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NASA NTRS1972

Compositional data for twenty-one Fra Mauro lunar materials.

Major, minor, and trace element analyses are presented for two igneous rocks, six breccias, four microbreccias, two breccia clasts, and six soils, as well as a sample of sawdust from rock 14066. Evaluation of the data suggests that the samples from the Fra Mauro highlands have the same nonterrestrial characteristics shown previously by the samples returned from the mare regions by Apollo 11 and 12 - namely, a high refractory element content, a lower volatile element content, and an excess reducing capacity above that due to FeO. The Fra Mauro soils have higher concentrations of Al2O3, Na2O, and K2O and lower amounts of FeO and TiO2 than do the mare soils. They also show a bimodal distribution of Ni, B, and Nb. The highland breccias are richer in SiO2, Al2O3, MgO, Na2O, and K2O than those returned from the mare lowlands. FeO, TiO2, and MnO are lower in concentration at Fra Mauro, and the highland breccias are more complex mineralogically than those collected previously.

Rose, H. J., Jr.↗

NASA NTRS1975

Lava flows in Mare Imbrium - An evaluation of anomalously low earth-based radar reflectivity

The surface of Mare Imbrium contains some of the most distinct red-blue colorimetric boundaries and depolarized 70-cm wavelength-reflectivity variations on the near side of the moon. The weakest levels of both 3.8-cm and 70-cm reflectivity within Imbrium are confined to spectrally blue regional mare surfaces that can be recognized as stratigraphically unique flow surfaces. Frequency distributions of the 70-cm polarized and depolarized radar-return power for five mare surfaces within the basin indicate that signal absorption, and probably ilmenite content, increases generally from the beginning of the Imbrium Period to the end of the Eratosthenian Period with slight reversal between the end of the Imbrium and beginning of the Eratosthenian. TiO2 calibrated radar-reflectivity curves can be utilized for lunar-maria geochemical mapping in the same manner as the TiO2 calibrated spectral-reflectivity curves of Charette et al. (1974).

Schaber, G. D.↗

NASA NTRS1976

Correlation of photocurrent-voltage curves with flat-band potential for stable photoelectrodes for the photoelectrolysis of water

Using the differential capacitance technique, the flat-band potential of n-type TiO2, SnO2, SrTiO3, KTaO3, and KTa(0.77)Nb(0.23)O3 electrodes has been determined as a function of pH in aqueous electrolytes. Plots of flat-band potential vs. pH are linear in all cases and have a slope of approximately 0.059 V/pH unit. The flat-band potential correlates nicely with the onset for photoanodic currents corresponding to O2 evolution at the n-type semiconductor and H2 at the dark Pt cathode. The ordering of flat-band potentials at a given pH is SrTiO3 of the order of KTaO3 of the order of KTa(0.77)Nb(0.23)O3 greater than TiO2 greater than SnO2 (SnO2 most positive vs a saturated calomel electrode).

Bolts, J. M.↗

NASA NTRS1977

Complex refractive index of Martian dust - Wavelength dependence and composition

The size distribution and complex refractive index of Martian dust-cloud particles observed in 1971 with the Mariner 9 UV spectrometer are determined by matching the observed single-scattering albedo and phase function with Mie-scattering calculations for size distributions of spheres. Values of phase function times single-scattering albedo are presented for 12 wavelength intervals in the range from 190 to 350 nm, and best-fit values are obtained for the absorption index. It is found that the absorption index of the dust particles increases with decreasing wavelength from 350 to about 210 nm and then drops off shortward of 210 nm, with a structural shoulder occurring in the absorption spectrum between 240 and 250 nm. A search for a candidate material that can explain the strong UV absorption yields TiO2, whose anatase polymorph has an absorption spectrum matching that of the Martian dust. The TiO2 content of the dust particles is estimated to be a few percent or less.

Pang, K.↗

NASA NTRS1977

Very low-Ti mare basalts

Bulk compositions, petrology, and mineralogy of lithic fragments discovered in polished sections of Apollo 17 drill core samples 70007, 70008, and 70009 and Luna 24 soil 24077, 43 are described. The fragments have unambiguous affinities to mare basalts, but are exceptionally low in TiO2 (less than 1.0 wt.% TiO2). Apollo 17 rake sample 78526 is a green glassy rock of similar composition. Together the samples represent a distinct variety of mare basalts. Bulk compositional relationships suggest that they are related to Apollo 15 green glass, but the data do not permit one to discern the precise nature of the relationship. Both fractional crystallization and partial melting models can explain the observed compositional trends.

