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At least 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Physical properties of surface materials on Martian volcanoes: Dust-covered lava and ash

Remote sensing measurements provide information about the Martian surface at scales smaller than can be inferred from imaging data alone. Measurements of Martian volcanoes obtained at visual, infrared, and radar wavelengths are discussed in order to evaluate the physical properties. A related issue involves identifying possible ash deposits by distinctive or anomalous physical characteristics.

Zimbelman, James R.↗
NASA NTRS1988

Volcanic ash layers in blue ice fields (Beardmore Glacier Area, Antarctica): Iridium enrichments

Dust bands on blue ice fields in Antarctica have been studied and have been identified to originate from two main sources: bedrock debris scraped up from the ground by the glacial movement (these bands are found predominantly at fractures and shear zones in the ice near moraines), and volcanic debris deposited on and incorporated in the ice by large-scale eruptions of Antarctic (or sub-Antractic) volcanoes. Ice core studies have revealed that most of the dust layers in the ice cores are volcanic (tephra) deposits which may be related to some specific volcanic eruptions. These eruptions have to be related to some specific volcanic eruptions. These eruptions have to be relatively recent (a few thousand years old) since ice cores usually incorporate younger ice. In contrast, dust bands on bare blue ice fields are much older, up to a few hundred thousand years, which may be inferred from the rather high terrestrial age of meteorites found on the ice and from dating the ice using the uranium series method. Also for the volcanic ash layers found on blue ice fields correlations between some specific volcanoes (late Cenozoic) and the volcanic debris have been inferred, mainly using chemical arguments. During a recent field expedition samples of several dust bands found on blue ice fields at the Lewis Cliff Ice Tongue were taken. These dust band samples were divided for age determination using the uranium series method, and chemical investigations to determine the source and origin of the dust bands. The investigations have shown that most of the dust bands found at the Ice Tongue are of volcanic origin and, for chemical and petrological reasons, may be correlated with Cenozoic volcanoes in the Melbourne volcanic province, Northern Victoria Land, which is at least 1500 km away. Major and trace element data have been obtained and have been used for identification and correlation purposes. Recently, some additional trace elements were determined in some of the dust band samples, including Ir. Iridium determinations were made using INAA, with synthetical and natural (meteorite) standards. These findings are discussed.

Koeberl, Christian↗
NASA NTRS1989

Ellipsometric study of Al2O3/Ag/Si and SiO2/Ag/quartz ashed in an oxygen plasma

The growth of silver oxide (proposed as a potentially useful protective coating for space environment) on a silver mirror coated with an Al2O3 or a SiO2 protective layer was investigated using the monolayer-sensitive variable angle of incidence spectroscopic ellipsometry technique. The samples were exposed to a pure oxygen plasma in a plasma asher, and the silver oxide growth was monitored as a function of the exposure time. It was found that atomic oxygen in the asher penetrated through the SiO2 or Al2O3 coatings to convert the silver underneath to silver oxide, and that the quantity of the silver oxide formed was proportional to the ashing time. The band gap of silver oxide was determined to be 1.3 eV. A schematic diagram of the variable angle of incidence spectroscopic ellipsometer is included.

De, Bhola N.↗
NASA NTRS1992

Mid-infrared spectroscopy of Pahala ash palagonite and implications for remote sensing studies of Mars

The mid-IR (7-20 micron range) spectral properties of Pahala ash palagonite and the effect of thin dustings of the palagonite on reflectance characteristics of quartzite and basalt were investigated. Unlike the reflectance of quartzite and basalt, the reflectance of the palagonite is flat and low (1-2 percent). It was found that a dusting of 1-20 micron palagonite particles and 20-250 micron particle clumps, covering 50 percent of the quartzite of the basalt host reduced the quartizite mid-IR reflectance by about 50 percent. The reflectance of the underlying rock was found to be linearly related to the exposed surface area even for extremely small amounts of palagonite (2-100 micron thickness, averaging 5 microns), indicating that mid-IR remote sensing of rocks on Mars will be practical only for dust-free areas.

Crisp, Joy↗
NASA NTRS1998

Global Distribution of Dust, Smoke, Volcanic Ash, and Pollutant Aerosols Seen from Space

New technique for observing aerosols from space, using ultraviolet (UV) wavelengths, have been developed during the past three years. The chief benefit from observing aerosols in the UV is that they are easily visible over both land and water. While there is presently more than one satellite that can observe aerosols in the UV, only Total Ozone Mapping Spectrometer (TOMS) has a long-term record (since 1979) and adequate spatial resolutions (50 to 100 km) to observe the seasonal and interannual variations, and to locate some of the land sources of dust, smoke, volcanic ash and sulfate pollutants. The data has been assembled into daily images of the atmospheric aerosol loading in terms of optical depth and UV transmittance. For the major sources of aerosols, it is common for at least 50% of the total UV to be absorbed underneath aerosol plumes. This is particularly true for the spectacular smoke plumes originating from the recent Indonesian and Mexican fires, as well as under the huge African dust plumes. The sulfate pollutants are mostly present in the Northern Hemisphere and are associated with regions of high industrial activity. The location and seasonal dependence of these aerosol plumes over Europe and North America will be contrasted with the relatively clean Southern Hemisphere. Because of the success of this technique, it has formed the basis for a new generation of space-borne aerosol detection instruments. These new instruments combine the UV observations with the more traditional visible-wavelength data to obtain a more comprehensive characterization of aerosols that is possible with either UV or visible techniques by themselves.

