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  • 1
    Publication Date: 2013-08-29
    Description: The morphology of lava flows is often taken as an indicator of the broad chemical composition of the lava, especially when interpreting extraterrestrial volcanoes using spacecraft images. The historical lavas of the active volcano Mount Etna in Sicily provide an excellent opportunity to examine the controls on flow field morphology. In this study only flow produced by flank eruptions after the middle of the 18th century are examined. The final form of a flow-field may be more indicative of the internal plumbing of the volcano, which may control such factors as the effusion, rate, duration of eruption, volume of available magma, rate of de-gassing, and lava rheology. Different flow morphologies on Etna appear to be a good indicator of differing conditions within the volcanic pile. Thus the spatial distribution of different flow types on an extraterrestrial volcano may provide useful information about the plumbing conditions of that volcano, rather than necessarily providing information on the composition of materials erupted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., MEVTV Workshop on Nature and Composition of Surface Units on Mars; p 69-71
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  • 2
    Publication Date: 2011-08-17
    Description: A Lagrangian computer program is used to study the effects of large impacts on planetary surfaces. More specifically, the global seismic effects for cratering energies of 10 to the 24th and 10 to the 25th J between the Copernicus and Imbrium lunar events are investigated. The phenomenologies for assumed solid and molten planetary interiors are compared. The main results of this investigation are: (1) far-field effects are found to be largely independent of cratering mechanisms, (2) antipodal seismic effects, which are of substantial magnitude, are greatly enhanced by focusing, (3) the most violent activity takes place at significant depth, (4) seismic effects are more pronounced for a molten planet than for a solid one, and (5) tensile failure may occur at depths of tens of kilometers beneath the antipode, or over the entire surface at shallower depths. These results suggest that the unusual terrains antipodal to large planetary basins may have been greatly modified by seismicity generated by the basin-forming impacts, and that the impacts may have brecciated the entire lithospheres of the terrestrial planets as the lithospheres formed and thickened
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 3
    Publication Date: 2019-06-28
    Description: Thirty-six aluminous mare basalt fragments from breccia 14321 and other Apollo 14 basalts are statistically divided into two broad groups, comprising five subgroups, using La, Sm, and Yb data. Major element compositions, petrographic characteristics, and mineral compositions are similar for the five groups. However, there is an eight-fold increase in REE abundances from Group 5 to Group 1, with Group 1 having a REE pattern similar to KREEP. Groups 1 to 3 may be related by partial melting of a source similar to that proposed by Unruh et al. (1984) for feldspathic basalt 12038. However, Groups 4 and 5 cannot be as closely matched by larger degrees of partial melting of this source. Groups 1 to 4 could also be produced by assimilation of a KREEP component by a magma similar in composition to Group 5. Such a magma can be produced by partial melting of an olivine-orthopyroxene source that crystallized from a magma with chondritic relative REE abundances.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; C365-C37
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  • 4
    Publication Date: 2019-06-27
    Description: Enhanced levels of N2O and CO were measured in tropospheric air samples exposed to a 17,500-J laboratory discharge. These enhanced levels correspond to an N2O production rate of about 4 trillion molecules/J and a CO production rate of about 10 to the 14th molecules/J. The CO measurements suggest that the primary region of chemical production in the discharge is the shocked air surrounding the lightning channel, as opposed to the slower-cooling inner core. Additional experiments in a simulated Venus atmosphere (CO2 - 95%, N2 - 5%, at one atmosphere) indicate an enhancement of CO from less than 0.1 ppm prior to the laboratory discharge to more than 2000 ppm after the discharge. Comparison with theoretical calculations appears to confirm the ability of a shock-wave/thermochemical model to predict the rate of production of trace species by an electrical discharge.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 6; July 197
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  • 5
    Publication Date: 2019-07-12
    Description: Electron microprobe and INAA were used to analyze forty spherules of Apollo 15 yellow-brown glass for major and trace elements. The glass is one of twenty-five high-Mg primary magmas emplaced on the lunar surface in pyroclastic eruptions. The abundances show that the magma was produced by partial melting of differentiated cumulates in the lunar mantle. Models to explain the possible source-regions of several Apollo 15 and Apollo 12 low-Ti mare magmas are presented.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 52; 2379-239
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  • 6
    Publication Date: 2019-08-14