Taylor, G. J.↗

NASA NTRS1977

Photoelectrolysis of water at high current density - Use of ultraviolet laser excitation

The behavior of TiO2 and SrTiO3 photoanodes in cells for the photoelectrolysis of H2O has been investigated for high-intensity 351-,364-nm excitation from an Ar ion laser. Intensities up to 380 W/sq cm have been used. For TiO2 a small amount of surface decomposition is found after irradiation at high intensity, whereas SrTiO3 undergoes no detectable changes. Current-voltage properties for both electrodes are essentially independent of light intensity up to the level of 380 W/sq cm, and there is little if any change in quantum efficiency for electron flow. Photocurrent densities have been shown to exceed 5 A/sq cm for O2 evolution. Data show that the energy storage rate associated with the SrTiO3 photoelectrolysis can exceed 30 W/sq cm; this represents the highest demonstrated rate of sustained optical-to-chemical energy conversion.

Bocarsly, A. B.↗

NASA NTRS1977

Basalts from Mare Crisium

The stratified core sample returned from Mare Crisium by the Luna 24 unmanned space probe is composed primarily of a variety of subophitic to ophitic basalt with very low contents of TiO2 and MgO. This consists of clinopyroxene, calcic plagioclase, olivine, and minor amounts of silica, chromite, ulvoespinel, ilmenite, troilite, apatite, and Fe-metal. Granular metabasalts have the same bulk composition, but mineral phases exhibit less compositional variation. Fine-grained impact melts have similar compositions and are apparently derived from these basalts. It is concluded that the basalts, which are chemically distinct from the very-low-titanium basalts found elsewhere on the moon, represent the local surface flows of Mare Crisium. Sparse fragments of an olivine vitrophyre that is low in TiO2 but high in MgO and approaches the composition of the Apollo 15 green glasses may be derived from patches of dark mantling materials 20 km from the landing site.

Ryder, G.↗

NASA NTRS1975

On high-alumina mare basalts

Aluminous mare basalts have been found at several lunar sites, although they are not abundant. A group of crystalline clasts in breccia 14063 are also aluminous mare basalts with higher TiO2, Na2O, Mg/Fe ratio and lower FeO than other aluminous mare basalts. Composition of ilmenite clinopyroxene, and plagioclase confirm that crystallization took place from a melt with high TiO2 and Mg/Fe. A review of ages and siderophile trace-element abundances for aluminous mare basalts, suggests they are not hybrid rocks produced by melting of a mare + terra rock mix, but are pristine igneous melts from the lunar interior. Consideration of rare-earth element abundances indicate the source for aluminous mare basalts is pyroxenitic, with variable clinopyroxene/orthopyroxene ratio, and is not significantly different from the sources(s) of normal mare basalts.

Ridley, W. I.↗

NASA NTRS1975

Minor elements in lunar olivine as a petrologic indicator

Accurate electron microprobe analyses (approximately 50 ppm) were made for Al, Ca, Ti, Cr, Mn, and Ni in Mg-rich olivines which may derive from early lunar crust or deeper environments. Low-Ca contents consistently occur only in olivines from dunitic and troctolitic breccia: spinel troctolite and other rock types have high-Ca olivines suggesting derivation by near-surface processes. Rock 15445 has olivine with distinctly low CaO (approximately 0.01 wt.%). Chromium ranges to higher values (max.0.2 oxide wt.%) than for terrestrial harzburgites and lherzolites but is similar to the range in terrestrial komatiites. Divalent chromium may be indicated over trivalent Cr because olivines lack sufficient other elements for charge balance of the latter. NiO values in lunar specimens range from 0.00 to 0.07 wt.% and a weak anticorrelation with Cr2O3 suggests an oxidation state effect. Al2O3 values are mostly below 0.04-wt.% and show no obvious correlation with fragment type. TiO2 values lie below 0.13-wt.% and seem to correlate best with crystallization rate and plagioclase content of the host rock. High values of Al2O3 and TiO2 reported by other workers have not been confirmed, and are probably wrong.

Steele, I. M.↗

NASA NTRS1978

Chemical and Sr-isotopic characteristics of the Luna 24 samples

The chemical and Sr isotopic characteristics of Luna 24 bulk soil samples are determined and interpreted within the framework of lunar mare basalt evolution. Major and trace element compositions lead to the suggestion of candidate rock types consisting of a basalt/gabbro with very low TiO2 and MgO content (52%), a very low TiO2 basalt with 10% MgO (23%), olivine vitrophyre (20%), low K Fra Mauro basalt (4%) and anorthositic gabbro (1%). The proposed compositions are supported by the agreement of mixing models based on the proposed compositions with observed soil compositions. Sr ratios for plagioclase samples imply a lower Sr-87/Sr-86 value for low Mg soils than for other mare basalts and higher Rb/Sr and a more evolved Sr ratio in high Mg basalts. Rb, Sr and rare earth element compositions for low Mg basalts fit a model of partial remelting of cumulates containing small amounts of plagioclase.

