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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
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NASA NTRS1975

Origin of lunar light plains

In order to determine the origin of Cayley-type lunar light plains, their physical properties, distribution, and relative ages are examined from Apollo orbital and Lunar Orbiter photographs. The distribution and apparent age of the plains deposits and data on highly feldspathic breccias indicate that these superficial materials are neither locally derived nor part of the Imbrium ejecta. The existence of a planar facies of continuous ejecta at Orientale and in the ejecta blankets of small craters is demonstrated. The data and interpretation presented support the hypothesis that the surface and near-surface materials of some light plains, including those at the Apollo 16 site, are at least partly composed of ejecta from the Orientale basin and that the materials of many rugged areas, such as the Descartes highlands, are overlain by similar material. The possibility that some Cayley-type plains may have a different origin is not excluded.

Chao, E. C. T.↗
NASA NTRS1976

The origin of optical polarization in NGC 1068

The polarization of emission lines in the nucleus of NGC 1068 has been measured with a digicon, a single-channel scanner, and interference filters. It is found that the permitted lines of H and probably also He II are polarized at nearly the same position angle and by the same amount as the neighboring continuum. This argues strongly that a common dust scattering mechanism is responsible for all the polarization. The forbidden lines are weakly polarized at a position angle quite different from the continuum, indicating an origin outside the nuclear scattering region. The continuum radiation has been found to be circularly polarized with ellipticity of the order of 5 percent in the red. Such high ellipticity is very unlikely to be of nonthermal origin. We take it as evidence that the nuclear dust is in the form of clouds in an asymmetric skew geometry; the polarization then arises from multiple scattering within these clouds.

Angel, J. R. P.↗
NASA NTRS1977

Origin of the earth's ocean basins

The earth's original ocean basins were mare-type basins produced 4 billion years ago by the flux of asteroid-sized objects responsible for the lunar mare basins. Scaling upwards from the observed number of lunar basins for the greater capture cross-section and impact velocity of the Earth indicates that at least 50 percent of an original global crust would have been converted to basin topography. These basins were flooded by basaltic liquids in times short compared to the isostatic adjustment time for the basin. The modern crustal dichotomy (60 percent oceanic, 40 percent continental crust) was established early in the history of the earth, making possible the later onset of plate tectonic processes. These later processes have subsequently reworked, in several cycles, principally the oceanic parts of the earth's crust, changing the configuration of the continents in the process. Ocean basins (and oceans themselves) may be rare occurrences on planets in other star systems.

Frex, H.↗
NASA NTRS1976

On the origin of the solar system and of Jupiter and its satellites

The evolution of the middle part of the primitive solar nebula is traced through seven stages: (1) a gravitational instability which clumps condensed material into bodies of appreciable size; (2) the formation of a larger body as a result of mutual collisions; (3) gravitational condensation of the gas in the nebula; (4) subsequent hydrodynamic collapse of the gas onto a heavy-element planetary core; (5) the attainment of a highly distended hydrostatic configuration and its subsequent slow gravitational contraction; (6) the formation of a gaseous disk around proto-Jupiter; and (7) the formation of the Galilean satellites (and Amalthea) within this disk. Different theories on the origin of the primitive solar nebula are reviewed, models of Jupiter are evaluated, and the origin and evolution of the planet are traced through the indicated stages. It is proposed that Jupiter's current excess luminosity is due mostly to a loss of internal energy generated during the initially more rapid contraction period and, to a lesser degree, to the planet's current release of gravitational energy. The question of when the icy constituent was added to the outer two Galilean satellites is considered.

Cameron, A. G. W.↗
NASA NTRS1976

Tektites and their origin

Questions concerning the tektite distribution are examined, taking into account the Australasian strewn field, the Ivory Coast strewn field, the Moldavite strewn field, the North American strewn field, the Libyan desert glass, the Aouelloul crater glass, and amerikanites. Attention is given to the shapes of tektites, the internal structure of tektites, the physical properties of tektite glass, the chemical composition of tektites, isotopes, fission tracks, cosmic ray tracks, and arguments in favor and against the terrestrial origin of tektites. It is concluded that tektites cannot be terrestrial in origin. They are probably volcanic ejects, of geologically recent epochs, from one or a number of lunar volcanoes.

Okeefe, J. A.↗
NASA NTRS1977

The origin of stellar winds - Subatmospheric nonthermal storage modes versus radiation pressure

Most current models of matter-flux in hot stars place its origin in radiation pressure, and then model the flow explicitly to produce no chromosphere-corona. Our model of the stellar atmosphere as a transition zone between stellar interior and interstellar medium places the origin of matter-flux, chromosphere-corona, and spectral 'emission classes' in subatmospheric nonthermal kinetic energy storage, equally for all stars, hot or cold. Current observations of both hot and cold stars suggest chromospheres to be a universal phenomenon, correlated with matter-fluxes, and enhanced in 'emission-class' stars. To clarify the difference between the two kinds of models above, we reformulate the wind-tunnel analogy to stellar winds, suggesting that stars satisfy an 'imperfect,' rather than 'perfect,' such model; i.e., transonic shocks occur before the throat, corresponding to an imposed outward velocity in the storage section, or subatmosphere. We then investigate the stability of an arbitrary stellar atmosphere, hot or cold, to suggest a cause for such an outward subatmospheric velocity.

