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All sourcesNASA NTRSDOE OSTI
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↗
NASA NTRS2008

Extant and Extinct Lunar Regolith Simulants: Modal Analyses of NU-LHT-1M and -2m, OB-1, JSC-1, JSC-1A and -1AF,FJS-1, and MLS-1

This work is part of a larger effort to compile an internally consistent database on lunar regolith (Apollo samples) and lunar regolith simulants. Characterize existing lunar regolith and simulants in terms of: a) Particle type; b) Particle size distribution; c) Particle shape distribution; d) Bulk density; and e) Other compositional characteristics. Evaluate regolith simulants (Figure of Merit) by above properties by comparison to lunar regolith (Apollo sample) This presentation covers new data on lunar simulants.

Schrader, Christian↗
NASA NTRS2009

Lunar Regolith Characterization for Simulant Design and Evaluation using Figure of Merit Algorithms

NASA's Marshall Space Flight Center (MSFC), in conjunction with the United States Geological Survey (USGS) and aided by personnel from the Astromaterials Research and Exploration Science group at Johnson Space Center (ARES-JSC), is implementing a new data acquisition strategy to support the development and evaluation of lunar regolith simulants. The first analyses of lunar regolith samples by the simulant group were carried out in early 2008 on samples from Apollo 16 core 64001/64002. The results of these analyses are combined with data compiled from the literature to generate a reference composition and particle size distribution (PSD)) for lunar highlands regolith. In this paper we present the specifics of particle type composition and PSD for this reference composition. Furthermore. we use Figure-of-Merit (FoM) routines to measure the characteristics of a number of lunar regolith simulants against this reference composition. The lunar highlands regolith reference composition and the FoM results are presented to guide simulant producers and simulant users in their research and development processes.

Schrader, Christian M.↗
NASA NTRS2009

The Lunar Regolith as a Remote Sensing Target for the Lunar Reconnaissance Orbiter (LRO)

Of the 6 instruments and one technology demonstration aboard the LRO, only CRaTER does not measure some kind of interaction of particles with the lunar regolith. LEND detects neutron fluence that contains information about the number density of protons in the upper regolith. To infer the presence of protons, the PI must assume a model that characterizes the surface as a collection of atoms. Thus, LEND does not sense the regolith as a structure. LROC, LOLA, and LAMP sense reflected photons whose wavelength is much shorter than the median particle size in the regolith. The photons interact with electrons, either in atomic shells or in chemical bonds. These interactions occur within a nanometer or so of the surface of a particle. Thus, the particles are macroscopic objects and models of the reflection process invoke ray-tracing optics. DIVINER senses photons that have been emitted by surface particles through thermal phonon processes. The wavelengths detected by the instrument are of the same order as the median particle size, and the photons contain information on particle dimensions as well as the molecular bonds in the constituent compounds. The Mini-RF synthetic aperture radar generates and detects photons of a few centimeters wavelength that interact with the regolith as a dielectric, the dielectric properties of the particulate component being described through effective medium theory. However, the interaction with rocks (macroscopic objects of interest to geologists) can be characterized using Fresnel or Mie models of electromagnetic properties.

