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At least 253 records · Page 14
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Apollo 16 geochemical X-ray fluorescence experiment - Preliminary report.

Mapping of the lunar surface with respect to magnesium, aluminum, and silicon as aluminum/silicon and magnesium/silicon intensity ratios along the projected ground tracks swept out by the orbiting Apollo 16 spacecraft. The results confirm the observations made during the Apollo 15 flight and provide new data for a number of features not covered before. The data are consistent with the idea that the moon has a widespread differentiated crust (the highlands). The aluminum/silicon and magnesium/silicon concentration ratios correspond to those for anorthositic gabbros through gabbroic anorthosites or feldspathic basalts. The X-ray results suggest the occurrence of this premare crust or material similar to it at the Descartes landing site.

Adler, I.↗
NASA NTRS1973

Geological and geochemical studies in the Robinson Mining District, White Pine County, Nevada, using Skylab S190A imagery

The author has identified the following significant results. In the Robinson mining district which included the Ruth porphyry copper mines, three large positive aeromagnetic anomalies exist over a Tertiary volcanic area north west of Ruth. Prior studies of this area have suggested that the volcanics may or may not be the cause of the anomalies. Skylab Sl90A imagery, however, indicates possible outcrops in the volcanic area of the Paleozoic sediments. Field studies or ground truth verify the existence of these inliers suggesting that the magnetic anomaly may be the result of a buried intrusive body for which potential mineralization has been covered by the post-ore blanket of volcanics. The area is being mapped in more detail and samples of mercury-bearing soil-gas area being collected within and outside the area.

Jensen, M. L.↗
NASA NTRS1972

Thermogravimetric-quadrupole mass-spectrometric analysis of geochemical samples.

Thermogravimetric-quadrupole mass-spectrometric-analysis techniques can be used to study a wide variety of problems involving decomposition processes and identification of released volatile components. A recording vacuum thermoanalyzer has been coupled with a quadrupole mass spectrometer. The rapid scan capabilities of the quadrupole mass spectrometer are used to identify the gaseous components released. The capability of the thermogravimetric-quadrupole mass spectrometer to provide analytical data for identification of the released volatile components, for determination of their sequence of release and for correlation of thermal-decomposition studies is illustrated by an analysis of the Orgueil carbonaceous chondrite.

Gibson, E. K., Jr.↗
NASA NTRS1972

Apollo 14 - Some geochemical aspects.

Chemical analyses have been obtained for five samples of Apollo 14 regolith fines, three 14230 core samples, 14049 soil clod, 14305 and 14319 breccias, 14310 basalt, and some separated phases. The chemical uniformity of these Apollo 14 samples indicates thorough mixing and/or uniform source rocks. Basalt 14310 can be matched well in composition by a four-to-one mixture of soil and plagioclase. Eu(2+)/Eu(3+) ratios calculated for 14310 pigeonite and plagioclase are similar to those for Apollo 12 and 15 mare-type basalt phases; this indicates similar redox conditions. The investigated Apollo 14 samples are chemically similar to Apollo 12 and 15 KREEP as distinct from Apollo 11, 12, and 15, and Luna 16 mare-type basalts. A relationship between the two types of basalt, in which mare-basalts would represent fused cumulates, is suggested.

Philpotts, J. A.↗
NASA NTRS1973

Perylene and its geochemical significance.

Perylene was found in a variety of marine sediments, in a shale and in peat. It is suggested that its precursors arise predominantly from land organisms and are carried into oceanic traps along with detrital minerals. When rates of deposition are fast, and reducing conditions are established within the sediment, biogenic pigment precursors of perylene are converted to the polycyclic aromatic hydrocarbon, which is then stabilized by pi-bonding with metals and protected from degradation.

Aizenshtat, Z.↗
NASA NTRS1972

A new approach to the isolation of milligram amounts of significant geochemical compounds.

The modification of an automatic preparative collection system for gas-liquid chromatography is described that is designed to make the system operational for milligram-scale high-efficiency separations of selected components in a geological sample. The sample in question is an organic extract from the Green River Formation Oil Shale, and the compounds selected are the sterane and triterpane hydrocarbons.

Wszolek, P. C.↗
NASA NTRS1972

Applications of activation analysis to geochemical, meteoritic and lunar studies.

The application of activation analysis techniques to the analysis of cosmological materials, i.e., terrestrial, tektitic, meteoritic, and lunar matter, is reviewed. Elemental determinations can be made by instrumental fast-neutron and thermal-neutron activation analysis, photonuclear and charged-particle activation analysis, and by radiochemical neutron activation analysis. Partition-coefficient methods, autoradiography studies, gamma-gamma coincidence counting, and age determination by neutron activation are discussed. Attention is given to K-Ar and I-Xe dating of meteorites.

Showalter, D. L.↗
NASA NTRS1973

Apollo 15 and 16 results of the integrated geochemical experiment.

A number of experiments carried in orbit on the Apollo 15 and 16 spacecraft were used in the compositional mapping of the lunar surface. The observations involved measurements of secondary (fluorescent) X-rays, gamma rays and alpha particle emissions. A large scale compositional map of over 20% of the lunar surface was obtained for the first time. It was possible to demonstrate significant chemical differences between the mare and the highlands, to find specific areas of high radioactivity and to learn something about the composition of the moon's hidden side.

Adler, I.↗
NASA NTRS1973

Ultraminiature X-ray fluorescence spectrometer for in-situ geochemical analysis on Mars.

