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Noble, S. K.

Publications and source records attributed to Noble, S. K..

At least 19 records
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Natural Environments Definition for Design

Planning for future National Aeronautics and Space Administration (NASA) missions will encompass a variety of operational and engineering activities that involve a multitude of issues, constraints, and influences derived from the natural environment. This Technical Memorandum (TM) presents a definition of the natural environment, i.e., a description in engineering handbook format of models and data specifically selected to support the architecture development, engineering design, and technology development for NASA's Exploration Systems Development (ESD) initiatives.

Justh, H. L.↗
NASA NTRS2016

Evolution of Shock Melt Compositions in Lunar Regoliths

Space weathering processes - driven primarily by solar wind ion and micrometeorite bombardment, are constantly changing the surface regoliths of airless bodies, such as the Moon. It is essential to study lunar soils in order to fully under-stand the processes of space weathering, and how they alter the optical reflectance spectral properties of the lunar surface relative to bedrock. Lunar agglutinates are aggregates of regolith grains fused together in a glassy matrix of shock melt produced during micrometeorite impacts into the lunar regolith. The formation of the shock melt component in agglutinates involves reduction of Fe in the target material to generate nm-scale spherules of metallic Fe (nanophase Fe0 or npFe0). The ratio of elemental Fe, in the form of npFe0, to FeO in a given bulk soil indicates its maturity, which increases with length of surface exposure as well as being typically higher in the finer-size fraction of soils. The melting and mixing process in agglutinate formation remain poorly understood. This includes incomplete knowledge regarding how the homogeneity and overall compositional trends of the agglutinate glass portions (agglutinitic glass) evolve with maturity. The aim of this study is to use sub-micrometer scale X-ray compositional mapping and image analysis to quantify the chemical homogeneity of agglutinitic glass, correlate its homogeneity to its parent soil maturity, and identify the principal chemical components contributing to the shock melt composition variations. An additional focus is to see if agglutinitic glass contains anomalously high Fe sub-micron scale compositional domains similar to those recently reported in glassy patina coatings on lunar rocks.

Vance, A. M.↗
NASA NTRS2016

The Microstructure of Lunar Micrometeorite Impact Craters

The peak of the mass flux of impactors striking the lunar surface is made up of objects approximately 200 micrometers in diameter that erode rocks, comminute regolith grains, and produce agglutinates. The effects of these micro-scale impacts are still not fully understood. Much effort has focused on evaluating the physical and optical effects of micrometeorite impacts on lunar and meteoritic material using pulsed lasers to simulate the energy deposited into a substrate in a typical hypervelocity impact. Here we characterize the physical and chemical changes that accompany natural micrometeorite impacts into lunar rocks with long surface exposure to the space environment (12075 and 76015). Transmission electron microscope (TEM) observations were obtained from cross-sections of approximately 10-20 micrometers diameter craters that revealed important micro-structural details of micrometeorite impact processes, including the creation of npFe (sup 0) in the melt, and extensive deformation around the impact site.

Noble, S. K.↗
NASA NTRS2015

LADEE Science Results and Implications for Exploration

NASA's Lunar Atmosphere and Dust Environment Explorer, LADEE, concluded a fully successful investigation of the Moon's tenuous gas and dust atmosphere on April 18, 2014. LADEE hosted three science instruments to address atmospheric and dust objectives, and a technology demonstration of deep-space optical communication. The three science instruments were an ultraviolet-visible spectrometer (UVS), a neutral mass spectrometer (NMS), and a lunar dust experiment (LDEX). All data acquired by these instruments have been submitted to the Planetary Data System. A mission overview and science instrument descriptions are readily available. LADEE inserted into a low-altitude, retrograde lunar orbit optimized for observations at the sunrise terminator, where surface temperatures rise abruptly. LADEE also carried out observations over a wide range of local times and altitudes. Here we describe some of the initial results.

