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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Evaluation of ERTS data for certain oceanographic uses

The author has identified the following significant results. According to Lake Michigan records, the pH levels have been steadily increasing as the lake becomes more eutrophic. Numerous upwellings during the summer of 1973, beginning with the late July event, appear to be triggering a chemical precipitation of calcium carbonate. The upwelling provides abundant carbon dioxide into the surface water and results in massive blooms of phytoplankton. As the CO2 is utilized by these microscopic plants the pH is increased (acidity decreases) and CaCO3 no longer is able to remain in solution. The precipitation takes place where the phytoplankton are living, near depths of 10 meters. Therefore, the whiting observed by ERTS-1 is only seen in the green band, as red cannot penetrate but a few meters. With these whitings, secci disc readings lower in July from 10-15 meters to 3-5 meters and green, milky water is observed by research vessels. It appears that whitings have been becoming more frequent since the middle 60's but until ERTS-1 the extent had never been realized. Calcium levels are too low, presently, for a similar precipitate in Lakes Huron or Superior. However, whitings have been seen by ERTS-1 in Lakes Erie and Ontario where the calcium ion and pH levels are more like those found in Lake Michigan.

Strong, A. E.↗
NASA NTRS1977

Use of LANDSAT data for natural resources investigation in the lower basin of Danube and Danube Delta

The author has identified the following significant results. Monitoring of excess humidity was possible at the Baragan test site. Qualitative improvements of 20-50% were obtained in regards to soil inventory in the eastern Danube Delta, comparing data with conventional maps. The pedological situation was observed after drainage in impounded enclosures. The appearance of stagnate water was surveyed due to difference in color shades on LANDSAT imagery. Areas with gluey soils, such as lake bottoms rich in CaCO3 and shell grist, were clearly represented. Sediment discharges into the sea at the Danube mouth and plumes over 100 km at sea could be easily distinguished on LANDSAT MSS 4 and 5.

Oprescu, N.↗
NASA NTRS1978

Near-opposition limb darkening of solids of planetary interest

Results are presented for a general laboratory study of the limb darkening at small phase angles of various materials of planetary interest, with particular attention given to the wavelength dependence of limb darkening. Only substances stable at room temperature were measured, including basalt, graphite, mixtures of MgO and charcoal powders, olivine, goethite, bronzite, CaCO3, MgSO4, BaSO4, limonite, and hematite. Previous studies aimed at determining the nature of limb darkening at opposition for different common materials are reviewed. It is found that the scattering properties of most particulate materials near phase zero can be described adequately by Minnaert's law, but that such a representation is totally inadequate for materials that tend to fracture into flakes with mirrorlike surfaces (e.g., bronzite and graphite). The results also indicate that materials such as olivine have scattering properties within deep absorption bands which exhibit definite departures from Minnaert's law at large angles of incidence or emission.

Veverka, J.↗
NASA NTRS1978

Infrared spectroscopy of simulated Martian surface materials

Mineralogy inferred from the Viking X-ray fluorescence spectrometry (XRFS) is compared with mineralogy indicated by spectral data. The comparison is done by taking laboratory spectra of Viking analog minerals. Both XRFS and infrared data are consistent with clays as the dominant SiO2 containing minerals on Mars. The X-ray fluorescence data might also be consistent with the dominance of certain mafic SiO2 igneous minerals, but the spectral data are probably inconsistent with such materials. Sulfates, inferred by XRFS, are consistent with the spectral data. Inferences following Mariner 9 that high-SiO2 minerals were important on Mars may have been biased by the presence of sulfates. Calcium carbonate, in the quantities indirectly suggested by XRFS are inconsistent with the spectral data, but smaller quantities of CaCO3 are consistent, as are large quantities of other carbonates.