Cannon, C. J.↗
NASA NTRS1977

On the origin of the magnetic field in type-1 comet tails - A reply to Ershkovich

Ershkovich (1976) employed the observed geometry of the type 1 tail of comet Arend-Roland 1957 III to show that any magnetic field present there cannot be of 'internal' origin but must have been 'captured' from the magnetized solar wind. Such an 'external' origin for the magnetic field in type 1 comet tails is not disputed, but several other points raised by Ershkovich are discussed. These concern the generation of substantial magnetic fields within the coma during periods when the comet's heliocentric distance is typically not greater than 1 AU, Ershkovich's use of the pressure balance across the tail 'tangential discontinuity' to estimate that the 'captured' magnetic field is of the order of the solar wind-field, his interpretation of certain observations of motions in the tail of comet Arend-Roland, and his assertion that the distant comet tail will be transformed into a turbulent wake due to the Kelvin-Helmholtz instability. It is argued that the 'captured' magnetic field should be substantially amplified relative to the solar-wind field, that the pressure-balance equation is of limited use, and that the real configuration of a type 1 tail must be treated in detail before any definite conclusions can be reached about the Kelvin-Helmholtz instability.

Mendis, D. A.↗
NASA NTRS1977

The origin of biological macromolecules on the earth. The hypothesis of inorganic template

Studies about the origin of life are reviewed. The nonrandom organization of organelles is discussed from a structural and functional point of view. After postulating that the origin of biomacromolecules was not a random event, the paper develops the hypothesis that polypeptides and polynucleotides were formed on an inorganic template. Only information-containing structures can pass natural selection and develop through evolution.

Lu, T. S.↗
NASA NTRS1977

Origin of the earth's ocean basins

The earth's original ocean basins are proposed to be mare-type basins produced 4 billion y.a. by the flux of asteroid-sized objects responsible for the lunar mare basins. Scaling upward from the observed number of lunar basins for the greater capture cross-section and impact velocity of the earth indicates that at least 50% of an original global crust would have been converted to basin topography. These basins were flooded by basaltic liquids in times short compared to the isostatic adjustment time for the basin. The modern crustal dichotomy (60% oceanic, 40% continental crust) was established early in the history of the earth, making possible the later onset of plate tectonic processes. These later processes have subsequently reworked, in several cycles, principally the oceanic parts of the earth's crust, changing the configuration of the continents in the process. Ocean basins (and oceans themselves) may be rare occurrences on planets in other star systems.

Frey, H.↗
NASA NTRS1977

The origin of comets

Empirical data related to questions regarding the origin of comets are examined, taking into account the primitive temperature and its evolution, the cometary C-12/C-13 isotope ratio, the chemistry of comets, and the solar-system related orbits of the comets. The theories of cometary origin considered are related to a condensation of comets from the solar nebula and a later ejection into Oort's cloud, a recent condensation of comets in situ, a capture of interstellar comets, and a reversal of the arrow of time in the traditional evolution of comets. The only hypothesis which seems to survive an evaluation of the theories on the basis of the existing data is that the comets were condensed some five billion years ago in the vicinity of the giant planets or beyond, at the outer edge of the solar nebula.

Delsemme, A. H.↗
NASA NTRS1977

Origin of asteroids and the missing planet

Consideration is given to Ovenden's (1972) theory concerning the existence of a planet of 90 earth masses which existed from the beginning of the solar system and then disappeared 16 million years ago, leaving only asteroids. His model for secular perturbations is reviewed along with the principle of least interaction action (1972, 1973, 1975) on which the model is based. It is suggested that the structure of the asteroid belt and the origin of meteorites are associated with the vanished planet. A figure of 0.001 earth masses is proposed as a close estimate of the mass of the asteroidal belt. The hypothesis that the planet was removed through an explosion is discussed, noting the possible origin of asteroids in such a manner. Various effects of the explosion are postulated, including the direct impact of fragments on the earth, their impact on the sun and its decreased radiation, and the direct radiation of the explosion. A model for the disappearance of the planet by ejection in a gravitational encounter with a passing mass is also described.

Opik, E. J.↗
NASA NTRS1978

A core origin for group IVA iron meteorites - A reply to Moren and Goldstein

Because uncertainties in experimental data are large, one has considerable latitude in choosing the input parameters needed to calculate iron meteorite cooling rates. The best way to test input parameters is by examining their ability to yield the observed properties of the meteorites. Our phase diagram yields fits to kamacite profiles that are superior to those based on the Moren-Goldstein phase diagram. Our method of allowing for the effect of P on the Ni diffusion coefficient takes into account the enhancement in this effect with decreasing temperature; Moren and Goldstein use a relationship derived for a temperature of 1100 C, well outside the 700-350 C range where kamacite growth occurs. Use of our input parameters yields cooling rates in IVA irons that are independent of composition, consistent with a core origin. Since the fractionation of siderophiles in group IVA also indicates a core origin, we conclude that this is the correct model for this group.

