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At least 1,513 records · Page 84
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Outflow of chromospheric emission features from the rim of a sunspot

In viewing a 16 mm movie made from a time sequence of spectroheliograms, some of these emission features are found to move outward from the rim of the sunspot until they are eventually lost in the small plage. There are two interpretations for the streaming of the magnetic features. It is possible that kinks in the line of force propagate along a horizontal extension of the penumbral magnetic field. Alternatively, fragments of the sunspot magnetic field are carried away by the photospheric velocity field.

Liu, S.-Y.↗
NASA NTRS1973

Vitrification darkening of rock powders - Implications for optical properties of the lunar surface

Laboratory experiments show that albedoes as low as those on the moon can be produced by vacuum vitrification and associated chemical fractionation of ordinary terrestrial basaltic material. Vitrification is established as an unequivocal process that can account for the low albedo and apparent local darkening with age of the lunar surface. The spectral reflectance curves of glass powders are significantly different than those of the parent rock mineralogy; thus, the presence of ubiquitous glass in lunar surface material complicates compositional determinations by interpretation of spectral reflectance curves. Vitrification of rocks on the moon may highly modify the chemical composition of the resulting glass; thus, glass fragments found in lunar fines cannot be assumed to represent bulk parent rock material. Progressive impact vitrification of lunar surface material throughout the moon's history may have led to a fine-grain, opaque, refractory-rich material we call 'ultimate glass.' This unidentified and, at this point, hypothetical component may exist in dark regolith material; if found, it may be a useful indicator of regolith maturity.

Nash, D. B.↗
NASA NTRS1973

The relative abundance of the isotopes of Li, Be and B and the age of cosmic rays

Using a balloon borne double dE/dx total energy telescope, we have determined the isotopic composition of cosmic ray Li, Be and B nuclei in the energy range 100-250 MeV/nuc. The measured mass resolution for these nuclei is about 0.3 AMU. The observed isotopic composition is in agreement with that predicted on the basis of interstellar fragmentation with the exception of a deficiency of Be-10. If the low abundance of Be-10 is attributed to the decay of this radioactive isotope, we obtain a mean cosmic ray lifetime of 3.4 (plus 3.4 or minus 1.3) m.y.

Webber, W. R.↗
NASA NTRS1973

Photoionization of carbon dioxide

Investigation of the mechanism for dissociative ionization of CO2 on the basis of measurements of the yields of photoions from CO2. It is found that at photon energies immediately above the molecular ionization limit of 13.773 plus or minus 0.002 eV the photoion yield curve exhibits a number of closely spaced peaks in a pattern not resembling Rydberg series. Two fragment ions, O(+) and CO(+), are observed as products of dissociative ionization. The yield of O(+) follows a weak, oscillatory curve from the thermochemical threshold at 19.07 eV to 19.39 eV, where a sudden increase in O(+) yield is observed exactly at the onset of the state CO2(+)/C 2 Sigma g (+)/, indicating predissociation of this state of the molecular ion. The magnitude of the jump in O(+) yield at 19.39 eV suggests that this predissociation is the principal mechanism for dissociative ionization.

Mcculloh, K. E.↗
NASA NTRS1973

Origin of lunar feldspathic rocks

Melting experiments and petrographic studies of lunar feldspathic rocks reveal possible genetic relationships among several compositionally and mineralogically distinct groups of lunar rocks and soil fragments. Dry, low PO2 partial melting of crustal anorthositic norites of the anorthositic-noritic-troctolitic (ANT) suite produces liquids of the KREEP-Fra Mauro basalt type; dry, low PO2 partial melting of pink spinel troctolite (PST) produces liquids of the 'very high alumina basalt' or microtroctolite type. Both ANT and PST are probable components of the primitive terra crust. If crystal fractionation in a cooling basaltic liquid could have produced such a crust, it would also produce a mafic interior capable of yielding mare basalts by later remelting at depth.

Walker, D.↗
NASA NTRS1973

The South Ray Crater age paradox

Relative exposure ages based on agglutinate content are calculated for 26 Apollo 16 surface and core samples. These ages increase from the northern part of the traverse to the southern part and are in general agreement with cosmogenic gas ages and particle track ages. An apparent paradox exists in which presumed ray soil from South Ray Crater is much older than the age of South Ray Crater itself as determined by a variety of methods. The most likely explanation for the paradox is that the presumed South Ray Crater soil is not ejecta from South Ray Crater but is pre-existing regolith upon which blocks and fragments from South Ray Crater are scattered.

