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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

The soft X-ray spectrum of Sirius B - Evidence for the photospheric hypothesis

The soft X-ray spectrum of Sirius obtained by the HEAO 1 A-2 experiment is used to investigate the origin of the X-radiation from that system. It is shown that, if the emission is coronal, then the coronal temperature must be less than 150,000 K, and the coronal luminosity must be greater than 10 to the 33rd ergs/s. Such a corona conflicts severely with EUV observations and is physically untenable. White dwarf atmosphere models are fitted to the spectrum and it is shown that a photospheric temperature of 28,000 K is much more consistent with the data. The relative consistency of the soft X-ray, EUV, and UV observations of Sirius B is discussed and it is concluded that the evidence favors the white dwarf photosphere as the origin of the soft X-rays.

Martin, C.↗
NASA NTRS1983

Large numbers hypothesis. IV - The cosmological constant and quantum physics

In standard physics quantum field theory is based on a flat vacuum space-time. This quantum field theory predicts a nonzero cosmological constant. Hence the gravitational field equations do not admit a flat vacuum space-time. This dilemma is resolved using the units covariant gravitational field equations. This paper shows that the field equations admit a flat vacuum space-time with nonzero cosmological constant if and only if the canonical LNH is valid. This allows an interpretation of the LNH phenomena in terms of a time-dependent vacuum state. If this is correct then the cosmological constant must be positive.

Adams, P. J.↗
NASA NTRS1984

The Solar Constant, Climate, and Some Tests of the Storage Hypothesis

Activity related modulation of the solar constant can have practical consequences for climate only if storage is involved, as opposed to a detailed balance between sunspot blocking and facular reemission. Four empirical tests are considered that might distinguish between these opposing interpretations: monochromatic measurements of positive and negative flux; comparison of modelled and measured irradiance variations; the interpretation of secular trends in irradiance data; and the direct test of an anticipated signal in climate records of surface air temperature. The yet unanswered question of the role of faculae as possible reemitters of blocked radiation precludes a definitive answer, although other tests suggest their role to be minor, and that storage and an 11 year modulation is implicated. A crucial test is the behavior of the secular trend in irradiance in the declining years of the present activity cycle.

Eddy, J. A.↗
NASA NTRS1983

A climate hypothesis describing the solar-terrestrial system as a frequency domain with specific response characteristics

A climatological model of the earth-sun system based on an analogy to Planck's law of quantum mechanics is developed. The role of the diabatically important trace gases O3, H2O, and CO2 in the complex processes by which solar cycles affect tropospheric-stratospheric stability, and the value of the resonance concept in understanding these phenomena are examined. Consideration is given to climate complexity and the Laplace transform of the solar cycle, direct versus indirect solar signals, intense convection in coupled dynamics, the basic mechanisms of solar-terrestrial interaction, and the Planck's-law analog. The quantum approach, taking complexity into account, is shown to be more appropriate for evaluating the effects of anthropogenic modifications of the atmosphere (e.,g., increasing CO2) than the linear bulk-heating approaches usually applied.

Paine, D. A.↗
NASA NTRS1983

Geochemical evidence bearing on the origin of aerobiosis, a speculative hypothesis

It is pointed out that the atmosphere and hydrosphere of the early Archean earth were essentially anoxic. The paleontological record shows that life existed in spite of the absence of oxygen. The present investigation is concerned with the presentation of a plausible sequence of events, linking features in the carbon isotopic record to the origin of oxygenic photosynthesis. The investigation takes into account that the record of carbon isotopic abundances in sedimentary organic matter displays marked variations about 2.8 Ga before the present. At least by 2.8 Ga before the present, if not before, something in the carbon cycle began to allow the incorporation in sediments of organic material extraordinarily depleted in C-13. Attention is given to a model for the development of C-13 depleted kerogens, conclusions regarding the late Archean carbon cycle, and the transition in the global ecosystem.

Hayes, J. M.↗
NASA NTRS1984

Hypothesis on the origin of lineaments in the LANDSAT and SLAR images of precambrian soil in the low Contas River Valley (southern Bahia)

Examination of LANDSAT and SLAR images in southern Bahia reveals numerous linear features, which are grouped in five sets, based on their trends: N65 degrees E, N70 degrees W, N45 degrees E and NS/N15 degrees E. Owing to their topographic expressions, distributive patterns, spacing between individual lineaments and their mutual relationships, the lineament sets of N65 degrees E and N70 degrees W, as well as the sets of N40 degrees E and N45 degrees W, are considered as two groups of conjugate shear fractures and the former is older and is always cut by the latter. Their conjugate shear angles are 45 degrees and 85 degrees and their bisector lines are approximately in east-west and north-south directions, respectively. According to Badgeley's argumentation on the conjugate shear angles, the former conjugate shear fractures would be caused by: (1) vertical movements, and the bisector of their conjugate angle would be parallel to the long axis of horsting or folding, or (2) by a compressive force in the east-west direction and under a condition of low confining pressure and temperature.

