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  • LUNAR AND PLANETARY EXPLORATION  (723)
  • 1975-1979  (723)
  • 1930-1934
  • 1977  (723)
  • 1
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    In:  CASI
    Publication Date: 2019-08-28
    Description: The Viking spacecraft are described as well as the instruments carried to accomplish the combined goal of studying the atmosphere and geology of the entire planet, and to analyze the Martian soil and search for life in two specific locations. Imagery received from the spacecraft illustrate discussions of the planetary surface, composition, and winds. Suggestions for further reading are included along with a list of available NASA film. Experiments and activities for classroom use are described.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: EP-146
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  • 2
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    In:  CASI
    Publication Date: 2019-08-28
    Description: An overview of the Viking Mars probe is presented. The Viking spacecraft is described and a brief history of the earlier observations and exploration of Mars is provided. A number of the Viking photographs of the Martian surface are presented and a discussion of the experiments Viking performed including a confirmation of the general theory of relativity are reported. Martian surface chemistry is discussed and experiments to study the weather on Mars are reported.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-EP-146
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  • 3
    Publication Date: 2019-08-28
    Description: Global mean distributions of Martian atmospheric components concentrations from the planet's surface up to an altitude of 250 km are calculated. Improved data on the turbulent mixing coefficient, as a function of altitude, on temperature distribution and on chemical and photochemical reaction rates are used. The model data agree well with available measurements of some components concentrations. Variations of composition due to long-period variations of temperature, moisture and turbulent mixing are investigated. The relative significance of different catalytic cycles and the important role of excited atoms 0 (d-1) are revealed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-75048
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  • 4
    Publication Date: 2019-08-28
    Description: Formation of the equatorial jet of the Jovian surface was explained as a consequence of the Taylor-Proudman theorem. The asymptotic theory of motion of low viscosity fluids in a rotating spherical shear layer was included. The model shows the straited structure of the Jovian surface as the outflow of convective cells having the shape of axisymmetric rolls extended along the axis of rotation in the meridional direction. Depth of the layer was found to be of the order of 1000 kilometers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-75247
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  • 5
    Publication Date: 2019-08-28
    Description: The science objectives of a first comet mission are reviewed and related to what is known or can be expected to be learned in the near future from ground-based and near earth observations. A set of instruments and their science objectives are defined for a mission to Comet Halley during its 1985/86 apparition. The benefits from a fast flyby, a slow flyby, or a rendezvous mission and the relative impact of each on the instrument payload were assessed. The relative scientific value of encounters with the comet at distances from the sun ranging from 1 AU to 2.5 AU, including possible tradeoffs between flyby velocity and distance was considered. Pre- and post-perihelion encounters were likewise evaluated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-78420
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  • 6
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    In:  CASI
    Publication Date: 2019-08-28
    Description: The NASA Voyager mission to explore planets of the outer solar system is summarized. The mission schedule and profiles for encounters with Jupiter and Saturn, and possibly with Uranus and Pluto are included along with a description of the spacecraft and its trajectories. Scientific investigations to be made and the instruments carried are also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-SP-420
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  • 7
    Publication Date: 2019-08-28
    Description: The history of naming the details of the relief on the near and reverse sides of the moon is examined. The book contains lists of the names of craters of the reverse side of the moon in Russian and the Latin spellings.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-75035
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  • 8
    Publication Date: 2019-08-28
    Description: From near-infrared photometry (JHKL) of small bodies in the outer solar system a previously unrecognized class of planetary satellites is identified which may have surfaces mostly free of frosts of water, methane, or ammonia. These bodies - including two satellites of Uranus (Titania and Oberon), and one each of Saturn (Hyperion) and Neptune (Triton) - have surfaces characterized by neutral reflectance between J and H (1.25 and 1.60 microns) and rapidly decreasing reflectance at K (2.2 microns) and L (3.5 microns). It is pointed out that the 15 solid bodies in the outer solar system that have been satisfactorily observed (excluding the asteroids) fall into six classes according to spectral reflectance. The presence of water frost or ice on the surface of Enceladus is established.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 217
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  • 9
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    In:  Other Sources
    Publication Date: 2019-08-28
    Description: The article gives a general discussion of the state of knowledge concerning the composition, structure, and history of the moon, with attention focused on the new data obtained from the study of the results of Apollo and Luna experiments. The general characteristics of the lunar rocks are mentioned and compared with those of the earth. A possible structure for the lunar interior, as revealed by data on moonquakes, heat flow measurements, and meteorite impacts is sketched. A scenario for the history of the moon is outlined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Sky and Telescope; 53; Mar. 197
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  • 10
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    In:  Other Sources
    Publication Date: 2019-08-28
    Description: The purpose of the present paper is to review all asteroid diameter measurements, current through mid-1976, and to combine them in a consistent way to give the best available estimates for a sample totalling 187 objects. From these diameters it is possible to determine the size-distributions of minor planets down to diameters of 50 km in the inner belt and 100 km in the outer belt. The associated albedos further indicate the distribution of objects of the C, S, and M classes throughout the belt.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: International Colloquium; Aug 17, 1976 - Aug 20, 1976; Lyons; France
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  • 11
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    In:  CASI
    Publication Date: 2019-08-28
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-NEWS-RELEASE-77-203 , P77-10201
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  • 12
    Publication Date: 2019-08-28
    Description: Data obtained from the Viking missions to Mars have lead to comparisons between characteristics of that planet and certain aspects of earth. Topics discussed include: thermal and compositional evolution of the planets' interiors, the origin of their atmospheres, the history of their fluid environments, the evolution of organic material, and climatic changes. Examples of convective and magmatic activity on the crusts of the two planets are contrasted; outgassing evidenced in the crustal zones is related to the evolution of atmosphere. Analysis of experimental degassing of meteorites provides further insight into the origin and composition of planetary atmospheres. Attributes of the Martian surface, which is apparently an oxidizing rather than reducing medium, are reviewed, and explanations proposed to account for its lack of an organic richness comparable to that found on earth. Data on long-range climatic changes on earth, related to precession, obliquity, and eccentricity of the planet, may contribute to understanding of the Martian polar caps, and vice versa.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Physics Today; 30; July 197
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  • 13
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    In:  Other Sources
    Publication Date: 2019-08-28
    Description: The paper discusses the tremendous improvements in measurements of the asteroids since 1970, when polarimetric and radiometric methods began to replace the visual methods. A table is given which gives the sizes and albedos of 187 of the larger asteroids. When the asteroids are sorted according to albedo, they are seen to fall into two distinct groups: C-type, or carbonaceous, asteroids, with albedos of 2-5%, and a group of primarily stony or silicate bodies, the S asteroids, clustered around an albedo of 15%. The majority of the asteroids are seen to be very dark, and the maximum density in the asteroid belt must lie somewhere beyond 3.0 astronomical units.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Sky and Telescope; 53; Mar. 197
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  • 14
    Publication Date: 2019-08-28
    Description: The density of the Martian soil is evaluated at a depth up to one meter using the results of radar measurement at lambda sub 0 = 3.8 cm and polarized radio astronomical measurement at lambda sub 0 = 3.4 cm conducted onboard the automatic interplanetary stations Mars 3 and Mars 5. The average value of the soil density according to all measurements is rho bar = 1.37 plus or minus 0.33 g/ cu cm. A map of the distribution of the permittivity and soil density is derived, which was drawn up according to radiophysical data in the 3 centimeter range.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-75047
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  • 15
    Publication Date: 2019-08-27
    Description: The early evolution of the atmospheres and climate of the Earth, Mars and Venus is discussed, based on a concept of common initial conditions and main processes (besides known differences in chemical composition and outgassing rate). It is concluded that: (1) liquid water appeared on the surface of the earth in the first few hundred million years; the average surface temperature was near the melting point for about the first two eons; CO2 was the main component of the atmosphere in the first 100-500 million years; (2) much more temperate outgassing and low solar heating led to the much later appearance of liquid water on the Martian surface, only one to two billion years ago; the Martian era of rivers, relatively dense atmosphere and warm climate ended as a result of irreversible chemical bonding of CO2 by Urey equilibrium processes; (3) a great lack of water in the primordial material of Venus is proposed; liquid water never was present on the surface of the planet, and there was practically no chemical bonding of CO2; the surface temperature was over 600 K four billion years ago.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-75054 , PR-337