Mckay, D. S.↗
NASA NTRS1973

Analysis of the ultrafine fraction of the Apollo 14 regolith

Analyses were obtained on more than 2400 randomly selected particles from the sub-37 micron (ultrafine) fraction of ten Apollo 14 regolith samples. The analyses were conducted with an energy dispersive electron microprobe system. The semiquantitative data were used to group the particles into ten categories. The pyroxene/plagioclase and olivine/plagioclase ratios are inconsistent with those ratios in the Apollo 14 breccias and rocks. The data suggest that fragmented basalts similar to Apollo 12 olivine basalts may have made significant contributions to the ultrafine fraction of the Fra Mauro regolith. Among a number of unusual particles encountered are brown, birefringent lath-shaped grains with 60 wt % SiO2 and 34 wt % FeO(FeSi2O5) and a glass with 20 to 25 wt % CaO, 0 to 8 wt % MgO, 40 to 45 wt % Al2O3 and approximately 30 wt % SiO2.

Finkelman, R. B.↗
NASA NTRS1973

Preliminary stratigraphy of the Apollo 15 drill core

The crew of Apollo 15 collected a 242-cm-long core of the regolith developed on the surface of Palus Putredinus (3 deg 39 min 20 sec E, 26 deg 26 min 00 sec N). This core consists of 42 major textural units, which range from a few millimeters to 13 cm thick. The regolith at this site was deposited layer by layer, each layer having been reworked, to some degree, by micrometeorite bombardment. The particle composition of six layers for which samples were obtained varies in a random fashion, thus supporting the heterogeneous, layered model of the regolith. The ratio of lithic fragments derived from the Apennine Front to that derived from the mare surface is about 1:1. This lithic ratio, in a regolith section 3.75 km from the base of the front, is an indication of the efficiency of lateral transport of soil by impact processes and mass wasting.

Heiken, G.↗
NASA NTRS1973

Apollo 16 rocks - Classification and petrogenetic model

The Apollo 16 rocks include cataclastic anorthosites, two varieties of unequilibrated breccia, two varieties of partly to fully equilibrated breccia, and a sequence of partially melted breccias. The latter, which dominate the Apollo 16 collection, include glass, divitrified glass, mesostasis-olivine-plagioclase rock, mesostasis-rich basalt, basalt, and poikilitic rocks. All sequence members contain vesicles and relics of plagioclase, olivine, pink spinel, and lithic fragments. Their equilibrated matrices define a series from glass, to a plagioclase-olivine-mesostasis assemblage displaying spherulitic and skeletal shaped crystals, through a plagioclase-pyroxene-olivine assemblage displaying euhedral shaped crystals. Such data suggest that the sequence lithologies were derived from breccias or soils that were partially melted in an impact event.

Warner, J. L.↗
NASA NTRS1973

Mineralogy and petrology of some Apollo 16 rocks and fines - General petrologic model of moon

Data published in the literature and original results of mineralogical and petrological analyses of Apollo 16 rocks and fines indicate that Apollo 16 and Luna 20 sites are dominated by plagioclase-rich rocks with minor olivine and/or pyroxene. Data suggest that shock, brecciation, and recrystallization have largely eliminated primary textures. In general, all data are consistent with derivation from ejecta blankets produced from plagioclase-rich rocks by impacts. The lunar crust is discussed as a product of an early differentiation of the entire moon, and Mg/Fe data for experimental olivine-liquid and olivine-orthopyroxene equilibria are used as constraints to examine compositional data for rocks, glasses, and fragments in the light of specific models for crystal-liquid differentiation.

Steele, I. M.↗
NASA NTRS1973

The distribution in lunar soil of carbon released by pyrolysis

The carbon contents of various lunar soil particle types and sieve fractions of Apollo 15 and 16 samples have been determined by the pyrolysis method. The mineral, glass, and high-grade breccia fragments in the soils examined contain relatively low amounts of carbon (approximately 8, 25, and 25 microg C/g sample respectively in 149-250 micron grains). Most low-grade breccias and all agglutinates examined have high carbon contents (approximately 52 and 80 microg C/g sample respectively), and agglutinate abundance is indicative of the carbon content and maturity of a soil. The distribution of carbon with respect to particle size in mature soils generally reveals a minimum in carbon content at about 100 micron particle diameter. At smaller particle diameters, carbon content is directly proportional to particle surface area and therefore increases with the ratio (surface area)/(particle mass). A model relating the cycle of comminution and aggregation of soil particles to the redistribution of surface implanted carbon is developed.

Desmarais, D. J.↗
NASA NTRS1973

Rb-Sr systematics for chemically defined Apollo 15 and 16 materials

Concentrations of Rb and Sr and the Sr87/86 ratios are determined in a large number of Apollo 15 samples, including KREEP basalts, mare basalts, anorthosite breccia clasts, lithic fragments, a spinel-bearing clast, green glass samples, breccia matrix, and soils. Relative concentrations of Sm, Eu, Rb, and Sr are also examined in the samples, with particular attention to Rb/Sr systematics vs other trace element abundances and total chemical compositions of rocks. Analysis of crystalline KREEP samples rich in trace elements indicates that the differentiation of these rocks has extended to -4.25 AE age, a significantly later time than the presumed time of accretion of the moon.

