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NASA NTRS1978

Numerical solution of a three-dimensional shock wave and turbulent boundary-layer interaction

A rapid numerical scheme is used to solve the complete mass-averaged Navier-Stokes equations for supersonic turbulent flow over a three-dimensional compression corner. A simple eddy viscosity model is developed, and the interaction of a swept shock wave and a three-dimensional turbulent boundary layer is studied. Good agreement is obtained between the present results and experimental measurements for the case of a wedge with an angle of 6 deg on a flat-plate sidewall. For the case of a 12-deg wedge angle, the computed results do not show the existence of a peak pressure found experimentally. However, the range of interaction, the plateau pressure, and the peak heat transfer are closely predicted for all cases. The high heat transfer near the axial corner is due to the thinning of the boundary layer and inflow of fresh high-momentum fluid. The heat transfer is relieved through pressure reduction and boundary-layer thickening.

Hung, C. M.↗

NASA NTRS1978

Arecibo radar observations of Martian surface characteristics near the equator

Mars radar observations at 12.6-cm wavelength indicate that many of what were potential Viking landing sites along the planet's equator are rougher than interpretations of Mariner 9 images suggested. Root mean square surface slopes are typically 5 degrees in the region bounded by 160 and 200 degrees W, 0 and 12 degrees S. From Tharsis Montes west to 160 degrees W, radar-scattering characteristics suggest extreme roughness on small scales, perhaps exceeding 10 degrees in rms magnitude. East of Tharsis and north of Valles Marineris the surface is smooth, with values of rms slope as low as 1 degree; the elevation of this plateau was too high for a Viking landing. Study of spectral shapes indicates the Hagfors scattering law remains the best descriptor of quasi-specular surface scattering properties in an average sense; widespread variations in the surface argue against its indiscriminate use, however. Backscattering at moderate (25-40 degrees) incidence angles was studied qualitatively and was found to be significantly above the level predicted by a strictly quasi-specular (e.g., Hagfors) process; it also is variable over the surface.

Simpson, R. A.↗

NASA NTRS1978

Emptying patterns of the lung studied by multiple-breath N2 washout

Changes in the nitrogen concentration seen during the single-breath nitrogen washout reflect changes in relative flow (ventilation) from units with differing ventilation/volume ratios. The multiple-breath washout provides sufficient data on ventilation for units with varying ventilation/volume ratios to be plotted as a function of the volume expired. Flow from the dead space may also be determined. In young normals the emptying patterns are narrow and unimodal throughout the alveolar plateau with little or no flow from the dead space at the end of the breath. Older normals show more flow from the dead space, particularly toward the end of the breath, and some show a high ventilation/volume ratio mode early in the breath. Patients with obstructive lung disease have a high flow from the dead space which is present throughout the breath. A well ventilated mode at the end of the breath is seen in some obstructed subjects. Patients with cystic fibrosis showed a poorly ventilated mode appearing at the end of the breath as well as a very high dead space.

Lewis, S. M.↗

NASA NTRS1978

Are two photographic infrared sensors required

The possible redundancy of photographic infrared (0.70-1.00 micron) sensors for monitoring vegetation and plant stresses was investigated using previously published data and the analysis of in situ narrow bandpass spectral data from experimental grass plots. Results of the analysis showed that a 0.76-0.90 micron photographic infrared sensor would combine excellent general vegetational utility with the ability to discriminate photographic infrared plateau-rounding stress conditions. A 0.76-0.90 micron sensor is therefore suggested for Landsat-D.

Tucker, C. J.↗

NASA NTRS1978

Mars, highlands - lowlands: Viking contributions to Mariner relative age studies

Stratigraphic relations between lowland plains and highlands, two major types of Martian geologic-terrain units, were not directly distinguishable on Mariner-9 images. Morphologic characteristics and crater densities suggested that the lava plains beneath their eolian cover were younger than adjacent highland rocks, which form a plateau bounded in many places by highly dissected escarpments. Alternatively, the lowland plains could be the older unit and represent a broad erosional surface exhumed by southward retreat of the highlands along their frontal scarp. Viking photos across five areas of the highland-lowland boundary, however, tend to confirm the younger age of the plains-forming lava flows. A time interval of several hundred million years probably occurred between the retreat of the highland scarp and its latest embayment by lava extrusions in the lowlands.