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  • 16
    Publication Date: 2019-08-27
    Description: The justification, scientific objectives, instrumentation, and strategy for a first comet mission are discussed. Topics include: mission target; rendezous, propulsion system requirements, measurement objectives, instrument capabilities for rendezvous and the tail probe payload, and backup missions if rendezvous with Halley's comet is not possible to achieve. Support research to be done by NASA is recommended.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-78420-PT-2
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  • 17
    Publication Date: 2019-08-27
    Description: Recent measurements of rare gas abundances on Mars by Viking are used in testing an inhomogeneous accretion model for Mars. It is found that not only the relative abundance of H, C, N, Ne-20, A-36, Kr, and Xe, but their total amounts can be best explained if the outer layers of earth and Mars were made of a material similar to ordinary chondrites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 266; Apr. 28
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  • 18
    Publication Date: 2019-08-27
    Description: Lunar features provide a valuable interpretation data base for comparison with features on other planets which are believed to have been formed by the cratering process. The paper adopts the comparative approach by examining the smooth plains of the moon and Mercury, with special emphasis on crater degradation on the moon, Mercury, and Mars. A possible cause for the observed deficiency of craters with diameters no more than 50 km on certain areas of lunar uplands and on the entire uplands of Mercury and Mars is discussed. It is suggested that pertinent differences can be predicted on the basis of new concepts for production population and of effects of changes in planetary conditions on the secondary cratering process. It is concluded that the deficiency of craters with diameters no more than 50 km on parts of the lunar uplands and on the Mercurian and Martian uplands may be evidence for a deficiency in production of primary craters in this size range. Origin of the late heavy bombardment in the inner solar system is examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 82; Apr. 10
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  • 19
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    In:  Other Sources
    Publication Date: 2019-08-27
    Description: The radiometric method of determining asteroid diameters is described, and a synthesis of radiometric and polarimetric measurements of the diameters and geometric albedos of a total of 187 asteroids is presented. An analysis is offered of the size distributions of different albedo classes down to 80-km diameter for the entire main asteroid belt (2.0-3.5 AU). The distribution of albedos is found to be strongly bimodal, with mean albedos for the C and S group of 0.035 and 0.15, respectively. The C asteroids outnumber the S asteroids at all sizes and all values of semimajor axis, with the proportion of C asteroids increasing from a little over half inside 2.5 AU to more than 95% beyond 3.0 AU. Other aspects of the distribution of C, S, and M asteroids are discussed, and the total mass of main-belt asteroids larger than 70 km is estimated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 31; June 197
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  • 20
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    In:  Other Sources
    Publication Date: 2019-08-13
    Description: Apollo missions and returned lunar samples have provided new information about the moon, the earth, the sun, and the universe. Analyses show that all the planets were formed by the rapid accumulation of small bodies into larger ones about 4.6 billion years ago. The existence of simple molecules formed by reactions between the soil particles and atoms of carbon, oxygen, and nitrogen that have come from the sun, suggests that the basic ingredients for life are common in the universe. The ratio of hydrogen to helium in the solar wind reaching the moon is found to be 20 to 1, whereas the earth-based measurements show this ratio to be 10 to 1. Although the moon does not have any magnetic field at the present, the analyses revealed the existence of such a field three billion years ago. The understanding of the reasons for the disappearance of this field is vital for understanding planetary magnetic fields. The determination of the chemical composition of the whole moon, the explanation of the moon's observed asymmetry, and the understanding of the nature of moon's interior will have to be achieved by future, possibly unmanned, missions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Sky and Telescope; 53; Apr. 197
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  • 21
    Publication Date: 2019-08-13
    Description: Various aspects of the large comet of 1858 including the luminosity of the core and the shape, intensity and position of the tail with respect to the sun and stars are described and then compared with the large comet of 1744 described by Heinsius and Halley's comet of 1835. The purpose of these observations is to try to gain a clearer understanding of the nature of the polar force from the sun acting on the comet. This force is said to differ from the usual force of gravity.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-75193
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  • 22
    Publication Date: 2019-08-13
    Description: One hundred seventeen investigations undertaken in the NASA Planetary Geology Program in 1976-1977 are reported in abstract form. Topics discussed include solar system formation; planetary interiors; planetary evolution; asteroids, comets and moons; cratering; volcanic, eolian, fluvial and mass wasting processes; volatiles and the Martian regolith; mapping; and instrument development and techniques. An author index is provided.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-X-3511
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  • 23
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 24
    Publication Date: 2019-07-13
    Description: Petrographic and structural relations of rocks resulting from melting of target materials during impact indicate constraints that can be applied to theoretical models and experimental production of craters. Topics discussed in this context include the motion of shock melted material, the mixing of melts, the energies required for heating and melting the necessary volumes of target rocks, diameter to depth ratios, and the formation of structural modifications. The motion of shock melted material involves ejection of some of the lowermost parts of the target, incorporation of distant fragmental material, outward flow, settling into cracks after breccia formation, and completion in a short time span. Melts must be completed within tens of seconds to a couple of minutes after impact.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 25
    Publication Date: 2019-07-13
    Description: It is demonstrated that the process of jetting which occurs when particles collide at oblique angles may produce melt at much lower velocities than are required for melt production in head-on collisions. The minimum velocities of impact required for jetting in aluminum, bronzitite, dunite, and quartz are calculated by the method of shock polars. The analysis, which depends on stated assumptions about attained pressures and the occurrence of jetting, uses shock-velocity particle-velocity equations of state with three shock regimes. The treatment indicates that jetting should arise in bronzitite, dunite, and quartz at relative velocities as low as 1-2 km/sec. At such velocities material which passes near the stagnation point in the jet-forming region is subjected to sufficiently high pressures so that it is probably melted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 26
    Publication Date: 2019-07-13
    Description: In 1968, a series of 0.5-ton and 100-ton TNT explosion experiments were conducted in granitic rock near Cedar City, Utah, as part of a basic research program on cratering and shock wave propagation. Of special interest was the formation of an important type of shock metamorphic feature, shatter cones. A description is presented of the first reported occurrence of shatter cones in high explosion trials. A background to shatter cone studies is presented and attention is given to the test program, geology and physical properties of the test medium, the observed cratering, and the formational pressures for shatter cones. The high explosion trials conducted demonstrate beyond any doubt, that shatter cones can be formed by shock wave processes during cratering and that average formational pressures in these crystalline rocks are in the 20-60 kb range.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 27
    Publication Date: 2019-07-13
    Description: Equation of state formulations are considered in a framework that permits comparison with one-dimensional impedance match solutions. The problem considered is the peak pressures attained along the impact symmetry axis when a sphere impacts with a half-space. The regimes of melting and vaporization - in particular, incipiently melted, completely melted, incipiently vaporized, and completely vaporized states - are examined, and the pressures at which critical isentropes intersect the Hugoniots of iron and gabbroic anorthosite are considered. A means of representing the spatial attenuation of shock pressure along the impact axis by two regimes is introduced, and results for the near-field and far-field regime are presented. It is thought that the treatment can be used to obtain quantitative bounds on the impact velocity of the meteorite.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 28
    Publication Date: 2019-07-13
    Description: A brief review of Martian crater data is presented and a short summary is provided of Martian fresh crater morphology and morphometry based on pre-Viking information. The pre-Viking Mars missions are considered, taking into account the flyby of Mariner 4 in July 1965, the flyby of Mariner 6 in July 1969, the flyby of Mariner 7 in August 1969, and the insertion of Mariner 9 into a Martian orbit in November 1971. The 7329 photographs of the planet and its moons transmitted by Mariner 9 to earth provide a substantial basis for formulating a large body of data on crater morphometry, morphology, and location. In general, fresh Martian crater morphology follows a diameter-dependent progression. The simplest morphology is found in the smallest craters. The morphology remains essentially constant through diameters of approximately 10 km. Morphologies rapidly become more complex in the diameter range of 10-40 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 29