Toon, O. B.↗
NASA NTRS1978

Laboratory analogues to cosmic dust

Results are reported for a study of the condensation of a number of solids that are likely candidates for dust formed in astronomical environments. The condensate materials were produced by vaporizing a portion of a solid target of chosen composition by a laser pulse in an atmosphere of H2, O2, or Ar at 1 atm pressure. The systems studied include olivine, pyroxene, Fe-Ni alloy, Al2O3, carbon, CaCO3, SiC, Au-olivine powders, and Au-Al2O3 powders. Possible relations among the sizes, chainlike structures, and chemistries of the condensates and of grains formed in astronomical systems are investigated. The results indicate that the laser evaporation technique is useful for providing a wide variety of grain systems that are analogous to astronomical grain systems and that the grain materials produced are useful for spectral studies of materials believed to exist in astronomical environments, both as single materials and as multicomponent grain systems

Stephens, J. R.↗
NASA NTRS1981

Hydrazines and carbohydrazides produced from oxidized carbon in earth's primitive environment

Whether abiological organic compounds can be formed from the interactions of energy sources with nitrogen, oxidized carbon and water is held to be of importance in geochemical models of the primordial earth atmosphere. It is reported that experiments using quenched spark discharges through molecular nitrogen on aqueous suspensions of CaCO3 and other reactants to simulate the hydrosphere/atmosphere interface yield hydrazine and carbohydrazine in significant but low yields. Such reactions in primitive aquatic environments may have supplied a pathway for chemical evolution and the origin of life, on a primitive earth in which fully oxidized states of carbon were available for the primary synthesis of organic matter.

Folsome, C. E.↗
NASA NTRS1984

Radar backscatter modelling

The terrain analysis software package was restructured and documentation was added. A program was written to test Johnson Space Center's four band scatterometer data for spurious signals data. A catalog of terrain roughness statistics and calibrated four frequency multipolarization scatterometer data is being published to support the maintenance of Death Valley as a radar backscatter calibration test site for all future airborne and spacecraft missions. Test pits were dug through sand covered terrains in the Eastern Sahara to define the depth and character of subsurface interfaces responsible for either backscatter or specular response in SIR-A imagery. Blocky sandstone bedrock surfaces at about 1 m depth were responsible for the brightest SIR-A returns. Irregular very dense CaCO3 cemented sand interfaces were responsible for intermediate grey tones. Ancient river valleys had the weakest response. Reexamination of SEASAT l-band imagery of U.S. deserts continues.

Schaber, G. G.↗
NASA NTRS1982

Chemical consequences of major impact events on earth

Violent cometary or asteroidal impact events comparable to that which terminated the Cretaceous era must produce large amounts of nitrogen oxides, sufficient to provide NOx mole fractions much larger than 100 ppm over areas of millions of square kilometers. Rapid production of NO2, and subsequent rainout of HNO3 and other strong acids can acidify surface waters, selectively destroying CaCO3 shells. This scenario holds the promise of explaining both the scope of Cretaceous biological extinctions and their extraordinary selectivity.

Lewis, J. S.↗
NASA NTRS1985

Impact and collisional processes in the solar system

The mechanical and thermodynamic aspects of shock impact cratering and accretionary processes on solid planets and satellites are being investigated experimentally. The recently proposed model of Melosh, describing the physics controlling the size and velocity of only lightly shocked spalled ejecta surrounding the crushed rock region of an impact crater, was studied at the Ames gun facility. Spall velocity measurements using lead and aluminum bullets were conducted. In addition, shock temperatures of silicates and volatile-bearing minerals were measured using radiative techniques. Finally impact devolatilization of minerals and accretion of planetary atmospheres were examined. Measurements of the release isentropes of CaCO3 were carried out. The effect on the water budgets of planets of reactions which occur when metallic iron (which would be present in chondritic material) is introduced into a simple accretion model is under investigation.

Ahrens, T. J.↗
NASA NTRS1985

Impact and Collisional Processes in the Solar System

The mechanical and thermodynamic aspects of shock impact cratering and accretionary processes on solid planets and satellites are being investigated experimentally. The recently proposed model of Melosh, describing the physics controlling the size and velocity of only lightly shocked spalled ejecta surrounding the crushed rock region of an impact crater, was studied at the Ames gun facility. Spall velocity measurements using lead and aluminum bullets were conducted. In addition, shock temperatures of silicates and volatile bearing minerals were measured using radiative techniques. Finally impact devolatilization of minerals and accretion of planetary atmospheres were examined. Measurements of the release isentropes of CaCO3 were carried out. The effect on the water budgets of planets of reactions which occur when metallic iron (which would be present in chondritic material) is introduced into a simple accretion model is under investigation.

