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At least 685 records · Page 38
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

The latitudinal distribution of a debris mantle on the Martian surface

A relatively young mantling deposit of debris surrounds both Martian polar regions and extends toward the equator. This mantle apparently has been derived by wind erosion of sedimentary deposits in the polar regions, a process that is probably continuing now. The distribution of the mantle is not correlated with any particular terrain type for it has masked the small crater populations on young and old terrains alike. The paucity of small fresh craters at high latitudes can be directly attributed to the presence of this debris blanket. It is clear that extreme care should be exercised in using the populations of small craters to establish the chronology of the evolution of geologic provinces on Mars.

Soderblom, L. A.↗
NASA NTRS1973

Mars: South polar pits and etched terrain

Martian south polar pits and etched terrain attest to alternating episodes of eolian deposition and erosion. Sometimes the south polar area has served as a sump for the accumulation of airborne debris and associated particles of frozen volatiles. At other times, the wind patterns or wind effectiveness change, and the atmosphere begins to remove the blanket of material it has earlier spread over the south polar region.

Sharp, R. P.↗
NASA NTRS1972

Hydrodynamic prediction of peak pool-boiling heat fluxes from finite bodies.

Previous theoretical models are considered, giving attention to the original formulation proposed by Zuber (1959), an infinite horizontal flat plate, a horizontal cylinder, and a sphere. Some general features of any hydrodynamic prediction are inferred by examining the characteristics of the models. It is found possible to eliminate the need for observed values of the vapor-blanket thickness. The concepts obtained are utilized in the derivation of expressions for the prediction of the peak pool-boiling heat flux in the case of some new configurations.

Lienhard, J. H.↗
NASA NTRS1972

Metamorphism of Apollo 14 breccias.

All Apollo 14 breccias for which thin sections are available (27 rocks) were studied petrographically. From one sample in each of six groups, electron microprobe analyses were performed on matrix (less than 25 microns) plagioclase, pyroxene, and olivine and of rims and cores of plagioclase and pyroxene clasts (50 to 300 microns). Matrix plagioclase, pyroxene, and olivine in the high-grade rocks display a narrow range of compositions, suggesting an equilibrated or metamorphic origin. However, in the low-grade rocks a wide range of compositions, suggesting a detrital or unequilibrated origin, is observed. Partially equilibrated states are observed in medium-grade samples. It is concluded that the Apollo 14 breccias formed as part of the Imbrium Basin ejecta blanket - the Fra Mauro formation. The continuous nature of the metamorphic series suggests that the medium- and high-grade breccias were derived from unmetamorphosed equivalents by autometamorphism in the thick, hot Fra Mauro formation at the Apollo 14 site.

Warner, J. L.↗
NASA NTRS1972

Vapor phase crystallization in Apollo 14 breccia.

The vugs contained in many of the highly recrystallized breccias from Apollo 14 are discussed, along with the well-developed crystals of plagioclase, pyroxene, ilmenite, apatite, whitlockite, iron, nickel-iron, and troilite that extend from the vug walls and bridge open spaces. These crystals are interpreted as having formed by deposition from a hot vapor containing oxides, halides, sulfides, alkali metals, iron and possibly other chemical species. The hot vapor was associated with the thermal metamorphism and subsequent cooling of the Fra Mauro formation after it had been deposited as an ejecta blanket by the Imbrian impact.

Mckay, D. S.↗
NASA NTRS1973

Lunar cinder cones.

Data on terrestrial eruptions of pyroclastic material and ballistic considerations suggest that in the lunar environment (vacuum and reduced gravity) low-rimmed pyroclastic rings are formed rather than the high-rimmed cinder cones so abundant on the earth. Dark blanketing deposits in the Taurus-Littrow region (Apollo 17 landing area) are interpreted as being at least partly composed of lunar counterparts of terrestrial cinder cones.

Mcgetchin, T. R.↗
NASA NTRS1973

Particle track record of the Luna missions.