Scott, D. H.↗

NASA NTRS1978

Manicouagan impact melt, Quebec. I - Stratigraphy, petrology, and chemistry

A sheet of clast-laden impact melt 230 m thick and 55 km in diameter forms an annular plateau surrounding an uplift of shocked anorthosite within the moderately eroded Manicouagan structure. Three gradational units of the melt sheet are characterized with respect to grain size, inclusions, texture, and mineralogy. The melt rocks as a group are chemically homogeneous with a bulk composition similar to that of latite and with no statistically significant regional chemical variations. The melt is not completely chemically homogeneous as a local mafic variant represented by two samples with poikilitic texture was found. These poikilitic rocks texturally resemble some Apollo 17 impact melt rocks and are inferred to have had a similar origin and thermal history.

Floran, R. J.↗

NASA NTRS1977

4.2-4.3 AE anorthositic soil fragments - Equilibrated or unequilibrated polycomponent systems

The petrographies and phase chemistries of five lunar crystalline anorthositic fragments with Ar-40/Ar-39 plateau 'ages' ranging from 4.1 to 4.3 AE are reported. An investigation is conducted to determine whether the individual fragments are monomict or polymict breccias. For polymict breccias it is attempted to establish whether clasts and matrix have equilibrated chemically. On the basis of the results of the investigation it is suggested that sample 73263,1,1 was a breccia (possibly a clast-laden melt) containing old clasts, incorporated in an ejecta blanket that was annealed at about 4.1 AE in a transient high-temperature event. The sample 73263,1,6 studied is an annealed anorthositic breccia containing approximately 20% clasts dominated by single-crystal plagioclase fragments. The obtained data are consistent with a two-component system containing old plagioclase clasts in a young (about 4.0 AE) annealed, matrix. The annealing event at approximately 4.0 AE was insufficient to equilibrate the argon. It is found that four of the breccias having ages of about 4.2 AE or more are polymict. The most striking feature of all of the samples studied is the presence of a significant amount of 4.2-4.3 AE argon.

Delano, J. W.↗

NASA NTRS1977

The Procellarum volcanic complexes - Contrasting styles of volcanism

Three major volcanic complexes have long been recognized in the Oceanus Procellarum region. Detailed study shows that the complexes share some characteristics and also display major differences which provide clues to eruption style. The Rumker Hills occupy 5000 sq km in northern Procellarum and are apparently Imbrian-Eratosthenian in age; they are dominated by domes, suggesting relatively low effusion rates. The Aristarchus Plateau-Prinz/Harbinger region occupies 40,000 sq km in central Procellarum and is predominantly Imbrian in age; it is dominated by large sinuous rilles and associated dark mantling deposits of probable pyroclastic origin, suggesting relatively high eruption rates. The Marius Hills occupy 35,000 sq km in south-central Procellarum and appear to be predominantly Eratosthenian in age; they are dominated by low domes, steep domes, cones, and sinuous rilles, suggesting variable eruption rates and possible different volatile contents associated with eruption conditions that produced each type of feature. The volcanic complexes, particularly Aristarchus and Marius, appear to be the sources for much of the central Procellarum mare fill.

Whitford-Stark, J. L.↗

NASA NTRS1978

Performance characteristics of high-conductivity channel electron multipliers

The paper describes a new type of continuous channel multiplier (CEM) fabricated from a low-resistance glass to produce a high-conductivity channel section and thereby obtain a high count-rate capability. The flat-cone cathode configuration of the CEM is specifically designed for the detection of astigmatic exit images from grazing-incidence spectrometers at the optimum angle of illumination for high detection efficiencies at XUV wavelengths. Typical operating voltages are in the range of 2500-2900 V with stable counting plateau slopes in the range 3-6% per 100-V increment. The modal gain at 2800 V was typically in the range (50-80) million. The modal gain falls off at count rates in excess of about 20,000 per sec. The detection efficiency remains essentially constant to count rates in excess of 2 million per sec. Higher detection efficiencies (better than 20%) are obtained by coating the CEM with MgF2. In life tests of coated CEMs, no measurable change in detection efficiency was measured to a total accumulated signal of 2 times 10 to the 11th power counts.

