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Zeigler, R. A.

Publications and source records attributed to Zeigler, R. A..

At least 55 records · Page 3
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NASA NTRS2015

Using Technology to Better Characterize the Apollo Sample Suite: A Retroactive PET Analysis and Potential Model for Future Sample Return Missions

From 1969-1972 the Apollo missions collected 382 kg of lunar samples from six distinct locations on the Moon. Studies of the Apollo sample suite have shaped our understanding of the formation and early evolution of the Earth-Moon system, and have had important implications for studies of the other terrestrial planets (e.g., through the calibration of the crater counting record) and even the outer planets (e.g., the Nice model of the dynamical evolution of the Solar System). Despite nearly 50 years of detailed research on Apollo samples, scientists are still developing new theories about the origin and evolution of the Moon. Three areas of active research are: (1) the abundance of water (and other volatiles) in the lunar mantle, (2) the timing of the formation of the Moon and the duration of lunar magma ocean crystallization, (3) the formation of evolved lunar lithologies (e.g., granites) and implications for tertiary crustal processes on the Moon. In order to fully understand these (and many other) theories about the Moon, scientists need access to "new" lunar samples, particularly new plutonic samples. Over 100 lunar meteorites have been identified over the past 30 years, and the study of these samples has greatly aided in our understanding of the Moon. However, terrestrial alteration and the lack of geologic context limit what can be learned from the lunar meteorites. Although no "new" large plutonic samples (i.e., hand-samples) remain to be discovered in the Apollo sample collection, there are many large polymict breccias in the Apollo collection containing relatively large (approximately 1 cm or larger) previously identified plutonic clasts, as well as a large number of unclassified lithic clasts. In addition, new, previously unidentified plutonic clasts are potentially discoverable within these breccias. The question becomes how to non-destructively locate and identify new lithic clasts of interest while minimizing the contamination and physical degradation of the samples.

Zeigler, R. A.↗
NASA NTRS2015

Comprehensive Non-Destructive Conservation Documentation of Lunar Samples Using High-Resolution Image-Based 3D Reconstructions and X-Ray CT Data

Established contemporary conservation methods within the fields of Natural and Cultural Heritage encourage an interdisciplinary approach to preservation of heritage material (both tangible and intangible) that holds "Outstanding Universal Value" for our global community. NASA's lunar samples were acquired from the moon for the primary purpose of intensive scientific investigation. These samples, however, also invoke cultural significance, as evidenced by the millions of people per year that visit lunar displays in museums and heritage centers around the world. Being both scientifically and culturally significant, the lunar samples require a unique conservation approach. Government mandate dictates that NASA's Astromaterials Acquisition and Curation Office develop and maintain protocols for "documentation, preservation, preparation and distribution of samples for research, education and public outreach" for both current and future collections of astromaterials. Documentation, considered the first stage within the conservation methodology, has evolved many new techniques since curation protocols for the lunar samples were first implemented, and the development of new documentation strategies for current and future astromaterials is beneficial to keeping curation protocols up to date. We have developed and tested a comprehensive non-destructive documentation technique using high-resolution image-based 3D reconstruction and X-ray CT (XCT) data in order to create interactive 3D models of lunar samples that would ultimately be served to both researchers and the public. These data enhance preliminary scientific investigations including targeted sample requests, and also provide a new visual platform for the public to experience and interact with the lunar samples. We intend to serve these data as they are acquired on NASA's Astromaterials Acquisistion and Curation website at http://curator.jsc.nasa.gov/. Providing 3D interior and exterior documentation of astromaterial samples addresses the increasing demands for accessability to data and contemporary techniques for documentation, which can be realized for both current collections as well as future sample return missions.

Blumenfeld, E. H.↗
NASA NTRS2014

High-Resolution Imaged-Based 3D Reconstruction Combined with X-Ray CT Data Enables Comprehensive Non-Destructive Documentation and Targeted Research of Astromaterials

Providing web-based data of complex and sensitive astromaterials (including meteorites and lunar samples) in novel formats enhances existing preliminary examination data on these samples and supports targeted sample requests and analyses. We have developed and tested a rigorous protocol for collecting highly detailed imagery of meteorites and complex lunar samples in non-contaminating environments. These data are reduced to create interactive 3D models of the samples. We intend to provide these data as they are acquired on NASA's Astromaterials Acquisition and Curation website at http://curator.jsc.nasa.gov/.