    Publication Date: 2019-07-13
    Description: We propose a model for the origin of impact-basin rings whereby the main topographic rim of a basin approximates the limit of excavation and inner rings approximate the rims of craters formed inside the transient crater by some perturbation in the cratering process. The cause of this complexity in transient cavities may be the presence of discontinuities in the target material. The second inward ring may have formed at the seismic discontinuity about 20 km deep in the lunar crust, and the third, innermost ring of a few large basins at the crust-mantle interface about 60 km deep. Slumping increased the original diameters of many rings and split some initially coherent rings into subsidiary or partial rings. Deformation outside the transient crater produced external arcs. This model differs from prevalent hypotheses of ring formation whereby an inner ring approximates the transient crater rim and major faulting of the flank produced the outer ring structures.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 30
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    Publication Date: 2019-07-13
    Description: The transition from small simple craters to large complex or modified craters is characterized by eleven changes in the shape of fresh lunar craters which occur within a diameter range of 10 to 30 km. In the present paper, seven ratio-level variations - those of rim-crest diameter with depth, rim height, flank width, rimwall slope, floor diameter, circularity, and rim-crest evenness - are defined for fresh-appearing craters from the new Apollo data and are expressed mathematically where practicable. These relations constitute a shape model for interpreting fresh craters on the moon. The size dependent changes reflect the occurrence of central peaks, rimwall terraces, and a flat floor within craters measuring 10 to 20 km in diameter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 31
    Publication Date: 2019-07-13
    Description: The paper is a field report concerning a shallow core drilling program in the multicolored breccia deposits which constitute 90% of all the impact breccias beyond the outer rim of the Ries, a 26-km-diam impact crater. About 480 m of core was recovered from 11 locations with radial ranges between 16.5 and 35 km from the crater center. The cores consist of breccias, whose components are derived from the crater itself and the terrain outside the crater. The local components dominate the breccias at the larger ranges, and possibly constitute more than 90% of the breccia volume at the greatest distances investigated. The great depth of the Bunte Breccia (84 m at 27 km range), together with the preponderance of local components, necessitates an emplacement mechanism that ploughed up and mixed the crater surroundings to depths greater than 50 m.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 32
    Publication Date: 2019-07-13
    Description: The Decaturville structure is a small area of intense disturbance marked by surface exposure of Precambrian rock and minor lead-zinc mineralization. The present paper gives a detailed analysis of the associated deformation processes on the basis of detailed mapping and study of drill core. The presence of shock-deformation features and the complex structural pattern revealed from the analysis are strong indications that the Decaturville structure was formed by impact of an extraterrestrial body.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 33
    Publication Date: 2019-07-13
    Description: A description is presented of a preliminary outline for the cratering processes at Flynn Creek, Tennessee, a large, flat-floored, terrestrial impact crater with a central uplift. The initial preimpact conditions in terms of terrain, target media, and structure are defined, taking into account the possibility of impact into a shallow sea. A brief outline is provided of the generalized sequence of events from the time of entry of the impacting body into the atmosphere through the termination of late-stage cratering motions. The abbreviated sequence of cratering events is based upon a composite of recently assembled physical constraints, including new field data, experimental laboratory impact and field explosion trials, and theoretical numerical simulation studies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 34
    Publication Date: 2019-07-13
    Description: The present paper deals with the conditions of explosion or nuclear cratering required to simulate impact crater formation. Some planetary problems associated with three different aspects of crater formation are discussed, and solutions based on high-explosion data are proposed. Structures of impact craters and some selected explosion craters formed in layered media are examined and are related to the structure of lunar basins. The mode of ejection of material from impact craters is identified using explosion analogs. The ejection mode is shown to have important implications for the origin of material in crater and basin deposits. Equally important are the populations of secondary craters on lunar and planetary surfaces.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Symposium on Planetary Cratering Mechanics; Sep 13, 1976 - Sep 17, 1976; Flagstaff, AZ
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  • 35
    Publication Date: 2019-07-13
    Description: Ca has been measured in a lunar soil in order to establish the presence of isotopically mass-fractionated components. Ca was extracted by a series of water leaches after the soils were 'activated' by brief exposures to fluorine gas. The O2 obtained by this fluorination is found to have delta (O-18) of +21 per mil and to be, therefore, significantly mass-fractionated. Ca obtained in the leaches was analyzed using the double-spike technique. Very small Ca isotope fractionation is found in the leaches of this soil of up to 1 per mil per mass unit difference. The small Ca effects are in marked contrast to the measured delta (O-18) for the same sample and to large effects observed in many soils for oxygen, silicon, sulfur, and potassium. The data on Ca provide stringent constraints on models which attempt to explain the isotope mass-fractionation effects in lunar soils.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 36
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 37
    Publication Date: 2019-07-13
    Description: A description is presented of a simple two-part model which relates the retention of solar-wind-implanted noble gases and N in different grain sizes of lunar soils to the maturation level of that soil. It is assumed that concentrations of solar-wind gases are implanted into surfaces of soil grains in inverse proportion to grain diameter and that differences in irradiation probability and surface saturation as a function of grain diameter generally are not a major factor. The model demonstrates that incorporation of a major fraction of this surface-correlated gas into constructional particles such as agglutinates causes much of the gas to become volume-correlated in mature soils. This volume-correlated gas produces a relative enrichment in gas concentrations in coarser grains and a selective enrichment of more retentive gases (e.g., N) over less retentive gases (e.g., He). It is shown that the maturity model plays a major role in determining the complexities of the distribution of solar-wind gases in soils.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 38
    facet.materialart.
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    Publication Date: 2019-07-13
    Description: Mineralogical evolution of lunar soils as a function of agglutinate content can be described with the help of a two-component model. Steady-state condition of exposed lunar soils can be achieved only by the balance of comminution, agglutination, and replenishment processes. Rate of replenishment depends on the meteoroid flux and the nature of the substrate which varies both in space and time. Rates of agglutination and comminution depend not only on the micrometeoritic flux but also on the chemical and modal composition of an exposed soil. It is concluded from modeling the above that steady-state condition of lunar soils is independent of its maturity or exposure age. Agglutinate content of a lunar soil can be used to estimate the relative exposure age of the soil only if the soil is in a non-steady-state condition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 39
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 40
    Publication Date: 2019-07-13
    Description: Some of the wide variations in the crater-size distributions in lunar photography and in the resulting statistics were interpreted as different degradation rates on different surfaces, different scaling laws in different targets, and a possible population of endogenic craters. These possibilities are reexamined for statistics of 26 different regions. In contrast to most other studies, crater diameters as small as 5 m were measured from enlarged Lunar Orbiter framelets. According to the results of the reported analysis, the different crater distribution types appear to be most consistent with the hypotheses of differential degradation and a superposed crater population. Differential degradation can account for the low level of equilibrium in incompetent materials such as ejecta deposits, mantle deposits, and deep regoliths where scaling law changes and catastrophic processes introduce contradictions with other observations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 41
    Publication Date: 2019-07-13
    Description: A preliminary investigation was conducted regarding the variations in the morphological characteristics of Mercurian craters that appear to be associated with a degradation of fresh craters. Craters are classified according to relative states of degradation in order to provide evidence on degradation styles and rates on Mercury, and to correlate degradation with major geologic events in the history of the planet. Processes and relative rates of degradation on Mercury and the moon are also compared. Degradation trends of crater morphology are found to be parallel on Mercury and the moon. The severe destruction of interior structures in lunar craters may have resulted from more widespread distribution of ejecta due to the moon's lower gravity. The possibility is considered that the smooth plains on the surface of Mercury were formed early in the history of that planet.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 42
    Publication Date: 2019-07-13