Timothy, J. G.↗

NASA NTRS1978

Use of manual densitometry in land cover classification

Through use of manual spot densitometry values derived from multitemporal 1:24,000 color infrared aircraft photography, areas as small as one hectare in the Cumberland Plateau in Kentucky were accurately classified into one of eight ground cover groups. If distinguishing between undisturbed and disturbed forest areas is the sole criterion of interest, classification results are highly accurate if based on imagery taken during foliated ground cover conditions. Multiseasonal imagery analysis was superior to single data analysis, and transparencies from prefoliated conditions gave better separation of conifers and hardwoods than did those from foliated conditions.

Jordan, D. C.↗

NASA NTRS1978

Synoptic analysis of interplanetary radio scintillation spectra observed at 34 MHz

Synoptic observations of the temporal power spectrum of interplanetary scintillations were made in the summer of 1976 on the University of Iowa's Cocoa Cross radio telescope and the University of Maryland's TPT array. Most of the observations were at large (larger than 40 deg) solar elongations. It was found that the power spectrum broadens when enhanced turbulence at the front of a high-speed solar wind stream sweeps over the earth. In the case with sufficient synoptic coverage, the broadening appeared to result from the relative closeness of the enhanced scattering region rather than from an increase in velocity. A small percentage of the spectra displayed two power law components with a plateau between them. These may result from a flattening in the spatial turbulence spectrum such as has been observed by spacecraft.

Gotwols, B. L.↗

NASA NTRS1979

Implications of very long baseline interferometry measurements on North American intra-plate crustal deformation

Very Long Baseline Interferometry experiments over the last 1-3/4 years between Owens Valley, CA and Haystack, MA Radio Observatories suggest an upper limit of east-west crustal deformation between the two sites of about 1 cm/yr. In view of the fact that the baseline between the two sites traverses most of the major geological provinces of the United States, this low rate of crustal deformation has direct relevance to intra-plate crustal tectonics. The most active region traversed by this baseline is the Basin and Range province, which was estimated by various researchers to be expanding in an east-west direction at rates of .3 to 1.5 cm/yr. The Colorado Plateau and Rocky Mountain system also appear to be expanding, but at a somewhat lower rate, while east of the Rocky Mountains, the predominant stress appears to be compressional, nearly horizontal, and east to northeast trending.

Allenby, R. J.↗

NASA NTRS1978

The Spokane flood controversy and the Martian outflow channels

The controversy over Bretz's hypothesis concerning the cataclysmic Spokane flood is discussed. Attention is directed to similarities between the Channeled Scabland of Washington and some Martian land features considered to be catastrophic flood channels. Characteristics of the enormous plexus of proglacial stream channels eroded into the loess and basalt of the Columbia Plateau in eastern Washington are described. The controversiality of the suggestion that a catastrophic flood is responsible for the Martian features is considered with respect to the Spokane flood controversy.

Baker, V. R.↗

NASA NTRS1978

Feldspathic granulite 79215 - Limitations on T-fo2 conditions and time of metamorphism

Feldspathic granulite 79215, an annealed polymict breccia which has a bulk composition between anorthositic gabbro and gabbroic anorthosite, contains numerous oxide complexes in the matrix. An Ar-39-Ar-40 stepwise heating experiment gives a well-defined plateau corresponding to an age of 4.03 + or - 0.02 AE. The polmict character of this breccia and the variability of the complexes suggest that they formed as a consequence of reactions between spinel-rich clasts and matrix under the high-T low-P conditions of an ejecta blanket. The duration of annealing is estimated to have been less than 10 million yr; the absence of a KREEP component may indicate an inhomogeneous distribution of this component at the lunar surface at 4.0 AE.

