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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 73 records · Page 4
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NASA NTRS1980

Mars Tharsis region - Volcanotectonic events in the stratigraphic record

It is pointed out that the most recent volcanism and much of the oldest tectonic activity on Mars have apparently occurred within the Tharsis region. Detailed geologic mapping from Viking images has provided new information on the evolutionary history of the region. The eruptive sequence and areal extent of lava flows in the Tharsis region have been defined by stratigraphic studies and crater counts made on individual flow units. Faults and fractures transecting these units provide a record of changing tectonic intensity during the period of high volcanic activity. Volcanism began with the resurfacing of basement rocks early in the history of the region and continued without large interruptions through nine major eruptive episodes. Volcanic centers shifted from place to place but resurgent activity occurred at several volcanoes. Volcanism culminated during the foration of large shield volcanoes along Tharsis Montes and thereafter appears to have gradually declined.

Scott, D. H.↗
NASA NTRS1981

Precursor active galaxies, active galaxies and the X-ray and gamma-ray background

A description is presented of a model in which the X-ray and gamma-ray background can result from the superposition of radiation from active galaxies in different stages of their evolutionary history. This scheme is based on the generalization of a black-hole model developed for gamma-ray production in active galaxies by Leiter (1980). Both thermal and nonthermal accretion disk processes around massive rotating Kerr black holes are considered. Attention is given to cosmological conditions leading to precursor active galaxies (PAG), PAG as origin of the cosmic X-ray background, and the evolution of PAG into Seyfert galaxies as origin of the gamma-ray background. It is found that after spin-up of the central black hole an active galactic nucleus can generate nonthermal radiation very efficiently up to a few MeV.

Leiter, D.↗
NASA NTRS1981

Photochemistry in planetary atmospheres

Widely varying paths of evolutionary history, atmospheric processes, solar fluxes, and temperatures have produced vastly different planetary atmospheres. The similarities and differences between the earth atmosphere and those of the terrestrial planets (Venus and Mars) and of the Jovian planets are discussed in detail; consideration is also given to the photochemistry of Saturn, Uranus, Pluto, Neptune, Titan, and Triton. Changes in the earth's ancient atmosphere are described, and problems of interest in the earth's present troposphere are discussed, including the down wind effect, plume interactions, aerosol nucleation and growth, acid rain, and the fate of terpenes. Temperature fluctuations in the four principal layers of the earth's atmosphere, predicted decreases in the ozone concentration as a function of time, and spectra of particles in the earth's upper atmosphere are also presented. Finally, the vertical structure of the Venus cloud system and the thermal structure of the Jovian planets are shown graphically.

Levine, J. S.↗
NASA NTRS1982

The dynamics of the nucleus of M31

Self-consistent dynamic models of the M31 nucleus were constructed which satisfy Stratoscope II and ground-based photometry, as well as ground-based velocity dispersion measurements. Two models designed to yield the highest and lowest mass-to-light ratios (M/L) consistent with observations are concentrated on. It is found that self-consistent static models of the M31 nucleus can be constructed with a nuclear mass-to-blue magnitude ratio between 0 and 50, and that it is very difficult to construct high M/L models with plausible evolutionary histories. The low values of M/L that were found suggest that the nucleus must be composed of stars on nearly radial orbits whose apocenters lie well outside the observable part of the nucleus. Such nuclei may be formed either during core collapse of a preexisting dense nucleus or by orbital decay of globular clusters in a triaxial bulge.

Tremaine, S.↗
NASA NTRS1982

Active region coronal evolution

Scaling relations between coronal base pressure and longitudinal photospheric magnetic field strength are tested for the case of a single active region observed for five solar rotations from Skylab. The evolution of measureable quantities, such as coronal thermal energy content, total longitudinal photospheric magnetic flux, region scale size, and peak energy density, is traced throughout the five rotations observed. The theoretically derived scaling law of Golub et al. (1980) is found to provide an acceptable fit to the data throughout the entire evolutionary history of the region from an age of about 3 days to the fully evolved state in which the mature active region merges into the general large-scale structure of the quiet corona. An alternative scaling law obtained by including the results of Galeev et al. (1981), however, is found to provide a somewhat better fit to the data. The study is seen as providing additional justification for the belief that magnetic field-related heating is the operative mechanism in the solar corona.

Golub, L.↗
NASA NTRS1982

Paradigm transition in cosmic plasma physics

New discoveries in cosmic plasma physics are described, and their applications to solar, interstellar, galactic, and cosmological problems are discussed. The new discoveries include the existence of double layers in magnetized plasmas and in the low magnetosphere, and energy transfer by electric current in the auroral circuit. It is argued that solar flares and the solar wind-magnetosphere interaction should not be interpreted in terms of magnetic merging theories, and that electric current needs to be explicitly taken account of in understanding these phenomena. The filamentary structure of cosmic plasmas may be caused by electric currents in space, and the pinch effect may have a central role to play in the evolutionary history of interstellar clouds, stars, and solar systems. Space may have a cellular structure, with the cell walls formed by thin electric current layers. Annihilation may be the source of energy for quasars and the Hubble expansion, and the big bang cosmology may well be wrong.