Liu, C. C.↗
NASA NTRS1984

Geophysical and geochemical constraints favoring the capture hypothesis

The early fractionation of the Moon as a result of melting the outer layer of the Moon is discussed. This melting can be attributed to the accretional heating of the moon. Computations of the early thermal evolution of the Earth and Moon based on the assumption that these bodies accreted independently were carried out. The results are consistent with many observations. The concept of geochemical reservoirs was also applied to the Moon.

Turcotte, D. L.↗
NASA NTRS1984

A reappraisal of Darwin's fission hypothesis and a possible limit to the primordial angular momentum of the Earth

G. H. Darwin proposed that the primordial Earth may have rotated fast enough that the solar tidal period was nearly resonant with the fundamental free oscillation period of a fluid Earth and that a large and unstable tidal oscillation split off to become the moon. Jeffreys argumented that dissipation during resonance would be sufficient to prevent such an unstable oscillation greater than the tidal frequency (period - 2.68 hr). It is considered that solar tides have extracted angular momentum from the Earth-Moon system over 4.5 b.y. The correspondence of the primordial tidal and resonant frequencies is nearly exact. (The effect of central condensation of the proto earth is to increase both frequencies by a similar amount, though the resonance is not precisely known. This result, was unknown to Darwin or Jeffreys. The effects of resonance were evaluated. The resonance is likely to be too damped for fission. This argument is more general than Jeffreys', who considered friction between the oscillating mantle and a rigid core. It is argued that the fact that Q must be so great for fission that equilibrium can not be maintained; the fluid proto Earth passes so quickly through resonance that maximum amplitude is not reached. It is suggested that solar resonant tides acted as a brake on the spin of the primordial partially molten Earth. Certain proposed origins for the Moon do not necessarily involve addition of substantial amounts of angular momentum to the Earth-Moon system. The primordial Earth-Moon system may have had nearly the same angular momentum as it has today.

Mckinnon, W. B.↗
NASA NTRS1985

The coorbital hypothesis

Voyager I and II have revealed the existence of 1980S1 and 1980S3 in the same orbit that add to the discovery of the Lagrange satellite 1980S6 for Dione and 1980S13 - 1980S25 for Thetys as a replica to the Trojan planets in the Jupiter orbit. These bodies may issue from the rupture of a primitive gaseous ring through a disturbance. The Lagrange figures keep stable while the rest of the objects drift in near paths and interact at each transit so as to form a gradual binary. The Moon - Earth system may have a such origin.

Andlauer, G.↗
NASA NTRS1985

Analysis of the electron component of EAS at observational level 700 g x cm(-2) with a scale breaking interaction model and gammaisation hypothesis

Scale breaking model and gammaisation processes for high energies give a correct description of the longitudinal development of extensive air showers (E.A.S.). From the analysis of phenomenological characteristics of E.A.S. at Tien-Shan experiment, it follows that for energies near 10 to the 6 GeV the secondary particle multiplicity increases with energy faster than is predicted by the accepted scale breaking model.

Procureur, J.↗
NASA NTRS1987

A test of the hypothesis that impact-induced fractures are preferred sites for later tectonic activity

Impact cratering has been an important process in the solar system. The cratering event is generally accompanied by faulting in adjacent terrain. Impact-induced faults are nearly ubiquitous over large areas on the terrestrial planets. The suggestion is made that these fault systems, particularly those associated with the largest impact features are preferred sites for later deformation in response to lithospheric stresses generated by other processes. The evidence is a perceived clustering of orientations of tectonic features either radial or concentric to the crater or basin in question. An opportunity exists to test this suggestion more directly on Earth. The terrestrial continents contain more than 100 known or probable impact craters, with associated geological structures mapped to varying levels of detail. Prime facie evidence for reactivation of crater-induced faults would be the occurrence of earthquakes on these faults in response to the intraplate stress field. Either an alignment of epicenters with mapped fault traces or fault plane solutions indicating slip on a plane approximately coincident with that inferred for a crater-induced fault would be sufficient to demonstrate such an association.