A spectrometer based upon the X-ray fluorescence method of elemental analysis has been developed in an ultraminiature, rugged form suitable for a spacecraft mission to Mars. The instrument employs two radioisotope sources (Fe-55 and Cd-109) which irradiate adjacent areas on a regolith sample. Fluorescent X rays emitted by the sample are detected by four thin-window proportional counters. Using pulse-height discrimination, the energy spectra are determined. Virtually all elements above sodium in the periodic table are detected if present at sufficient levels. Minimum detection limits range from 30 ppm to 2% depending upon the element and the matrix. For most elements, they are below 0.5%. Accuracies also depend upon the matrix, but are generally better than plus or minus 0.5% for all elements of atomic number greater than 14. Elements below sodium are also detected, but as a single group. Ambiguities of identification of the elements producing the observed spectra are minimal.

Clark, B. C.↗
NASA NTRS1974

On the petrological, geochemical, and geophysical characterization of a returned Mars surface sample and the impact of biological sterilization on the analyses

A study was conducted: to identify those experiments that could and should be done on a returned Martian sample in order to characterize its inorganic properties; to evaluate, insofar as can be done, the effects of potential biological sterilization of the sample by heating prior to its return; to identify particular analytical techniques needing further improvement in order to make optimum use of a returned sample; and to identify experiments to be done on simulants, with and without sterilization, that better define the limits of information available about the planet from analyses of returned samples.

Source record↗
NASA NTRS1974

Geochemical affinities of cobalt and germanium toward metal, silicate, and sulfide phases at high temperature

Hydrothermal studies indicate that Co and Ge are strongly siderophile when metallic iron is in equilibrium with olivine at 900 C and 500 bars. If the metal is replaced by troilite (FeS), Ge is strongly lithophile whereas Co tends to concentrate in the sulfide phase. If iron meteorites were formed in a core derived from the sulfide phase, they would be depleted in Ge but retain Co.

Wai, C. M.↗
NASA NTRS1976

Martian volatiles - Their degassing history and geochemical fate

Implications of the Ar-40 content of the Martian atmosphere for Martian volatile history are considered. It is assumed that the potassium content of both Mars and earth is similar to that of normal chondrites, that Mars possesses a water content similar to that of normal chondrites, and that earth's water content is equal to or somewhat less than Mars'. A simple earth-analogous Mars degassing model is outlined in which the Martian surface volatile inventory is presumed to be identical to earth's, but scaled to the smaller mass and surface area of Mars. Physical storage of volatiles in the Martian regolith is examined along with the occurrence of volatile-containing mineral phases in the regolith, exospheric escape as a massive volatile sink, and the effect of the time history of degassing on the surface volatile inventory. Implications of earth's degassing history for Mars are assessed, and models describing the overall intensity of Mars degassing are presented. It is concluded that the maximum amounts of water and other volatiles that could be stored in the Martian regolith are marginally compatible with those required by the earth-analogous model, although a lower atmospheric Ar-40 concentration and regolith volatile inventory would be easier to reconcile with observational constraints.

Fanale, F. P.↗
NASA NTRS1976

Mineralogic and petrologic implications of Viking geochemical results from Mars - Interim report

Chemical results from four samples of Martian fines delivered to Viking landers 1 and 2 are remarkably similar in that they all have high iron; moderate magnesium, calcium, and sulfur; low aluminum; and apparently very low alkalies and trace elements. This composition is best interpreted as representing the weathering products of mafic igneous rocks. A mineralogic model, derived from computer mixing studies and laboratory analog preparations, suggests that Mars fines could be an intimate mixture of about 80% iron-rich clay, about 10% magnesium sulfate (kieserite), about 5% carbonate (calcite), and about 5% iron oxides (hematite, magnetite, maghemite, goethite). The mafic nature of the present fines (distributed globally) and their probable source rocks seems to preclude large-scale planetary differentiation of a terrestrial nature.

Baird, A. K.↗
NASA NTRS1977

Diterpenoid compounds and other lipids in deep-sea sediments and their geochemical significance

Cyclic diterpenoid compounds have been found by various investigators in the geosphere (e.g., fossil resins, coals, soil, shale, and deep-sea sediments). These compounds occur in significant amounts only in higher plants and are therefore potential markers of terrigenous plant lipids. Diterpenoids with the abietane skeleton (mainly dehydroabietic acid) have been identified in the lipids of sediment samples from the northeast Pacific Ocean, Black Sea, and North Atlantic Ocean. The presence of these resin-derived compounds was correlated with the terrigenous clay components and with the presence of pollen. The presence of polycyclic diterpenoids was also correlated with the distribution patterns and inferred sources of other sediment lipid constituents. Potamic transport, followed by turbidite redistribution, is the probable input mechanism of these resin-derived compounds to the deep-sea sediments. These diterpenoids appear to be excellent biological markers of resinous higher plants.

Simoneit, B. R. T.↗
NASA NTRS1977

Geochemical zoning and early differentiation in the moon

The volatile elements (e.g., Rb, Pb, Tl, Bi, Cs) seem to have been depleted at the time of lunar accretion. Accordingly, it may be assumed that the moon initially accreted from refractory material. The good correlation between volatile/involatile element ratios (e.g., Cs/U, K/La, K/Zr) in both highland and maria samples means that element distribution in lunar crustal rocks is not governed by volatility differences. This and other evidence encourages the view that the moon was accreted homogeneously. A consequence of homogeneous accretion theories is that very efficient large-scale element fractionation is required to account both for the high near-surface concentrations of refractory elements (e.g., Th, U, REE, Zr, Ba, etc.) and for the Ca-Al-rich crust.

Taylor, S. R.↗