    Description: A report is presented regarding the dynamic properties of a rock indigenous to the mare basins of the moon. The reported data were obtained in a study of sample 70215, a very titanium-rich basalt (58% pyroxene, 18% ilmenite, 15% plagioclase, 6% olivine, and 3% quartz by weight). This rock is probably representative of a class of the earliest mare-filling extrusive rocks which are exposed on the present lunar surface. Two series of experiments were performed. One set of experiments involved the measuring of Hugoniot and release adiabats to 15.7 GPa with a propellant gun apparatus. In the second set of experiments, a light-gas gun was employed to yield Hugoniot data at about 120 GPa and release states at about 90 GPa. Lunar basalt 70215 appears to be among the densest rocks in the present lunar sample collection, having a crystal density of 3.38 g/cu cm and a porosity of about 1.3%. The results of the experiments have important implications for both the degree of shock metamorphism expected for impact processes and the extent of ejecta transport on mare surfaces with high-titanium basalt composition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 43
    Publication Date: 2019-07-13
    Description: The results are reported of an analysis of the characteristics of fresh crater samples occurring on the two major geologic units on the moon (maria and highlands) and on Mercury (smooth plains and cratered terrain). In particular, the onset diameters and abundances of central peaks and terraces are examined and compared for both geologic units on each planet in order to detect any variations that might be due to geologic unit characteristics. The analysis of lunar crater characteristics is based on information provided in the LPL Catalog of Lunar Craters of Wood and Andersson (1977). The Mercurian data set utilized is related to a program involving the cataloguing of Mercurian craters visible in Mariner 10 photography. It is concluded that the characteristics of the substrate have exerted a measurable influence on the occurrence of central peaks, terraces, and scallops in flash crater samples. Therefore, in order to compare the morphologic characteristics of fresh crater populations between planets, an analysis of possible substrate-related differences must first be undertaken for each planet under consideration. It is suggested that large variations in gravity do not produce major variations in crater wall failure.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 44
    Publication Date: 2019-07-13
    Description: As the ejecta curtain sweeps outward from the crater which forms after meteorite impact, fine particles may receive a hyperballistic boost from the expanding gas cloud created by vaporization. In modeling the phenomenon, this paper considers both spatial and frequency variations of the particle size parameter. Two models which preserve spatial homogeneity within the elliptical transient crater serve to test the effects of different particle-frequency distributions. Three models which feature identical spatial nonhomogeneity of particle sizes serve to test different crater-formation rates. From 1 to 6% of the total ejected mass is sent beyond the maximum ballistic range of 437 km, according to the five models, each of which is a possible simulation of the lunar crater Copernicus.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 45
    Publication Date: 2019-07-13
    Description: The reported investigation was conducted in connection with the desirability to obtain information regarding the response of a solidified planetary surface to the primary impact of a meteoroid whose dimensions are small compared to that of the planet. The investigation is an extension of studies conducted by Ahrens and O'Keefe (1977) concerned with a calculation via finite-difference techniques of the entire flow field, the energy partitioning, and the quantity of melt and vapor produced upon impact of an iron object on a gabbroic anorthosite half-space at 15 km/sec. The assumptions used in these calculations are summarized. Calculations based on an equation of state for the low- and high-pressure mineral assemblage of gabbroic anorthosite, initial density 2.94 g/cu cm are considered. An algorithm is formulated for the description of the phase transformation upon shock loading. It is shown that the relative volume of melt and the equivalent volume of shock-induced vapor is proportional to the meteoroid kinetic energy (at high speeds) using the similarity scaling of projectile and target properties as suggested by Dienes and Walsh (1970).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 46
    Publication Date: 2019-07-13
    Description: The origin is considered of droplets of ultramafic composition which are present in all soils collected from the mare surface at the Apollo 17 landing site. The droplets consist of homogeneous orange glass or their partially crystallized equivalent, the black droplets. These clastic deposits have a mean grain size of 40 micrometers. The droplet formation ages range from 3.5 to 3.83 b.y. It has been proposed that the droplets formed as a spray of low viscosity melt during lava fountaining. Based upon the thermal history as determined by studying olivine and particle shapes, two models for the formation of the sequence of droplets represented by samples 74001 and 74220 are presented. Both models assume, as proposed by Heiken et al. (1974), that the droplets were formed as a spray from a lava fountain and the compound forms were evidence for 'recycling' of solid, cooler droplets back into the fountain, encountering molten droplets before being deposited.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 47
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 48
    Publication Date: 2019-07-13
    Description: On the basis of modal petrography the upper, mare basalt-rich portion of the Apollo 17 drill core (sections 70007, 70008, 70009) can be subdivided into three major stratigraphic units. The lower unit (a) falls within 70007, is relatively mature, and contains evidence of an increase in highland component and decrease of mare component within the lower approximately 8 cm. The middle unit (b) is coarse-grained and relatively immature; this unit has the highest concentration of mare basalt lithic and mineral fragments and mare orange/black glasses. The top unit (c) falls within 70009 and is relatively mature. Within these three sections of the drill core, there are compositional clusters of glass beads that correspond to high Ti subfloor basalt (orange/black glass), anorthositic gabbro (clear glass), and a new very low Ti (VLT) mare basalt (yellow/green glass).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 49
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    Publication Date: 2019-07-13
    Description: Rare-gas isotopic analyses have been performed on lunar rocks 71135 and 71569. The conventional (Kr-81)-Kr cosmic-ray exposure ages are 103 + or - 3 m.y. for 71135 and 134 + or - 7 m.y. for 71569. An approach is outlined to deducing complex exposure histories from rare-gas data using depth profiles of the production rates of the cosmogenic rare-gas isotopes. Examination of the Xe isotopes by means of a 'concordia' plot suggests that 71569 may have a simple one-stage exposure history whereas 71135 has a more complex history. An attempt is made to construct exposure models for these two rocks which account for the abundances of all the cosmogenic rare gases, the Xe isotopic compositions, and the apparent (Kr-81)-Kr exposure ages. This study demonstrates the depreciation of (Kr-81)-Kr ages for rocks exposed at shallow depths, caused by the relatively rapid variation of the Kr-81 production as the rock is eroded. Possible implications of the tentative results for the formation age of the Central Cluster unit are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 50
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 51
    Publication Date: 2019-07-13
    Description: Recent surface history at Taurus-Littrow is dominated by emplacement of the Central Cluster and Bright Mantle morphological units, both believed to have resulted from arrival of ejecta from a large primary crater, probably Tycho. This paper reports new noble gas data for eight Apollo 17 rocks. Kr-81 - Kr cosmic ray exposure ages for these rocks affirm the observation of a pronounced grouping of ages, reinforcing the photogeologic evidence for the site-wide nature of the Central Cluster event. The consequences of post-cratering shielding changes are considered and it is concluded that the differences can reasonably be attributed to these changes, particularly because of the greater likelihood of rollover and impact fragmentation of the relatively smaller rocks from which most age data have been obtained. These considerations also lead to a more refined age estimate of 109 plus or minus 4 m.y. for Central Cluster, the Bright Mantle, and Tycho.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 52
    facet.materialart.
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    Publication Date: 2019-07-13
    Description: Twenty-eight major, minor, and trace-element abundances have been determined in nine fines fractions of core 60010 by instrumental thermal and 14 MeV neutron activation analysis. With the exception of the elements Fe, Co, and Ni, core section 60010 exhibits a much more uniform composition than the lower section (60009) of the double drive tube collected at the Apollo 16 LM site. The siderophilic meteorite indicator elements Fe, Co, and Ni are significantly enriched in subsample 40, which is located 3.0-4.5 cm below the lunar surface, and are highly variable throughout the 60010 core section. Microscopic examination of subsample 40 revealed the presence of numerous metallic fragments including an approximately 1-mm metal fragment exhibiting only Fe, Co, Ni, and Ir gamma-ray peaks and having a composition typical of a coarse octahedrite. Composition profiles of 60010 exhibit small variations in lithophilic element abundances which can be related to most of the seven stratigraphic units of Duke and Nagle (1976). Although the basal portion of 60010 has been described as texturally similar to the upper unit of 60009, the present chemical studies show a marked compositional difference at this interface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 53
    facet.materialart.
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    Publication Date: 2019-07-13
    Description: Ferromagnetic resonance and magnetic hysteresis loop measurements were performed on 212 samples from the Apollo 16 deep drill core. The total iron content is generally uniform with a mean value of 5.7 plus or minus 0.9 wt%. The soils range in maturity from immature to mature. Two major contacts were observed. The contact at 13 cm depth represents a fossil surface whereas the contact at 190 cm depth has no time-stratigraphic significance. The data suggest that the core section below 13 cm depth was deposited in a single impact event and subjected to meteoritic gardening for about 450 m.y. However, our data do not preclude deposition by a series of closely spaced events. About 50 m.y. ago, the top 13 cm were added. Comparison with the Apollo 16 double drive tube 60009/60010 does not yield any evidence for a stratigraphic correlation with the deep drill core.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 54
    facet.materialart.