Ahrens, T. J.↗
NASA NTRS1986

Photochemical reactions of various model protocell systems

Models for the emergence of cellular life on the primitive Earth, and for physical environments of that era have been studied that embody these assumptions: (1) pregenetic cellular forms were phase-bounded systems primarily photosynthetic in nature, and (2) the early Earth environment was anoxic (lacking appreciable amounts of free hydrogen). It was found that organic structures can also be formed under anoxic conditions (N2, CO3=, H2O) by protracted longwavelength UV radiation. Apparently these structures form initially as organic layers upon CaCO3 crystalloids. The question remains as to whether the UV photosynthetic ability of such phase bounded structures is a curiosity, or a general property of phase bounded systems which is of direct interest to the emergence of cellular life. The question of the requirement and sailient features of a phase boundary for UV photosynthetic abilities was addressed by searching for similar general physical properties which might be manifest in a variety of other simple protocell-like structures. Since it has been shown that laboratory protocell models can effect the UV photosynthesis of low molecular weight compounds, this reaction is being used as an assay to survey other types of structures for similar UV photosynthetic reactions. Various kinds of structures surveyed are: (1) proteinoids; (2) liposomes; (3) reconstituted cell membrane spheroids; (4) coacervates; and (5) model protocells formed under anoxic conditions.

Folsome, C. E.↗
NASA NTRS1986

Determination of CA-41, I-129 and OS-187 in the Rochester tandem accelerator and some applications of these isotopes

The measurement of Ca-41 and I-129 utilizing the Rochester Tanden Accelerator Mass Spectrometer (TAMS) is discussed. Ca-41, having a half-life of 100,000 yrs., is of potential use for the dating of ground water as well as of bones in the age range between 50,000 and 1 million yrs. A major problem for the measurement of Ca-41 with TAMS is the fact that calcium does not readily form negative atomic ions. It does, however, form negative molecular ions. The production of CaO ions from compounds such as CaO and CaCO3 and from free Ca molecules sprayed with oxygen gas was studied. A project to utilize I-129 as a tracer for hydrothermal convection in sediment-covered oceanic crust is also briefly described. Finally, plans to use the Os-187/Os-186 ratio for the determination of extraterrestrial material in the Ries crater in Germany are summarized.

Fehn, U.↗
NASA NTRS1988

Kinetics of thermochemical gas-solid reactions important in the Venus sulfur cycle

The thermochemical net reaction CaCO3 + SO2 yields CaSO4 + CO is predicted to be an important sink for incorporation of SO2 into the Venus crust. The reaction rate law was established to understand the dependence of rate on experimental variables such as temperature and partial pressure of SO2, CO2, and O2. The experimental approach was a variant of the thermogravimetric method often employed to study the kinetics of thermochemical gas-solid reactions. Clear calcite crystals were heated at constant temperature in SO2-bearing gas streams for varying time periods. Reaction rate was determined by three independent methods. A weighted linear least squares fit to all rate data yielded a rate equation. Based on the Venera 13, 14 and Vega 2 observations of CaO content of the Venus atmosphere, SO2 at the calculated rate would be removed from the Venus atmosphere in about 1,900,00 years. The most plausible endogenic source of the sulfur needed to replenish atmospheric SO2 is volcanism. The annual amount of erupted material needed for the replenishment depends on sulfur content; three ratios are used to calculate rates ranging from 0.4 to 11 cu km/year. This geochemically derived volcanism rate can be used to test if geophysically derived rates are correct. The work also suggests that Venus is less volcanically active than the Earth.

Fegley, Bruce, Jr.↗
NASA NTRS1988

The rate of volcanism on Venus

The maintenance of the global H2SO4 clouds on Venus requires volcanism to replenish the atmospheric SO2 which is continually being removed from the atmosphere by reaction with calcium minerals on the surface of Venus. The first laboratory measurements of the rate of one such reaction, between SO2 and calcite (CaCO3) to form anhydrite (CaSO4), are reported. If the rate of this reaction is representative of the SO2 reaction rate at the Venus surface, then we estimate that all SO2 in the Venus atmosphere (and thus the H2SO4 clouds) will be removed in 1.9 million years unless the lost SO2 is replenished by volcanism. The required rate of volcanism ranges from about 0.4 to about 11 cu km of magma erupted per year, depending on the assumed sulfur content of the erupted material. If this material has the same composition as the Venus surface at the Venera 13, 14 and Vega 2 landing sites, then the required rate of volcanism is about 1 cu km per year. This independent geochemically estimated rate can be used to determine if either (or neither) of the two discordant (2 cu km/year vs. 200 to 300 cu km/year) geophysically estimated rates is correct. The geochemically estimated rate also suggests that Venus is less volcanically active than the Earth.