Blumenfeld, E. H.↗
NASA NTRS2014

Crystal Stratigraphy of Two Basalts from Apollo 16: Unique Crystallization of Picritic Basalt 606063,10-16 and Very-Low-Titanium Basalt 65703,9-13

A geochemical survey of Apollo 16 regolith fragments found five basaltic samples from among hundreds of 2-4 mm regolith fragments of the Apollo 16 site. These included a high-Ti vitrophyric basalt (60603,10-16) and one very-low-titanium (VLT) crystalline basalt (65703,9-13). Apollo 16 was the only highlands sample return mission distant from the maria (approx. 200 km). Identification of basaltic samples at the site not from the ancient regolith breccia indicates input of material via lateral transport by post-basin impacts. The presence of basaltic rocklets and glass at the site is not unprecedented and is required to satisfy mass-balance constraints of regolith compositions. However, preliminary characterization of olivine and plagioclase crystal size distributions indicated the sample textures were distinct from other known mare basalts, and instead had affinities to impact melt textures. Impact melt textures can appear qualitatively similar to pristine basalts, and quantitative analysis is required to distinguish between the two in thin section. The crystal stratigraphy method is a powerful tool in studying of igneous systems, utilizing geochemical analyses across minerals and textural analyses of phases. In particular, trace element signatures can aid in determining the ultimate origin of these samples and variations document subtle changes occurring during their petrogenesis.

Donohue, P. H.↗
NASA NTRS2014

Connecting Lunar Meteorites to Source Terrains on the Moon

The number of named stones found on Earth that have proven to be meteorites from the Moon is approx. 180 so far. Since the Moon has been mapped globally in composition and mineralogy from orbit, it has become possible to speculate broadly on the region of origin on the basis of distinctive compositional characteristics of some of the lunar meteorites. In particular, Lunar Prospector in 1998 [1,2] mapped Fe and Th at 0.5 degree/pixel and major elements at 5 degree/pixel using gamma ray spectroscopy. Also, various multispectral datasets have been used to derive FeO and TiO2 concentrations at 100 m/pixel spatial resolution or better using UV-VIS spectral features [e.g., 3]. Using these data, several lunar meteorite bulk compositions can be related to regions of the Moon that share their distinctive compositional characteristics. We then use EPMA to characterize the petrographic characteristics, including lithic clast components of the meteorites, which typically are breccias. In this way, we can extend knowledge of the Moon's crust to regions beyond the Apollo and Luna sample-return sites, including sites on the lunar farside. Feldspathic Regolith Breccias. One of the most distinctive general characteristics of many lunar meteorites is that they have highly feldspathic compositions (Al2O3 approx. 28% wt.%, FeO <5 wt.%, Th <1 ppm). These compositions are significant because they are similar to a vast region of the Moon's farside highlands, the Feldspathic Highlands Terrane, which are characterized by low Fe and Th in remotely sensed data [4]. The meteorites provide a perspective on the lithologic makeup of this part of the Moon, specifically, how anorthositic is the surface and what, if any, are the mafic lithic components? These meteorites are mostly regolith breccias dominated by anorthositic lithic clasts and feldspathic glasses, but they do also contain a variety of more mafic clasts. On the basis of textures, we infer these clasts to have formed by large impacts that excavated and mixed rocks from depth within the lunar crust and possibly the upper mantle. One of the key questions is whether the mafic materials are ferroan or magnesian, which remote sensing does not clearly distinguish, and if mafic, whether they might contain mantlederived components such as olivine (dunite). Many but not all have mainly ferroan mafic components, consistent with a ferroan crustal source that is complementary to the ferroan anorthositic suite and that represents primary magma-ocean-derived feldspathic crust. Meteorites such as ALH 81005 [5] and Shişr 161 [6], however, contain coarse-grained magnesian mafic clasts (Fig. 1a) derived from deeply seated and melted material associated with impact basins. Comparison to LP gamma-ray data [2] supports an origin for magnesian feldspathic meteorites such as these (e.g., Shişr 161) as shown in Fig. 1b. Sayh al Uhaymir (SaU) 169. Another distinctive but much less common composition is represented by relatively mafic impact-melt breccia that is rich in incompatible elements known as KREEP. These meteorites can be related to the western nearside Procellarum KREEP Terrane, especially through a combination of Fe and Th contents. Among the most enriched is SaU 169, which has been related to high- Th impact-melt breccia found at the Apollo 12 site [7]. Through detailed EPMA and ion microprobe analysis we have shown that these two rock types are related in age and origin.

