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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 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS1974

Silicate spherules in sample of regolith returned by Lunar 16 automatic station

The content of spherical fused particles in Sea of Fertility regolith increases with decrease in particle size and varies from 1 to 2 percent in the relatively coarse fractions to 3 to 4 percent in the fine fractions. Among the spherical formations was noted a wide diversity of shapes, and the most common are particles that are similar in shape to a regular sphere, which indicates the acquisition of shape in the liquid phase under the action of surface tension. As to color, the most common are the black and dark colored particles. No regularities of any kind were noted in the distribution of spherical particles by core zones. The considerable difference of the granulometric characteristics of the spherical particles and the regolith as a whole indicates that the formation of regolith particles and the spherules included in its composition occurred as the result of different, even though possibly simultaneous, processes.

Ivanov, A. V.↗
NASA NTRS1974

The distribution of Sr and REE between diopside and silicate liquid

Experimental determination of the distribution coefficients in diopside-liquid pairs for strontium and nine rare-earth elements in the system CaMgSi2O6-NaAlSi3O8-CaAl2Si2O8. In experiments in air at 1265 C it is found that most of the Sr(2+), Eu(2+), and RE(3+) ions substitute for Ca(2+) and, in addition, a coupled substitution of Al(3+) for Si(4+) occurs. All of the trace ions considered are found to be excluded from the diopside lattice relative to the liquid. In the case of the trivalent ions the exclusion is much more pronounced for La and Ce, which have ionic radii larger than that of Ca(2+) in 8-fold oxygen coordination. Divalent Sr and Eu with even larger radii are also strongly excluded.

Grutzeck, M.↗
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 NTRS1974

Spinel-silicate co-crystallization relations in sample 15555

The results on the crystallization history of medium-grained mare basalt sample 15555,171, based on microprobe analyses (Dalton, 1973) of host and inclusion mineral pairs are summarized with emphasis placed on that part of the crystallization history during which chromite and ulvospinel were crystallizing. Compositional data on pyroxene olivine, chromite and ulvospinel in 15555,171 were collected using microprobe; data are based on corrected counts ratios for nine elements. It is concluded that systematic chemical relations between host and inclusion minerals suggest continuous in situ nucleation and growth of these minerals; that the data allow the possibility of some minerals, especially chromite, settling out of the melt during crystallization; and that the chromite to ulvospinel transition is correlated with a compositional change of the melt resulting from nucleation and growth of plagioclase.

Dalton, J.↗
NASA NTRS1974

Equilibria bearing on the behavior of titanate phases during crystallization of iron silicate melts under strongly reducing conditions

Titanate phase relations at liquidus temperatures are determined for the CaAl2Si2O8-Fe2TiO4-FeTi2O5 system in contact with metallic iron by reflected- and transmitted-light microscopy, electron microprobe, and X-ray diffraction analyses. Results of critical equilibration runs are presented, various primary phase areas and liquidus isotherms are illustrated, and the geometry of the system is described. Three piercing points are determined, and it is noted that the compositional interrelations among coexisting crystalline and liquid phases as well as the sequence of the various titanate phases are indicative of the significant effects of the various cations on the relative stability of these phases. It is found that Al2O3 exerts a strong stabilizing effect on the phase assemblage of ulvospinel plus ferropseudobrookite relative to ilemite.

Lipin, B. R.↗
NASA NTRS1974

Metal silicate relationships in Apollo 17 soils

A petrographic, metallographic, and electron probe study of particles from two Apollo 17 soils is reported. A mixing model for the formation of the Apollo 17 soils is proposed. It is found that equilibration temperatures for two-phase metal aggregates range from 375 to 475 C for metal-phosphide particles and from 480 to 630 C for alpha-gamma particles, and that the anorthositic soil particles contain metal of meteoritic Ni-Co content. The Camelot Crater and the Sculptured Hills soil compositions are discussed.

Goldstein, J. I.↗
NASA NTRS1976

High-silica /greater than 60%/ lunar glasses in an Apollo 14 soil sample - Evidence for silicic lunar volcanism

The major-element compositions of 93 low-specific-gravity (less than 2.60) high-silica (greater than 60%) glass particles from a sample of lunar fines (14259,20) were determined by electron microprobe analyses. The size, shape, abundance, mineralogy, and major-element composition of more than 60% of the high-silica glasses is consistent with their being fragments of interstitial glass from mare basalts. However, one group of 30 glasses with between 72% and 78% SiO2 and an average of approximately 2.6% FeO can be distinguished from other high-silica glasses both chemically and petrographically. Glass particles with this composition do not contain crystalline inclusions and are fairly homogeneous not only within a single particle but also from particle to particle. The chemistry and petrology of these glasses suggest that they are not fragments of interstitial glass or shock-melted particles from a 'granitic' source rock. Rather, the homogeneity and lack of crystalline inclusions suggest that this group of high-silica glasses was the product of lunar acidic volcanism.

Glass, B. P.↗
NASA NTRS1976

Partitioning of chromium between silicate crystals and melts

Experiments were performed determining the distribution of chromium between olivine, pyroxenes, and melt at oxygen fugacity values near those of lunar rocks for a wide range of bulk compositions. The range of values of D-Cr (wt% of Cr2O3 in crystals/Cr2O3 in melt) is 0.6-1.3 for olivine and 1.6-3.5 for pyroxene; this ratio shows no obvious dependence on any experimental parameter.

Huebner, J. S.↗
NASA NTRS1977

Chemical compositions and possible immiscibility of two silicate melts in 12013

The lunar sample 12013, a complex mixture of gray breccia and black breccia, is described. The gray breccia consists of mostly basaltic and gabbroic lithic clasts as well as plagioclase and pyroxene mineral clasts set in a matrix of smaller clasts and a felsite of granitic composition, while the black breccia is comprised of mostly mineral clasts, some lithic clasts, and felsite blebs enclosed in an aphanitic groundmass of basaltic composition. Textural relationships indicate that the felsite and the black breccia groundmass crystallized from melts which coexisted prior to the final lithification of 12013 but failed to mix. Both the felsite and the black breccia groundmass have extreme enrichments of incompatible elements. The critical feature of their compositions is a 'splitting up' of incompatible element associations so that the highest REE and P concentrations are in the black breccia groundmass, and the highest K, Ba, and Rb concentrations are in the felsite.

Quick, J. E.↗