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    Publication Date: 2019-07-13
    Description: Modal analysis and electron probe microanalysis were performed on polished thin sections prepared from Apollo 15 deep drill core soils in an effort to characterize their provenance. The particles were in the 0.25-1.00 mm size range. The particles were classified into mineral fragments, agglutinates, glasses, rock fragments, and breccias. The results show that highland and mare material occur in the core in an approximately 60:40 ratio, with mare component generally increasing from bottom to top in the core. Quartz-normative basalts are nearly twice as abundant as olivine basalts. Nonmare sources include KREEP basalt flow units from some depth in the crust, excavated by cratering events and supplied to the site as 'rays'.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 55
    Publication Date: 2019-07-13
    Description: Noble gas and trace element analyses of matrix and a clast from breccia 14307 are reported. This sample was exposed to a large neutron fluence, as seen by an elevated Sm-150/Sm-149 ratio and by noble gases, particularly Xe-136 from neutron fission of U-235. Strong constraints on the exposure history result from combined consideration of Sm-150, Xe-136, and spallation noble gases. Both clast and matrix were irradiated for about 1 AE under substantial shielding beginning at least 2 AE ago, probably more than 3 AE ago. The manifestations of soil exposure seen in the matrix - solar wind gases, glass formation, etc. - thus must have been acquired in an ancient epoch. The matrix has had a longer exposure to cosmic rays than the clast, presumably during its prebrecciation history as a soil. Brecciation probably occurred more than 1 AE ago, perhaps more than 3 AE ago, but at least 0.4 AE after the formation of the matrix constituents.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 56
    Publication Date: 2019-07-13
    Description: Three major volcanic complexes have long been recognized in the Oceanus Procellarum region. Detailed study shows that the complexes share some characteristics and also display major differences which provide clues to eruption style. The Rumker Hills occupy 5000 sq km in northern Procellarum and are apparently Imbrian-Eratosthenian in age; they are dominated by domes, suggesting relatively low effusion rates. The Aristarchus Plateau-Prinz/Harbinger region occupies 40,000 sq km in central Procellarum and is predominantly Imbrian in age; it is dominated by large sinuous rilles and associated dark mantling deposits of probable pyroclastic origin, suggesting relatively high eruption rates. The Marius Hills occupy 35,000 sq km in south-central Procellarum and appear to be predominantly Eratosthenian in age; they are dominated by low domes, steep domes, cones, and sinuous rilles, suggesting variable eruption rates and possible different volatile contents associated with eruption conditions that produced each type of feature. The volcanic complexes, particularly Aristarchus and Marius, appear to be the sources for much of the central Procellarum mare fill.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 57
    Publication Date: 2019-07-13
    Description: Several objects have been found in sections of lunar igneous spinel troctolite 62295 that resemble certain meteoritic barred olivine chondrules. Each consists of an apparently spherical single crystal of Fo90 olivine, approximately 0.6-0.8 mm in diameter, containing a set of approximately 30-40 subparallel stringers of An95 plagioclase, whereas the stringers in ordinary meteoritic chondrules consist of glass. The olivine of the 62295 chondrules is also more magnesian, and is radially zoned, having a relatively iron-rich core and rim and an iron-poor intermediate zone. Several possible origins are proposed: impact-generated melt globules solidified in flight, spherical phenocrysts, and meteoritic chondrules, but none of these seems adequate to explain the detailed observations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 58
    Publication Date: 2019-07-13
    Description: The viscous flow and crystallization behavior of the matrix composition of breccia 15286 have been determined in the 1159-1307 C and 644-770 C temperature ranges. The Shaw (1972) model and, to a slightly lesser extent, the semiempirical Bottinga and Weill (1972) model describe the variation of viscosity with temperature. The crystal growth rate has been determined over the temperature range 821-1185 C. Time-temperature-transformation, logarithmic cooling, and continuous cooling curves were constructed; a nucleation barrier of 60 kT at a relative undercooling of 0.2 is assumed. It is estimated that the matrix of 15286 breccia cooled at a rate greater than 80 K/min through the glass transition region. The increase in density that occurs when the matrix glass is annealed suggests that the breccia was formed by cooling from the molten state rather than by direct shock-induced transition from crystal to glass. Viscous sintering under continuous cooling and logarithmic cooling conditions is analyzed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 59
    Publication Date: 2019-07-13
    Description: Six samples from the upper core 60010 of the double drive core 60009/60010 were analyzed for grain size distribution, petrographic particle types and abundances, magnetic fraction, and ferromagnetic resonance. It was found that the magnetic fraction of these soils is not equivalent to the agglutinate fraction, and magnetic separation partitions high-FeO agglutinate from low-FeO agglutinates. Various maturity indices are in essential agreement. The deposition of most or all of the core could have occurred in a single event. If that is the case, the core units have no time-stratigraphic significance and do not reflect individual cratering events.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 60
    Publication Date: 2019-07-13
    Description: Depth dependent fluctuations have been observed in the natural remanent magnetizations (NRM) of drive cores and drill strings from Apollo 16 and 17 missions. Partial demagnetization of unstable secondary magnetizations and identification of characteristic error signals from a core which is known to have been recently disturbed allow us to identify and isolate the stable NRM stratigraphy in double drive core 60010/60009 and drill strings 60002-60004. The observed magnetization fluctuations persist after normalization to take into account depth dependent variations in the carriers of stable NRM. We tentatively ascribe the stable NRM stratigraphy to instantaneous records of past magnetic fields at the lunar surface and suggest that the stable NRM stratigraphy technique could develop as a new relative time-stratigraphic tool, to be used with other physical measurements such as relative intensity of ferromagnetic resonance and charged particle track density to study the evolution of the lunar regolith.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 61
    facet.materialart.
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    Publication Date: 2019-07-13
    Description: Numerous investigations have been undertaken on samples from the Apollo 16 deep drill core. These studies are diverse in character and range from grain size analyses, through chemical and mineralogical studies to investigations of nuclear particle tracks, rare gases, and isotopic abundances. In order to comprehend the significance of the studies of the mineral chemistry of the clasts below 1 mm in size in several samples with respect to other studies, it became obvious that a review of all previous works was desireable. After reviewing the available literature it can be concluded that only four major stratigraphic divisions exist in the core section. Whether these represent four single events or multi-stage events within one unit is uncertain; however, it appears that accumulation of the material in the core has taken place during a period of 1 billion years, and that the material is predominantly of locally derived Highlands origin.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 62
    Publication Date: 2019-07-13
    Description: Petrological and geochemical analysis of lithic fragments separated from the Apollo 15 deep-drill core showed these fragments to fall into the essentially the same range of rock types as observed in surface soil samples and large rock samples. Three particles are singled out as being of special interest. One sample is a mare basalt containing extremely evolved phases. The particle may represent small-scale imperfect crystal/liquid separation in a lava flow. A green glass particle is not the ultramafic emerald green glass described from the Apollo 15 site, but rather an ANT-like light green color, and has a quite different chemical composition from the ultramafic variety. One mare basalt displays a positive Eu anomaly and is enriched in plagioclase relative to olivine plus pyroxene.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 63
    Publication Date: 2019-07-13
    Description: Detailed mapping of the Imbrium Basin Apennine Mountains has emphasized several important factors in the geologic evolution of this region. Pre-Imbrian topography was composed of two types of landforms: (1) the nearby Serenitatis, South Imbrium, Aestuum, and Vaporum basins which produced widely spaced regional lows and a sequence of basin deposits; (2) pre-Imbrian craters that reworked existing basin deposits and produced local topographic lows. The sequence of events during the Imbrium impact can be summarized as follows: intensive structural uplift along the Apennine Front occurred prior to the emplacement of ballistic ejecta. Ejecta became more discontinuous toward the backslope and produced radial texture by sedimentary erosional and depositional processes. Post-ejecta-emplacement downfaulting exposed pre-Imbrian deposits along the front and caused severe seismic disturbances that reworked many of the previous units and accentuated pre-basin structures. Tectonic mapping and orbital geophysical data support the idea that little structural modification has occurred in the Apennines since their formation 3.9 b.y. ago.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 64
    Publication Date: 2019-07-13
    Description: Pre-Imbrian impact structures in a large area surrounding the Apollo 14 site were identified in a study of the pre-Imbrian history of the Fra Mauro region. Calculations suggest that a total ejecta thickness of over 1700 m could have accumulated during Phase I (time prior to the Imbrium event) in the area of the ridge on which the Cone crater later formed. The majority (53%) of the ejecta at the site just prior to the Imbrium event was contributed by the numerous large Phase IB and IC craters in the vicinity and not by the lunar basins. Evidence exists for extensive pre-Imbrian volcanic activity in the Fra Mauro region. Early KREEP volcanic deposits may have existed in the target sites of many Phase IB and IC craters and would have been incorporated into their ejecta.