Willis, J.↗
NASA NTRS1975

Origin of the Station 7 boulder - A note

The origin of the matrix types from the Apollo 17 Station 7 boulder is considered along with the origin of boulder material from Station 2, Boulder 1, and 73215. It is pointed out that the formation of the matrix rocks in this boulder and in the other Apollo 17 boulders in a single impact event is consistent with the isotopic evidence, ages, major-element chemistry, large ion lithophile (LIL) trace-element abundances, and textures. It had been suggested by Winzer et al. (1974), based on calculations from crystal-liquid partition coefficients for LIL trace elements, that target rocks corresponding in trace-element composition to the matrix types could have been produced by partial fusion of rocks similar to 77215. Using the same type of calculation, liquids quite similar in trace-element composition to the Station 7 boulder matrix types can be produced.

Winzer, S. R.↗
NASA NTRS1978

Gamma-ray astronomy and the origin of cosmic rays

Recent observations of cosmic gamma radiation are reviewed. It is shown that this radiation consists of an extragalactic background as well as a bright band of galactic radiation lying in the plane of the Milky Way and produced primarily by cosmic-ray collisions with interstellar gas atoms. The galactic gamma radiation is divided into a near component apparently associated with Gould's belt and a far component originating about 15,000 light years away and narrowly confined to the galactic plane. A Great Galactic Ring is identified which is 35,000 light years in diameter and in which most galactic cosmic rays are produced and supernovae and pulsars are concentrated. The physical mechanisms responsible for the production of most of the cosmic gamma rays in the Galaxy are examined, and the origin of galactic cosmic rays is considered. It is concluded that the cosmic rays are produced either in supernova explosions or in the pulsars they leave behind

Stecker, F. W.↗
NASA NTRS1978

Origin and evolution of the Saturn system: Observational consequences

A number of important cosmogonic questions concerning the Saturn system can be addressed with a Saturn-orbiter-dual-probe spacecraft mission. These questions include: The origin of the Saturn system; the source of Saturn's excess luminosity; the mechanism by which the irregular satellites were captured; the influence of Saturn's early luminosity on the composition of its regular satellites; and the origin of the rings. The first two topics can be studied by measurements made from an entry probe into Saturn's atmosphere, while the remaining issues can be investigated by measurements conducted from an orbiter. Background information is provided on these five questions describing the critical experiments needed to help resolve them.

Pollack, J. B.↗
NASA NTRS1978

Luna 24 origins - Some trace element constraints

Luna 24 basaltic material originated in the particular volume of the lunar crust that produced Apollo 11 and Luna 16 basaltic material; it has the same Clr/P2O5 (r = residual) signature. Ru-Os contents (Barsukov et al., 1977) and a number of radiogenic age measurements place Luna 24 basalt origins stratigraphically in a layer between those from which Apollo 15 and Apollo 11 and 17 basalts were derived.

Jovanovic, S.↗
NASA NTRS1979

Isotopic anomalies of noble gases in meteorites and their origins. IV - C3 /Ornans/ carbonaceous chondrites

The C3O chondrites Kainsaz, Lance, and Ornans were studied by an acid dissolution technique to characterize the noble gas components in 3 mineral fractions: HF, HCl-solubles, chromite and carbon, and 'phase Q', a trace mineral containing Ar, Kr, Xe. For all fractions, gas contents decline in the order Kainsaz, Lance, Ornans; this trend parallels volatile contents but not heterogeneity of olivine composition or degree of metamorphism, and reflects progressively higher condensation temperature from the solar nebula. The Ar/Xe ratios and compositions of the three mineral fractions are discussed, and it is concluded that in all primitive chondrites the amount and the chemical separability of CCFXe parallel the abundance of primordial noble gases and other volatiles, such as C, N, Tl, Bi, and In. The close correlation of CCFXe with properties of local origin, such as volatile content and petrologic type, is more consistent with a local than with an extrasolar origin of the component.

Alaerts, L.↗
NASA NTRS1979

Comets: Cosmic connections with carbonaceous meteorites, interstellar molecules and the origin of life

The ions, radicals, and molecules observed in comets may be derived intact or by partial decomposition from parent compounds of the sort found either in the interstellar medium or in carbonaceous meteorites. The early loss of highly reducing primitive atmosphere and its replacement by a secondary atmosphere dominated by H2O, CO2, and N2, as depicted in current models of the earth's evolution, pose a dilemma for the origin of life: the synthesis of organic compounds necessary for life from components of the secondary atmosphere appears to be difficult, and plausible mechanisms have not been evaluated. Both comets and carbonaceous meteorites are implicated as sources for the earth's atmophilic and organogenic elements. A mass balance argument involving the estimated ratios of hydrogen to carbon in carbonaceous meteorites, comets, and the crust and upper mantle suggests that comets supplied the earth with a large fraction of its volatiles. The probability that comets contributed significantly to the earth's volatile inventory suggests a chemical evolutionary link between comets, prebiotic organic synthesis, and the origin of life.

Chang, S.↗