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All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

From regolith to rock by shock

The purpose of this study is to relate the various mechanisms by which material is shock-lithified in terrestrial analogs of the lunar regolith to specific conditions of cratering, thereby making more specific the possible conditions of formation of rock from regolith by shock processes on the lunar surface. A model for shock-lithification of terrestrial and lunar regolith is proposed in which air or an air-water mixture initially in the pores of terrestrial soil affects the behavior of a soil-air-water system under shock-loading. Shock compression of porous terrestrial regolith by relatively small impact events give rise to three pressure regimes: (1) regime 1 - at pressures below 100 kb, material is compacted and weakly shock-lithified; (2) regime 2 - at pressures between 100 and 200 kb, material may be fragmented if the induced pore pressure exceeds the strength of the weak lithification mechanisms; and (3) at pressure above 200 kb, material is strongly lithified but may greatly expand in volume due to the pressure of pore gases. The three other regimes (below 50 kb, between 50 and 100 kb, and above 100 kb) associated with shock compression of lunar regolith are identified and discussed.

Kieffer, S. W.↗
NASA NTRS1978

Mars - The role of the regolith in determining atmospheric pressure and the atmosphere's response to insolation changes

A quantitative model for atmosphere-regolith exchange of CO2 on Mars is presented. The model, based on new laboratory measurements of CO2 adsorption on ground rock at 158, 175, 196, and 231 K for CO2 pressures from 1.0 to 80 mbar, is consistent with Viking observations, while models involving a massive residual CO2 cap and no long-term atmosphere-regolith CO2 exchange are not consistent. The model indicates: (1) the atmosphere-plus-cap system is buffered on a long-term basis by exchangeable CO2 adsorbed in the regolith; (2) if the atmosphere-plus-cap system suddenly disappeared, the system would eventually be almost completely restored by reequilibration with the regolith; (3) exchange with the adsorbed phase in the regolith has greatly restricted O-18 enrichment of the atmosphere; (4) the layered terrain primarily represents current periodic pressure increases; and (5) pressures of 100-300 nbar might have existed during the early history of the planet.

Fanale, F. P.↗
NASA NTRS1979

Asteroidal regoliths

A physical model is developed for the evolution of regoliths on small bodies and applied to the asteroid and meteorite parent bodies. The model considers global deposition of that fraction of cratering ejecta that is not lost to space. In addition, it is applied to cases of both strong, cohesive bodies and to bodies of weak, unconsolidated materials. It is found that large, strong asteroids generate surficial regoliths of a few kilometers depth while strong asteroids smaller than 10-km diameter generate negligible regoliths. In conclusion, it is noted that the theory that substantial regoliths are produced predominantly by blanketing differs from earlier hypotheses that asteroidal regoliths might be thin or absent and that short surface exposure of asteroidal materials is due chiefly to erosion rather than blanketing.

Housen, K. R.↗
NASA NTRS1979

Regolith development and evolution on asteroids and the moon

Early descriptions of regoliths on small bodies were devised to account for observations of asteroids (Chapman 1971, 1976) and the gas-rich meteorites (Anders 1975). Lack of agreement between these approaches prompted Housen et al. (1978, 1979) to examine the problem in detail. The resulting model predicted that moderate-sized (100-300 km) asteroids should evolve regoliths up to a few kilometers deep which could be source regions of gas-rich meteorites. Smaller objects should have regoliths ranging from dust coatings to meters-thick layers depending on the strength of the object. The earlier model could not treat asteroids larger than 300 km in diameter. The model, now modified to treat larger-sized objects, predicts regolith depths, on asteroids larger than 300 km, which decrease with increasing size. A regolith depth of 7 m is predicted for the lunar maria in reasonable agreement with the observed depths of 5 m.

