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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 397 records · Page 22
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NASA NTRS1978

Mars - Regolith adsorption and the relative concentrations of atmospheric rare gases

Laboratory measurements of Kr and Xe adsorption on samples of ground montmorillonite, limonite and basalt at -77 C have been performed. Results suggest that (1) most degassed martian Xe could be adsorbed on a regolith with a large effective surface area, and (2) if this is the case the elemental composition of martian nonradiogenic rare gas (counting that in the regolith) may be virtually identical to that of ordinary chondrites.

Fanale, F. P.↗
NASA NTRS1978

Some consequences of a liquid water saturated regolith in early Martian history

Flooding of low-lying areas of the Martian regolith may have occurred early in the planet's history when a comparatively dense primitive atmosphere existed. If this model is valid, the following are some pedogenic and mineralogical consequences to be expected. Fluctuation of the water table in response to any seasonal or longer term causes would have resulted in precipitation of ferric oxyhydroxides with the development of a vesicular duricrust (or hardpan). Disruption of such a crust by scarp undercutting or frost heaving accompanied by wind deflation of fines could account for the boulders visible on Utopia Planitia in the vicinity of the second Viking lander site. Laboratory and field evidence on earth suggests that under weakly oxidizing conditions lepidocrocite (rather than goethite) would have preferentially formed in the Martian regolith from the weathering of ferrous silicates, accompanied by montmorillonite, nontronite, and cronstedtite. Maghemite may have formed as a low-temperature dehydrate of lepidocrocite or directly from ferrous precursors.

Fuller, A. O.↗
NASA NTRS1977

Soil maturity and planetary regoliths - The Moon, Mercury, and the asteroids

Observations of the Moon, Mercury and the asteroids provide data which can be used to assess current ideas about the optical maturation of regoliths of bodies without atmospheres. Telescopic data show Mercury's surface to be as optically mature as the Moon's while the asteroids appear to have 'fresh' surfaces. We suggest that these cases illustrate two different paths of regolith evolution caused by differing micrometeoroid impact velocities, gravity, and in some cases composition.

Matson, D. L.↗
NASA NTRS1975

Track studies bearing on solar-system regoliths

The paper reports a comparative study of solar-flare tracks and other microscopic features in unmetamorphosed lunar breccias, carbonaceous chondrites, and noncarbonaceous gas-rich meteoritic breccias. The data suggest that these objects originated from material once on and just below the surface of solar-system regoliths. Characteristics of these regoliths are discussed with reference to the track-rich olivines in Orgueil and the impregnated Apollo 16 deep drill core. The use of a variant of the fission-track method to determine the time of compaction of soil grains into a breccia is explained.

Price, P. B.↗
NASA NTRS1978

Luna 24: 90-150 micrometer fraction - Implications for remote sampling of regolith

An analysis of the mineral grains and glasses found in the 90 to 150 micron fraction of the Luna 24 core sample is presented and implications for the automatic collection of planetary and asteroidal regoliths are discussed. Electron microprobe analysis for pyroxene, olivine, plagioclase, opaque minerals and glass in samples at various depths indicate that polymineralic grains have compositions similar to those of gabbroic and basaltic fragments from coarser samples, while monomineralic grains contain an additional population of Mg-rich olivines and pyroxene. Most of the glasses are found to be related to mare basalts or local regolith, with nonmare material represented by glasses of highland basalt and low K Fra Mauro composition. It is concluded that as regards mineralogy and petrology, a single grab sample would have been as useful and a series of grab samples on a long traverse would have been more useful than the Luna 24 core sample, with the fine sample being more informative than the coarse.

Papp, H. A.↗
NASA NTRS1978

Interpretation of ground-based microwave measurements of the moon using a detailed regolith properties model

A detailed model for the regolith's thermophysical and microwave properties has been used for the interpretation of ground-based measurements of the moon's microwave brightness temperature variation with lunar phase and changes during eclipses. The ground-based measurements include some crucial new lunation variation observations at 2.8, 6.0 and 13.1 cm. The many parameters in the regolith properties model were assigned values based on a careful review of Apollo in situ and lab sample measurements of thermophysical and electrical properties. The first identification of a wavelength-dependent component of scattering is reported.