Nyquist, L. E.↗

NASA NTRS1980

The effects of titanium impurities in N/+//P silicon solar cells

Microscopic and electrical measurements were performed to explain the degradation mechanisms associated with the presence of titanium impurities in silicon. The measurements included X-ray topography, transmission electron microscopy, and deep level transient spectroscopy, before and after processing. The results indicated the presence of TiO2 precipitates, the density of which increased after phosphorus diffusion. A majority carrier trapping level was observed in the wafers before processing. It was concluded that 10% of the Ti in the N(+)/P silicon solar cells formed electrically active centers which caused degradation of the cell junction. 14% of the remaining Ti precipitated out as TiO2, forming electrically active defects, which also caused junction degradation.

Salama, A. M.↗

NASA NTRS1981

Development of silane-hydrolysate binder for UV-resistant thermal control coatings

Detailed characterizaton and formulation studies were performed on a methyltriakoxysilane hydrolysate as a binder for thermal control coatings. The binder was optimized by varying hydrolysis temperature, time, catalyst type, and water concentration. The candidate coating formulations, based on this binder with TiO2 pigment, were optimized via a detailed series of sprayed test panels that included the parameters of binder/pigment ratio, ethanol content, pigment particle size, coating thickness and cure conditions. A typical optimized coating was prepared by acetic acid catalyzed hydrolysis of methyltriethoxysilane with 3.25 mol-equivalents of water over a 24 hour period at room temperature. The resulting hydrolysate was directly mixed with pre-milled TiO2 (12 grams pigment/26 grams binder) to yield a sprayable consistency. Panels were sprayed to result in a nominal cure coating thickness of 2 mils. Cure was affected by air drying for 24 hr at room temperature plus 72 hr at 150 F. These coatings are typically extremely tough and abrasion-resistant, with an absorptance (alpha) of 0.20 and emittance (e) of 0.89. No significant coating damage was observed in the mandrel bend test, even after exposure to thermal cycling from -160 to 160 F. Vacuum exposure of the coatings for 930 hours at 1 equivalent UV sun resulted in no visible degradation and no significant increase in absorptance.

Patterson, W. J.↗

NASA NTRS1983

Surface characterization of Ti and Ti (6 percent, Al-4 percent, V) metal powders and interaction with primer solutions

The interaction of Ti and Ti 6-4 powders with water and primer solutions was investigated experimentally by measuring the heats of immersion. Similar comparative studies were made on anatase and rutile TiO2 powders. The surface oxide layers of Ti and Ti 6-4 cracked on heating in vacuum between 300 and 400 C as evidenced by high heats of immersion in both water and primer solutions. Polyimide and polyphenylquinoxaline interacted preferentially, compared with the solvents with both metal powders after outgassing at room temperature. The heats of immersion of Ti 6-4 in water, solvents, and primer solutions increased significantly after pretreatment of the powder by an alkaline etch and a phosphate-fluoride process. The TiO2 powders were not satisfactory models for the surface oxide layer on either Ti or Ti 6-4 powder.

Siriwardane, R. V.↗

NASA NTRS1984

Achondrite ALHA77005 - Alteration of chromite and olivine

The olivine crystals of the 77005 achondrite are brown except for colorless shock lamellae, mottled patches, and grains adjacent to pools of impact melt. Sporadic dark alteration patches in brown olivine and Cr-rich spinel gave the following average electron-microprobe analyses: (olivine) P2O5 0.9, SiO2 57.9, TiO2 0, Al2O3 0.7, Cr2O3 0.4, V2O3 0, Fe2O3 (assumed oxidation state) 17.0, MgO 1.6, CaO 0.2, Na2O 0, K2O 1.8, SO3 (assumed oxidation state) 9.2, Cl 0.1, sum 89.8 wt pct; (spinel) P2O5 3.5, SiO2 2.1, TiO2 2.2, Al2O3 2.1, Cr2O3 13.4, V2O3 0.8, Fe2O3 40.7, MgO 0.9, CaO 0.1, Na2O 0, K2O 2.0, SO3 11.1, Cl 0.1, sum 79.0 wt pct. Ion-microprobe analyses revealed H in both. Rare orange patches in brown olivine from another area gave SiO2 33-35, FeO 30-28, MgO 28-32, sum 93 wt pct. Thermal metamorphism under dry oxidizing conditions is discussed as a possible alternative to shock-induced oxidation for generation of the brown olivine (McSween and Stoeffler, 1980). Because alteration patches transgress shock lamellae, and because sulfatic alteration occurs in fusion crusts of Antarctic meteorites (Gibson et al., 1983), alteration of the 77005 achondrite at the Antarctic surface is preferred to a complex series of processes needed for preterrestrial alteration.