Housen, K. R.↗
NASA NTRS1984

Petrology of Apollo 11 regolith breccias

Petrographic and mineral chemical data for 16 Apollo 11 regolith breccias show that: (1) the regolith breccias differ from soil 10084 with respect to agglutinate content, glass population, plagioclase compositions, and proportions of high-K mare and low-K mare basalt components; (2) the A-11 breccias and soil have highland components that are similar both in abundance and petrology; and (3) lunar regolith breccias provide a better comparison with howardites than do lunar soils. The data and observations are consistent with formation of the regolith breccias from immature soil. It appears that little or no highland material has been added to the Tranquillitatis regolith since the formation of the breccias.

Simon, S. B.↗
NASA NTRS1984

Particle track measurements in lunar regolith breccias

Particle track measurements have been reported for 25 (5 percent) of the regolith breccias in the collection; they have been reported for 16 breccias (30 percent) in the reference suite. The most frequently reported measurement for these 25 breccias is the maximum surface exposure age of the compacted rock (48 percent of the published breccia measurements). Information on the nature of the precompaction regolith is given for 9 rocks (36 percent) and on the nature of the compaction event for 6 rocks (24 percent). Most of the breccias appear to have simple post-compaction surface exposure histories (89 percent). From the few track density frequency distributions (7) that are available and inferring from the low exposure ages of these rocks (75 percent were younger than 10 to the 6th years), it appears that most of these breccias are amenable to studies which separate the contemporary surface exposure age from information about the precompaction regolith. If the number of immature-submature precompaction soils (6 out of 10 of the breccias for which appropriate data are available) represents many regolith breccias, then we can infer that regolith breccias may sample the deeper, less reworked materials in the lunar soil and compliment the samples available from the returned cores.

Blanford, G. E.↗
NASA NTRS1986

Particle track measurements in lunar regolith breccias

Particle track measurements have been reported for 25 (5 percent) of the regolith breccias in the collection; they have been reported for 16 breccias (30%) in the reference suite. The most frequently reported measurement for these 25 breccias is the maximum surface exposure age of the compacted rock (48% of the published breccia measurements). Information on the nature of the precompaction regolith is given for 9 rocks (36%) and on the nature of the compaction event for 6 rocks (24%). Most of the breccias appear to have simple post compaction surface exposure histories (89%). From the few track density frequency distributions (7) that are available and inferring from the low exposure ages of these rocks (75% were younger than 10 to the 6th years), it appears that most of these breccias are amenable to studies which separate the contemporary surface exposure age from information about the precompaction regolith. If the number of immature submature precompaction soils (6 out of 10 of the breccias for which appropriate data are available) represents many regolith breccias, then it is inferred that regolith breccias may sample the deeper, less reworked materials in the lunar soil and compliment the samples available from the returned cores.

Blanford, G. E.↗
NASA NTRS1987

On the sputter alteration of regoliths of outer solar system bodies

Several processes that are expected to occur when the porous regoliths of outer solar system bodies (without atmospheres) are subjected to energetic ion bombardment are discussed. The conclusions reached in much of the literature addressing sputtering are quantitatively or qualitatively incorrect because effects of soil porosity have been neglected. It is shown theoretically and experimentally that porosity reduces the effective sputtering yield of a soil by more than an order of magnitude. Between 90 and 97% of the sputtered atoms are trapped within the regolith, where they are factionated by differential desorption. Experiments indicate that more volatile species have higher desorption probabilities. This process is the most important way in which alteration of chemical and optical properties occurs when a regolith is sputtered. When a basic silicate soil is irradiated these effects lead to sputter-deposited films enriched in metallic iron, while O, Na and K are preferentially lost. The Na and K are present in the atmosphere above the sputtered silicate in quantities much greater than their abundances in the regolith. Icy regoliths of SO2 should be enriched in elemental S and/or S2O. This prediction is supported by the probable identification of S2O and polysulfur oxide bands in the IR spectra of H-sputtered SO2 reported by Moore. When porous mixtures of water, ammonia and methane frosts are sputtered, the loss of H and surface reactions of C, N and O in the deposits should produce complex hydrocarbons and carbohydrates, some of which may be quite dark. Such reactions may have played a role in the formation of the matrix material of carbonaceous chondrites prior to agglomeration.