Nyquist, L. E.↗
NASA NTRS1973

The relative density of lunar soil

The specific gravity and minimum and maximum bulk densities were determined for three one-gram lunar soil samples containing particles less than 1 mm in diameter: 14163,148; 14259,3; and 15601,82. The specific gravity varied from 2.90 to 2.93 for the Apollo 14 samples to 3.24 for the Apollo 15 sample. The difference is attributed to the higher proportion of agglutinates and breccias and fewer mineral fragments and basalts in the Apollo 14 soils. The minimum bulk densities varied from 0.87 to 1.10 g/cu cm, while the maximum densities varied from 1.51 to 1.89 g/cu cm. The ranges in values were due to differences in the specific gravity, re-entrant intragranular voids, particle shape, surface texture, and grain arrangements. The in situ lunar soil in the plains areas of the moon can have a low to medium relative density at the surface, increasing rapidly to a very high relative density at depths greater than 10 to 20 cm.

Carrier, W. D., III↗
NASA NTRS1973

Characterization of fines from the Apollo 16 site

We describe the characteristics of Apollo 16 fines samples 61281,8; 65701,13; 66031,6; 67701,26; and 67712,16 observed microscopically during the course of size and magnetic separations. Sample 67712,16 is unique in that almost all grains are rounded and no glass welded aggregates are present. All samples except 67712,16 contained about 0.5 wt.% of metal fragments 45 microns or more in diameter including occasional spheres and large single crystals. Some of this metal showed rust spots. Moessbauer spectra showed all the samples to be high in olivine compared to samples from other Apollo sites and to vary significantly in modal composition from each other. The fine grained Fe metal content and the excess absorption area near zero velocity in the Moessbauer spectra both vary with particle size and regolith maturity in the way one would predict from our model of Fe metal reduction and agglomeration during glass aggregate formation.

Housley, R. M.↗
NASA NTRS1974

Organic synthesis in a simulated Jovian atmosphere. III - Synthesis of aminonitriles

The products from spark and semicorona discharges through mixtures simulating the Jovian atmosphere were analyzed by gas chromatography combined with mass spectrometry. When the reaction was performed at -80 C, 3-ethylaminopropionitrile and a number of higher homologs were formed. On the other hand, at +20 C, higher molecular-weight material appeared which yielded aminonitrile-derived fragments on mass spectrometry. Although the spectra were not identical, there were notable similarities between these and the mass spectra of some compounds present in the Murray and Orgeuil meteorites. Aminonitriles may occur as minor constituents of the Jovian atmosphere and perhaps by cyclization may produce pyrimidines.

Molton, P. M.↗
NASA NTRS1974

Comment on radar scattering from Saturn's rings

Strong 12.5 cm-wavelength radar echoes from Saturn's rings have been observed recently. The observed radar cross section of 0.62 (plus or minus 0.15) times the geometric area occupied by the optically observed A, B, and C rings seems too high based on radar experience with the terrestrial planets and the asteroids Icarus and Toro. An explanation of this phenomenon is proposed, based on the fact that backscattering from transparent spheres can show considerable gain over the simple external reflection from the front surface of an equivalent dielectric sphere. It is shown that only 10% of the optically observed material in the A, B, and C rings need consist of smooth ice fragments larger than 8 cm in radius to yield the radar results.

Pettengill, G. H.↗
NASA NTRS1974

Laboratory simulation of the herringbone pattern associated with lunar secondary crater chains

V-shaped ridge components of the herringbone pattern associated with lunar secondary crater chains have been simulated by simultaneous and nearly simultaneous impact of two projectiles near one another. The impact velocities and angles of the projectiles were similar to those of the fragments that produced secondary craters found at various ranges from large lunar craters. Variables found to affect the included angles of the V-shaped ridges are: relative time of impact of the projectiles, impact angle, relative projectile mass, and azimuth angle of the crater chain relative to the projection of the flight line onto the target surface. The functional relationships between the forms of the ridges and many of these variables are similar to those observed for lunar V-shaped ridges. Comparison of the magnitudes of the ridge angles of both laboratory crater pairs and secondary crater chains of the crater Copernicus implies that material was ejected from Copernicus at angles in excess of 60 deg, measured from the normal, to form many of Copernicus' satellite craters.

Oberbeck, V. R.↗
NASA NTRS1974

Measurements of the cosmic-ray Be/B ratio and the age of cosmic rays

The ratio Be/B depends on whether the confinement time of cosmic rays in the Galaxy is long or short compared to the radioactive half-life of Be-10. We report observations of this ratio which were obtained with a dE/dx-Cerenkov detector launched into a polar orbit on OGO-6 as part of the Caltech Solar and Galactic Cosmic Ray Experiment. Be/B ratios were determined for various rigidity thresholds up to 15 GV. We find no statistically significant rigidity dependence of the ratio, which is 0.41 plus or minus 0.02 when averaged over all observed cutoffs. Additional calculations suggest that if the present fragmentation parameters are correct, then the lifetime of cosmic rays in the Galaxy is less then 10 m.y.

Brown, J. W.↗