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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

A lunar soil evolution model

Comminution, agglutination, and replenishment processes in a lunar soil are modeled by a system of time-dependent linear differential equations. In the model, a soil is subdivided into coarse-particle, fine-particle, and agglutinate fractions. The relative mass abundance of each component in a mature soil is found to be proportional to rates for the reworking processes. Evolution of the grain-size distribution from a fresh ejecta blanket to a mature soil is described quantitatively in terms of the changing proportions of the three soil constituents. If size data are available for an immature soil and a mature soil of the same system, rates for the various processes can be calculated under certain simplifying assumptions.

Mendell, W. W.↗
NASA NTRS1976

Sample preparation of metal alloys by electric discharge machining

Electric discharge machining was investigated as a noncontaminating method of comminuting alloys for subsequent chemical analysis. Particulate dispersions in water were produced from bulk alloys at a rate of about 5 mg/min by using a commercially available machining instrument. The utility of this approach was demonstrated by results obtained when acidified dispersions were substituted for true acid solutions in an established spectrochemical method. The analysis results were not significantly different for the two sample forms. Particle size measurements and preliminary results from other spectrochemical methods which require direct aspiration of liquid into flame or plasma sources are reported.

Chapman, G. B., II↗
NASA NTRS1976

Apollo 14 and 16 Active Seismic Experiments, and Apollo 17 Lunar Seismic Profiling

Seismic refraction experiments were conducted on the moon by Apollo astronauts during missions 14, 16, and 17. Seismic velocities of 104, 108, 92, 114 and 100 m/sec were inferred for the lunar regolith at the Apollo 12, 14, 15, 16, and 17 landing sites, respectively. These data indicate that fragmentation and comminution caused by meteoroid impacts has produced a layer of remarkably uniform seismic properties moonwide. Brecciation and high porosity are the probable causes of the very low velocities observed in the lunar regolith. Apollo 17 seismic data revealed that the seismic velocity increases very rapidly with depth to 4.7 km/sec at a depth of 1.4 km. Such a large velocity change is suggestive of compositional and textural changes and is compatible with a model of fractured basaltic flows overlying anorthositic breccias. 'Thermal' moonquakes were also detected at the Apollo 17 site, becoming increasingly frequent after sunrise and reaching a maximum at sunset. The source of these quakes could possibly be landsliding.

Source record↗
NASA NTRS1975

Experimental hypervelocity impact into quartz sand - Distribution and shock metamorphism of ejecta

Results are presented for vertical impacts of 0.3-g cylindrical plastic projectiles into noncohesive quartz sand in which vertical and horizontal reference strate were employed by using layers of colored sand. The impacts were performed at velocities of 5.9-6.9 km/sec with a vertical gun ballistic range. The craters, 30-33 cm in diameter, reveal a radial decay of the ejecta mass per unit area with a power of -2.8 to -3.5. Material displaced from the upper 15% of the crater depth d is represented within the whole ejecta blanked, material from deeper than 28% of d is deposited inside 2 crater radii, and no material from deeper than 33% of d was ejected beyond the crater rim. Shock-metamorphosed particles (glassy agglutinates, cataclastic breccias, and comminuted quartz) amount to some 4% of the total displaced mass and indicate progressive zones of decay of shock intensity from a peak pressure of 300 kbar. The shock-metamorphosed particles and the shock-induced change in the grain size distribution of ejected samples have close analogies to the basic characteristics of the lunar regolith. Possible applications to regolith formation and to ejecta formations of large-scale impact craters are discussed.

Stoeffler, D.↗
NASA NTRS1975

Integrated investigation of the mixed origin of lunar sample 72161,11

The comminution-agglutination model and the solar-wind implantation-retention model are used to postulate the origins of the particulate components of lunar sample (72161,11), a submillimeter fraction of a surface sample for the dark mantle regolith at LRV-3. Grain-size analysis was performed by wet sieving with liquid argon, and analyses for CO2, CO, CH4, and H2 were carried out by stepwise pyrolysis in a helium atmosphere. The results indicate that the present sample is from a mature regolith, but the agglutinate content is only 30% in the particle-size range between 90 and 177 microns, indicating an apparent departure from steady state. Analyses of the carbon, methane, and hydrogen concentrations in size fractions larger than 149 microns show that the volume-correlated component of these species increases with increased grain size. It is suggested that the observed increase can be explained in terms of mixing of a dominant local population of coarser agglutinates having high carbon and hydrogen concentrations with an imported population of finer agglutinates relatively poor in carbon and hydrogen.

