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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 415 records · Page 23
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

Laser remote sensing of marine sediment load and algal pigments: Laboratory experiments

The fluorescence emission spectra for estuarine water samples excited by an argon laser at 514.5 nm were analyzed. The features of interest were: (1) scattering at the laser wavelength by particulates (Mie); (2) fluorescence from the pigments chlorophyl a and phycoerythrin; (3) Raman scattering by water; and (4) fluorescence by dissolved organic matter. It is shown that these intensities increase with the concentration of the corresponding material and decrease with attenuation. Since the concentration of water is constant the Raman intensity provides a direct measure of attenuation.

Exton, R. J.↗
NASA NTRS1981

Study of the relation between soil use, vegetation coverage, and the discharge of sediments from artificial reservoirs using MSS/LANDSAT images. Example: The Tres Marias reservoir and its supply basin

The land use and types of vegetation in the region of the upper Sao Francisco River, Brazil, are identified. This region comprises the supply basin of the Tres Marias reservoir. Imagery from channels 5 and 7 of the LANDSAT multispectral band scanner during wet and rainy seasons and ground truth data were employed to characterize and map the vegetation, land use, and sedimentary discharges from the reservoir. Agricultural and reforested lands, meadows, and forests are identified. Changes in land use due to human activity are demonstrated.

Dejesusparada, N.↗
NASA NTRS1982

Criteria for the use of regression analysis for remote sensing of sediment and pollutants

Data analysis procedures for quantification of water quality parameters that are already identified and are known to exist within the water body are considered. The liner multiple-regression technique was examined as a procedure for defining and calibrating data analysis algorithms for such instruments as spectrometers and multispectral scanners.

Whitlock, C. H.↗
NASA NTRS1982

Criteria for the use of regression analysis for remote sensing of sediment and pollutants

An examination of limitations, requirements, and precision of the linear multiple-regression technique for quantification of marine environmental parameters is conducted. Both environmental and optical physics conditions have been defined for which an exact solution to the signal response equations is of the same form as the multiple regression equation. Various statistical parameters are examined to define a criteria for selection of an unbiased fit when upwelled radiance values contain error and are correlated with each other. Field experimental data are examined to define data smoothing requirements in order to satisfy the criteria of Daniel and Wood (1971). Recommendations are made concerning improved selection of ground-truth locations to maximize variance and to minimize physical errors associated with the remote sensing experiment.

Whitlock, C. H.↗
NASA NTRS1982

Wind streaks in Tharsis and Elysium - Implications for sediment transport by slope winds

Detailed maps of wind streaks in Tharsis and Elysium have been compiled from Viking Orbiter observations spanning one complete Martian year. The streak pattern is controlled by slope winds on the central volcanoes and on the flanks of the Tharsis bulge, while the global circulation dominates in Elysium. Dust erosion by downslope winds occurs over much of Tharsis and in the vicinity of Elysium Mons; this process is effective even at the low atmospheric pressures found near the summits of the large volcanoes. Erosional streaks are largely absent in Elysium Planitia; net deposition of dust might have occurred during the period of the observations. Surface properties such as slope, thermal inertia, and roughness may influence the efficiency of slope wind production sufficiently to account for the pronounced differences in streak types and patterns present in these two regions.

Lee, S. W.↗
NASA NTRS1983

Feasibility study to conduct windblown sediment experiments aboard a space station

A feasibility study was undertaken to determine if a suitable apparatus could be designed to analyze aeolian processes for operation in space and to assess the feasibility of conducting meaningful experiments to address key aspects of aeolian processes. To meet this objective a prototype apparatus was fabricated and some limited experiments were run to determine its suitability for this application. At least three general types of experiments were devised that could be carried out aboard a space station: threshold studies, swirl (dust devil) experiments, and analyses of windblown particle trajectories. How experiments in a zero-g environment could advance knowledge of aeolian processes was studied.

Greeley, R.↗
NASA NTRS1984

Long range transport of fine grained sediments on Mars: Atmospheric dust loading, as inferred from Viking Lander imaging data

During the first Viking year, two global dust storms occurred and they contributed about 90% of the dust suspended in the Martian atmosphere on a global average, over the course of this year. The remainder was due to the cumulative effect of local dust storms. When globally distributed, the amount of suspended dust introduced into the atmosphere this Martian year was about 5x10(-3) g/sq cm. This mass loading was derived from the incremental optical depths measured over this year and estimates of the mean size of the dust particles (2.5 microns). During the second Martian year, global dust storms were far more muted than during the first year. No near perihelion dust storm occurred, and a somewhat weaker dust storm may have occurred near the start of the spring season in the Southern Hemisphere, at about the same time that the first global dust storm of the first year occurred. Thus, the dust loading derived for the first Martian year may be somewhat higher than the average over many Martian years, a conclusion that appears to be supported by preliminary studies of Martian years beyond the second Viking year on Mars.