Mendell, Wendell W.↗
NASA NTRS2008

Constraining Particle Variation in Lunar Regolith for Simulant Design

Simulants are used by the lunar engineering community to develop and test technologies for In Situ Resource Utilization (ISRU), excavation and drilling, and for mitigation of hazards to machinery and human health. Working with the United States Geological Survey (USGS), other NASA centers, private industry and academia, Marshall Space Flight Center (MSFC) is leading NASA s lunar regolith simulant program. There are two main efforts: simulant production and simulant evaluation. This work requires a highly detailed understanding of regolith particle type, size, and shape distribution, and of bulk density. The project has developed Figure of Merit (FoM) algorithms to quantitatively compare these characteristics between two materials. The FoM can be used to compare two lunar regolith samples, regolith to simulant, or two parcels of simulant. In work presented here, we use the FoM algorithm to examine the variance of particle type in Apollo 16 highlands regolith core and surface samples. For this analysis we have used internally consistent particle type data for the 90-150 m fraction of Apollo core 64001/64002 from station 4, core 60009/60010 from station 10, and surface samples from various Apollo 16 stations. We calculate mean modal compositions for each core and for the group of surface samples and quantitatively compare samples of each group to its mean as a measurement of within-group variance; we also calculate an FoM for every sample against the mean composition of 64001/64002. This gives variation with depth at two locations and between Apollo 16 stations. Of the tested groups, core 60009/60010 has the highest internal variance with an average FoM score of 0.76 and core 64001/64002 has the lowest with an average FoM of 0.92. The surface samples have a low but intermediate internal variance with an average FoM of 0.79. FoM s calculated against the 64001/64002 mean reference composition range from 0.79-0.97 for 64001/64002, from 0.41-0.91 for 60009/60010, and from 0.54-0.93 for the surface samples. Six samples fall below 0.70, and they are also the least mature (i.e., have the lowest I(sub s)/FeO). Because agglutinates are the dominant particle type and the agglutinate population increases with sample maturity (I(sub s)/FeO), the maturity of the sample relative to the reference is a prime determinant of the particle type FoM score within these highland samples.

Schrader, Christian M.↗
NASA NTRS2010

Formation Ages of the Apollo 16 Regolith Breccias: Implications for Accessing the Bombardment History of the Moon

Regolith breccias are lithified samples of the regolith that have been fused together by impact shock and thermal metamorphism. In lunar regolith samples, the ratio of trapped 40Ar/36Ar is a useful indicator of antiquity and can be used to model the closure age/lifithication event of the regolith (i.e. the apparent time when Ar became trapped [1]), thus providing an important insight into specific times when that regolith was interacting with the the dynamic inner solar system space environment [2-4].

Joy, K. H.↗
NASA NTRS2010

The 2010 Field Demonstration of the Solar Carbothermal Reduction of Regolith to Produce Oxygen

The Moon and other space exploration destinations are comprised of a variety of oxygen-bearing minerals, providing a virtually unlimited quantity of raw material which can be processed to produce oxygen. One attractive method to extract oxygen from the regolith is the carbothermal reduction process, which is not sensitive to variations in the mineral composition of the regolith. It also creates other valuable resources within the processed regolith, such as iron and silicon metals. Using funding from NASA, ORBITEC recently built and tested the Carbothermal Regolith Reduction Module to process lunar regolith simulants using concentrated solar energy. This paper summarizes the experimental test results obtained during a demonstration of the system at a lunar analog test site on the Mauna Kea volcano on Hawaii in February 2010.

Gustafson, R. J.↗
NASA NTRS2010

Pneumatic Regolith Transfer Systems for In-Situ Resource Utilization

One aspect of In-Situ Resource Utilization (lSRU) in a lunar environment is to extract oxygen and other elements from the minerals that make up the lunar regolith. Typical ISRU oxygen production processes include but are not limited to hydrogen reduction, carbothermal and molten oxide electrolysis. All of these processes require the transfer of regolith from a supply hopper into a reactor for chemical reaction processing, and the subsequent extraction of the reacted regolith from the reactor. This paper will discuss recent activities in the NASA ISRU project involved with developing pneumatic conveying methods to achieve lunar regolith simulant transfer under I-g and 1/6-g gravitational environments. Examples will be given of hardware that has been developed and tested by NASA on reduced gravity flights. Lessons learned and details of pneumatic regolith transfer systems will be examined as well as the relative performance in a 1/6th G environment