LADEE↗
NASA NTRS2015

Distribution and Origin of Amino Acids in Lunar Regolith Samples

The existence of organic compounds on the lunar surface has been a question of interest from the Apollo era to the present. Investigations of amino acids immediately after collection of lunar samples yielded inconclusive identifications, in part due to analytical limitations including insensitivity to certain compounds, an inability to separate enantiomers, and lack of compound-specific isotopic measurements. It was not possible to determine if the detected amino acids were indigenous to the lunar samples or the result of terrestrial contamination. Recently, we presented initial data from the analysis of amino acid abundances in 12 lunar regolith samples and discussed those results in the context of four potential amino acid sources [5]. Here, we expand on our previous work, focusing on amino acid abundances and distributions in seven regolith samples and presenting the first compound-specific carbon isotopic ratios measured for amino acids in a lunar sample.

Elsila, J. E.↗
NASA NTRS2014

Distribution of Amino Acids in Lunar Regolith

One of the most eagerly studied questions upon initial return of lunar samples was whether significant amounts of organic compounds, including amino acids, were present. Analyses during the 1970s produced only tentative and inconclusive identifications of indigenous amino acids. Those analyses were hampered by analytical difficulties including relative insensitivity to certain compounds, the inability to separate chiral enantiomers, and the lack of compound-specific isotopic measurements, which made it impossible to determine whether the detected amino acids were indigenous to the lunar samples or the results of contamination. Numerous advances have been made in instrumentation and methodology for amino acid characterization in extraterrestrial samples in the intervening years, yet the origin of amino acids in lunar regolith samples has been revisited only once for a single lunar sample, (3) and remains unclear. Here, we present initial data from the analyses of amino acid abundances in 12 lunar regolith samples. We discuss these abundances in the context of four potential amino acid sources: (1) terrestrial biological contamination; (2) contamination from lunar module (LM) exhaust; (3) derivation from solar windimplanted precursors; and (4) exogenous delivery from meteorites.

Elsila, J. E.↗
NASA NTRS2014

Nanoscale Compositional Relations in Lunar Rock Patina: Deciphering Sources for Patina Components on an Apollo 17 Station 6 Boulder

Space weathering on the Moon and other airless bodies modifies the surfaces of regolith grains as well as the space-exposed surfaces of larger rocks and boulders. As space weathering witness plates, rocks and boulders are distinguished from regolith grains based on their ability to persist as physically intact substrates over longer time scales before being disaggregated by impact processes. Because lunar surfaces, including exposed rocks, quickly develop an optically thick layer of patina, it is important to understand the compositional relationship between patinas and their underlying rock substrates, particularly to support remote-sensing of rocky lunar terrains. Based on analytical TEM techniques, supported by focused ion beam (FIB) cross-sectioning, we have begun to systematize the multi-layer microstructural complexity of patinas on rock samples with a range of space exposure histories. Our on-going work has particularly focused on lunar rock 76015, both because it has a long (approx. 22 my) exposure history, and because its surface was exposed to patina development approximately 1 m off the regolith surface on a boulder in the Apollo 17 Station 6 boulder field. Potential sources for the 76015 patina therefore include impact-melted and vaporized material derived from the local rock substrate, as well as from the mix of large boulders and regolith in the Station 6 area. While similar, there are differences in the mineralogy and chemistry of the rocks and regolith at Station 6. We were interested to see if these, or other sources, could be distinguished in the average composition, as well as the compositional nanostratigraphy of the 76015 patina. To date we have acquired a total of 9 TEM FIB cross-sections from the 76015 patina, giving us reasonable confidence of being able to arrive at an integrated average for the patina major element composition based on analytical TEM methods.

Christoffersen, R.↗
NASA NTRS2013

Lateral Variations in Lunar Weathering Patina on Centimeter to Nanometer Scales

All materials exposed at the lunar surface undergo space weathering processes. On the Moon, boulders make up only a small percentage of the exposed surface, and areas where such rocks are exposed, like central peaks, are often among the least space weathered regions identified from remote sensing data. Yet space weathered surfaces (patina) are relatively common on returned rock samples, some of which directly sample the surface of larger boulders. Because, as witness plates to lunar space weathering, rocks and boulders experience longer exposure times compared to lunar soil grains, they allow us to develop a deeper perspective on the relative importance of various weathering processes as a function of time.