Measurements are reported of particle-track densities in 100 to 200-micron crystalline grains taken from one level of the soil column returned from the lunar highlands between Mare Fecunditatis and Mare Crisium by Luna 20 and from two levels in the soil column from Mare Fecunditatis by Luna 16. Ninety-three percent of the grains from Luna 16 have very high densities, greater than 10 to the 8th power per cu cm and the lower-track density grains are all in the deeper soil level. In contrast, most Luna 20 grains show densities less than 10 to the 8th power per cu cm. Track density gradients and exposure times have been measured for six Luna 16 grains with a wide spread in absolute track densities. The more extensive track counts in crystals strengthens an earlier conclusion that the Luna 16 soil has received long irradiations very close to the surface. Two possible histories are that the highly irradiated soil blanket at the Luna 16 site is either well mixed and thin, or else has accumulated by transport from surrounding higher regions.

Comstock, G. M.↗
NASA NTRS1973

The ultraviolet flux envelopes of main-sequence B stars.

Flux envelopes in the range from 1100 to 6000 A for representative, nearby, thus unreddened main sequence stars are assembled. These envelopes are compared with the flux envelopes predicted from the classical LTE theory of model atmospheres. An investigation is conducted concerning the UV spectral distributions in the case of stars of the types B 0.5 V to A 1 V. It is found that the observed UV flux envelopes fall significantly below the envelopes predicted from lightly line-blanketed models.

Underhill, A. B.↗
NASA NTRS1973

Spacecraft microbial burden reduction due to atmospheric entry heating - Jupiter.

An effort has been underway at Jet Propulsion Laboratory to develop the tools necessary to predict temperature histories for a typical spacecraft during inadvertent entry. In order that the results have general applicability, parametric analyses are performed. The thermal response of the spacecraft components and debris resulting from disintegration is determined. The temperature histories of small particles and composite materials, such as thermal blankets and an antenna, are given special attention. Guidelines are given to indicate the types of components and debris most likely to contain viable organisms, which could contaminate the lower layers of the Jovian atmosphere.

Gonzalez, C. C.↗
NASA NTRS1973

Latitudinal distribution of a debris mantle on the Martian surface.

Mariner 9 narrow angle pictures show that many areas on Mars are buried by debris mantles that later have been partially eroded. A survey of the present debris distributions shows that they are symmetrically disposed about the polar regions, extending poleward from the 30 N and 30 S latitudes. These blankets are inferred to represent eolian debris derived from circumpolar layered deposits; the process of equatorward redistribution of debris by wind action is probably still continuing.

Soderblom, L. A.↗
NASA NTRS1973

Studies related to the evolution of the lunar soil materials

Studies of the chemistry and morphology of the lunar samples are reported. The presence of fragments of plagoclase in the centers of the impact craters indicate that the glass spheres were derived by meteoritic impact from high velocity particles, while the glass was at high temperatures. From the study of the Apollo 16 samples, it is suggested that this material was formed in a hot impact ejecta blanket, or in an igneous environment, and later exposed to meteoritic impact. It is suggested that particles from Apollo 17 were formed in a cloud of siliceous vapors.

Carter, J. L.↗
NASA NTRS1973

Mini-Brayton heat source assembly design study. Volume 2: Titan 3C mission

Major conclusions of the space shuttle heat source assembly study are reported that project a minimum weight design for a Titan 3 C synchronous orbit mission; requirements to recover the heat source in orbit are eliminated. This concept permits location of the heat source end enclosure supports and heat source assembly support housing in a low temperature region external to the insulation enclosure and considers titanium and beryllium alloys for these support elements. A high melting insulation blanket consisting of nickel foil coated with zirconia, or of gold foil separated with glass fiber layers, is selected to provide emergency cooling in the range 2000 to 2700 F to prevent the isotope heat source from reaching unsafe temperatures. A graphic view of the baseline heat source assembly is included.

