up to 100 kilometers define a morning atmosphere with an isothermal region near the surface; a surface pressure 10% greater than that recorded simultaneously at the Viking 1 site; and a thermal structure to 100 kilometers at least qualitatively consistent with pre-Viking modeling of thermal tides. The temperature profile exhibits waves whose amplitude grows with altitude, to about 25 K at 90 kilometers. The atmosphere is stable against convection, except possibly in some very local regions. Temperature is everywhere appreciably above the carbon dioxide condensation boundary at both landing sites, precluding the occurrence of carbon dioxide hazes in northern summer at latitudes to at least 50 deg N. Thus, ground-level mists seen in these latitudes would appear to be condensed water vapor.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 194; Dec. 17
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  • 56
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    Publication Date: 2011-08-17
    Description: The two Viking missions to Mars have been extraordinarily successful. Thirteen scientific investigations yielded information about the atmosphere and surface. Two orbiters and landers operating for several months photographed the surface extensively from 1500 kilometers and directly on the surface. Measurements were made of the atmospheric composition, the surface elemental abundance, the atmospheric water vapor, temperature of the surface, and meteorological conditions; direct tests were made for organic material and living organisms. The question of life on Mars remains unanswered. The Viking spacecraft are designed to continue the investigations for at least one Mars year.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 194; Dec. 17
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  • 57
    Publication Date: 2011-08-17
    Description: Mariner 9 spacecraft images showing evidence of variable surface features and surface erosion resulting from atmospheric wind on Mars have caused a renewed interest in the eolian mechanics of saltating grains. To study this phenomenon, both experimental investigation in an atmospheric wind tunnel and numerical solutions of the equations of motion of a single grain under Martian surface conditions were conducted. The numerical solutions for earth were used and empirically adjusted to correlate with existing experimental data for Mars. These modified equations were then solved to estimate grain motion for Mars. These calculations show the importance of a lifting force on the grain to initiate motion in both earth and Mars calculations. Major findings include a comparison of earth and Mars grain trajectories that show Mars length scales to be longer and to fall with a higher terminal grain velocity. The grains in the Mars calculation also made a smaller collision angle with the surface on rebound.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 81; Nov. 10
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  • 58
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    Publication Date: 2011-08-17
    Description: A description is presented of the results of a nondestructive analysis conducted with a 42-g slice of the Kenna ureilite. The sample was analyzed in a gamma-gamma coincidence counting system, using a dual-parameter, 4096-channel pulse height analyzer. Data concerning Al-26 and Ne-22/Ne-21 in ureilites and Chassigny are presented in a table. A graph shows the ratio of measured Al-26 activity to that calculated from elemental production rates vs spallation Ne-22/Ne-21 for ureilites and Chassigny. The significance of the data with respect to findings reported by Wilkening et al. (1973) is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 40; Dec. 197
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  • 59
    Publication Date: 2011-08-17
    Description: Vertical components of photoelectron fluxes in the atmosphere of Venus are computed by solving an appropriate form of the Boltzmann equation in the cases where there is no flux of either photoelectrons or solar-wind particles across the ionopause and where photoelectrons are free to escape from the atmosphere. It is assumed that Venus has no magnetic field and that the atmosphere is composed of carbon dioxide, atomic oxygen, and helium. The results are plotted as a function of altitude for several energies in the range from 100 eV to a cutoff of the order of 1 eV. Heating rates for the two upper boundary conditions and the case of no spatial transport are determined which show that transport effects dominate at altitudes greater than about 200 km. Electron temperatures are calculated for the adopted model atmosphere and ionosphere by solving the pertinent conservation equation, and excitation rates are computed for the CO Cameron band as well as the CO2(+) A and B bands.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 81; Oct. 1
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  • 60
    Publication Date: 2011-08-16
    Description: The immediate environs of the Viking 1 lander are described, and the techniques employed to deduce the properties of the two different 'soil' types there are summarized. It is shown that the surface in the immediate vicinity of the lander consists of an area with fine-grained materials ('Sandy Flats') and a rocky area set in a matrix of finer-grained material ('Rocky Flats'). Estimates are given for the bulk density, particle density, particle size distribution, cohesion, angle of internal friction, and penetration resistance of the surface layer in each area. Footpad penetration into the surface layer is discussed, and wind removal of particles is examined. It is concluded that the surface layer of the Viking 1 landing site contains loess, dune sand, lunar nominal soil, lag gravel, and bare rock.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 194; Oct. 1
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  • 61
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    Publication Date: 2011-08-16
    Description: A chronology of Viking 1 lander activities is presented for the first 43 sols (Martian days) of surface sampling and analysis. The orbital insertion of the second Viking spacecraft is reviewed along with the search for the second landing site. A general assessment of the planet is made on the basis of the data thus far obtained. Some of the findings reported are that: (1) there is extensive evidence of volcanism, fluvial and aeolian erosion, and deposition over the entire surface; (2) the floor of Vallis Marineris is significantly younger than the planet's surface; (3) the morphology of Martian crater ejecta is indicative of surface flow rather than ballistic deposition; (4) the rocks in the immediate vicinity of the lander are all covered by a layer of fine red dust; (5) the atmosphere is optically thick and well mixed, with suspended particles giving the sky a pink color; (6) the N and Ar isotopic ratios are different from those on earth; (7) atmospheric water vapor varies with both time of day and location; (8) the summer northern polar regions have a high water concentration in the atmosphere; (9) a large fraction of magnetic material resides in the surface; and (10) no complex organic compounds have been detected in the two samples analyzed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 194; Oct. 1
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  • 62
    Publication Date: 2011-08-16