Hapke, Bruce↗
NASA NTRS1986

Petrology, chemistry, and origin of Apollo 15 regolith breccias

Variations in modal petrology, mineral compositions, and bulk compositions were determined for ten Apollo 15 regolith breccias for comparison with local soils and assessment of the intrasite petrologic variability of the Apollo 15 regolith. Based on the above criteria the breccias are of local origin and mimic the soils from the corresponding sampling stations, with the exception of station 2 breccia 15205. This sample formed from an anomalous regolith, and although not considered exotic to the site is not representative of the soil at the site. KREEP basalt and green glass components vary from trace amounts to dominant in the breccias, evidence that these materials entered the regolith prior to formation of the breccias. Breccias from the edge of Hadley Rille are modally richer in highland fragments than the soils, whereas at the base of Hadley Delta the reverse is true. This is explained by the loss of material into the Rille to be replaced by basalt-derived material, making the soils more basalt-rich. At the base of Hadley Delta highland material is accumulating and the soils are becoming more highland-rich. Over billions of years these processes have developed differences between the present day, evolving soils, and 'fossil' nonevolving soils represented by the regolith breccias. This shows that there has been little change in the geology and the morphology of the Apollo 15 site, probably since the eruption of mare basalts at the site (about 3.3 b.y.).

Simon, S. B.↗
NASA NTRS1988

Apollo 16 regolith breccias and soils - Recorders of exotic component addition to the Descartes region of the moon

Using the subdivision of Apollo 16 regolith breccias into ancient (about 4 Gyr) and younger samples (McKay et al., 1986), with the present-day soils as a third sample, a petrologic and chemical determination of regolith evolution and exotic component addition at the A-16 site was performed. The modal petrologies and mineral and chemical compositions of the regolith breccias in the region are presented. It is shown that the early regolith was composed of fragments of plutonic rocks, impact melt rocks, and minerals and impact glasses. It is found that KREEP lithologies and impact melts formed early in lunar history. The mare components, mainly orange high-TiO2 glass and green low-TiO2 glass, were added to the site after formation of the ancient breccias and prior to the formation of young breccias. The major change in the regolith since the formation of the young breccias is an increase in maturity represented by the formation of fused soil particles with prolonged exposure to micrometeorite impacts.

Simon, S. B.↗
NASA NTRS1992

Regolith thermal energy storage for lunar nighttime power

A scheme for providing nighttime electric power to a lunar base is described. This scheme stores thermal energy in a pile of regolith. Any such scheme must somehow improve on the poor thermal conductivity of lunar regolith in vacuum. Two previous schemes accomplish this by casting or melting the regolith. The scheme described here wraps the regolith in a gas-tight bag and introduces a light gas to enhance thermal conductivity. This allows the system to be assembled with less energy and equipment than schemes which require melting of regolith. A point design based on the new scheme is presented. Its mass from Earth compares favorably with the mass of a regenerative fuel cell of equal capacity.

Tillotson, Brian↗
NASA NTRS1992

Experimental determination of in situ utilization of lunar regolith for thermal energy storage

A Lunar Thermal Energy from Regolith (LUTHER) experiment has been designed and fabricated at the NASA Lewis Research Center to determine the feasibility of using lunar soil as thermal energy storage media. The experimental apparatus includes an alumina ceramic canister which contains simulated lunar regolith, a heater, nine heat shields, a heat transfer cold jacket, and 19 type-B platinum rhodium thermocouples. The simulated lunar regolith is a basalt that closely resembles the lunar basalt returned to earth by the Apollo missions. The experiment will test the effects of vacuum, particle size, and density on the thermophysical properties of the regolith, which include melt temperature, specific heat thermal conductivity, and latent heat of storage. Two separate tests, using two different heaters, will be performed to study the effect of heating the system using radiative and conductive heat transfer. A finite differencing SINDA model was developed at NASA Lewis Research Center to predict the performance of the LUTHER experiment. The code will predict the effects of vacuum, particle size, and density has on the heat transfer to the simulated regolith.