Pollack, J. B.↗
NASA NTRS1984

Extraterrestrial platinum group nuggets in deep-sea sediments

A previously unrecognized property of iron cosmic spheres is reported. The most common spheres larger than 300 microns do not, in fact, contain FeNi metal cores, but instead contain a micrometer-sized nugget composed almost entirely of platinum group elements. These elements appear to have been concentrated by the oxidation of molten meteoritic metal during atmospheric entry. This process is critically dependent on the relative abundance of oxygen in the atmosphere, and the first appearance of the nuggets in the geological record may provide a marker indicating when the oxygen abundance attained half of its present level.

Brownlee, D. E.↗
NASA NTRS1984

Chemistry of fuel deposits and sediments and their predursors

The mechanism of solid deposit formation on hot engine parts from turbine fuels is investigated. Deposit formation is associated with oxidation of the hydrocarbon fuel. Therefore, oxidation rates and soluble gum formation were measured for several jet turbine fuels and pure hydrocarbon mixtures. Experiments were performed at 130 C using thermal initiation and at 100 C using ditertiary butyl peroxide as a chemical initiator. Correlation of the data shows that the ratio of rate of oxidation to rate of gum formation for a single fuel is not much affected by experimental conditions, even though there are differences in the abilities of different hydrocarbons to initiate and continue the oxidation. This indicates a close association of gum formation with the oxidation process. Oxidations of n-dodecane, tetralin and the more unstable jet fuels are autocatalytic, while those of 2-ethylnaphthalene and a stable jet fuel are self-retarding. However, the ratio of oxidation rate to gum formation rate appear to be nearly constant for each substrate. The effect of oxygen pressure on gum and oxidation formation was also studied. Dependence of gum formation on the concentration of initiator at 100 C is discussed and problems for future study are suggested.

Mayo, F. R.↗
NASA NTRS1984

Archean sedimentation and tectonics in southern Africa

Sequences in the Barberton Mountain Land greenstone belt (southern Africa) were examined to determine the nature of the sedimentary rocks, their tectonic implications, and their bearing on the present large-scale structural condition of the belt. Also assessed was whether there was evidence for a significant component of shallow-water-deposited sedimentary rocks in the parent materials of the Limpopo belt. The nature of a largehigh strain zone on the southern margin of the central Limpopo belt was examined.

Kidd, W. S. F.↗
NASA NTRS1985

A First Evaluation of LANDSAT TM Data to Monitor Suspended Sediments in Lakes

The use of LANDSAT to monitor and track changes in the water quality of Lake Chicot, Arizona was assessed using MSS and TM digital data from nine water sites. Results show that: (1) TM Bands 1, 2, 3, and 4 appear to be providing information on concentrations of particulate matter suspended in surface waters. These bands are also highly interrelated for water samples; (2) preliminary evaluation indicates that TM Band 3 showed the best relationship to surface suspended solids; (3) TM Bands 5 and 7 are useful for separating water from nonwater areas; (4) the MSS Bands 2 and 3 can be related to suspended solids in surface water, as has already been shown from previous LANDSAT research; and (5) analysis of TM Band 6 indicates that while synoptic temperature patterns may be discerned, the digital sensitivity to a two degree temperature difference is low.

Schiebe, F. R.↗
NASA NTRS1986

Sediment-transport (wind) experiments in zero-gravity

The carousel wind tunnel (CWT) can be a significant tool for the determination of the nature and magnitude of interparticlar forces at threshold of motion. By altering particle and drum surface electrical properties and/or by applying electric potential difference across the inner and outer drums, it should be possible to separate electrostatic effects from other forces of cohesion. Besides particle trajectory and bedform analyses, suggestions for research include particle aggregation in zero and subgravity environments, effect of suspension-saltation ratio on soil abrasion, and the effects of shear and shearfree turbulence on particle aggregation as applied to evolution of solar nebula.