Mueller, Robert P.↗
NASA NTRS2011

Space Environmental Erosion of Polar Icy Regolith

While regions at the floors of permanently shadowed polar craters are isolated from direct sunlight, these regions are still exposed to the harsh space environment, including the interplanetary Lyman-a background, meteoric impacts, and obstacle-affected solar wind. We demonstrate that each of these processes can act to erode the polar icy regolith located at or near the surface along the crater floor. The Lyman-a background can remove/erode the icy-regolith via photon stimulated desorption [1], meteoric impacts can vaporize the regolith [2], and redirected solar wind ions can sputter the ice-regolith mix [3]. As an example we shall examine in detail the inflow of solar wind ions and electrons into polar craters, One might expect such ions to flow horizontally over the crater top (see Figure). However, we find that plasma ambipolar processes act to deflect passing ions into the craters [3]. We examine this plasma process and determine the ion flux as a function of position across a notional crater floor. We demonstrate that inflowing solar wind ions can indeed create sputtering along the crater floor, effectively eroding the surface. Erosion time scales rrom sputtering will be presented. We shall also consider the effect of impact vaporization on buried icy-regolith regions. There will also be a discussion of solar wind electrons that enter into the PSR, demonstrating that these also have the ability rree surface-bound atoms via electron stimulated desorption processes [l].

Farrell, William M.↗
NASA NTRS2012

Regolith Depth, Mobility, and Variability on Vesta from Dawn's Low Altitude Mapping Orbit

Regolith, the fragmental debris layer formed from impact events of all sizes, covers the surface of all asteroids imaged by spacecraft to date. Here we use Framing Camera (FC) images [1] acquired by the Dawn spacecraft [2] from its low-altitude mapping orbit (LAMO) of 210 km (pixel scales of ~20 m) to characterize regolith depth, variability, and mobility on Vesta, and to locate areas of especially thin regolith and exposures of competent material. These results will help to evaluate how the surface of this differentiated asteroid has evolved over time, and provide key contextual information for understanding the origin and degree of mixing of the surficial materials for which compositions are estimated [3,4] and the causes of the relative spectral immaturity of the surface [5]. Vestan regolith samples, in the form of howardite meteorites, can be studied in the laboratory to provide complementary constraints on the regolith process [6].

Denevi, B. W.↗
NASA NTRS2012

Solar Ion Sputter Deposition in the Lunar Regolith: Experimental Simulation Using Focused-Ion Beam Techniques

As regions of the lunar regolith undergo space weathering, their component grains develop compositionally and microstructurally complex outer coatings or "rims" ranging in thickness from a few 10 s to a few 100's of nm. Rims on grains in the finest size fractions (e.g., <20 m) of mature lunar regoliths contain optically-active concentrations of nm size metallic Fe spherules, or "nanophase Fe(sup o)" that redden and attenuate optical reflectance spectral features important in lunar remote sensing. Understanding the mechanisms for rim formation is therefore a key part of connecting the drivers of mineralogical and chemical changes in the lunar regolith with how lunar terrains are observed to become space weathered from a remotely-sensed point of view. As interpreted based on analytical transmission electron microscope (TEM) studies, rims are produced from varying relative contributions from: 1) direct solar ion irradiation effects that amorphize or otherwise modify the outer surface of the original host grain, and 2) nanoscale, layer-like, deposition of extrinsic material processed from the surrounding soil. This extrinsic/deposited material is the dominant physical host for nanophase Fe(sup o) in the rims. An important lingering uncertainty is whether this deposited material condensed from regolith components locally vaporized in micrometeorite or larger impacts, or whether it formed as solar wind ions sputtered exposed soil and re-deposited the sputtered ions on less exposed areas. Deciding which of these mechanisms is dominant, or possibility exclusive, has been hampered because there is an insufficient library of chemical and microstructural "fingerprints" to distinguish deposits produced by the two processes. Experimental sputter deposition / characterization studies relevant to rim formation have particularly lagged since the early post-Apollo experiments of Hapke and others, especially with regard to application of TEM-based characterization techniques. Here we report on a novel design for simulating solar ion sputter deposition in the lunar regolith, with characterization of the resulting sputter deposits by an array of advanced analytical TEM techniques.