Source record↗
NASA NTRS1973

Aitken crater and its environs

The physical characteristics of the fresh looking Aitken Crater and its surrounding environment are studied. Rim deposits and ejecta blanket indicate the crater has a probable impact origin or is formed during post-Aitken events. Data also indicate the crater's dark floor fill, its flow scarps, and smaller craters with domical structures are volcanic in origin. Landform varieties suggest episodic erruptions may also cause such craters.

El-Baz, F.↗
NASA NTRS1974

Preliminary results of experiments to duplicate Boulder textures by thermal sintering of powders

Experiments seem to indicate that at the low pressures characteristic of an ejecta blanket, sintering or sintering/devitrification could have lithified boulder 1 matrix materials and produced the textural types observed in 72255 and 72275. This very preliminary conclusion is consistent with other observations that granitic clasts have undergone a slight degree of partial melting (and have therefore experienced temperatures on the order of 1000 C). It is concluded that maskelynite in the boulder is completely devitrified.

Hallam, M. E.↗
NASA NTRS1973

Statistical models of lunar rocks and regolith

The mathematical, statistical, and computational approaches used in the investigation of the interrelationship of lunar fragmental material, regolith, lunar rocks, and lunar craters are described. The first two phases of the work explored the sensitivity of the production model of fragmental material to mathematical assumptions, and then completed earlier studies on the survival of lunar surface rocks with respect to competing processes. The third phase combined earlier work into a detailed statistical analysis and probabilistic model of regolith formation by lithologically distinct layers, interpreted as modified crater ejecta blankets. The fourth phase of the work dealt with problems encountered in combining the results of the entire project into a comprehensive, multipurpose computer simulation model for the craters and regolith. Highlights of each phase of research are given.

Marcus, A. H.↗
NASA NTRS1974

Seismic effects from major basin formation on the Moon and Mercury

Grooved and hilly terrains are reported which occur at the antipode of major basins on the Moon (Imbrium, Orientale) and Mercury (Caloris). Order-of-magnitude calculations, for an Imbrium-size impact on the Moon, indicate P-wave-induced surface displacements of 10 m at the basin antipode that would arrive prior to secondary ejecta. Comparable surface waves are reported which would arrive subsequent to secondary ejecta impacts and would increase in magnitude as they converge at the antipode. Other seismically induced surface features include: subdued, furrowed crater walls produced by landslides and concomitant secondary impacts; emplacement and leveling of light plains units owing to seismically induced "fluidization" of slide material; knobby, pitted terrain around old basins from enhancement of seismic waves in ancient ejecta blankets; and the production and enhancement of deep-seated fractures that led to the concentration of farside lunar maria in the Apollo-Ingenii region.

Schultz, P. H.↗
NASA NTRS1974

Evaluation of coated columbium alloy heat shields for space shuttle thermal protection system application. Volume 3, phase 3: Full size TPS evaluation

The thermal protection system (TPS), designed for incorporation with space shuttle orbiter systems, consists of one primary heat shield thermally and structurally isolated from the test fixture by eight peripheral guard panels, all encompassing an area of approximately 12 sq ft. TPS components include tee-stiffened Cb 752/R-512E heat shields, bi-metallic support posts, panel retainers, and high temperature insulation blankets. The vehicle primary structure was simulated by a titanium skin, frames, and stiffeners. Test procedures, manufacturing processes, and methods of analysis are fully documented. For Vol. 1, see N72-30948; for Vol. 2, see N74-15660.

Baer, J. W.↗
NASA NTRS1973

Igneous vs impact processes for the origin of the Mare lavas

The respective role of external vs internal processes is considered. The inner Orientale basin was formed by the explosive impact of an asteroidal body. Within minutes after the impact, the concentric fracture system developed as an adjustment to the stresses generated by the shock wave. Examples are presented to illustrate that the upwelling of lava in the center of Mare Orientale and several craters on its ejecta blanket occurred well after the asteroidal collision which generated the bulls-eye structure. Thus, the lavas were not strictly impact melts. However, a close relationship may have existed between the impact and subsequent volcanism.

Gornitz, V.↗