Mcgee, J. J.↗

NASA NTRS1978

Ar-40-Ar-39 microanalysis of single 74220 glass balls and 72435 breccia clasts

Ar-40-Ar-39 age measurements on single orange glass balls from the Apollo 17 soil 74220 and individual clasts from the Apollo 17 highland breccia 72435 are reported. The measurements required the use of newly established microanalytical techniques to obtain high quality analyses on about 0.5 mg particles with only a few hundred ppm K. An age of 3.60 plus or minus 0.04 b.y. is determined for the orange glass. No corrections for a trapped Ar-40 component were required. The glass forming event occurred at the very end of or after the extrusion of the mare basalts at the Apollo 17 site. An extremely well defined age plateau at 3.86 plus or minus 0.04 b.y. was determined for a 72435 plagioclase clast with attached matrix. A second large plagioclase crystal yielded significantly older ages over the last 60% of Ar release at high temperatures and is a relict clast incompletely degassed at the time of breccia formation. 72435 also contains plagioclase clasts with primitive Sr and a 4.55 AE old dunite clast. The Ar results provide additional evidence for the association of chemically unequilibrated, relict clasts with both primitive Sr and older K/Ar ages.

Huneke, J. C.↗

NASA NTRS1978

Ar-39-Ar-40 and petrologic study of Luna 24 samples 24077,13 and 24077,63

The ferrogabbro 24077,13, with pyroxene and plagioclase major and minor element chemical ranges comparable to the dominant ferrogabbro component in the Luna 24 core, has a Ar-39-Ar-40 temperature release age of 3.33 plus or minus 0.21 billion years. The metaferrobasalt 24077,63 is very fine-grained with a texture and mineralogy consistent with contact metamorphism between superimposed basalt flows or within a single flow. The Ar-39-Ar-40 plateau age of 24077,63 is 3.26 plus or minus 0.4 billion years. The basalt flows in Mare Crisium are about the same age as those of Mare Imbrium and younger than those of Mare Tranquillitatis and Mare Serenitatis.

Schaeffer, O. A.↗

NASA NTRS1979

Venus - Preliminary topographic and surface imaging results from the Pioneer Orbiter

Three large Venus surface features, identified previously in images obtained from earth-based radar observations, are shown by the Pioneer Venus radar mapper to be elevated 5 to 10 km above the surrounding terrain. Two of these features, one bright and the other dark, lie adjacent to each other astride the 65 N parallel between longitudes 310 E and 10 E. The combined region forms a huge tectonically uplifted plateau, surmounted by radar-bright ridges that may have either a volcanic or tectonic origin. The third feature, located at 30 N, 283 E, is radar-bright and may consist of volcanic material extruded along a fault zone. A first radar-scattering image, compiled from data obtained by the mapper in its imaging mode, shows a region north of the equator; several circular depressions seen in this area may result from meteoritic impact.

Pettengill, G. H.↗

NASA NTRS1979

Ar-40/Ar-39 age of the Shergotty achondrite and implications for its post-shock thermal history

Ar-40/Ar-39 measurements are used to determine the age of the Shergotty achondrite and the chronology of the shock event responsible for the complete conversion of its plagioclase to maskelynite is discussed. Apparent ages are found to vary between 240 and 640 million years for the whole rock sample, with a plateau age of 254 million years for a maskelynite separate. The Rb-Sr age of 165 million years determined by Nyquist at al (1978) suggests that the maskelynite as well as the whole rock was incompletely degassed. Argon diffusion characteristics indicate a post-shock cooling time greater than 1000 years and a burial depth greater than 300 m for a thermal model of a cooling ejecta blanket of variable thickness. It is concluded that the shock event which degassed the argon and reset the Rb-Sr systematics occurred between 165 and 250 million years ago when the parent body experienced a collision in the asteroid belt.

Bogard, D. D.↗