Gary, B. L.↗
NASA NTRS1979

Volatiles in the Martian regolith

An inventory of released volatiles on Mars has been derived based upon Viking measurements of atmospheric and surface chemical composition, and upon the inferred mineralogy of a ubiquitous regolith, assumed to average 200m in depth. This model is consistent with the relative abundances of volatiles (except for S) on the earth's surface, but implies one-fifteenth of the volatile release of earth if starting materials were comparable. All constituents are accommodated as chemical components of, or absorbed phases on, regolith materials - without the necessity of invoking unobservable deposits of carbonates, nitrates, or permafrost ice.

Clark, B. C.↗
NASA NTRS1980

Toward a model of grain surface exposure in planetary regoliths

The interpretation of solar wind implanted gas concentration versus particle size for lunar regolith samples is considered. In so doing, interparticle adhesive forces are considered explicitly and the simplest possible grain exposure law consistent with the existence of such forces is hypothesized. Namely, for particles small enough that these forces exceed the lunar gravitational force, any element of area has equal probability of being in the regolith surface regardless of the size of the grain on which it is situated. This law leads to the expectation that concentrations will depend inversely on mean grain radius for small grains and gradually become independent of radius for very large grains consistent with observations. Therefore, such a concentration dependence cannot by used to infer the presence of saturation losses.

Housley, R. M.↗
NASA NTRS1981

Vertical-structure effects on planetary microwave brightness temperature measurements - Applications to the lunar regolith

An attempt to constrain the effects of vertical variations in dielectric properties on lunar microwave observations is presented. A numerical approach for deriving the reflectivity and microwave weighting function of a vertically varying half-space is used, assuming variance in the dielectric properties with depth only, and negligible magnetic effects. The cases of continuous and stratified models of vertical structures are discussed, and a concentration of emitted energy in upper layers is found. The total emitted energy oscillates, varying with the thickness of the upper soil layer, but averaging out interference effects due to random variations in the substrate depth. Consideration is also given to the vertical structure effects on the lunation-mean disk-center brightness temperature, its variations, and the regolith electrical loss, and predicted reflectivity effects by feasible models of the lunar regolith dielectric profile.

Keihm, S. J.↗
NASA NTRS1980

Howardites - Samples of the regolith of the eucrite parent-body: Petrology of Frankfort, Pavlovka, Yurtuk, Malvern, and ALHA 77302

Modal petrographic methods have been applied to the meteorites Frankfort, Pavlovka, Yurtuk, Malvern, and ALHA 77302, to determine some of the characteristics of the regolith of the eucrite parent body. Lithic clasts in the meteorites fall into three major groups: pyroxene + plagioclase rocks, orthopyroxenites, and fused-soil clasts. Lithic clasts make up a small proportion of the soil; mineral clasts from orthopyroxenites dominate the coarse-grained fraction; and the fine-grained fraction contains minerals from both orthopyroxenites and plagioclase + pyroxene rocks. The eucrite regolith appears to have the following characteristics: the source rocks are friable, the soils are immature, comminution is the major soil-forming process, and the soil is well mixed.

Labotka, T. C.↗
NASA NTRS1980

The lunar regolith - Comparative petrology of the Apollo sites

A description is presented of the modal petrology of eight surface soils from the Apollo 11, 12, 14, 15, and 16 landing sites. One of the most striking features of the petrology of the considered soils is found to be the similarity in distribution of pyroxene composition between the soil and the local rock types. The considered investigation is concerned with certain difficulties with respect to an understanding of regolith evolution. Lunar soils contain material foreign to the local geology. The foreign material must have been transported over long distances. However, models of regolith formation on the moon indicate that lateral transport is inefficient. It is found in the investigation that the soil is predominantly of local derivation, that lateral homogenization is a minor process, that foreign material is present in the amounts indicated by bulk chemical mixing models, and that preferential transport of fine-grained material does not occur.