Herman, Jay R.↗
NASA NTRS2003

Subgrid Scale Modeling in Solar Convection Simulations using the ASH Code

The turbulent solar convection zone has remained one of the most challenging and important subjects in physics. Understanding the complex dynamics in the solar con- vection zone is crucial for gaining insight into the solar dynamo problem. Many solar observatories have generated revealing data with great details of large scale motions in the solar convection zone. For example, a strong di erential rotation is observed: the angular rotation is observed to be faster at the equator than near the poles not only near the solar surface, but also deep in the convection zone. On the other hand, due to the wide range of dynamical scales of turbulence in the solar convection zone, both theory and simulation have limited success. Thus, cutting edge solar models and numerical simulations of the solar convection zone have focused more narrowly on a few key features of the solar convection zone, such as the time-averaged di erential rotation. For example, Brun & Toomre (2002) report computational finding of differential rotation in an anelastic model for solar convection. A critical shortcoming in this model is that the viscous dissipation is based on application of mixing length theory to stellar dynamics with some ad hoc parameter tuning. The goal of our work is to implement the subgrid scale model developed at CTR into the solar simulation code and examine how the differential rotation will be a affected as a result. Specifically, we implement a Smagorinsky-Lilly subgrid scale model into the ASH (anelastic spherical harmonic) code developed over the years by various authors. This paper is organized as follows. In x2 we briefly formulate the anelastic system that describes the solar convection. In x3 we formulate the Smagorinsky-Lilly subgrid scale model for unstably stratifed convection. We then present some preliminary results in x4, where we also provide some conclusions and future directions.

Young, Y.-N.↗
NASA NTRS2006

Aviation Applications for Satellite-Based Observations of Cloud Properties, Convection Initiation, In-flight Icing, Turbulence and Volcanic Ash

Advanced Satellite Aviation Weather Products (ASAP) was jointly initiated by the NASA Applied Sciences Program and the NASA Aviation Safety and Security Program in 2002. The initiative provides a valuable bridge for transitioning new and existing satellite information and products into Federal Aviation Administration (FAA) Aviation Weather Research Program (AWRP) efforts to increase the safety and efficiency of the airspace system. The ASAP project addresses hazards such as convective weather, turbulence (clear-air and cloud-induced), icing and volcanic ash and is particularly applicable in extending the monitoring of weather over data-sparse areas such as the oceans and other observationally remote locations. ASAP research is conducted by scientists from NASA, the FAA AWRP's Product Development Teams (PDT), NOAA and the academic research community. In this paper we provide a summary of activities since the inception of ASAP that emphasize the use of current-generation satellite technologies toward observing and mitigating specified aviation hazards. A brief overview of future ASAP goals is also provided in light of the next generation of satellite sensors (e.g., hyperspectral; high spatial resolution) to become operational in the 2006-2013 timeframe.

Mecikalski, John R.↗
DOE OSTI2025

Magnetic fly-ash geopolymer for heavy metal removal in aqueous solutions

Novel magnetic geopolymers were manufactured by synthesizing magnetic Fe 3 O 4 particles on the surface of prepared geopolymer (Method 1) or by incorporating pre-synthesized magnetic Fe 3 O 4 particles into the geopolymer during the manufacture of the geopolymer (Method 2). This study evaluated the effect of the incorporated magnetic Fe 3 O 4 on the geopolymer magnetic, physical, and adsorption properties and its separation in aqueous solutions. Based on several preliminary measurements on the synthesized magnetic geopolymers, Method 2 was found to be a better method for producing magnetic geopolymer. Magnetic geopolymer synthesized by Method 2 exhibited ferromagnetic properties comparable to that of magnetic Fe 3 O 4 , with a saturation magnetization of 8 emu·g −1 and an intrinsic coercivity of 265 Oe. The magnetic geopolymer was efficiently separated from an aqueous solution within 2 min using a 0.48-T magnetic field. In addition, the magnetic geopolymer has a maximum copper adsorption capacity of 111.1 mg·g −1 , which was similar to the non-magnetic reference geopolymer indicating that the addition of magnetic Fe 3 O 4 did not compromise the geopolymer adsorption capacity. The magnetic geopolymer is a promising material with good adsorption and separation properties that can be used for heavy metals removal and recovery in wastewater and metals separation in industrial processes.

fly ash↗