Alfven, H.↗
NASA NTRS1986

Volcanological constraints of Archaean tectonics

Volcanological and trace element geochemical data can be integrated to place some constraints upon the size, character and evolutionary history of Archean volcanic plumbing, and hence indirectly, Archean tectonics. The earliest volcanism in any greenhouse belt is almost universally tholeitic basalt. Archean mafic magma chambers were usually the site of low pressure fractionation of olivine, plagioclase and later Cpx + or - an oxide phase during evolution of tholeitic liquids. Several models suggest basalt becoming more contaminated by sial with time. Data in the Uchi Subprovince shows early felsic volcanics to have fractionated REE patterns followed by flat REE pattern rhyolites. This is interpreted as initial felsic liquids produced by melting of a garnetiferous mafic source followed by large scale melting of LIL-rich sial. Rare andesites in the Uchi Subprovince are produced by basalt fractionation, direct mantle melts and mixing of basaltic and tonalitic liquids. Composite dikes in the Abitibi Subprovince have a basaltic edge with a chill margin, a rhyolitic interior with no basalt-rhyolite chill margin and partially melted sialic inclusions. Ignimbrites in the Uchi and Abitibi Subprovinces have mafic pumice toward the top. Integration of these data suggest initial mantle-derived basaltic liquids pond in a sialic crust, fractionate and melt sial. The inirial melts low in heavy REE are melts of mafic material, subsequently melting of adjacent sial produces a chamber with a felsic upper part underlain by mafic magma.

Thurston, P. C.↗
NASA NTRS1986

The western Wabigoon Subprovince, Superior Province, Canada: Archean greenstone succession in rifted basement complex

The Wabigoon Subprovince, interposed between the predominantly metasedimentary-plutonic and gneissic English River and Quetico Subprovinces to the north and south respectively, exposed Archean greenstone and granitoid rocks for a strike length of greater than 700 km. Based on predominating rock types, the western part of the subprovince is divided into two terrains: the northern Wabigoon volcano-sedimentary and pluonic terrain (NWW) and the Wabigoon Diapiric Axis terrain (WDA). Both the NWW and WDA are described according to volcanic sequence, geological faults, chemical composition and evolutionary history.

Edwards, G. R.↗
NASA NTRS1986

Synsedimentary deformation and thrusting on the eatern margin of the Barberton Greenstone belt, Swaziland

Mapping on the eastern margin of the 3.6 to 3.3 Ga Barberton Greenstone Belt NW Swaziland has revealed a tectonic complex which is more than 5 km thick. The area consists of fault bound units made up of three lithological associations. Some of these were affected by four phases of deformation. Fold structures, foliations, and lineations are associated with the deformation. Sedimentation, geological structures, and evolutionary history of the area are explained.

Lamb, S. H.↗
NASA NTRS1986

Terrestrial analogues of the surface rocks of Mars?

Evidence is presented which suggests that hisingerite, iddingsite, and several ferric sulfate minerals derived from deuteric alteration of iron-rich basalts on earth may provide clues to the evolutionary history of the surface of Mars. The characteristics of these minerals are pointed out, and their strong compositional and paragenetic similarities to Martian regolith materials are pointed out. These similarities are consistent with a mineral assemblage on Mars consisting of ferric-bearing phyllosilicate, sulfate, and oxyhydroxide phases. These phases could have been derived from postmagmatic deuteric alteration of volatile-rich iron-rich basaltic rocks containing fayalitic olivine, Fe pyroxenes, and accessory pyrrhotite.

Burns, R. G.↗
NASA NTRS1988

Lyman-alpha clouds as a relic of primordial density fluctuations

Primordial density fluctuations are studied using a CDM model and primordial clouds some of which are expanding, driven by pressure gradients created when the medium is photionized, and some of which are massive enough to continue collapsing in spite of the pressure. Normalization of CDM models to the clustering properties on large scales are used to predict the parameters of collapsing clouds of subgalactic mass at early epochs. It is shown that the abundance and dimensions of these clouds are comparable to those of the Lyman-alpha systems. The evolutionary history of the clouds is computed, utilizing a spherically symmetric hydrodynamics code with the dark matter treated as a collisionless fluid, and the H I column density distribution is evaluated as a function of N(H I) and redshift. The observed cloud parameters come out naturally in the CDM model and suggest that Lyman-alpha clouds are the missing link between primordial density fluctuations and the formation of galaxies.