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  • 65
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 66
    Publication Date: 2019-07-13
    Description: The petrographies and phase chemistries of five lunar crystalline anorthositic fragments with Ar-40/Ar-39 plateau 'ages' ranging from 4.1 to 4.3 AE are reported. An investigation is conducted to determine whether the individual fragments are monomict or polymict breccias. For polymict breccias it is attempted to establish whether clasts and matrix have equilibrated chemically. On the basis of the results of the investigation it is suggested that sample 73263,1,1 was a breccia (possibly a clast-laden melt) containing old clasts, incorporated in an ejecta blanket that was annealed at about 4.1 AE in a transient high-temperature event. The sample 73263,1,6 studied is an annealed anorthositic breccia containing approximately 20% clasts dominated by single-crystal plagioclase fragments. The obtained data are consistent with a two-component system containing old plagioclase clasts in a young (about 4.0 AE) annealed, matrix. The annealing event at approximately 4.0 AE was insufficient to equilibrate the argon. It is found that four of the breccias having ages of about 4.2 AE or more are polymict. The most striking feature of all of the samples studied is the presence of a significant amount of 4.2-4.3 AE argon.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 67
    Publication Date: 2019-07-13
    Description: Polymict breccia 78155, which has a bulk composition of anorthositic norite, was brecciated and thermally metamorphosed before the final lunar bombardment of 4.0-3.9 eons. The constituents of the granoblastic matrix and the characteristics of the clasts and the mafic silicates are described. The clasts represent the lunar crust prior to 4.2 eons, the age of the granoblastic matrix. The persistence of uninverted pigeonite in matrix and clasts indicates that metamorphism was at a very high temperature and may have been terminated catastrophically. Evidence that the rock was further brecciated after thermal metamorphism is reported.
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    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 68
    Publication Date: 2019-07-13
    Description: The petrology, mineralogy, and composition of 13 crystalline matrix breccias from the Apollo 17 rake samples are described. The breccias have matrices of uniform modal mineralogy (plagioclase, 50-54%; olivine and pyroxene, 41-46%) but diverse textures. Clast characteristics, including the proportion of plagioclase, the composition in comparison with matrix, and the textures of different clast types, are reported. The majority of bulk matrix compositions plot on or very near the plagioclase-olivine cotectic in the system olivine-anorthite-silica. If the matrix compositions represent impact total melts, the inferred cotectic control requires that the source material was itself an igneous differentiate with compositions along the plagioclase-olivine cotectic. Alternatively, the proximity of the matrix compositions to the plagioclase-olivine cotectic could be accounted for if the breccia matrices represent a suite of impact-generated partial melts.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 69
    Publication Date: 2019-07-13
    Description: The matrix and 58 clasts from breccia 61175 were analyzed for major, minor, and trace elements. The matrix is anorthositic and has lithophile trace element abundances 20 to 40 times chondrite. Clasts comprise impact melt rocks, xenocryst and xenolith-free very high aluminum (VHA) and anorthositic basalts, anorthosite, anorthosite-norite-troctolite granulites, and hornfelses. The VHA and anorthositic basalts are considered to be impact melts, and the hornfelses were probably formed by incorporation of breccias or preexisting melt rocks into a melt sheet prior to cooling. The range of melt-rock lithophile trace element abundances might indicate more than one melt sheet.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 70
    Publication Date: 2019-07-13
    Description: Major features of 22 Apollo 15 breccia rake samples and 30 lithic clasts in these samples are described. The range of compositions of exsolved pyroxene grains (bulk and individual lamellae) indicates a slowly cooled mare basalt source. In terms of these data the pyroxenes closely resemble pyroxenes in large anorthosite 67075. It is suggested that the pyroxene-plagioclase-olivine clast in 15146 as well as some anomalous chemical data might result from metamorphism of a mare-type basalt or from plutonic crystallization of magma with mare basalt affinity. The bulk composition of the clast in 15146 closely matches that of Apollo 15 'green glass' to which it may be related. A unique ultrabasic clast in 15360 has an unusually low CaO content and other chemical features which suggest that this sample is unlike ultrabasic samples described to date.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 71
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 72
    Publication Date: 2019-07-13
    Description: Data on 226 melt inclusions and their host olivines (173 new analyses) are presented and interpreted in terms of general liquid lines of descent and olivine fractionation. The melt inclusions in olivine along with those in ilmenite and late-stage mesostasis in mare basalts define a complex trend. The trend is complicated by the effects of ilmenite, plagioclase, and pyroxene fractionation within the melt inclusions in olivine, the fact that most of the basalts were multiply saturated during olivine fractionation, and the phenomenon of late-stage silicate immiscibility. It is suggested that the first two factors can account for the observed marked divergence of the melt inclusion data from simple early olivine fractionation trends. The elimination of the effects of daughter mineral fractionation by homogenization experiments is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 73
    Publication Date: 2019-07-13
    Description: One of three primary objectives of the reported study is related to the definition of the distribution of troilite and Fe and the evaluation of the role of FeS in subsolidus reduction assemblages. Another objective was concerned with the definition of the lower limit of stabilizing elements such as Mg, Al, and Cr in ulvospinel to determine the terminal compositions at which reduction is inhibited. The third objective involves a comparison of the mineral chemistries of decomposed olivine with unaltered olivine in an attempt to determine the temperature limits. The sample was selected because it is one of the most intensely reduced samples returned from the moon. The model invoked for reduction is a magmatic-deuteric process which requires an environment approximating that of a closed system in which the volatile constituents are contained and in which reduction proceeds continuously with crystallization.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 74
    Publication Date: 2019-07-13
    Description: An attempt has been made to gain more insight into mare-basalt evolution by performing a very detailed leaching and mineral-separation U-Th-Pb systematics study on mare basalt 15085. It is found that about 20-50% of the U, Th, and Pb reside on the grain boundaries or in the mesostasis and that the Pb-207/Pb-206 ratios of the grain boundaries and crystal interiors are distinctly different. These distinct trends appear to represent either continuous or episodic postcrystallizational disturbances to the U-Th-Pb system of this rock. Using U and Pb partition coefficients, it is concluded that existing two- and three-stage U-Pb evolution models do not accurately describe mare-basalt genesis. An alternative two-stage + KREEP mixing model is proposed as a simple approximation to U-Pb evolution in lunar rocks. Most Rb-Sr and Sm-Nd data are compatible with this model.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 75
    Publication Date: 2019-07-13
    Description: Rb-Sr and Sm-Nd ages of two Apollo 11 mare basalts, high-K basalt 10072 and low-K basalt 10062, are reported. Rb-Sr, Sm-Nd, and Ar-40-Ar-39 ages are in good agreement and indicate an extensive time interval for filling of the Sea of Tranquility, presumably by thin lava flows, in agreement with similar observations for the Ocean of Storms. Initial Sr and Nd isotopic compositions on Apollo 11 basalts reveal at least two parent sources producing basalts. The Sm-Nd isotopic data demonstrate that low-K and high-Ti basalts from Apollo 11 and 17 derived from distinct reservoirs, while low-Ti Apollo 15 mare basalt sources have Sm/Nd similar to the sources of Apollo 11 basalts. Groupings of mare basalt based on Ti content and on isotopic data do not coincide.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 76
    Publication Date: 2019-07-13
    Description: An experimental study involving equilibration of Apollo 15 samples 15555 and 15065 in high-purity iron capsules is described. Comparison of mineral zoning trends with the experimental sequence suggests that the early crystallizing phases in the rock maintained surface equilibrium with the liquid. Olivine and pyroxene chemistry indicates that 15555 cooled slightly more rapidly than 15065, which cooled at approximately 0.2-0.3 C/day. It is suggested that 15065 and 15555 represent liquid compositions, and that these liquids appear to have been fractionated during ascent through the crust (15065), or to have been derived from an olivine-pyroxene source (15555) with Fe/(Fe + Mg) approximately equal to 0.73 at a depth between 150-200 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 77
    Publication Date: 2019-07-13