Richter, Scott W.↗
NASA NTRS1993

Impact comminution of glasses: Implications for lunar regolith evolution

Glasses are important parts of every lunar regolith sample, whether in the form of indigenous melts such as mesostasis or pyroclastics, or as quenched impact melts. The modal proportions of agglutinitic impact melts alone can exceed 50 percent for some mature regoliths, and glasses are commonly the most dominant single component of lunar soils. They therefore participate in and possibly affect all evolutionary processes to which regoliths are subjected, such as comminution and attendant chemical fractionation as a function of grain size, the retention of solar-wind products, the production of superparamagnetic iron, and others. Because they are such an integral part of lunar regoliths, a more complete understanding of regolith evolution must include the role played by these vitreous components. This contribution examines the comminution behavior of a variety of glasses and a fine-grained basalt under conditions of repetitive impact, and compares this behavior to those of crystalline components, such as lithic fragments and major rock-forming minerals.

Cintala, Mark J.↗
NASA NTRS1993

Consortium study of the unusual H chondrite regolith breccia, Noblesville

The Noblesville meteorite is a genomict, regolith breccia (H6 clasts in H4 matrix). Moessbauer analysis confirms that Noblesville is unusually fresh, not surprising in view of its recovery immediately after its fall. It resembles 'normal' H4-6 chondrites in its chemical composition and induced thermoluminescence (TL) levels. Thus, at least in its contents of volatile trace elements, Noblesville differs from other H chondrite, class A regolith breccias. Noblesville's small pre-atmospheric mass and fall near solar maximum and/or its peculiar orbit (with perihelion less than 0.8 AU as shown by natural TL intensity) may partly explain its levels of cosmogenic radionuclides. Its cosmic ray exposure age of about 44 Ma is long, is equalled or exceeded by less than 3 percent of all H chondrites, and also differs from the 33 +/- 3 Ma mean exposure age peak of other H chondrite regolith breccias. While Noblesville is now among the chondritic regolithic breccias richest in solar gases, elemental ratios indicate some loss, especially of He, perhaps by impacts in the regolith that heated individual grains. While general shock-loading levels in Noblesville did not exceed 4 GPa, individual clasts record shock levels of 5-10 GPa, doubtless acquired prior to lithification of the whole-rock meteoroid.

Lipschutz, Michael E.↗
NASA NTRS1998

Comparison of Martian Meteorites and Martian Regolith as Shield Materials for Galactic Cosmic Rays

Theoretical calculations of radiation attenuation due to energetic galactic cosmic rays behind Martian rock and Martian regolith material have been made to compare their utilization as shields for advanced manned missions to Mars because the detailed chemical signature of Mars is distinctly different from Earth. The modified radiation fields behind the Martian rocks and the soil model were generated by solving the Boltzmann equation using a HZETRN system with the 1977 Solar Minimum environmental model. For the comparison of the attenuation characteristics, dose and dose equivalent are calculated for the five different subgroups of Martian rocks and the Martian regolith. The results indicate that changes in composition of subgroups of Martian rocks have negligible effects on the overall shielding properties because of the similarity of their constituents. The differences for dose and dose equivalent of these materials relative to those of Martian regolith are within 0.5 and 1 percent, respectively. Therefore, the analysis of Martian habitat construction options using in situ materials according to the Martian regolith model composition is reasonably accurate. Adding an epoxy to Martian regolith, which changes the major constituents of the material, enhances shielding properties because of the added hydrogenous constituents.