Fegley, Bruce, Jr.↗
NASA NTRS1988

Calcium carbonate and sulfate of possible extraterrestrial origin in the EETA 79001 meteorite

Two varieties of Ca-carbonate were found in a total of three interior (greater than 2-cm depth) samples of glass inclusions from the shergottite meteorite, Elephant Moraine, Antarctica, A79001. Two of the samples, including the largest deposit around a vug near the center of the meteorite (8-cm depth), contained veins of granular calcite with significant Mg and P, either as Mg-calcite with dissolved P or as calcite with very finely intergrown Mg-bearing phosphate. The second variety, which occurred in a third sample with a previously documented high concentration of trapped gases, consisted of disseminated 10-20-micron anhedral grains of nearly pure CaCO3 and was intimately associated with laths and needles of Ca-sulfate (possibly gypsum). All evidence considered, it is probable that both varieties of Ca-carbonate (and the Ca-sulfate) formed on a planetary body (probably Mars) before the meteorite fell on earth.

Gooding, James L.↗
NASA NTRS1988

Enthalpies of formation of CaAl4O7 and CaAl12O19 (hibonite) by high temperature, alkali borate solution calorimetry

Enthalpies of formation were determined for two calcium aluminate phases, CaAl4O7 and CaAl12O19, using high-temperature alkali borate solution calorimetry. The aluminates were synthesized by multiple-cycle heating and grinding stoichiometric mixtures of CaCO3 and Al2O3, and the products were characteized by X-ray diffraction and SEM microbeam analysis. The data on impurities (CaAl4O7 was found to be about 89.00 percent pure by weight and the CaAl12O19 samples about 91.48 percent pure) were used to correct the heat of solution values of the synthetic products. The enthalpies of formation, at 1063 K, from oxides, were found to be equal to -(25.6 + or - 4.7) kJ/g.f.w. for CaAl4O7 and -(33.0 + or - 9.7) kJ/g.f.w. for CaAl12O19; the respective standard enthalpies of formation from elements, at 298 K, were estimated to be -4007 + or - 5.2 kJ/g.f.w. and -10,722 + or - 12 kJ/g.f.w.

Geiger, C. A.↗
NASA NTRS1988

How well do we know the Martian abundances of highly volatile elements

The table is given that summarizes four models based on observations and gives some reasonable inferences of each for Martian volatiles. The table columns give: (1) the volatile assumptions of the model; (2) the inferred Martian volatile concentrations relative to earth; (3) the N/36 Ar and C/36 Ar ratios; (4) the percentage of Martian degassing inferred by the model, and 5 and 6) the equivalent global column heights of liquid water and solid CaCO3 over the entire surface of Mars that would be formed from the model quantities of degassed volatiles.

Bogard, Donald↗
NASA NTRS1988

Response of marine and freshwater algae to nitric acid and elevated carbon dioxide levels simulating environmental effects of bolide impact

One of the intriguing facets of the Cretaceous-Tertiary extinction is the apparently selective pattern of mortality amongst taxa. Some groups of organisms were severely affected and some remained relatively unscathed as they went through the K/T boundary. While there is argument concerning the exact interpretation of the fossil record, one of the best documented extinctions at the Cretaceous-Tertiary boundary is that of the calcareous nannoplankton. These organisms include coccolithic algae and foraminiferans. Attempts to explain their decline at the K/T boundary center around chemistry which could affect their calcium carbonate shells while leaving their silica-shelled cousins less affected or unaffected. Two environmental consequences of an extraterrestrial body impact which were suggested are the production of large quantities of nitrogen oxides generated by the shock heating of the atmosphere and the possible rise in CO2 from the dissolution of CaCO3 shells. Both of these phenomena would acidify the upper layers of the oceans and bodies of freshwater not otherwise buffered. The effects of nitric acid, carbon dioxide, or both factors on the growth and reproduction of calcareous marine coccoliths and non-calcareous marine and freshwater species of algae were considered. These experiments demonstrate that nitric acid and carbon dioxide have significant effects on important aspects of the physiology and reproduction of modern algae representative of extinct taxa thought to have suffered significant declines at the Cretaceous-Tertiary boundary. Furthermore, calcareous species showed more marked effects than siliceous species and marine species tested were more sensitive than freshwater species.

Boston, P. J.↗