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At least 1,081 records · Page 60
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NASA NTRS1971

Mineralogy of Apollo 15415 ?genesis rock' - Source of anorthosite on moon.

Results of electron microprobe analyses of plagioclase points and pyroxene grains of Apollo 15415 ?genesis rock.' It is pointed out that no evidence of cumulate textures has yet appeared to support suggestions of extensive crystal-liquid differentiation producing an anorthositic crust or a lunar crust composed of a mixture of plagioclase-rich rock, basalts and minor ultramafic material, which require that plagioclase crystals float in a basaltic liquid. The plagioclase in 15415 does not show cumulate texture either. It is noted that it remains to be seen whether rock 15415 is correctly named the ?genesis rock.'

Steele, I. M.↗
NASA NTRS1972

Petrology of basaltic and monomineralic soil fragments from the Sea of Fertility.

Basaltic and monomineralic fragments from the 150-425 micron size fractions of the Luna 16 core obtained from the Sea of Fertility were studied by optical petrographic, electron microprobe, and single-crystal X-ray diffraction techniques. Three textural varieties were identified in the basalts (intersertal, subophitic, and recrystallized). These textures, the assemblages, and individual mineral compositions (especially pyroxenes) indicate that these basalts crystallized under conditions very similar to those from Apollo 11. The pyroxenes have slightly lower Ti/Al (atomic) ratios than the Apollo 11 pyroxenes. We interpret the presence of octahedral Al as being due to the low TiO2/Al2O3 (weight %) ratio in the bulk rock. All observations made on the fine-grained basalt fragments are consistent with a rapid, near-surface, one-stage crystallization history.

Bence, A. E.↗
NASA NTRS1972

An evaluation of some unbraked tire cornering force characteristics

An investigation to determine the effects of pavement surface condition on the cornering forces developed by a group of 6.50x13 automobile tires of different tread design was conducted at the Langley aircraft landing loads and traction facility. The tests were made at fixed yaw angles of 3,4.5, and 6 deg at forward speeds up to 80 knots on two concrete surfaces of different texture under dry, damp, and flooded conditions. The results showed that the cornering forces were extremely sensitive to tread pattern and runway surface texture under all conditions and that under flooded conditions tire hydroplaning and complete loss of cornering force occurred at a forward velocity predicted from an existing formula based on tire inflation pressure. Futher, tests on the damp concrete with a smooth tire and a four-groove tire showed higher cornering forces at a yaw angle of 3 deg than at 4.5 deg; this indicated that maximum cornering forces are developed at extremely small steering angles under these conditions.

Leland, T. J. W.↗
NASA NTRS1972

Preliminary examination of lunar samples. Part A: A petrographic and chemical description of samples from the lunar highlands

Chemical, petrographic, and textural characteristics of a representative collection of the Apollo 16 rock and soil samples are reported. The macroscopic and microscopic texture are the result of two or more events in the history of any given sample. Cataclastic, highly crushed rocks are common along with complex intergrowths of shock-produced glass, devitrified glass, and pre-existing clasts. The dominant chemical feature is the high abundance of aluminum and calcium. In terms of their petrogenesis, the rocks are typed as cataclastically, and cataclysmically modified anorthosites; igneous; and polymict breccias.

Source record↗
NASA NTRS1973

Combined spectral and spatial processing of ERTS imagery data

A procedure for extracting a set of textural features for ERTS-1 MSS data is presented. The textural features were combined with a set of spectral features and were used to develop a classification algorithm for identifying the land use categories of blocks of digital MSS data. The classification algorithm was derived from a training set of 314 blocks and tested on a set of 310 blocks. The overall accuracy of the classifier was found to be 83.5% on seven land use categories.

Haralick, R. M.↗
NASA NTRS1972

Sedimentology of clastic rocks returned from the moon by Apollo 15.

A petrographic study of eleven samples of clastic rock returned from the moon by Apollo 15 suggests that two lithologies are present. The distinction between the two lithologies is based on the glass content of the rock matrices and the morphology of the detrital particles. Group I rocks have abundant, glass-rich, porous matrices and glass particles with morphologies comparable to those of glass particles in the lunar soil. The group I rocks were probably formed by welding or sintering of surficial soil deposits by impact-generated base surges of limited extent. Group II rocks have an essentially mineralic matrix and have an abundance of rounded mineral grains. Sample 15455 is the only Apollo 15 sample assigned to this group. In its general textural features, sample 15455 is comparable with the group II rocks from the Fra Mauro Formation at the Apollo 14 site. Textural features such as shock modification and rounding of mineral grains suggest that this sample is the product of a large-scale impact-generated base surge which possibly resulted from the Imbrian event.