    Description: Mare basalt 15388, a feldspathic microgabbro from the Apennine Front, is chemically and petrographically distinct from Apollo 15 picritic, olivine-normative (ON), and quartz-normative basalts. The evolved chemistry, coarse texture, lack of olivine, and occurrence of cristobalite in 15388 argue for derivation by a late-stage magmatic process that is significantly removed from parental magma. It either crystallized from a magma evolved from the more mafic Apollo 15 basalts, or it crystallized from a currently unrepresented magma. Rb-Sr and Sm-Nd isotopic systematics yield isochron ages of 3.391 plus or minus 0.036 and 3.42 plus or minus 0.07 Ga, respectively, and epsilon(sub Nd) = 8.6 plus or minus 2.4, which is relatively high for Apollo 15 mare basalts. In contrast to chemical patterns of average Apollo 15 ON basalts and Apollo 15 picritic basalt, 15388 has a strongly positive LREE slope, high Ti, shallower HREE slope and a slightly positive Eu anomaly. These features argue against 15388 evolution by simple olivine fractionation of a parental ON or picritic basalt magma, although olivine is a dominant liquidus phase in both potential parents.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Inst., Twenty-Fourth Lunar and Planetary Science Conference. Part 2: G-M; p 683-684
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  • 7
    Publication Date: 2019-07-12
    Description: Whole-rock and mineral analyses of 26 'new' type A and B Apollo 17 basalts are reported. The petrography and mineral chemistry of these basalts are similar to previously reported Apollo 17 basalts. However, these 'new' whole-rock data extend the compositional ranges of previously reported type A and B basalts and require the division of the type B basalts into type B1 and B2 varieties. These three types display similar trends when both major and trace elements are plotted against a fractionation index of Cr/La ratio. Major element compositions of basalts from all three types fall on olivine + Ti oxide control lines. This study demonstrates that Apollo 17 type A, B1, and B2 basalts have a relatively simple petrogenesis, with the only postmagma-generation process being fractional crystallization.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 54; 1817-183
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  • 8
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    In:  Other Sources
    Publication Date: 2019-07-12
    Description: Zr/Hf ratios and other elemental data in 68 samples of various mare basalts, KREEP units, and lunar glasses have been determined using instrumental neutron activation analysis coupled with coincidence-anticoincidence counting for greater precision. The data are presented in order to quantify further the amount of Zr/Hf fractionation that has occurred during primordial crystallization and cumulate remelting or by any other process. Models of Zr-Hf evolution are developed to place additional constraints on the bulk lunar composition and on the effects of minor phases that may be responsible for the observed fractionations. The Hf-Ta fractionation in lunar compositions is also reviewed in order to characterize normal Hf(4+) versus Ta(4+) behavior and to delineate possible effects due to the oxidation of Ta(4+) to Ta(5+) during late-stage ilmenite crystallization.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research, Supplement (ISSN 0148-0227); 90; D31-D45
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  • 9
    Publication Date: 2019-07-12
    Description: Using the subdivision of Apollo 16 regolith breccias into ancient (about 4 Gyr) and younger samples (McKay et al., 1986), with the present-day soils as a third sample, a petrologic and chemical determination of regolith evolution and exotic component addition at the A-16 site was performed. The modal petrologies and mineral and chemical compositions of the regolith breccias in the region are presented. It is shown that the early regolith was composed of fragments of plutonic rocks, impact melt rocks, and minerals and impact glasses. It is found that KREEP lithologies and impact melts formed early in lunar history. The mare components, mainly orange high-TiO2 glass and green low-TiO2 glass, were added to the site after formation of the ancient breccias and prior to the formation of young breccias. The major change in the regolith since the formation of the young breccias is an increase in maturity represented by the formation of fused soil particles with prolonged exposure to micrometeorite impacts.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters (ISSN 0012-821X); 89; 2 Ju
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  • 10
    Publication Date: 2019-07-13
    Description: An INAA analysis of 16 individual spherules of orange volcanic glass extracted from the 74220,680 soil was performed in order to determine trace element signatures in a primary high-Ti mare magma. The composition of these glasses is shown to be nearly identical to that of 74220 bulk soil, indicating a general absence of constituents other than volcanic glass in the soil. The results suggest that the evolving lunar mantle included processes of cumulate-mass transport and/or segregation of the primordial lunar magma ocean into separate differentiating zones, allowing commingling of early and late components.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Lunar and Planetary Science Conference; Mar 14, 1988 - Mar 18, 1988; Houston, TX; United States
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