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  • 1
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    TIDAL DISSIPATION IN THE MOON (1963)
    In:  Other Sources
    Details
    Publication Date: 2011-08-10
    Description: Calculation of the dissipation of tidal energy in the moon due to imperfect elasticity, showing that heating by tidal dissipation is now insignificant
    Keywords: BIOTECHNOLOGY
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  • 2
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    Dynamics of volatile delivery from outer to inner solar system (1994)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Description: Owen et al. propose that the Ar excess of Venus compared to Earth was caused by impact of a large icy planetesimal from the outer solar system, where temperatures were low enough for Ar to adhere to ice, about 30 K. A body of solar Ar/Si and C/H similar to Pluto and Triton less than 100 km diameter would suffice. However, direct delivery from the Uranus-Neptune zone to Venus would result in a very high approach velocity, causing erosion rather than accretion of volatiles. It would also be an extremely improbable event. Virtually all icy bodies scattered from the Uranus-Neptune zone to the terrestrial zone were strongly perturbed by Jupiter, but even then arrived at Venus (or Earth) at too-high velocities. What is needed is a 'deboost' of bodies scattered inward from Jupiter by Earth and Venus perturbations, prior to impact into Venus. This has low probability, since the influence radii of Venus and Earth for the high velocities are small compared to that of Jupiter for the lower velocities further out. It is desirable that this problem be examined by an integerator that allows for close approaches, such as developed by Levison and Duncan. However, it would be a long and expensive computation compared to explaining short-period comets to accomplish the third 'deboost' phase. But since close encounters dominate in such distant scattering, an Opik algorithm seems the appropriate reconnaissance tool.
    Keywords: ASTROPHYSICS
    Type: Lunar and Planetary Inst., Conference on Deep Earth and Planetary Volatiles; p 21
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  • 3
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    Mechanical processess affecting differentiation of protolunar material (1977)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Mechanisms prior to lunar formation are sought to account for the loss of volatiles, the depletion of iron, and the enrichment of plagioclase. Some of the same mechanisms are necessary to account for achondritic, stony-iron, and iron meteorites. Collisions seem marginally capable of providing the heat to accomplish the differentiation into iron, magnesian silicates, and plagioclase. Once this differentiation is accomplished, the subsequent mechanical history should have been sufficient to sort material according to composition in the protolunar circumterrestrial cloud. Effects operating include the correlation of body size with mechanical strength; the lesser ability of the cloud to trap the larger, denser infalling bodies; the more rapid drawing into the Earth of the larger moonlets; and the higher energy orbits for dominantly plagioclase smaller pieces broken off by collision.
    Keywords: ASTROPHYSICS
    Type: NASA, Washington The Soviet-Am. Conf. on Cosmochem. of the Moon and Planets, Pt. 2; p 805-813
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  • 4
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    Formation of the sun and its planets (1986)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Aspects of star formation are considered, taking into account those observations and models which have a relation to the formation of the solar system. Attention is given to the galactic structure, the stellar properties, planetary indications, interstellar clouds, observations of forming stars, the conditions for cloud collapse, models of star formation, the modeling of secondary features, and aspects of dynamical evolution. Aspects of cosmochemistry are also explored. Questions of chronology are discussed along with nuclide variations, chemical variations among chondritic meteorites, and chemical variations among differentiated objects. A description of planet formation is provided, taking into consideration, gas-dust interaction, sun and accretion disk dynamics, planetesimal swarms, planet-disk interactions, planetary systems, terrestrial planet formation, and gaseous protoplanet contraction.
    Keywords: ASTROPHYSICS
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  • 5
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    International dictionary of geophysics, dynamic satellite geodesy (1964)
    In:  CASI
    Details
    Publication Date: 2019-05-21
    Description: Application of celestial mechanics to artificial satellite orbit calculations using orbit perturbations
    Keywords: BIOTECHNOLOGY
    Type: NASA-TM-X-51584
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  • 6
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    Fragmentation in stellar collapse (1991)
    In:  CASI
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    Publication Date: 2019-06-28
    Description: A three dimensional Cartesian code was developed to model molecular cloud collapse and protostellar formation. The basic Eulerian scheme employs spatially second-order accurate, finite difference methods to advance the fluid variables in time. The hydrodynamic equations governing the collapse include the effects of self-gravity, rotation, and radiative transfer. Supplementary equations include Poisson's equation which relates the gravitational potential to the density distribution and a mean intensity equation derived with the Eddington approximation for radiative transfer. The gas pressures and internal energies are determined from equations of state derived for a molecular cloud composed of hydrogen, helium, and heavier elements.
    Keywords: ASTROPHYSICS
    Type: NASA, Washington, Reports of Planetary Geology and Geophysics Program, 1990; p 420-421
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  • 7
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    A tidal theory for the origin of the solar nebula (1979)
    In:  Other Sources
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    Publication Date: 2019-06-27
    Description: A model for the origin of the solar nebula is developed with attention to the significance of angular momentum considerations. Evidence that stars are born in groups rather than singly is examined. It is shown that protostars which are members of typical galactic clusters have some probability of undergoing a gravitational encounter with another star while they are collapsing. According to the model, these encounters impart disproportionate amounts of angular momentum to the later material to fall in toward already centrally condensed fragments. The amount of central condensation of a fragment is the overriding factor in determining its stability against destruction by tidal forces. The encounter also imparts angular momentum to matter that is still accreting onto the protosun.
    Keywords: ASTROPHYSICS
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