Noble, S. K.↗
NASA NTRS2013

Asteroidal Space Weathering: The Major Role of FeS

Space weathering (SW) effects on the lunar surface are reasonably well-understood from sample analyses, remote-sensing data, and experiments, yet our knowledge of asteroidal SW effects are far less constrained. While the same SW processes are operating on asteroids and the Moon, namely solar wind irradiation, impact vaporization and condensation, and impact melting, their relative rates and efficiencies are poorly known, as are their effects on such vastly different parent materials. Asteroidal SW models based on remote-sensing data and experiments are in wide disagreement over the dominant mechanisms involved and their kinetics. Lunar space weathering effects observed in UVVIS-NIR spectra result from surface- and volume-correlated nanophase Fe metal (npFe(sup 0)) particles. In the lunar case, it is the tiny vapor-deposited npFe(sup 0) that provides much of the spectral reddening, while the coarser (largely melt-derived) npFe(sup 0) produce lowered albedos. Nanophase FeS (npFeS) particles are expected to modify reflectance spectra in much the same way as npFe(sup 0) particles. Here we report the results of experiments designed to explore the efficiency of npFeS production via the main space weathering processes operating in the asteroid belt.

Keller, L. P.↗
NASA NTRS2012

Space Weathering of Lunar Rocks

All materials exposed at the lunar surface undergo space weathering processes. On the Moon, boulders make up only a small percentage of the exposed surface, and areas where such rocks are exposed, like central peaks, are often among the least space weathered regions identified from remote sensing data. Yet space weathered surfaces (patina) are relatively common on returned rock samples, some of which directly sample the surface of larger boulders. Because, as witness plates to lunar space weathering, rocks and boulders experience longer exposure times compared to lunar soil grains, they allow us to develop a deeper perspective on the relative importance of various weathering processes as a function of time.

Noble, S. K.↗
NASA NTRS2012

Comparative Mineralogy, Microstructure and Compositional Trends in the Sub-Micron Size Fractions of Mare and Highland Lunar Soils

The morphology, mineralogy, chemical composition and optical properties of lunar soils show distinct correlations as a function of grain size and origin [1,2,3]. In the <20 m size fraction, there is an increased correlation between lunar surface properties observed through remote sensing techniques and those attributed to space weathering phenomenae [1,2]. Despite the establishment of recognizable trends in lunar grains <20 in size [1,2,3], the size fraction < 10 m is characterized as a collective population of grains without subdivision. This investigation focuses specifically on grains in the <1 m diameter size fraction for both highland and mare derived soils. The properties of these materials provide the focus for many aspects of lunar research including the nature of space weathering on surface properties, electrostatic grain transport [4,5] and dusty plasmas [5]. In this study, we have used analytical transmission and scanning transmission electron microscopy (S/TEM) to characterize the mineralogy type, microstructure and major element compositions of grains in this important size range in lunar soils.

Thompson, M. S.↗
NASA NTRS2011

Space Weathering of Ordinary Chondrite Parent Bodies, Its Impact on the Method of Distinguishing H, L, and LL Types and Implications for Itokawa Samples Returned by the Hayabusa Mission

As the most abundance meteorites in our collections, ordinary chondrites potentially have very important implications on the origin and formation of our Solar System. In order to map the distribution of ordinary chondrite-like asteroids through remote sensing, the space weathering effects of ordinary chondrite parent bodies must be addressed through experiments and modeling. Of particular importance is the impact on distinguishing different types (H/L/LL) of ordinary chondrites. In addition, samples of asteroid Itokawa returned by the Hayabusa spacecraft may re~ veal the mechanism of space weathering on an LLchondrite parent body. Results of space weathering simulations on ordinary chondrites and implications for Itokawa samples are presented here.