Christoffersen, R.↗
NASA NTRS2012

The Lunar Regolith as a Recorder of Cosmic History

The Moon can be considered a giant tape recorder containing the history of the solar system and Universe. The lunar regolith (soil) has recorded the early history of the Moon, Earth, the solar system and Universe. A major goal of future lunar exploration should be to find and play back existing fragments of that tape . By reading the lunar tape, we can uncover a record of planetary bombardment, as well as solar and stellar variability. The Moon can tell us much about our place in the Universe. The lunar regolith has likely recorded the original meteoritic bombardment of Earth and Moon, a violent cataclysm that may have peaked around 4 Gyr, and the less intense bombardment occurring since that time. This impact history is preserved on the Moon as regolith layers, ejecta layers, impact melt rocks, and ancient impact breccias. The impact history of the Earth and Moon possibly had profound effects on the origin and development of life. Decrease in meteor bombardment allowed life to develop on Earth. Life may have developed first on another body, such as Mars, then arrived via meteorite on Earth. The solar system may have experienced bursts of severe radiation from the Sun, other stars, or from unknown sources. The lunar regolith has recorded this radiation history in the form of implanted solar wind, solar flare materials and radiation damage. Lunar soil can be found sandwiched between layers of basalt or pyroclastic deposits. This filling constitutes a buried time capsule that is likely to contain well-preserved ancient regolith. Study of such samples will show us how the solar system has evolved and changed over time. The lunar tape recorder can provide detailed information on specific portions of solar and stellar variability. Data from the Moon also offers clues as to whether so-called fundamental constants have changed over time.

Cooper, Bonnie↗
NASA NTRS2012

Composition and Petrology of HED Polymict Breccias: The Regolith of (4) Vesta

The polymict breccias of the howardite, eucrite and diogenite (HED) clan of meteorites preserve records of regolith processes that occur on Vesta, their putative home world. These breccias -- howardites, polymict eucrites and polymict diogenites -- are impact-engendered mixtures of diogenites and eucrites. The compositions of polymict breccias can be used to constrain the lithologic diversity of the vestan crust and the excavation depths of these materials. We have done petrological and compositional studies of multiple samples of 5 polymict eucrites and 28 howardites to investigate these issues. Older analyses were done on samples of approx 0.5 gram mass by INAA; newer analyses on samples of approx 5 gram mass by XRF and ICP-MS. We estimate the percentage of eucritic material (POEM) of polymict breccias by comparing their Al and/or Ca contents to those of average basaltic eucrite and diogenite. Our samples have POEM ranging from 28 to 98; adding two polymict diogenites from extends the range to POEM 10. One hypothesis is that ancient, well-mixed vestan regolith has POEM approx 67 and has a higher content of admixed impactor material. Several of our howardites have POEM of 59-74 (Al and/or Ca contents +/- 10% of POEM 67); about a third have Ni contents >300 micro g/g suggesting they contain >2% chondritic material (CM and/or CR). These may be regolithic howardites. Only one (LEW 85313) contains Ne dominated by a solar wind (SW) component. PCA 02066 is dominated by impact-melt material of polymict parentage and petrologically appears to be a mature regolith breccia, yet it does not contain SW-Ne. GRO 95602 falls within the POEM window, contains SW-Ne], yet has a Ni content of 193 micro g/g. Its petrologic characteristics suggest it was formed from immature regolith (no polymict breccia clasts; no glass). Trace element characteristics of the polymict breccias demonstrate the dominance of main-group eucrites as the basaltic component. Mixing diagrams of Zr, Nb, Ba, Hf and Ta with Al show no evidence for a significant contribution from Stannern-trend eucrites. An exception is polymict eucrite LEW 86001 (POEM 92), which is dominated by Stannern-trend basaltic debris. Howardite LAP 04838 (POEM 84) has higher incompatible trace concentrations than other polymict breccias (excluding LEW 86001), and either contains a Stannern-trend basaltic component, or has a significant contributions from evolved eucrites like Nuevo Laredo.

Mittlefehldt, David W.↗