Bond, J. R.↗
NASA NTRS1988

U-Th-Pb, Sm-Nd, Rb-Sr, and Lu-Hf systematics of returned Mars samples

The advantage of studying returned planetary samples cannot be overstated. A wider range of analytical techniques with higher sensitivities and accuracies can be applied to returned samples. Measurement of U-Th-Pb, Sm-Nd, Rb-Sr, and Lu-Hf isotopic systematics for chronology and isotopic tracer studies of planetary specimens cannot be done in situ with desirable precision. Returned Mars samples will be examined using all the physical, chemical, and geologic methods necessary to gain information on the origin and evolution of Mars. A returned Martian sample would provide ample information regarding the accretionary and evolutionary history of the Martian planetary body and possibly other planets of our solar system.

Tatsumoto, M.↗
NASA NTRS1988

Geochemical characteristics of charnockite and high grade gneisses from Southern Peninsular Shield and their significance in crustal evolution

Presented here are the results of detailed investigations encompassing externsive structural mapping in the charnockite-high grade gneiss terrain of North Arcot district and the type area in Pallavaram in Tamil Nadu supported by petrography, mineral chemistry, major, minor and REE distribution patterns in various lithounits. This has helped in understanding the evolutionary history of the southern peninsular shield. A possible tectonic model is also suggested. The results of these studies are compared with similar rock types from parts of Andhra Pradesh, Kerala, Sri Lanka, Lapland and Nigeria which has brought about a well defined correlation in geochemical characteristics. The area investigated has an interbanded sequence of thick pile of charnockite and a supracrustal succession of shelf type sediments, layered igneous complex, basic and ultrabasic rocks involved in a complex structural, tectonic, igneous and metamorphic events.

Sugavanam, E. B.↗
NASA NTRS1988

The red envelope and the age of the universe

The photometric evolution of old stellar populations is slow in the optical/IR. Consequently, observational error is a strongly limiting factor in the accuracy possible for determining galaxy ages or estimating q0 at high redshifts from indices such as the 4000-A break. Existing observations of the red envelope at z above about 0.3 are consistent with a wide range of evolutionary histories. The middle-UV spectral region (rest wavelengths = 2000-3300 A) appears to promise less ambiguous results.

O'Connell, Robert W.↗
NASA NTRS1988

Primitive material surviving in chondrites - Matrix

A logical place to search for surviving pristine nebular material is in the fine-grained matrices of ordinary and carbonaceous chondrites of petrographic type 3. Unfortunately, many of these chondrites have experienced brecciation, thermal metamorphism, and aqueous alteration, so that interpreting individual features in terms of specific nebular conditions and/or processes is difficult. It follows that the origin and evolutionary history of such matrix phases are controversial, and a consensus is difficult to define. In this chapter, therefore, after summarizing the salient mineralogical, petrographic, chemical, and isotopic features of matrix in apparently primitive chondrites, an attempt is made to provide an overview both of areas of agreement and of topics that are currently in dispute.

Scott, E. R. D.↗
NASA NTRS1989

Escape of atmospheres and loss of water

The properties and limitations of several loss processes for atmospheric gases are presented and discussed. They include thermal loss (Jeans and hydrodynamic); nonthermal loss (all processes involve charged particles); and impact erosion, including thermal escape from a molten body heated by rapid accretion. Hydrodynamic escape, or 'blowoff', is of particular interest because it offers the prospect of processing large quantities of gas and enriching the remainder in heavy elements and isotopes. In a second part, the water budgets and likely evolutionary histories of Venus, Earth and Mars are assessed. Although it is tempting to associate the great D/H enrichment on Venus with loss of a large initial endowment, a steady state with juvenile water (perhaps from comets) is equally probable.

Hunten, D. M.↗
NASA NTRS1989

Physical properties of Aten, Apollo and Amor asteroids

Data available on the physical properties of a group of planet-crossing asteroids, the Aten, Apollo, and Amor objects (AAAO) (include data on the taxonomy, mineralogical surface composition, diameter, rotation rate, shape, and surface texture) are presented together with the type of observations used for obtaining these data. These data show that the population of the AAAO is diverse in all of their physical characteristics. This diversity implies that the AAAO come from multiple sources and had different evolutionary histories.

Mcfadden, Lucy-Ann↗
NASA NTRS1989

Some unsolved problems in evolutionary dynamics in the solar system

Several unsolved problems in the evolutionary histories leading to current dynamical configurations of the planets and their systems of satellites are discussed. These include the possibilities of rather tight constraints on the primordial rotation states of Mercury and Venus and the stabilizing mechanism for the latter's retrograde spin, a brief mention of the problem of origin of the moons of earth and Mars, the excessive heat flow from Jupiter's satellite Io which is not compatible with an otherwise self-consistent model of origin of the Laplace three-body libration, the mechanism for the long history of resurfacing of Saturn's satellite Enceladus and the possibly short lifetime of the A ring and the mechanisms for resurfacing the satellites of Uranus, especially Ariel, if the high stability of the mean motion orbital resonances at the 2/1 commensurability involving Ariel and Umbriel precludes a long term occupancy of the resonance. Finally, excessive times of accumulation of the outer planets in current models may possibly be reducible from the effects of nebular gas drag.

Peale, S. J.↗