Iverson, J.↗
NASA NTRS1986

Red/violet contrast reversal on Mars - Significance for eolian sediments

Viking Orbiter images of Mars are analyzed to define relationships between the observed contrast reversals (CR) and specific surface features. The link between CR phenomena and surface composition was first detected in contrast comparisons between UV and visible wavelength Mariner 9 data. Viking data, taken through red and violet filters, showed that the CRs occurred only with crater splotches and splotch-related streaks and in bright depositional and dark erosional streaks, both being low-albedo markings presumably caused by eolian forces. The splotch phenomena is confined mainly to the Oxia Palus region, although there are other regions where splotches and streaks commingle. Laboratory tests to mimic the CR characteristics showed that CRs are a common phenomena of different size fractions of iron oxides, e.g., goethite, where particles under 5 microns have been removed. The splotches, including dune formations, are therefore believed to indicate the presence of particles in the 100-800 microns diam range. Finer particles ride on the tops of the dust storms, and are continually removed from the surface by saltation.

Thomas, P.↗
NASA NTRS1988

Zeolites on Mars: Possible environmental indicators in soils and sediments

Weathering products should serve as indicators of weathering environments and may provide the best evidence of the nature of climate change on Mars. No direct mineralogical measurements of Martian regolith were performed by the Viking missions, but the biology and X-ray fluorescence experiments provided some information on the physiochemical properties of Martian regolith. Most post-Viking studies of candidate weathering products have emphasized phyllosilicates and Fe-oxides; zeolites are potentially important, but overlooked, candidate Martian minerals. Zeolites would be important on Mars for three different reasons. First, they are major sinks of atmospheric gases and, per unit mass, are stronger and more efficient sorbents than are phyllosilicates. Secondly, they can be virtually unique sorbents and shelters for organic compounds and possible catalysts for organic-based reactions. Finally, their exchangeable ions are good indicators of the chemical properties of solutions with which they have communicated. Accordingly, the search for information on past compositions of the Martian atmosphere and hydrosphere should find zeolites to be rich repositories.

Ming, D. W.↗
NASA NTRS1988

Late Eocene impact events recorded in deep-sea sediments

Raup and Sepkoski proposed that mass extinctions have occurred every 26 Myr during the last 250 Myr. In order to explain this 26 Myr periodicity, it was proposed that the mass extinctions were caused by periodic increases in cometary impacts. One method to test this hypothesis is to determine if there were periodic increases in impact events (based on crater ages) that correlate with mass extinctions. A way to test the hypothesis that mass extinctions were caused by periodic increases in impact cratering is to look for evidence of impact events in deep-sea deposits. This method allows direct observation of the temporal relationship between impact events and extinctions as recorded in the sedimentary record. There is evidence in the deep-sea record for two (possibly three) impact events in the late Eocene. The younger event, represented by the North American microtektite layer, is not associated with an Ir anomaly. The older event, defined by the cpx spherule layer, is associated with an Ir anomaly. However, neither of the two impact events recorded in late Eocene deposits appears to be associated with an unusual number of extinctions. Thus there is little evidence in the deep-sea record for an impact-related mass extinction in the late Eocene.

Glass, B. P.↗
NASA NTRS1989

Extraterrestrial spherules in glacial sediment from the Transantarctic Mountains, Antarctica - Structure, mineralogy, and chemical composition

The morphological, mineralogical, and chemical characteristics of silicate and glassy spherules from a number of new localities in the Transantarctic Mountains were determined. The results indicate that these Antarctic spherules are of extraterrestrial origin. It is concluded that they, most likely, represent individual micrometeorites that melted during passage through the atmosphere; alternatively, they may be ablation spherules.

Koeberl, Christian↗
NASA NTRS1989

Triton - Stratospheric molecules and organic sediments

Continuous-flow plasma discharge techniques show production rates of hydrocarbons and nitriles in N2 + CH4 atmospheres appropriate to the stratosphere of Titan, and indicate that a simple eddy diffusion model together with the observed electron flux quantitatively matches the Voyager IRIS observations for all the hydrocarbons, except for the simplest ones. Charged particle chemistry is very important in Triton's stratosphere. In the more CH4-rich case of Titan, many hydrocarbons and nitriles are produced in high yield. If N2 is present, the CH4 fraction is low, but hydrocarbons and nitriles are produced in fair yield, abundances of HCN and C2H2 in Triton's stratosphere exceed 10 to the 19th molecules/sq cm per sec, and NCCN, C3H4, and other species are predicted to be present. These molecules may be detected by IRIS if the stratosphere is as warm as expected. Both organic haze and condensed gases will provide a substantial UV and visible opacity in Triton's atmosphere.

Thompson, W. Reid↗