    Description: Three Apollo 17 basalts were studied by the laser Ar-39-Ar-40 method. The 70215 basalt has a normal well-behaved Ar-39-Ar-40 release pattern; the 70017 basalt has a disturbed release pattern which indicates a limited intermediate maximum age followed by a broad low-age region; and the 75035 basalt has a pattern initially similar to 70017 that is followed by a high-temperature maximum age. The laser study shows that all mineral systems in 70215 have small and uniform temperature losses, while the laser-determined ages for 70017 and 75035 are, apparently, primarily controlled by the minerals containing mesostasis inclusions. It is possible that the drop in ages observed by the conventional Ar-39-Ar-40 method was due not only to recoil of Ar-39 during neutron irradiation but also to gas loss from some minerals. It is suggested that the plagioclases are the best minerals to use for a reliable age.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 78
    Publication Date: 2019-07-13
    Description: Uranium, thorium, and isotopic lead data for components of basalt 70017 are reported, and it is found that the whole rock, pyroxene, and ilmenite points in a concordia diagram plot along a chord intersecting the curve at 3.7 and 4.33 eons. The plagioclase data do not seem to lie on this line. The data for 70017 appear to plot along a distinctly different chord in a concordia diagram than do the data for 75055 and 75035, two other Apollo 17 mare basalts. The lead data are in accord with Sm-Nd results. A 3.7 eon crystallization age for 70017 would be consistent with the same kind of parentless lead that is indicated by previous studies of soils and soil breccias from stations at Taurus-Littrow. The Th/U ratio in ilmenite is 2.2, and the concentrations of these two elements are approximately twice those in pyroxene.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 79
    Publication Date: 2019-07-13
    Description: As part of a study of Apollo 12 basalts, crystallization ages and initial Sr-87/Sr-86 (I) were determined for pigeonite basalts 12039 and 12055 and ilmenite basalt 12051. Sr-86/Sr-87 measurements for a larger suite of whole rock and plagioclase samples were obtained, and it is found that I-values for olivine and pigeonite basalts are indistinguishable while I-values for ilmenite basalts are distinctly lower. A self-consistent model for the evolution of the Sr-isotopic composition and REE abundances suggests that basalt was formed by small (2-10%) degrees of melting of cumulate sources composed of varying proportions of olivine, orthopyroxene, and clinopyroxene. This model requires nonchondritic relative abundances of the REE in the parental liquid at the time of formation of the cumulate sources. The model also describes Sr-isotopic composition and REE abundances of Apollo 17 high-Ti basalts and Apollo 15 low-Ti basalts. A lunar 'scenario' involving open system crystallization of a magma ocean from the crust downward is proposed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 80
    Publication Date: 2019-07-13
    Description: The maximum crystal growth rate for the 67975 matrix composition, about 0.00073 cm/min, was found to occur at about 990 C (undercooling 220 C). The Shaw (1972) model and, to a slightly lesser extent, the Bottinga and Weill (1972) model indicate the variation of viscosity with temperature. Time-temperature-transformation and continuous cooling curves were constructed from the measured crystal growth rates and viscosities and used to estimate the cooling rate required to form bodies with the degree of crystallinity observed in the matrix of the breccia. It is estimated on the basis of kinetic analysis that the 67975 breccia cooled at a rate of about 0.06 C/min over the temperature range below the liquidus. Heat flow analyses indicate that the 67975 breccia did not cool in the size of the lunar sample but as part of a much larger body. Viscous singering as well as cooling of a melt-clast mixture are investigated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 81
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    Publication Date: 2019-07-13
    Description: The acoustic attenuation of a sample of lunar basalt 70215 was measured by the method of sphere resonance. A Q of 1185 was achieved under a vacuum of 7 millionths torr after heating the sample. He and CO2 gas caused a small decrease of Q. H2O vapor, however, resulted in a major decrease in Q. The Q of lunar material when measured on earth is low because of adsorbed gases. However, it is not clear that this effect explains completely the observed high lunar Q.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 82
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 83
    Publication Date: 2019-07-13
    Description: Comparison of the magnetic-field measurements of the Apollo subsatellite magnetometers with USGS geologic maps suggests that the ancient lunar field may have been greater during the Imbrian Period than the earlier Pre-Nectarian and Nectarian periods. Further, the field seems to have varied in direction. These data are consistent with a model in which the ancient lunar magnetizing field arises from a core dynamo which does not form until the Imbrian Period. Impacts during this period then result in magnetized crater melt and ejecta blankets. It is emphasized, however, that the area sampled by the subsatellite magnetometers is but a small fraction of the lunar surface. These results must be confirmed with studies of independent regions of the lunar surface before they can be considered conclusive.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 84
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    Publication Date: 2019-07-13
    Description: The reported study is primarily concerned with the identification and mapping of structural and volcanic features on the lunar farside. The study represents a continuation and extension of a similar investigation made of the nearside of the moon by Scott et al. (1975). Mapping reveals that tectonic structures on the moon's farside are comparatively scarce and such less prominently developed than those on the nearside. Rilles and mare-type ridges that form major linear and basin concentric systems on the nearside are nearly absent on the farside as are large normal faults like Rupes Recta and Rupes Cauchy. The azimuth orientations of five types of geologic structures were measured, including lineaments, crater chains, terra ridges, faults and linear rilles, and straight segments of crater rims. Mare basalts are concentrated in low regions, especially in a large southern basin which is also the site of relatively numerous volcanic constructs as well as geochemical and magnetic anomalies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 85
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 86
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 87
    Publication Date: 2019-07-13
    Description: Results are reported of Fe(++) crystal field spectral measurements for olivines and pyroxenes up to 400 C. The results are correlated with crystal structure data at elevated temperatures, and the validity of remote-sensed identifications of minerals on hot surfaces of the moon and Mercury is assessed. Two techniques were used to obtain spectra of minerals at elevated temperatures using a spectrophotometer. One employed a diamond cell assembly or a specially designed sample holder to measure polarized absorption spectra of heated single crystals. For the other technique, a sample holder was designed to attach to a diffuse reflectance accessory to produce reflectance spectra of heated powdered samples. Polarized absorption spectra of forsterite at 20-400 C are shown in a graph. Other graphs show the temperature dependence of Fe(++) crystal field bands in olivines, the diffuse reflectance spectra of olivine at 40-400 C, the polarization absorption spectra of orthopyroxene at 30-400 C, the diffuse reflectance spectra of pigeonite at 40-400 C, and unpolarized absorption spectra of lunar pyroxene from Apollo 15 rock 15058.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 88
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    Publication Date: 2019-07-13
    Description: Lonar Crater (India) basalt and lunar basalt 75035 were shock loaded under controlled laboratory conditions up to 1000 kbar, generally in a CO/CO2 (1:1) environment evacuated to 10 to the minus seventh power torr. The Kieffer et al. (1976) classification scheme of progressive shock metamorphism is found to apply to lunar basalts. The major shock features of the five classes that span the range 0 to 1000 kbar are described. Only three out of 152 basalt specimens show shock effects in their natural state as severe as Class 2 features. The scarcity of shocked basalt hand samples in contrast to the abundance of shock-produced agglutinates and homogeneous glass spheres in the lunar regolith indicates the dominant role of micrometeorite impact in the evolution of the lunar regolith. The overall glass content in asteroidal and Mercurian regoliths is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 89
    Publication Date: 2019-07-13
    Description: A numerical model for diffusion-controlled phase growth has been applied to the exsolution of phosphide lamellae in lunar metal grains. Computer simulations reproduce observed composition profiles, and reveal the influence of cooling rate on dimensional and compositional parameters of phosphide and metal. At lower cooling rates, phosphide lamellae are larger and the concentration of P in the metal host close to the interface is lower. Cooling rates inferred for Apollo 16 samples, based on compositions and dimensions of the phosphide-metal grains, are mostly in the range 1-100 C/day. These rates correspond to burial depths of 5-0.5 m for melt rocks and 3-0.3 m for breccias. This is in good agreement with thicknesses of lunar cooling units determined by other techniques.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 90
    Publication Date: 2019-07-13