Solomon, Sean C.↗
NASA NTRS1987

Tectites of Vietnam. Tectites delivered by a comet: A hypothesis

Tectites (tektites) are mysterious natural acid glasses that differ dramatically from terrestrial volcanic or impact glasses. There are many arguments that speak in favor of their non-terrestrial origin, and that is why the problem of their origin has an important scientific and historical significance. It is no accident that hundreds of publications written by specialists of various fields from all over the world are devoted to this issue. It is discussed at length in a collection of articles entitled 'Tectites' (1963,1973), as well as in the excellent monograph by O'Keefe (1976).

E.P. Izokh↗
NASA NTRS1987

The topology of large-scale structure. I - Topology and the random phase hypothesis

Many models for the formation of galaxies and large-scale structure assume a spectrum of random phase (Gaussian), small-amplitude density fluctuations as initial conditions. In such scenarios, the topology of the galaxy distribution on large scales relates directly to the topology of the initial density fluctuations. Here a quantitative measure of topology - the genus of contours in a smoothed density distribution - is described and applied to numerical simulations of galaxy clustering, to a variety of three-dimensional toy models, and to a volume-limited sample of the CfA redshift survey. For random phase distributions the genus of density contours exhibits a universal dependence on threshold density. The clustering simulations show that a smoothing length of 2-3 times the mass correlation length is sufficient to recover the topology of the initial fluctuations from the evolved galaxy distribution. Cold dark matter and white noise models retain a random phase topology at shorter smoothing lengths, but massive neutrino models develop a cellular topology.

Weinberg, David H.↗
NASA NTRS1987

The chronology of Mercury's geological and geophysical evolution - The Vulcanoid hypothesis

The possibility that constraints on Mercury's chronology can be relaxed through reference to a Mercury-specific bombarding population of planetesimals interior to its orbit, and therefore only occasionally encountering the planet at times of secular perturbations, is investigated. While such vulcanoids may have been a significant source of early cratering, those in the pertinent orbits are depleted by mutual collisions and can therefore only furnish a modest extension of the heavy bombardment period. A search is conducted for vulcanoids further within Mercury's orbit; evidence that Mercury's intercrater plains are of volcanic origin is discussed.

Leake, Martha A.↗
NASA NTRS1989

An alternate hypothesis for the origin of Angra dos Reis - Porphyry, not cumulate

The Angra dos Reis achondrite is a unique meteorite of potentially great importance for understanding the origins of the solar system and of the terrestrial planets. It is proposed that the meteorite, which consists of megacrysts of Al-Ti augite (fassaite) in skeletal or cellular shapes, olivine, and possibly whitlockite in a fine-grained groundmass of the same materials plus spinel, is a porphyritic igneous rock modified by metamorphism. In this interpretation, the megacrysts represent cellular-textured phenocrysts, and the fine-grain groundmass represents crystallized or devitrified magma. Phase equilibria suggest that Angra dos Reis-like compositions could grow phenocrysts of fassaite pyroxene, olivine, and whitlockite. These same compositions could crystallize, without crystal sorting or accumulation, to an almost monomineralic fassaite pyroxenite.

Treiman, A. H.↗
NASA NTRS1990

A reexamination of the spreading center hypothesis for Ovda and Thetis regiones, Venus

Crumpler et al. (1987) proposed that Ovda and Thetis Regiones are spreading centers. The strong positive correlation between geoid and topography observed in ovda and Thetis is unlike that observed for terrestrial spreading centers. The maximum elevation expected for spreading centers on Venus is 1.5 km, and a cooling plate thermal model predicts a maximum geoid anomaly of 8 m, both much less than observed. Even if a spreading center is operative in Ovda and Thetis, most of the geoid and topography must be due to other mechanisms. Crumplet et al. also proposed the existence of 'cross-strike discontinuities', interpreted as transform fault zones, but the evidence for these structures is not conclusive.

Kiefer, Walter S.↗
NASA NTRS1990

Triton's plumes - The dust devil hypothesis

Triton's plumes are narrow columns 10 km in height, with tails extending horizontally for distances over 100 km. This structure suggests that the plumes are an atmospheric rather than a surface phenomenon. The closest terrestrial analogs may be dust devils, which are atmospheric vortices originating in the unstable layer close to the ground. Since Triton has such a low surface pressure, extremely unstable layers could develop during the day. Patches of unfrosted ground near the subsolar point could act as sites for dust devil formation because they heat up relative to the surrounding nitrogen frost. The resulting convection would warm the atmosphere to temperatures of 48 k or higher, as observed by the Voyager radio science team. Assuming that velocity scales as the square root of temperature difference times the height of the mixed layer, a velocity of 20 m/sec is derived for the strongest dust devils on Triton. Winds of this speed could raise particles provided they are a factor of 1000 to 10,000 less cohesive than those on earth.

Ingersoll, Andrew P.↗