Kim, Myung-Hee Y.↗
NASA NTRS2002

Near-term lander experiments for growing plants on Mars: requirements for information on chemical and physical properties of Mars regolith

In order to support humans for long-duration missions to Mars, bioregenerative Advanced Life Support (ALS) systems have been proposed that would use higher plants as the primary candidates for photosynthesis. Hydroponic technologies have been suggested as the primary method of plant production in ALS systems, but the use of Mars regolith as a plant growth medium may have several advantages over hydroponic systems. The advantages for using Mars regolith include the likely bioavailability of plant-essential ions, mechanical support for plants, and easy access of the material once on the surface. We propose that plant biology experiments must be included in near-term Mars lander missions in order to begin defining the optimum approach for growing plants on Mars. Second, we discuss a range of soil chemistry and soil physics tests that must be conducted prior to, or in concert with, a plant biology experiment in order to properly interpret the results of plant growth studies in Mars regolith. The recommended chemical tests include measurements on soil pH, electrical conductivity and soluble salts, redox potential, bioavailability of essential plant nutrients, and bioavailability of phytotoxic elements. In addition, a future plant growth experiment should include procedures for determining the buffering and leaching requirements of Mars regolith prior to planting. Soil physical tests useful for plant biology studies in Mars regolith include bulk density, particle size distribution, porosity, water retention, and hydraulic conductivity.

NASA Center JSC↗
NASA NTRS2006

Development of Standardized Lunar Regolith Simulant Materials

Lunar exploration requires scientific and engineering studies using standardized testing procedures that ultimately support flight certification of technologies and hardware. It is necessary to anticipate the range of source materials and environmental constraints that are expected on the Moon and Mars, and to evaluate in-situ resource utilization (ISRU) coupled with testing and development. We describe here the development of standardized lunar regolith simulant (SLRS) materials that are traceable inter-laboratory standards for testing and technology development. These SLRS materials must simulate the lunar regolith in terms of physical, chemical, and mineralogical properties. A summary of these issues is contained in the 2005 Workshop on Lunar Regolith Simulant Materials [l]. Lunar mare basalt simulants MLS-1 and JSC-1 were developed in the late 1980s. MLS-1 approximates an Apollo 11 high-Ti basalt, and was produced by milling of a holocrystalline, coarse-grained intrusive gabbro (Fig. 1). JSC-1 approximates an Apollo 14 basalt with a relatively low-Ti content, and was obtained from a glassy volcanic ash (Fig. 2). Supplies of MLS-1 and JSC-1 have been exhausted and these materials are no longer available. No highland anorthosite simulant was previously developed. Upcoming lunar polar missions thus require the identification, assessment, and development of both mare and highland simulants. A lunar regolith simulant is manufactured from terrestrial components for the purpose of simulating the physical and chemical properties of the lunar regolith. Significant challenges exist in the identification of appropriate terrestrial source materials. Lunar materials formed under comparatively reducing conditions in the absence of water, and were modified by meteorite impact events. Terrestrial materials formed under more oxidizing conditions with significantly greater access to water, and were modified by a wide range of weathering processes. The composition space of lunar materials can be modeled by mixing programs utilizing a low-Ti basalt, ilmenite, KREEP component, high-Ca anorthosite, and meteoritic components. This approach has been used for genetic studies of lunar samples via chemical and modal analysis. A reduced composition space may be appropriate for simulant development, but it is necessary to determine the controlling properties that affect the physical, chemical and mineralogical components of the simulant.

Carpenter, P.↗
NASA NTRS2006

Materials Requirements for Standard Lunar Highlands Regolith Simulants as Defined by the NASA Simulant Development Program

The development of surface technologies for NASA's human and robotic lunar program beyond 2010 has begun. The multitude of projects underway and future ones will soon rely on the availability of lunar regolith simulant materials chosen to simulate the characteristics of lunar regoliths in order to design, test and qualify prototype hardware and flight equipment. The selection and development of standard lunar regolith simulants (SLRS) for the use of NASA technology programs was one of the main recommendations of the 2005 Workshop on Lunar Regolith Simulant Materials at Marshall Space Flight Center. The realization of that objective is now underway through the NASA simulant development program at the Marshall Space Flight Center. The approach adopted to define materials requirements for standard simulants of regolith from the Highlands regions of the Moon will be presented along with a discussion of limitations inherent to such an endeavor.

Sibille, Laurent↗