Lindsay, J. F.↗
NASA NTRS1972

Spatial frequency analysis of multispectral data.

This paper presents the definitions of texture dependent features which can be obtained in terms of the spatial frequencies of small sections of remotely sensed multispectral data. The features are made independent of the direction of view by defining them as symmetric functions of the spatial frequencies sensed with various viewing directions. Several textural features are defined and experimental results indicating existence of signatures in these features are presented. Preliminary experiments have been performed on the classification of 60 samples, 10 from each of the following 6 categories - grass, trees, water, staked tomatoes, treated ground tomatoes, and untreated ground tomatoes. Classifications of the training samples using only one feature at a time indicate that several of the features yield classification efficiencies higher than 65%. The efficiency increases considerably when combinations of these features are used.

Ramapriyan, H. K.↗
NASA NTRS1972

Mineralogy and origin of Fra Mauro fines and breccias.

Textural features, glassy spherule and glassy aggregate contents, and size-frequency distributions of lithic components of the regolith fines indicate that the Fra Mauro regolith of the smooth terrain is a highly reworked accumulation of debris derived primarily by impact comminution of annealed breccias. Analyses of the glassy spherules suggest that mare-derived debris must amount to less than 5% of the regolith, but exotic materials having the composition of the Fra Mauro breccias (highland-like) cannot be recognized. Breccia samples from the Fra Mauro site include (1) regolith breccias derived by lithification of local regolith material, (2) texturally and compositionally unique white rock breccias that may have been derived from ancient ejecta buried beneath the Fra Mauro formation, and (3) annealed breccias that are excavated samples of the Fra Mauro formation. The latter were deposited as heated impact ejecta, probably by avalanches produced by the Imbrian event and were annealed in situ in a thermal regime perhaps equivalent to that responsible for the pyroxene-hornfels facies of metamorphism in terrestrial rocks.

Quaide, W.↗
NASA NTRS1972

Experimental petrology and origin of Fra Mauro rocks and soil.

Results of melting experiments over the pressure range from 0 to 20 kb on Apollo 14 igneous rocks 14310 and 14072, and on comprehensive fines 14259. It is found that low-pressure crystallization of rocks 14310 and 14072 proceeds as predicted from the textural relationships displayed by thin sections of these rocks. The mineralogy and textures of these rocks are the result of near-surface crystallization. The chemical compositions of these lunar samples all show special relationships to multiply saturated liquids in the system anorthite-forsterite-fayalite-silica at low pressure. Partial melting of a lunar crust consisting largely of plagioclase, low-calcium pyroxene, and olivine, followed by crystal fractionation at the lunar surface, is a satisfactory mechanism for the production of the igneous rocks and soil glasses sampled by Apollo 14. The KREEP component of other lunar soils, may have a similar origin.

Walker, D.↗
NASA NTRS1972

The Haveroe ureilite - Petrographic notes.

Review of the mineralogy and texture of the Haveroe and of some of the six other known ureilites, and assessment of the implications of their observed characteristics. In common with other ureilites, Haveroe shows mineralogical and textural evidence of preterrestrial shock. The olivines and metal grains have been recrystallized, the fabric includes angular voids, and graphite-rich areas are present that have been partially converted to diamonds with some indication of lonsdaleite. On the basis of such features, a subdivision of ureilites into particular types is proposed.

Marvin, U. B.↗
NASA NTRS1973

Apollo 17 lunar samples - Chemical and petrographic description

Some of the Apollo 17 rocks have the cataclastic, highly crushed textures common in the Apollo 16 return. Many are crystalline breccias whose petrographic characteristics indicate varying degrees of recrystallization or partial melting. Others are friable and dark gray like the many regolith breccias of previous missions. A few have the coarse-grained igneous textures typically developed during the slow crystallization from basaltic melts. Petrographic and soil characteristics are discussed together with the results of X-ray fluorescence analyses.

Source record↗
NASA NTRS1973

The petrology of 76055,10, a thermally metamorphosed fragment-laden olivine micronorite hornfels

General petrographic description of a large regolith specimen collected at the Taurus-Littrow landing site of Apollo 17. The specimen consists of a large clast of olivine micronorite hornfels with well-devepoled porphyroblastic texture, surrounded by highly vesicular olivine micronorite hornfels with incipient development of the porphyroblastic textures. Pink spinels with radial anorthite rims occur in both the clast and the surrounding matrix.

