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

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS2014

On the Relationship between Cosmic Ray Exposure Ages and Petrography of CM Chondrites

Carbonaceous (C) chondrites are potentially the most primitive among chondrites because they mostly escaped thermal metamorphism that affected the other chondrite groups. C chondrites are chemically distinguished from other chondrites by their high Mg/Si ratios and refractory elements, and have experienced various degrees of aqueous alteration. They are subdivided into eight subgroups (CI, CM, CO, CV, CK, CR, CB and CH) based on major element and oxygen isotopic ratios. Their elemental ratios vary over a wide range, in contrast to those of ordinary and enstatite chondrites which are relatively uniform. It is critical to know how many separate bodies are represented by the C chondrites. In this study we defined 4 distinct cosmic-ray exposure (CRE) age groups of CMs and systematically characterized the petrography in each of the 4 CRE age groups to determine whether the groups have significant petrographic differences with such differences probably reflecting different parent body (asteroid) geological processing, or multiple original bodies. We have reported the results of a preliminary grouping at the NIPR Symp. in 2013 [3], however, we revised the grouping and here report our new results.

Takenouchi, A.↗
NASA NTRS2016

Petrography and Geochemistry of Lunar Meteorite Miller Range 13317

Miller Range (MIL) 13317 is a 32-g lunar meteorite collected during the 2013-2014 ANSMET (Antarctic Search for Meteorites) field season. It was initially described as having 25% black fusion crust covering a light- to dark-grey matrix, with numerous clasts ranging in size up to 1 cm; it was tenta-tively classified as a lunar anorthositic breccia. Here we present the petrography and geochemistry of MIL 13317, and examine possible pairing relationships with previously described lunar meteorites.

Zeigler, R. A.↗
DOE OSTI2025

Physical properties, internal structure, and the three‐dimensional petrography of CI chondrites

physical properties and the nature of their breccation, we investigated nine samples of the Ivuna and Orgueil CI chondrites ranging in size from 1 mm to 4 cm in approximate diameter. The combined mass of unique material investigated in this work is 113 g. For our investigations, we use ideal gas pycnometry, 3-D laser scanning, x-ray computed microtomography (μCT), and accompanying digital data extraction techniques. We found that the bulk density of the samples ranged from 1.61 to 2.10 g cm −3 . Larger samples tend to have a lower bulk density. Grain density (ranging from 2.44 to 2.55 g cm −3 ) is significantly less variable than the bulk density in our samples and the quantity of porosity (ranging from 14.6% to 33.8%) is the dominant factor in determining the bulk density of CI chondrite material. Our μCT results show that the visible porosity across all sizes of our CI chondrite samples is in the form of cracks, but these cracks can account for less than two-thirds of the porosity in the CI chondrites. Other porosity is not visible, even at μCT resolutions of 2.7 μm voxel edge −1 and we conclude that it is sub-micron in nature. It is not clear if the cracks seen in our samples are indigenous to the chondrites or are a result of terrestrial processes. We also find that the CI chondrites are excellent examples of the fractal-like nature of brecciation, where clasts can be observed at all scales we imaged. The breccias are composed of sub-equant-shaped and sub-rounded-textured clasts like melt-free impact breccias on other solar system bodies. From our μCT volume and digital data extraction, we determine that the Ivuna CI chondrite breccia is organized: the mostly sub-equant clasts within our ~2 cm chunk of Ivuna have a mean diameter of 1.33 mm and their aligned longest axes define a lineation structure. We speculate that the lineation was imparted after fragmentation of the clasts by slight shear on the parent asteroid which could be the result of seismic-related granular flow or mild non-axial impact-related compaction. These data will help to place returned asteroidal material from asteroids 162173 Ryugu and 101955 Bennu and the CI chondrites into a mutual geological context.

CI chondrite↗
NASA NTRS1972

Luminescence petrography of lunar samples

Light-colored metaclastic rock fragments, mainly anorthositic breccias, are dominant in the lithic clasts of rock 14321 and constitute about 25% of the Apollo 14 soils. Concentration of anorthositic breccias is less in the Apollo 15 soils, but is higher in the Front samples. The Rille edge soils are rich in basalt fragments. The Apollo 15 soils are also rich in green glasses. True anorthosites in the Hadley region were found only at the St. George Crater site. Varying degrees of metamorphism were found in the anorthositic fragments, and luminescence zonations give independent evidence of metamorphism. Compositional zoning verifies the interpretation of luminescence. Rock 14321 gives evidence of modest annealing, but the light metaclastic fragments were metamorphosed before incorporation into the rock. Reaction rimming on plagioclase results in mosaicism and preferentially affects grains. The spectral analysis of luminescence in plagioclase shows that a red-infrared emission band is present in a small fraction of plagioclase grains. Samples from trench bottoms and from beneath a large boulder were compared with surface samples. Large variations in soil composition indicate marked layering in the Apollo 15 soils.

Source record↗
NASA NTRS1972

Electron petrography of Apollo sample 14310.