Jolliff, B. L.↗
NASA NTRS2013

Consortium Study of the Chelyabinsk Meteorite

On February 15, 2013 approximately 17 m asteroid hit Earth, causing shock waves and air blasts over a portion of Russia. A significant amount of material has been recovered from this meteorite fall, officially named Chelyabinsk.

Righter, K.↗
NASA NTRS2013

Nondestructive Analysis of Astromaterials by Micro-CT and Micro-XRF Analysis for PET Examination

An integral part of any sample return mission is the initial description and classification of returned samples by the preliminary examination team (PET). The goal of the PET is to characterize and classify returned samples and make this information available to the larger research community who then conduct more in-depth studies on the samples. The PET tries to minimize the impact their work has on the sample suite, which has in the past limited the PET work to largely visual, nonquantitative measurements (e.g., optical microscopy). More modern techniques can also be utilized by a PET to nondestructively characterize astromaterials in much more rigorous way. Here we discuss our recent investigations into the applications of micro-CT and micro-XRF analyses with Apollo samples and ANSMET meteorites and assess the usefulness of these techniques in future PET. Results: The application of micro computerized tomography (micro-CT) to astromaterials is not a new concept. The technique involves scanning samples with high-energy x-rays and constructing 3-dimensional images of the density of materials within the sample. The technique can routinely measure large samples (up to approx. 2700 cu cm) with a small individual voxel size (approx. 30 cu m), and has the sensitivity to distinguish the major rock forming minerals and identify clast populations within brecciated samples. We have recently run a test sample of a terrestrial breccia with a carbonate matrix and multiple igneous clast lithologies. The test results are promising and we will soon analyze a approx. 600 g piece of Apollo sample 14321 to map out the clast population within the sample. Benchtop micro x-ray fluorescence (micro-XRF) instruments can rapidly scan large areas (approx. 100 sq cm) with a small pixel size (approx. 25 microns) and measure the (semi) quantitative composition of largely unprepared surfaces for all elements between Be and U, often with sensitivity on the order of a approx. 100 ppm. Our recent testing of meteorite and Apollo samples on micro-XRF instruments has shown that they can easily detect small zircons and phosphates (approx. 10 m), distinguish different clast lithologies within breccias, and identify different lithologies within small rock fragments (2-4 mm soil Apollo soil fragments).

Zeigler, R. A.↗
NASA NTRS2013

Testing the Origins of Basalt Fragments fro Apollo 16

Several 2-4 mm regolith fragments of basalt from the Apollo 16 site were recently described by [1]. These included a high-Ti vitrophyric basalts (60603,10-16) and one very-low-titanium (VLT) crystalline basalt (65703,9-13). As Apollo 16 was the only highlands sample return mission distant from the maria, identification of basaltic samples at the site indicates input from remote sites via impact processes [1]. However, distinguishing between impact melt and pristine basalt can be notoriously difficult and requires significant sample material [2-6]. The crystal stratigraphy method utilizes essentially non-destructive methods to make these distinctions [7,8]. Crystal stratigraphy combines quantitative petrography in the form of crystal size distributions (CSDs) coupled with mineral geochemistry to reveal the petrogenetic history of samples. The classic CSD plot of crystal size versus population density can reveal insights on growth/cooling rates, residence times, and magma history which in turn can be used to evaluate basaltic vs impact melt origin [7-9]. Electron microprobe (EMP) and laser ablation (LA)-ICP-MS analyses of mineral phases complement textural investigations. Trace element variations document subtle changes occurring during the formation of the samples, and are key in the interpretation and preservation of this rare lunar sample collection.