Basu, A.↗
NASA NTRS1976

Thermal regimes in cratered terrain with emphasis on the role of impact melt

The distribution of bombardment energy in the moon's crust and the types of phase transformation resulting from this energy input are investigated. It is seen that the major significance of impact melts in the period of intense cratering is that they transfer most of the high-temperature heat following cratering and thus take part in many of the phase transformations on planetary surfaces. Energy partitioning studies suggest that of the projectiles' total kinetic energy, 23 to 35% is converted into heat by passage of the shock fronts, 43 to 53% transports ejecta and then is dissipated at modest temperature increases over a broad area, 8 to 24% is consumed comminuting country rock, and less than 1% becomes seismic and radiant energy. Subsequent to its formation, the melt is violently mixed with much colder debris to form the sheets of impact melt and the breccias.

Simonds, C. H.↗
NASA NTRS1977

Ar-40 intercept values and young apparent /K-40/-/Ar-40/ ages of five Apollo 15 fines

Correlations between Ar-40 and Ar-36 from size fractions of three Apollo 15 fines (15071, 15421, 15501) have been obtained. The Ar-40 intercept values of these fines and of 15091 and 15601 are generally lower than what one would expect for fines resulting from the comminution of rocks having ages of about 3.3 billion yr, typical for basalts of the landing site. This is interpreted to be the result of contamination by ray material from the Copernican age (equal or less than about 1 billion yr) craters, Autolycus and Aristillus, north of the landing site.

Jordan, J. L.↗
NASA NTRS1977

Test of a model for trace element partition during closed-system solidification of a silicate liquid

Trace-element concentrations in separated minerals and rock fragments from a coarsely crushed and sieved sample of medium-grained lunar basalt are determined by high-precision instrumental neutron activation analysis for three main purposes. These are: (1) to test a previously proposed model for describing trace-element behavior during solidification of a silicate liquid under conditions of a closed system; (2) to compare trace-element concentrations among different size fractions of a comminuted basalt; and (3) to investigate small-scale heterogeneity within a single medium-grained basalt. It is found that an excellent mass balance for the whole rock is attained in terms of the trace-element concentrations of the component minerals and mesostasis, that the mixing model describing this mass balance yields a superior modal analysis for the whole rock, and that different size fractions of the coarsely crushed basalt vary in mineral composition. The closed-system model is shown to account properly for the average behavior of the trace elements during solidification of the basalt, and values of distribution coefficients are obtained for incompatible elements in that rock.

Haskin, L. A.↗
NASA NTRS1968

Apparatus for handling micron size range particulate material

An apparatus for handling, transporting, or size classifying comminuted material was described in detail. Electrostatic acceleration techniques for classifying particles as to size in the particle range from 0.1 to about 100 microns diameter were employed.

Friichtenicht, J. F.↗
NASA NTRS1977

Impact cratering and regolith dynamics

The most recent models concerning mechanical aspects of lunar regolith dynamics related to impact cratering use probabilistic approaches to account for the randomness of the meteorite environment in both space and time. Accordingly the absolute regolith thickness is strictly a function of total bombardment intensity and absolute regolith growth rate in nonlinear through geologic time. Regoliths of increasing median thickness will have larger and larger proportions of more and more deep seated materials. An especially active zone of reworking on the lunar surface of about 1 mm depth has been established. With increasing depth, the probability of excavation and regolith turnover decreases very rapidly. Thus small scale stratigraphy - observable in lunar core materials - is perfectly compatible with regolith gardening, though it is also demonstrated that any such stratigraphy does not necessarily present a complete record of the regolith's depositional history. At present, the lifetimes of exposed lunar rocks against comminution by impact processes can be modeled; it appears that catastrophic rupture dominates over single particle abrasion.

Hoerz, F.↗
NASA NTRS1975

Petrography and petrology of basaltic achondrite polymict breccias /Howardites/

The reported investigation is based on the results from petrographic observations, electron microprobe analyses of constituent phases, and defocused beam analyses of clasts and glasses. Howardites consist of mostly angular-to-rounded mineral, rock, and breccia clasts compacted in variable grain-sized matrices of finely comminuted materials. Attention is given to ophitic and subophitic rocks, granular basalts and microgabbros, mafic rocks, Al-rich rocks, breccia clasts, impact melt rocks, glasses, meteorite clasts, bulk composition, particle size distribution, howardite component composition, questions of breccia formation, and parent body implications. It is found that the four main rock types found in howardites do have certain analogies to lunar rocks. It is tempting to speculate that both the moon and the basaltic achondrite parent body formed similar rock suites in their evolutionary processes.