Thin sections prepared from Apollo sample 14310 have been examined with 100-kV transmission electron microscopy. The sample is composed principally of anorthite and pyroxene. The anorthites fall into two categories. The transitional anorthites that show the characteristic 'c' type diffraction maxima are characterized by very fine antiphase domain structures and some fine twinning. The body-centered anorthites that show no 'c' reflections are characterized by an absence of fine twinning and a less well-defined antiphase domain structure. Although both orthopyroxene and clinopyroxenes are reported in sample 14310, only clinopyroxenes were observed in this study and all show exsolution structures. The augite exsolved in pigeonite commonly is along lamellae parallel to (100), although (001) lamellae are also present. This unusual orientation was verified by diffraction patterns. The pigeonite commonly shows antiphase domains, attributed to stacking errors when the sample inverted from its high-temperature disordered form. In augite as the host phase, the pigeonite lamellae contain very complex structures including antiphase domains.

Smith, D. K.↗
NASA NTRS1972

Electron petrography of Apollo 14 and 15 rocks.

Comparative optical and high-voltage electron petrographic analyses of igneous rocks and several types of breccias the Fra Mauro and Apennine sites of Apollo 14 and 15 are reported and interpreted. The crystalline rocks are found to differ substantially from the Apollo 11 and 12 basalts. Substructures in the Apollo 14 breccias are complex. At least two bonding mechanisms can be discerned from the electron petrographic examination: (a) 'shock sintering' due to high pressures and temperatures associated with the shock waves of meteoritic impacts; and (b) lithification by glass bonding.

Lally, J. S.↗
NASA NTRS1973

The age and petrography of two Luna 20 fragments and inferences for widespread lunar metamorphism.

Ages were determined by the Ar-40/Ar-39 method on two metaclastic rocks returned from the lunar highlands north of Mare Fecunditatis by the Luna 20 probe. Both samples gave very well-defined argon retention ages of 3.90 plus or minus 0.04 AE which are indistinguishable from each other within a resolution of 0.02 AE. Both fragments, 22006 and 22007, are highly recrystallized polymict breccias; there is no evidence of radiogenic Ar-40, and the age almost surely dates the time of recrystallization. The cosmic ray exposure ages of these fragments are similar and high: 900 million years for 22006, 1300 million years for 22007. 22007 also contains substantial trapped argon with a high Ar-40/Ar-36. The Luna 20 results greatly extend the area of the moon's surface exhibiting a well-defined record of metamorphism at 3.9 AE. So far, lunar history in the interval from 4.6 to 3.9 AE is not preserved in the ages of surface rocks. This obliteration suggests lunar-wide metamorphic conditions occurring or terminating at this time as a result of major impacts.

Podosek, F. A.↗
NASA NTRS1973

Apollo 16 soils - Grain size analyses and petrography

Soils from South Ray Crater, North Ray Crater, and the interray area of Station 10 have a similar provenance, containing breccia fragments of low to medium metamorphic grade and low light/dark lithic fragment ratios; these appear to be characteristic of the Cayley Formation. The primary difference between soils possibly derived from North Ray and South Ray craters is in the agglutinate content. A soil from Stone Mountain (Station 4) is characterized by breccia fragments of medium to high metamorphic grade and a high light/dark lithic fragment ratio; this soil may be derived from the Descartes Formation. Differences between the selenomorphic units, the Descartes and Cayley formations, may be lithologic as well as structural. The mean grain size varies from 84 to 280 microns, and all of the samples are poorly to very poorly sorted. There appears to be a relation between the sorting, grain size, and agglutinate content, with the finer-grained, better sorted soils containing more than 30% agglutinates. 'Shadowed' soils, collected close to large boulders, are similar in all respects to the 'reference' soils collected at least 5 m from the boulders.

Heiken, G. H.↗
NASA NTRS1973

Electron petrography of Apollo 14 and 15 breccias and shock-produced analogs

Six lunar breccias were studied in detail by optical and transmission electron microscopy and separated into two classes on the basis of presence or absence of recovery and recrystallization textures: Class A breccias with no recrystallization include samples 14063, 14301, and 15498; Class B breccias with recrystallization include samples 14321, 15455, and 15418. Samples of Apollo 16 soil (65010) experimentally shocked to 50, 100, and 250 kilobars pressure were sectioned and studied for comparison with the breccias. It is concluded that the Class A breccias were formed from unconsolidated lunar regolith by deformation due to shock waves of a few tens of kilobars. The Class B breccias could also have been produced from unconsolidated material at higher shock stresses, the annealing being achieved by the heating resulting from the shock deformation.

Christie, J. M.↗
NASA NTRS1974

Petrography and classification of Apollo 17 non-mare rocks with emphasis on samples from the Station 6 boulder

The Apollo-17 nonmare rock collection consists largely of polymict breccias lithified by impact and characterized by a variety of types of lithic clasts, concentrations of siderophile elements that indicate substantial meteoritic contamination, and contents of metallic iron well above those of mare basalts. These materials may be subdivided into two compositional groups, one with 70-80% feldspar and the other with 50-60% feldspar. The high-feldspar group includes two characteristic textures: coarsely poikilitic and granulitic. The low-feldspar group includes (1) fragmental breccias with the most diverse lithic clast populations of all breccias and (2) crystalline breccias with poikilitic and subophitic to micropoikilitic textures containing tabular feldspar, granular textures with anhedral feldspar, and clast-rich ophitic textures containing less euhedral feldspar. In the poikilitic and subophitic to micropoikilitic textures, the clast population is dominated by the high-feldspar lithologies and An(94-47) plagioclase grains, indicating that these more refractory lithologies were abundant in the material from which the less feldspathic crystalline rocks formed.

Simonds, C. H.↗