Chao, E. C. T.↗
NASA NTRS1974

A chemical model for lunar non-mare rocks

Nearly all rocks returned from the moon are readily divided into three broad categories on the basis of their chemical compositions: (1) mare basalts, (2) non-mare rocks of basaltic composition (KREEP, VHA), and (3) anorthositic rocks. Only mare basalts may unambiguously be considered to have original igneous textures and are widely understood to have an igneous origin. Nearly all other lunar rocks have lost their original textures during metamorphic and impact processes. It is shown that for these rocks one must work primarily with chemical data in order to recognize and define rock groups and their possible modes of origin. Non-mare rocks of basaltic composition have chemical compositions consistent with an origin by partial melting of the lunar interior. The simplest origin for rocks of anorthositic chemical composition is the crystallization and removal of ferromagnesian minerals. It is proposed that the rock groups of anorthositic and non-mare basaltic chemical composition could have been generated from a single series of original but not necessarily primitive lunar materials.

Hubbard, N. J.↗
NASA NTRS1974

Lunar highland rock types: Their implications for impact induced fractionation

The first step in a petrologic study must be a classification based on observed textures and mineralogy. Lunar rocks, may be classified into three major groups: (1) coarse-grained igneous rocks, (2) fine-grained igneous rocks and (3) breccias. Group 1 is interpreted as primitive lunar crustal rocks that display various degrees of crushing and/or annealing. Group 2 is interpreted as volcanic rocks. Group 3 is interpreted as resulting from impacts on the lunar surface and is subdivided on the basis of matrix textures into fragmental breccias, crystalline breccias that have been annealed, and crystalline breccias with igneous matrices. A synthesis of the relevant data concerning lunar highlands polymict breccias from the fields of petrography, chemistry, photogeology, and impact studies compels the prediction that the breccias should have homogeneous matrices from rock to rock within regions of the highlands of limited size where impact mixing has been efficient and extensive.

Phinney, W. C.↗
NASA NTRS1975

V-grooved silicon solar cells

Silicon solar cells with macroscopic V-shaped grooves and microscopically texturized surfaces were made by preferential etching techniques. Various conditions for potassium hydroxide and hydrazine hydrate etching were investigated. Optical reflection losses from these surface were reduced. The reduced reflection occurred at all wavelengths and resulted in improved short circuit current and spectral response. Improved collection efficiency is also expected from this structure due to generation of carriers closer to the cell junction. Microscopic point measurements of collected current using a scanning electron microscope showed that current collected at the peaks of the texturized surface were only 80 percent of those collected in the valleys.

Baraona, C. R.↗
NASA NTRS1974

Dielectric properties of soils as a function of moisture content

Soil dielectric constant measurements are reviewed and the dependence of the dielectric constant on various soil parameters is determined. Moisture content is given special attention because of its practical significance in remote sensing and because it represents the single most influential parameter as far as soil dielectric properties are concerned. Relative complex dielectric constant curves are derived as a function of volumetric soil water content at three frequencies (1.3 GHz, 4.0 GHz, and 10.0 GHz) for each of three soil textures (sand, loam, and clay). These curves, presented in both tabular and graphical form, were chosen as representative of the reported experimental data. Calculations based on these curves showed that the power reflection coefficient and emissivity, unlike skin depth, vary only slightly as a function of frequency and soil texture.

Cihlar, J.↗
NASA NTRS1974

Plagioclase twin laws in lunar highland rocks - Possible petrogenetic significance

Plagioclases in different types of lunar highland rocks (all highly feldspathic) are twinned according to different laws and in different styles. Carlsbad and Carlsbad-albite twins, presumed to be growth twins, occur mainly in rocks which show igneous texture, and which have not been severely brecciated. These two twin laws appear to be absent from cataclastic rocks, including cataclastic anorthosite, possibly because the original twins were preferentially broken up in cataclasis (the composition plane being a plane of weakness). Pericline and lamellar albite twins, presumed to be deformation twins (except for some albite growth twins) occur in all types of rocks, and obvious deformation features, such as bending of lamellae, are well shown in many cataclastic rocks. Surprisingly, some Carlsbad and Carlsbad-albite twins are found in rocks with granoblastic texture, which presumably recrystallized in the solid state.

Dowty, E.↗
NASA NTRS1974

Lunar deposits of possible pyroclastic origin

Orange glass droplets sampled from the Apollo 17 site were found to be both chemically and texturally homogeneous. None of these droplets, which are of possible pyroclastic origin, contained shock-damaged crystals which are common in glass produced by meteorite impacts. Black droplets are apparently the partially crystallized equivalents of the orange glass. Since chemically and texturally homogeneous glass droplets are known to form in terrestrial lava fountains of basaltic melt, the orange glasses from Apollo 11 and 17 sites and the green glasses from the Apollo 15 site may have formed in lava fountains of low-viscosity lunar basaltic magmas.

Heiken, G. H.↗