Bunch, T. E.↗
NASA NTRS1975

Ancient meteoritic component in Apollo 17 boulders

The reported investigation is concerned with the resolution of a number of questions related to the ancient meteoritic component in Apollo 17 boulders. Numerical taxonomic methods have been adopted to objectively group the components. Only the nonvolatile siderophile elements have been used for the classification. Efforts were made to obtain data on the metal composition of breccias analyzed for trace elements, to determine if metal homogeneity was reflected in siderophile ratios. Thirty-one samples were analyzed of which twenty-eight have significant siderophile contents. It is concluded that highland breccias are largely the product of large basin-forming impacts. Highland soils are then produced by comminution of the breccias by small local impacts and micrometeorite bombardment. The long-lived component of bulk soils considered by Baedecker et al. (1974) is thought to contain a substantial micrometeorite contribution, plus assorted debris.

Higuchi, H.↗
NASA NTRS1975

A geochemical and petrographic study of 1-2-mm fines from Apollo 17

Samples of fines less than 1-mm and 155 1-2 mm particles from several Apollo 17 sites were analyzed for Na, Sc, Cr, Mn, Fe, Co, Ni, Hf, Ta, Th, and REE. Products of comminution and construction are present in the 1-2 mm particles, and the compositions of the rock fragments clearly indicate the general chemical characteristics of their parent rock types. The likely sources of materials for the glassy particles are considered. Glasses are enriched over their parent soils in Fe, Sc, Mn, and Cr, and are relatively enriched in light REE, so that some chemical fractionation accompanies glass-forming processes. Elements were determined by instrumental neutron activation analysis.

Blanchard, D. P.↗
NASA NTRS1978

Major and trace element chemistry of Luna 24 samples from Mare Crisium

Atomic absorption spectrometry and instrumental neutron activation analysis were employed to analyze six Luna 24 soils for major and trace elements. The analysis revealed well-mixed soils, though size fractions of each of the soils showed quite dissimilar compositions. Thus the regolith apparently has not been extensively reworked. Noritic breccia admixed preferentially to the finest size fractions and differential comminution of one or more other soil components accounted for the observed elemental distributions as a function of grain size. The ferrobasalt composition and one or more components with higher MgO contents have been identified in the samples.

Blanchard, D. P.↗
NASA NTRS1978

Luna 24 - Mineral chemistry of 90-150 micron clasts

The mineralogy, composition and source relations of monomineralic clasts in the size range 0.09 to 0.15 mm have been studied for seven grain mounts from the Luna 24 core, obtained in Mare Crisium. One of the core horizons, which showed the greatest number of mafic mineral clasts, apparently represents a less reworked level or one which received a greater average influx of gabbroic and/or basaltic ejecta. Most of the mafic minerals in the core were probably derived from the comminution of clasts of very low titanium basalts and/or gabbros. A small number of mineral clasts may have originated from a Mg-rich gabbro. A mixture of local mare basalts and ejecta from Fahrenheit crater probably makes up most of the regolith at the Luna 24 site.

Meyer, H. O. A.↗
NASA NTRS1979

Regional chemical variations in lunar basaltic lavas

The higher Al2O3 concentrations in mare soils at Apollo landing sites, relative to mare basalts, have generally been attributed to the presence of 20-30% of terra material in the mare surface regolith. This viewpoint is shown to be erroneous when entire maria are studied; the amount of terra material in typical mare surface regoliths is only about 5%, or less. The bulk of the mare soils are the comminuted remains of aluminous mare basalt flows. On a regional scale, the sample and orbital data for maria define prominent chemical variations that are well beyond those expected from simple igneous processes and therefore indicate that gradations in one or more of the major parameters of planetary differentiation caused these variations. The increasingly abundant evidence for regional variations in the chemical compositions of lunar basalts requires that regional petrogenetic provinces must be considered in models of lunar evolution.

Hubbard, N.↗
NASA NTRS1980

Underground mineral extraction

A method was developed for extracting underground minerals such as coal, which avoids the need for sending personnel underground and which enables the mining of steeply pitched seams of the mineral. The method includes the use of a narrow vehicle which moves underground along the mineral seam and which is connected by pipes or hoses to water pumps at the surface of the Earth. The vehicle hydraulically drills pilot holes during its entrances into the seam, and then directs sideward jets at the seam during its withdrawal from each pilot hole to comminute the mineral surrounding the pilot hole and combine it with water into a slurry, so that the slurried mineral can flow to a location where a pump raises the slurry to the surface.

Miller, C. G.↗
NASA NTRS1980

Sweeping of the Jovian resonances and the evolution of the asteroids

During the formation of the solar system the variation of the gravitational field produced by removal of a nebula with its moderately massive accretion disk led to sweeping of the Jovian commensurability resonances through the asteroid zone. This process produced increased eccentricities and random velocities of the early planetesimals which resulted in collisional comminution rather than accretion. The existence of the asteroids, their low mass density, and their high relative velocities are interpreted as due to disruption of the accretion processes of the terrestrial planets by the influences of Jupiter.

Torbett, M.↗