Donohue, P. H.↗
NASA NTRS2012

U-Pb Dating of Zircons and Phosphates in Lunar Meteorites, Acapulcoites and Angrites

Zircon U-Pb geochronology has made a great contribution to the timing of magmatism in the early Solar System [1-3]. Ca phosphates are another group of common accessory minerals in meteorites with great potential for U-Pb geochronology. Compared to zircons, the lower closure temperatures of the U-Pb system for apatite and merrillite (the most common phosphates in achondrites) makes them susceptible to resetting during thermal metamorphism. The different closure temperatures of the U-Pb system for zircon and apatite provide us an opportunity to discover the evolutionary history of meteoritic parent bodies, such as the crystallization ages of magmatism, as well as later impact events and thermal metamorphism. We have developed techniques using the Cameca IMS-1280 ion microprobe to date both zircon and phosphate grains in meteorites. Here we report U-Pb dating results for zircons and phosphates from lunar meteorites Dhofar 1442 and SaU 169. To test and verify the reliability of the newly developed phosphate dating technique, two additional meteorites, Acapulco, obtained from Acapulco consortium, and angrite NWA 4590 were also selected for this study as both have precisely known phosphate U-Pb ages by TIMS [4,5]. Both meteorites are from very fast cooled parent bodies with no sign of resetting [4,5], satisfying a necessity for precise dating.

Zhou, Q.↗
NASA NTRS2012

Magnesium and Silicon Isotopes in HASP Glasses from Apollo 16 Lunar Soil 61241

The high-Al (>28 wt %), silica-poor (<45 wt %) (HASP) feldspathic glasses of Apollo 16 are widely regarded as the evaporative residues of impacts in the lunar regolith [1-3]. By virtue of their small size, apparent homogeneity, and high inferred formation temperatures, the HASP glasses appear to be good samples in which to study fractionation processes that may accompany open system evaporation. Calculations suggest that HASP glasses with present-day Al2O3 concentrations of up to 40 wt% may have lost 19 wt% of their original masses, calculated as the oxides of iron and silicon, via evaporation [4]. We report Mg and Si isotope abundances in 10 HASP glasses and 2 impact-glass spherules from a 64-105 m grain-size fraction taken from Apollo 16 soil sample 61241.

Herzog, G. F.↗
NASA NTRS2012

What Lunar Meteorites Tell Us About the Lunar Highlands Crust

The first meteorite to be found1 that was eventually (1984) recognized to have originated from the Moon is Yamato 791197. The find date, November 20, 1979, was four days after the end of the first Conference on the Lunar Highland Crust. Since then, >75 other lunar meteorites have been found, and these meteorites provide information about the lunar highlands that was not known from studies of the Apollo and Luna samples

Korotev, R. L.↗
NASA NTRS2005

A Thorium-rich Mare Basalt Rock Fragment from the Apollo 12 Regolith: A Sample from a Young Procellarum Flow?

In this abstract, we report on the composition, mineralogy and petrography of a basaltic rock fragment, 12032,366-18, found in the Apollo 12 regolith. Age data, collected as part of an investigation by Barra et al., will be presented in detail in. Here, only the age dating result is summarized. This rock fragment garnered our attention because it is significantly enriched in incompatible elements, e.g., 7 ppm thorium, compared to other known lunar basalts. Its mineral- and trace-element chemistry set it apart from other Apollo 12 basalts and indeed from all Apollo and Luna basalts. What makes it potentially very significant is the possibility that it is a sample of a relatively young, thorium-rich basalt flow similar to those inferred to occur in the Procellarum region, especially northwestern Procellarum, on the basis of Lunar Prospector orbital data. Exploiting the lunar regolith for the diversity of rock types that have been delivered to a landing site by impact processes and correlating them to their likely site of origin using remote sensing will be an important part of future missions to the Moon. One such mission is Moonrise, which would collect regolith samples from the South Pole-Aitken Basin, concentrating thousands of rock fragments of 3-20 mm size from the regolith, and returning the samples to Earth.