Labotka, T. C.↗
NASA NTRS1980

Lunar core 15010/11 - Grain size, petrology, and implications for regolith dynamics

Petrographic observations of six samples from various depths show that core 15010/11 is relatively homogeneous and consists mostly of basalt fragments and minerals derived from basalts. However, it also contains an appreciable highland component nearly equally distributed among the fine-grained fraction, dark matrix breccia and identifiable highland grains, and agglutinates. Grain size data and agglutinates show that this core is not mature and does not contain a well developed reworking profile. The unusual properties of the core are thought to be a direct result of its close proximity to the rim of Hadley Rille. This location favors relatively rapid regolith erosion into the rille, produces a thin regolith, and provides an abundant supply of bedrock-derived ejecta.

Mckay, D. S.↗
NASA NTRS1985

Petrology of the Cangas de Onis and nulles regolith breccias Implications for parent body history

The present study of the Cangas de Onis and Nulles H chondrite regolith breccias indicates that the minerals in the matrices and equilibrated clasts have essentially the same compositional distributions, so that much of the material in the castic matrix would have to have been derived from the impact comminution of clats. The apparently exclusive occurrence of H6 clasts in Cangas de Onis, and H4 clasts in Nulles, suggests that, at the locations where these breccias formed, the regolith predominantly consisted of H6 and H4 material, respectively.

Williams, C. V.↗
NASA NTRS1987

Evaluation of the mechanical properties of Phobos' regolith

Slopes and heights in craters and grooves which appear to be overlain with regoliths make it possible to set lower limits for regolith strength. The mechanical properties for this material are set at c = 0.001-0.07 N/ sq cm, phi = 5-30 deg.

Kozenko, A. V.↗
NASA NTRS1987

The role of regolith adsorption in the transition from early to late Mars climate

Researchers reexamined radiative transfer models of early Mars that were advanced to show the existance of a greenhouse effect. These models were reexamined with regard to the effect that regolith adsorption may have had. It is argued that while the precipitation of carbonates has probably been an important process during Mars history, the rates at which this process could have taken place under early Mars conditions would have dropped sharply once liquid water was fairly scarce. Furthermore, conditions under which liquid water was available may have involved efficient recycling of carbonate so that steady state conditions rather than irreversible CO2 removal prevailed. In contrast, the growth of regolith surface area demands corresponding and predictable CO2 removal from the atmosphere-cap system and is fully capable of terminating any enhanced temperature regime on early Mars in the absence of any other effects.

Fanale, F. P.↗
NASA NTRS1987

Mineralogy of a basaltic clast in lunar highland regolith breccia 60019

Mineralogy of a basaltic clast, Ba-2, found on the cut surface of a new slab of lunar highland regolith breccia 60019 was studied and compared with that of lunar meteorites ALHA81005 and Y791197. The coarse-grained Ba-2 clast consists of Na-bearing plagioclase, high-Ca clinopyroxene, ilmenite, silica, and mesostasis. The mineralogy and chemical zoning trends in the Ba-2 clast suggest that this basalt is similar to the 60639,1 basalt in the Apollo 16 rake samples, and to Luna 16 high-alumina moderate-TiO2 mare basalts; however, olivine is not present in Ba-2. On the basis of these and other findings, and assuming the early formation of the Apollo 16 regolith breccia (as proposed by McKay et al., 1986), it is suggested that B-2 could represent a post-Nectaris lava flow older than the formation of 60019.

Takeda, Hiroshi↗
NASA NTRS1987

Some probable characteristics of the Martian regolith

A number of Mars surface environmental factors seriously affect the properties of the Martian regolith. The result is a regolith that is rather different from that of the moon. Some of the anticipated differences are discussed: weathering and lack of old glass; desert varnish; lack of micrometeorite impact products; abundance of meteorite fragments; and different grain size characteristics.

King, Elbert A.↗