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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

The thermoremanence hypothesis and the origin of magnetization in iron meteorites

The intensity, relative stability and directional behavior in alternating field demagnetization of natural, saturation, thermal and spontaneous magnetization were studied for a variety of iron meteorites. Results show that remanence and relative stability increase from the coarser to the finer-grained samples. In addition, natural remanent magnetization coercivity spectra are found to soften with coarsening of the grain size. The link between fine structure and magnetization direction in octahedrites is also discussed. The combined effect of magnetocrystalline- and shape-anisotropy of the crystallographically ordered ferromagnetic kamacite alpha-phase renders the iron meteorites of little use for the study of ancient solar system fields.

Brecher, A.↗
NASA NTRS1977

The permuted generator hypothesis for the origin of a genetic code

Protocells had no known means of ensuring that their randomly collected proteins would be duplicated. A possible, albeit inexact, mechanism for protein synthesis in a primitive t-RNA is presented, whereby an oligonucleotide (12 units) in a circular configuration is able to align a generator site with amino acid discriminator sites. In this way, unique anticodons could be specified for each site and replication could occur.

Folsome, C.↗
NASA NTRS1978

The Ramsey phase-change hypothesis

Ramsey's (1948, 1949, 1950, 1954) arguments for the phase-change interpretation of the nature of the terrestrial core are summarized. Some of the successes of the phase-change theory in accounting for hitherto unexplained properties of earth's interior are discussed. Evidence in favor of the phase-change theory is reviewed, and calculations are examined which indicate that the liquid-core material is far more compressible at any relevant pressure than is the mantle material. Implications of the phase-change theory for Venus, Mars, Mercury, and the moon are considered.

Lyttleton, R. A.↗
NASA NTRS1978

On the origin of ringing irregularities - A meteor hypothesis

Isolated ionospheric irregularities produce oscillating diffraction patterns on the ground. In the present study typical physical properties such as density, size, etc. of these irregularities are estimated on the basis of diffraction pattern characteristics. These properties agree well with those of meteor trail ionization and it has been found that most of these oscillating irregularities occur on meteor shower days. It is therefore suggested that the oscillating irregularities are caused by meteor showers.

Deshpande, M. R.↗
NASA NTRS1980

Primordial nucleosynthesis and Dirac's large numbers hypothesis

Consideration is given to the analysis of Falik (1979) which attempted to show that the cosmological model proposed by Canuto and Hsieh (1978) in which the gravitational constant varies with time contradicts observations of primordial helium. It is shown that the analysis was based on the assumptions that (1) the energy density of radiation in local thermodynamic equilibrium is approximately equal to the fourth power of the equilibrium temperature, where the product of the equilibrium temperature with the scale factor of the Robertson-Walker metric is constant, and (2) the gravitational constant is approximately equal to the inverse of the time even at early cosmological epochs. These assumptions are demonstrated to be invalid in the scale covariant theory of gravitation used to develop the model, thus negating the conclusion that the Canuto and Hsieh model excludes the primordial synthesis of helium.

Canuto, V.↗
NASA NTRS1981

Origin of Martian outflow channels - The eolian hypothesis

It has been recognized for many years that wind injects dust into the atmosphere on Mars and moves around thin layers of surface material. An investigation is conducted regarding the rates of eolian transport on Mars in the context of eolian channel formation. A model is developed for the formation of an erosional channel by sandblasting with materials transported by wind out of chaotic terrains. This model is applied to the interpretation of topographic measurements made in the chaotic terrain source area and channel of Aromatum Vallis, a small well-preserved channel system southwest of the Chryse basin, and constraints are developed on the eolian mechanism.

Cutts, J. A.↗
NASA NTRS1980

Selective decay hypothesis at high mechanical and magnetic Reynolds numbers

Implications of certain applications of turbulence theory to two-dimensional turbulence and magnetohydrodynamic flow are discussed. It is shown that the use of the Navier-Stokes equation (NSE) for measurements of turbulent fluctuations has been effective only for three-dimensional flows. For two-dimensional flows, used for the study of large-scale motions in the atmosphere or ocean, enstrophy is cascaded to high wave numbers and dissipated at a finite rate even at infinite Re. MHD flows are numerically calculated for the two-dimensional case and analytically for the three-dimensional case, for which discrepancies in the relative rates of energy and cross helicity decay lead to a recommendation that numerical calculations for the three-dimensional case be carried out to determine the precise decayed states.

Matthaeus, W. H.↗
NASA NTRS1981

Comet nucleus - Some characteristics and a hypothesis on origin and structure

The spectroscopic properties of comets are discussed, and consideration is given to the problems of the cosmic ray irradiation and the origin and structure of cometary nuclei. The classification of cometary spectra as continuum dominant, molecular emissions dominant and CO(+) dominant is examined, and changes in spectral characteristics with heliocentric distance although not with cometary age are pointed out. Spectral evidence for a variety of organic compounds in the cometary nucleus is noted, and a scenario is presented whereby these complex molecules may form as a result of cosmic ray irradiation of cometary ices in the Oort cloud. Finally, a model is proposed for the accumulation of small icy grains to form a cometary nucleus composed of cometesimals of size distribution following a -5th power dependence on mass.

Donn, B.↗
NASA NTRS1982

Ecological optimality in water-limited natural soil-vegetation systems. I - Theory and hypothesis

The solution space of an approximate statistical-dynamic model of the average annual water balance is explored with respect to the hydrologic parameters of both soil and vegetation. Within the accuracy of this model it is shown that water-limited natural vegetation systems are in stable equilibrium with their climatic and pedologic environments when the canopy density and species act to minimize average water demand stress. Theory shows a climatic limit to this equilibrium above which it is hypothesized that ecological pressure is toward maximization of biomass productivity. It is further hypothesized that natural soil-vegetation systems will develop gradually and synergistically, through vegetation-induced changes in soil structure, toward a set of hydraulic soil properties for which the minimum stress canopy density of a given species is maximum in a given climate. Using these hypotheses, only the soil effective porosity need be known to determine the optimum soil and vegetation parameters in a given climate.

Eagleson, P. S.↗
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.↗