    Description: A substantial nightside ionosphere has been observed on Venus by both Mariner 5 and Mariner 10. Major dayside ionic species such as O2(+) and other molecular ions have chemical lifetimes much shorter than the 244.3-day rotation period of the planet. Rapid transport of ions from the dayside to the nightside to the extent required seems most unlikely. Consequently, possibilities are investigated for local production of ions on the nightside itself. Constraints imposed by chemical lifetimes require atomic ions with low ionization potentials. It is suggested that metallic ions of meteoric origin are the positive charge carriers, and the plausibility of this mechanism is demonstrated. Other possibilities are examined and shown to be less likely. Meteor ablation on Venus, the aeronomy of metallic species, and the role of negative ions near the electron peaks of the atmosphere are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 81; Sept. 1
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  • 63
    Publication Date: 2011-08-16
    Description: During the past several years the Viking project developed plans to use Viking orbiter instruments and earth-based radar to certify the suitability of the landing sites selected as the safest and most scientifically rewarding using Mariner 9 data. During June and July 1976, the earth-based radar and orbital spacecraft observations of some of the prime and backup sites were completed. The results of these combined observations indicated that the Viking 1 prime landing area in the Chryse region of Mars is geologically varied and possibly more hazardous than expected, and was not certifiable as a site for the Viking 1 landing. Consequently, the site certification effort had to be drastically modified and lengthened to search for a site that might be safe enough to attempt to land. The selected site considered at 47.5 deg W, 22.4 deg N represented a compromise between desirable characteristics observed with visual images and those inferred from earth-based radar. It lies in the Chryse region about 900 kilometers northwest of the original site.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 193; Aug. 27
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  • 64
    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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  • 65
    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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  • 66
    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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  • 67
    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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  • 68
    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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  • 69
    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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  • 70
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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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  • 71
    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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  • 72
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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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  • 73
    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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  • 74
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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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  • 75
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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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  • 76
    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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  • 77
    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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  • 78
    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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  • 79
    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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  • 80
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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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  • 81
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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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  • 82
    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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  • 83
    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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  • 84
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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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  • 85
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 253; Feb. 27
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  • 86
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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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  • 87
    Publication Date: 2011-08-16
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; 195; Jan. 1
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  • 88
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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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  • 89
    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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  • 90
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    Publication Date: 2011-08-18
    Description: The possibility of using solar sails to achieve a rendezvous with Halley's Comet is explored. Rendezvous trajectories are calculated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Proc. of the Shuttle-Based Cometary Sci. Workshop; p 251-256
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  • 91
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    Publication Date: 2011-08-18
    Description: A model of the dissociative lifetime of the hydroxyl radical is computed where the H2O and OH velocities are vectorially added. A lifetime of approximately 3 x 100,000 seconds is determined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA. Marshall Space Flight Center Proc. of the Shuttle-Based Cometary Sci. Workshop; p 222-226
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  • 92
    Publication Date: 2011-08-17
    Description: Surface sampler activities on Mars during the Viking extended mission are considered, including excavation of deep trenches, construction of conical piles of materials, backhoe touchdown experiments, and acquisition of contiguous pictures of the surface beneath number 2 terminal descent engines using mirrors. Results of the Physical Properties Investigation that are relevant to aeolian processes are also discussed. Both pictures and surface sampler data indicate that the surface materials in the sample fields of the Viking landers may be grouped, in order of increasing strength, into drift material, crusty to cloddy material, blocky material and rocks.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 93
    Publication Date: 2011-08-17