Hiroi, T.↗
NASA NTRS2011

Sampling the Uppermost Surface of Airless Bodies

The uppermost surface of an airless body is a critical source of ground-truth information for the various remote sensing techniques that only penetrate nanometers to micrometers into the surface. Such samples will also be vital for understanding conditions at the surface and acquiring information about how the body interacts with its environment, including solar wind interaction, grain charging and levitation [1]. Sampling the uppermost surface while preserving its structure (e.g. porosity, grain-to-grain contacts) however, is a daunting task that has not been achieved on any sample return mission to date.

Noble, S. K.↗
NASA NTRS2011

Experimental Space Weathering of Ordinary Chondrites by Nanopulse Laser: TEM Results

A set of ordinary chondrite meteorites has been subjected to artificial space weathering by nanopulse laser to simulate the effects of micrometeorite bombardment. Three meteorites, an H (Ehole), L (Chateau Renard - CR), and LL (Appley Bridge - AB) were lasered following the method of Sasaki et al [1]. Near IR spectra were taken before and after exposure to examine the optical changes induced and the samples were examined by scanning and transmission electron microscopy (SEM and TEM) to understand the physical changes.

Noble, S. K.↗
NASA NTRS2010

The Epiregolith

The physical properties of the lunar regolith were originally inferred from remotely sensed data, first from the Earth and later from orbiting spacecraft. The Surveyor landings and the Apollo surface explorations produced a more concrete characterization of the macroscopic properties. In general, the upper regolith consists of a loosely consolidated layer centimeters thick underlain by a particulate but extremely compacted layer to depths of meters or tens of meters. The median particle size as determined by mechanical sieving in terrestrial laboratories is several tens of micrometers. However, the comminuting processes that form the layer produce particles in all sizes down to manometers. The smallest particles, having a high surface to volume ratio, tend to be electrostatically bound to larger particles and are quite difficult to separate mechanically in the laboratory. Particle size distributions determined from lunar soil samples often group particles smaller than 10 micrometers.

Mendell, Wendell W.↗
NASA NTRS2005

Extracting Quantitative Data from Lunar Soil Spectra

Using the modified Gaussian model (MGM) developed by Sunshine et al. [1] we compared the spectral properties of the Lunar Soil Characterization Consortium (LSCC) suite of lunar soils [2,3] with their petrologic and chemical compositions to obtain quantitative data. Our initial work on Apollo 17 soils [4] suggested that useful compositional data could be elicited from high quality soil spectra. We are now able to expand upon those results with the full suite of LSCC soils that allows us to explore a much wider range of compositions and maturity states. The model is shown to be sensitive to pyroxene abundance and can evaluate the relative portion of high-Ca and low-Ca pyroxenes in the soils. In addition, the dataset has provided unexpected insights into the nature and causes of absorption bands in lunar soils. For example, it was found that two distinct absorption bands are required in the 1.2 m region of the spectrum. Neither of these bands can be attributed to plagioclase or agglutinates, but both appear to be largely due to pyroxene.

Noble, S. K.↗
NASA NTRS2004

Quantitative Aspects of Space Weathering: Implications for Regolith Breccia Meteorites and Asteroids

Space weathering is defined as the physical and optical changes incurred by material exposed to the space environment. Through studies of lunar soils, these changes are becoming well understood. However, the effects of space weathering are dependent on the physical environment to which the host materials are exposed, and thus, the effects will likely vary from body to body. The optical effects of space weathering result from nanophase iron (npFe(sup 0)) created during micrometeorite bombardment and solar wind sputtering. In the asteroid belt, bodies are farther from the sun than our Moon, and are widely known to incur less solar wind implantation and sputtering. The velocity of impacts is smaller resulting in less melting and vaporization, and therefore fewer space weathering products. The impact rate in the asteroid belt is greater, which will result in more comminution, further diluting any weathering products. Ergo, asteroidal regoliths should contain fewer space weathering products than lunar soils. However, even very small degrees of space weathering can have dramatic consequences for the optical properties of soils. A discussion on the optical effects of space weathering is presented.

Noble, S. K.↗