    Description: A finite one-dimensional kinetic model was developed to estimate the cooling rates of lunar rocks. The model takes into consideration the compositional zonation of olivine and applies Buening and Buseck (1973) data on ion diffusion in olivine. Since the 'as-solidified' profile of a given olivine is not known, a step-function, with infinite gradient, is assumed; the position of this step is based on mass balance considerations of the measured compositional profile. A minimum cooling rate would be associated with the preservation of a given gradient. The linear cooling rates of lunar rocks 12002 and 15555 were estimated by use of the olivine cooling-rate indicator to be 10 C/day and 5 C/day, respectively. These values are lower than those obtained by dynamic crystallization studies (10-20 C/day).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 91
    Publication Date: 2019-07-13
    Description: Equilibrium and controlled cooling rate experiments on a synthetic analog of Apollo 15 quartz normative basalt 15597 are reported. While the partitioning of the major elements Ca, Mg, and Fe between pyroxene and liquid is rate independent, the K sub D parameter for Fe/Mg, which is calculated for low-Ca pyroxene, is temperature dependent. It is suggested that chemical trends observed in lunar pyroxenes are a consequence of three rate processes. The processes are (1) rate-dependent suppression of crystallization of other phases until lower temperature alters liquid composition and, therefore, the composition of the pyroxene that crystallizes; (2) the efficiency of fractional crystallization and the extent of crystal zoning are rate dependent; and (3) the partitioning of Al2O3, TiO2, and Cr2O3 between pyroxene and liquid depends on cooling rate.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 92
    Publication Date: 2019-07-13
    Description: Dynamic crystallization studies were performed on two synthetic glasses similar in composition to the mare olivine-normative basalt samples 12009 and 15555. The effects of viscosity (primarily a function of FeO) and the initial temperature of cooling on mineral chemistry, texture, and temperature of appearance of phases were investigated. Olivine compositions seem to indicate that, for the two types of melt cooled at the same rate, there are no significant differences in the degree of undercooling at which olivine nucleates, but it is found that olivine-nucleated densities differ. The cooling rate of 15555 is estimated. Since the temperature at which cooling is initiated affects texture, mineral chemistry, and temperature of appearance of phases so greatly, caution is recommended in the application of experimental data to natural rock systems.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 93
    Publication Date: 2019-07-13
    Description: An upper limit is placed on the average crustal conductivity from an investigation of toroidal (V x B) induction in the moon, using ten-minute data intervals of simultaneous lunar orbiting and surface magnetometer data. Crustal conductivity is determined as a function of crust thickness. For an average global crust thickness of about 80 km, the crust surface electrical conductivity is of the order of 1 hundred millionth mho/m. The toroidal-induction results lower the surface-conductivity limit obtained from poloidal-induction results by approximately four orders of magnitude. In addition, a thermoelectric (Seebeck effect) generator model is presented as a magnetic-field source for thermoremanent magnetization of the lunar crust during its solidification and cooling. Magnetic fields from 1000 to 10,000 gammas are calculated for various crater and crustal geometries. Solidified crustal material cooling through the iron Curie temperature in the presence of such ancient lunar fields could have received thermoremanent magnetization consistent with that measured in most returned lunar samples.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 94
    Publication Date: 2019-07-13
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 95
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    Publication Date: 2019-07-13
    Description: A description is presented of an empirical model of fractional crystallization which predicts that slightly modified versions of certain of the proposed whole moon compositions can reproduce the major-element chemistry and mineralogy of most of the primitive highland rocks through equilibrium and fractional crystallization processes combined with accumulation of crystals and trapping of residual liquids. These compositions contain sufficient Al to form a plagioclase-rich crust 60 km thick on top of a magma ocean that was initially no deeper than about 300 km. Implicit in the model are the assumptions that all cooling and crystallization take place at low pressure and that there are no compositional or thermal gradients in the liquid. Discussions of the cooling and crystallization of the proposed magma ocean show these assumptions to be disturbingly naive when applied to the ocean as a whole. However, the model need not be applied to the whole ocean, but only to layers of cooling liquid near the surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 96
    Publication Date: 2019-07-13
    Description: Rock 71597, a coarse-grained plagioclase-poikilitic basalt that contains 15.8% MgO and 19.3% modal olivine, is described. Olivine and ilmenite crystals occur in two size generations, and large subequant olivine crystals, small 'matrix' olivines, and large ilmenite crystals are characterized. Since large olivine and ilmenite crystals with skeletal habits suggestive of crystallization under relatively rapid cooling are found in a rock whose texture is consonant with slower cooling, it is suggested that the large skeletal crystals formed toward the more rapidly cooled margin of a flow and accumulated by gravitational crystal settling toward the flow's interior. In support of this hypothesis, calculations indicate that the observed olivine compositions are approximately 10 mol% too Fe-rich to have crystallized from a melt of composition corresponding to that of 71597.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 97
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    Publication Date: 2019-07-13
    Description: Helium is one of the dominant gases of the lunar atmosphere. Its presence is easily identified in data from the mass spectrometer at the Apollo 17 landing site. The major part of these data was obtained in lunar nighttime, where helium concentration reaches the maximum of its diurnal cyclic variation. The large night to day concentration ratio agrees with the basic theory of exospheric lateral transport reported by Hodges and Johnson (1968). A reasonable fraction of atmospheric helium atoms has a velocity in excess of the gravitational escape velocity. The result is a short average lifetime and a tenuous helium atmosphere. A description is presented of an investigation which shows that the atmosphere of the moon has two distinct components including low energy atoms, which are gravitationally bound in trajectories that intersect the lunar surface, and higher energy atoms, which are trapped in satellite orbits. The total helium abundance in the lunar corona is shown to be about 1.3 times 10 to the 30th power atoms.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 98
    facet.materialart.
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    Publication Date: 2019-07-13
    Description: Coupling of the global heat flow, crustal heat source enrichment, thermal conductivity, and temperature in the crust and upper mantle of the moon is examined. A steady-state moon in which conductive heat transfer dominates is assumed. Heat-flow measurements from the Apollo 15 and 17 missions and gamma-ray mapping of thorium conducted by the Apollo 15 and 16 missions provide data for the study of the lunar thermal regime. Temperatures in the range of 1100 to 1600 K are found for the 300-km depth level. In the upper mantle, temperature gradients are in the range of 1.8 to 3.2 K/km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 99
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    Publication Date: 2019-07-13
    Description: Data from 24 deep moonquakes are used to investigate the seismic structure of the lunar interior below the 300-500 km level. The deep moonquakes provide an uninterrupted ray-path coverage of the lunar mantle. Lower mantle seismic velocities are determined; the data suggest that moonquakes are confined to the near-side lower mantle. A compositional change rather than temperature effects is assumed to explain the upper mantle-lower mantle transition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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  • 100
    Publication Date: 2019-07-13
    Description: It is pointed out that speculation regarding the bulk chemical composition of the earth, especially its radial distribution, is important for testing ideas on the origin of the earth-moon system. Definitive solutions are, however, unattainable. The reported investigation is concerned with an attempt to select the more plausible possibilities. The evidence on the chemical distribution in the earth is examined and the resulting models of bulk composition are used to check the plausibility of the Ganapathy-Anders model. It is suggested that the chemistry of the earth and moon can be modeled more plausibly in the context of slow, cool accretion of the earth and either simultaneous accretion or disintegrative capture of the moon than by fission or volatilization models based on a hot earth. Many possible aspects need detailed quantitative study including the relation between U content, other heat sources, and heat flow on earth.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar Science Conference; Mar 14, 1977 - Mar 18, 1977; Houston, TX
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