Jolliff, B. L.↗
NASA NTRS2005

Petrography of Lunar Meteorite MET 01210, A New Basaltic Regolith Breccia

Lunar meteorite MET 01210 (hereafter referred to as MET) is a 22.8 g breccia collected during the 2001 field season in the Meteorite Hills, Antarctica. Although initially classified as an anorthositic breccia, MET is a regolith breccia composed predominantly of very-low-Ti (VLT) basaltic material. Four other brecciated lunar meteorites (NWA 773, QUE 94281, EET 87/96, Yamato 79/98) with a significant VLT basaltic component have been identified. We present here the petrography and bulk major element composition of MET and compare it to previously studied basaltic lunar meteorite breccias.

Zeigler, R. A.↗
NASA NTRS2004

Apollo 16 Mafic Glass: Geochemistry, Provenance, and Implications

Although the Apollo 16 mission landed in the feldspathic lunar highlands, mass-balance models suggest that there is a 5-6% mare component in the mature soils collected at the site. Only one mare basalt greater than 1 cm was found and two surveys of 2-4 mm particles found that less than 1% of this size fraction is mare basalt. Similar surveys of the less than 1 mm size fraction of A16 soils found very little lithic mare basalt, but several percent of basaltic green, yellow, and orange glass. The green glass beads were identified as VLT picritic glass and the orange/yellow glass shards were a mix of high and low Ti mare-like glass, high-Al basaltic glass, and KREEPy glasses. Most previous studies of glasses in the A16 regolith were surveys that identified a high proportion of feldspathic glass because most of the glass is produced by local impacts. Because the number of mafic glasses found was low, few compositional groupings were identified. As part of our ongoing study of the mafic components of the Apollo 16 site, we specifically targeted mafic glasses from Apollo 16, selecting against the more feldspathic glasses. In this way we were able to identify over 300 mafic glasses (greater than 10 wt % FeO). We present here the major- and trace-element chemistry of the main glass groups and discuss the likely provenance of each group.

Zeigler, R. A.↗
NASA NTRS2004

Ar-40 - Ar-39 Geochronology on Apollo 12 Regolith

The Apollo 12 landing site in Oceanus Procellarum is located about 400 km south of the rim of Copernicus. The geochemical and petrographical characterization of the Apollo 12 lunar samples have been extensively studied. The site is characterized by a high proportion of nonmare material with KREEP composition and mare basalts low in Th. Recent studies have focused on the geochemistry of the nonmare material and on inferring the origin of these materials. Previous geochronological investigations of Apollo 12 mare basalts have yielded ages ranging from 3.1 to 3.3 Ga. On the other hand, nonmare materials have yielded older ages between 3.8 to 4.0 Ga; with the sole exception of a single lunar granite fragment from sample 12033. This granite sample has an Ar-40 - Ar-39 age of 800 +/- 15 Ma. This resetting age has been interpreted as the age of the Copernicus crater since a ray from this crater crosses the landing site. Here we present new 40Ar-39Ar geochronological data on three samples of nonmare material from the Apollo 12 regolith in order to further constrain the age and source of this material.

Barra, F.↗
NASA NTRS2004

Petrography of Lunar Meteorite PCA02007, a New Feldspathic Regolith Breccia

PCA 02007 is a 22.4 g lunar meteorite collected in 2003 near the Pecora Escarpment in Antarctica [1]. PCA is a feldspathic regolith breccia composed of mature regolith. It is compositionally and texturally similar to other feldspathic lunar meteorites (FLMs) [2] and may be launch paired with Yamato 791197 [3]. Here we present a petrographic description and compositions of mineral clasts, glass clasts, lithic clasts, and the bulk meteorite.

Zeigler, R. A.↗