Smith, J. V.↗

NASA NTRS1984

Petrology and geochemistry of lunar dimict breccia 61015

The results of a petrological and geochemical study of the dimict breccia 61015 at the Apollo 16 site are presented and discussed. The breccia consists predominantly of granulated anorthosite and impact melt rock of very high aluminum-basalt composition. It probably formed in the floor of an expanding crater cavity when impact melt generated within the cavity was injected into underlying anorthositic bedrock and solidified rapidly, the anorthosite and melt rock being fragmented by deformation in the later stages of the impact. A possible source crater for the breccia is identified. The breccia has been affected by at least one recent small impact, which produced internal shock-induced melting of the breccia and injected and coated the rock with externally derived melts. The TiO2 content of the coating and vein glasses establish that they cannot be melted soils; their composition requires a mafic, low-TiO2 protolith component.

James, O. B.↗

NASA NTRS1986

Composition of the Cayley Formation at Apollo 16 as inferred from impact melt splashes

Abundances of major and trace elements and magnetic properties of 50 impact melt splashes (IMSs) from the Apollo 16 landing site are analzyed to determine the composition of their meteoritic component. MgO-Sc and Ca-Sc variation diagrams and least-squares mixing models are utilized to analyze the IMS, soil, and rock data. Consideration is given to progenitor lithologies of the IMS, the number of impact events represented by the IMS, and the heterogeneity of impact melts from single events. It is observed that the IMSs are composed of either a mixture of anorthosite and low-Sc impact melt rocks or anorthositic norite. It is determined that the surface Cayley layer is composed of TiO2, MgO, Sc, and La concentrations of 0.69, and 7.1 wt pct and 10.5 and 21.2 microg/g, respectively and 0.38 and 5.9 wt pct and 6.1 and 11.8 microg/g, respectively, for the subsurface Cayley layer. The Descartes Formation composition is estimated as TiO2, MgO, Sc, and La concentrations of 0.25, and 3.5 wt pct and 7.7 and 2.2 microg/g, respectively.

Morris, Richard V.↗

NASA NTRS1986

Dependence of the critical cooling rate for lithium-silicate glass on nucleating agents

The critical cooling rate, Rc, for glass formation of a glass containing 40 mol pct Li2O and 60 mol pct SiO2, doped with small amounts of Pt, Au, P2O5, and TiO2 nucleating agents, has been measured. Rc increases with increasing Pt and Au additions, but Pt has a larger effect than Au. Additions of P2O5 tend to decrease Rc, whereas TiO2 has practically no effect on Rc. The devitrified glass nucleated with Pt contains only crystalline Li2O-SiO2, but all the other devitrified glasses, including the undoped glass, contain both Li2O-SiO2 and Li2O-2SiO2. Analysis shows that Rc increases as the concentration of the Li2O-SiO2 phase in the devitrified glass increases.

Huang, W.↗

NASA NTRS1987

Origin of SNC kaersutitic amphibole: Experimental data

The SNC meteorites, a group of cumulus textured, fine grained diabases, pyroxenites, and dunites, appear to have crystallized at relatively shallow depths on the same SNC parent body. Hydrous minerals generally are not present among the cumulus and intercumulus minerals in these meteorites except for some iddingsite alteration of olivine. The presence of hydrous magmatic amphibole in the SNC melt inclusions indicates that crystallization of the melt inclusions had to take place at significant pressure, probably greater than 1 kb based on previous amphibole stability data. If experimental data for kaersutite amphibole were to be obtained, it should be possible to estimate this pressure more precisely then previously, and to estimate the volatile (H2O) content of the parent magma. At this point, the factors controlling the chemistry and stability of high TiO2, kaersutitic amphiboles are not known. In an attempt to determine the factors which control the stability and chemistry of TiO2-rich amphibole, data was refined and extrapolated from four experimental studies of amphibole-melt equilibria recently completed. At the same time, hypothermal experiments were performed on a composition considered to be an early melt in the Shergotty magma liquid line of descent. The latter experiments were an attempt to reproduce crystallization of the amphibole-bearing melt inclusions.

Rutherford, M. J.↗