    Description: The Western Desert of Egypt is one of the most arid regions on earth and is probably the closest terrestrial analog to the surface of Mars. An expedition to the area in 1978 revealed an abundance of quartzite and basalt rocks that have been pitted and fluted by wind erosion and deflation of the desert surface. These pitted rocks are internally homogeneous, show no internal holes or vesicles, and are considered an important but neglected type of ventifact. They bear a striking resemblance to the pitted and fluted rocks seen by the Viking Landers, rocks that have generally been interpreted as vesicular basalts only slightly modified by wind erosion. Wind tunnel studies of the air flow over and around nonstreamlined hand specimens from the Western Desert show that windward abrasion coupled with negative flow, secondary flow, and vorticity in a unidirectional wind can explain the complex arrays of pits and flutes. These field and laboratory observations suggest that the pitted rocks at the Viking Lander sites are also ventifacts, and thus the Martian surface may be far more wind eroded than previously thought.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 94
    Publication Date: 2011-08-17
    Description: A comparative study of Martian and terrestrial dunes was made based on Viking Orbiter pictures and aerial pictures of terrestrial deserts. The morphological similarity between the Martian dunes and terrestrial crescentic dunes implies that the dynamics of dune formation are similar on the two planets, despite Martian constraints on dune formation that include much higher velocity winds required to move 'sand' in saltation, the possible inhibition of sand movement by absorbed water vapor, the seasonal 'snow' cover in the north circumpolar erg, and a probably sparse sand supply. The absence of longitudinal dunes and the restriction of massive crescentic dunes to a few sites on Mars suggests that Mars may have a long eolian history in which much of the sand suitable for saltation has already been transported to the north polar erg and crater floor fields.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 95
    Publication Date: 2011-08-17
    Description: The backhoe magnets on Viking Lander (VL) 2 were successfully cleaned, followed by a test involving successive insertions of the cleaned backhoe into the surface. Rapid saturation of the magnets confirmed evidence from primary mission results that the magnetic mineral in the Martian surface is widely distributed, most probably in the form of composite particles of magnetic and nonmagnetic minerals. An image of the VL 2 backhoe taken via the X4 magnifying mirror demonstrates the fine-grained nature of the attracted magnetic material. The presence of maghemite and its occurrence as a pigment in, or a thin coating on, all mineral particles or as discrete, finely divided and widely distributed crystallites, are consistent with data from the inorganic analysis experiments and with laboratory simulations of results of the biology experiments on Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
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  • 96
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    Publication Date: 2011-08-17
    Description: Most meteorites show evidence of thermal processing either because of metamorphic changes or as a result of melting and differentiation. Proposed mechanisms for supplying this energy generally rely upon short-lived radioisotopes or electrical induction, though accretion is sometimes mentioned, and more exotic models have been discussed. Interest in isotopic heating has been heightened by the discovery of Al-26 in Allende inclusions and also by the proposal that a lunar core and dynamo resulted from the radioactive decay of superheavy elements during the early solar system. Electrical induction as a heat source can be scaled to a broad range of solar system conditions, but corroborative evidence for these conditions is inconclusive. The accretion mechanism is probably not viable for the asteroidal and meteorite parent bodies, because the high kinetic energy requirement is inconsistent with the formation of the objects and their regoliths in the presence of a weak gravitational field.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 97
    Publication Date: 2011-08-17
    Description: Carbonaceous chondrites of groups CI and CM were formed by impact brecciation and aqueous alteration of earlier generations of mineral phases within the surface regions of two or more parent bodies. Those parent bodies were probably asteroids, rather than comets, although a problem still exists in delivering such material safely to earth. Aqueous activity may have been widespread on asteroids.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 98
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    Publication Date: 2011-08-17
    Description: Recent observations have led to unconventional models of certain asteroids, suggesting previously unsuspected forms. Some of these include binary asteroids (e.g., 532 Herculina, 18 Melpomene), very irregular asteroids (e.g., the Mars-crossing 1580 Betulia), and very elongated asteroids, unlikely to be collisional fragments (e.g., 624 Hector). A connection is suggested between this observational work and ongoing theoretical work concerning collisions of large comparable-sized asteroids. Such collisions have different consequences from the collisions usually considered. The new work suggests possible sources of elongated and binary asteroids.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 99
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    Publication Date: 2011-08-17
    Description: Radio observations of the asteroids can provide information on the thermal and dielectric properties of the surface materials and, because the radio emission arises somewhat below the surface, the data give some indication of layering. Observational difficulty has limited the investigations to only 6 asteroids. 1 Ceres and 324 Bamberga appear to have a layer of dust covering a more compacted material; the data on 4 Vesta cannot be matched by any current models for the surface; and the results for 18 Melpomene, 31 Euphrosyne and 433 Eros are too incomplete for firm conclusions. Future possibilities include more accurate radiometry of a few selected asteroids of different taxonomic classes and actual resolution of some of the larger objects by aperture synthesis techniques.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 100
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    Publication Date: 2011-08-17
    Description: Interpretations of astronomical polarization data for more than 100 minor planets are summarized with reference to laboratory data for lunar, meteoritic, and terrestrial samples. All observed asteroids, including objects only a few kilometers in diameter, have microscopically intricate surfaces. Detailed comparisons between laboratory measurements of basaltic achondrites and telescopic results for Vesta show that its surface is particulate with a broad range of particle sizes, including a component of fine (1-5 micron) dust. The surface soils have not, however, undergone marked optical alterations as is the case for the lunar fines. For albedos greater than about 0.06, the albedo and hence the diameter can be determined with some reliability from the slope of the ascending branch of the polarization-phase curve. Many minor planets have surfaces that are remarkably uniform in albedo and texture on a hemispheric scale. A notable exception is 4 Vesta, which shows about ten percent albedo variegation between hemispheres.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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