SEARCH · Search NASA

Results for “Carbonaceous”

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.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 127 records · Page 7

All sources NASA NTRS DOE OSTI

NASA NTRS1984

Proposed structures for poorly characterized phases in C2M carbonaceous chondrite meteorites

A recent investigation of C2M carbonaceous chondrite meteorite matrices using electron microscopy and High-Resolution Transmission Electron Microscopy (HRTEM) has provided data on the structure and chemistry of Poorly Characterized Phases (PCP). It is suggested that a dominant matrix variety (10 A PCP) has a structure equivalent to iron-rich tochinilite (6Fe0.9S5/Fe, Mg//OHO2/), which consists of coherently intrastratified mackinawite and brucite sheets. In addition, it is proposed that 17 A PCP is a commensurate intergrowth of serpentine and tochinilite layers. Various forms of PCP observed in carbonaceous chondrites appear to be intergrowths of tochinilite, serpentine, and tochinilite-serpentine minerals.

Mackinnon, I. D. R.↗

NASA NTRS1984

Bulk compositions of Al-rich chondrules in ordinary and carbonaceous chondrites: Variations and similarities

An extended study of ordinary chondrites revealed that chondrules exist which are transitional in composition between Al-rich and Mg-Fe-rich types in contrast to the finding of Wlotzka, who inferred a gap in compositions between the Ca-Al-rich and Mg-Fe-rich chondrules. Transitional chondrule bulk compositions are plotted. They show that no compositional gap exists between the Mg-Fe-rich and Al-rich chondrules. Chondrules with Na2O-contents 3.0 wt.% are indicated. Variable CaO/Na2O-ratios for chondrule bulk compositions exist, similar to what was described for the subgroups of Al-rich chondrules. Al-rich and transitional chondrules similar to those described above were found also in carbonaceous chrondrites. Thirty-nine chondrules from the carbonaceous chondrites Leoville, Allende, Vigarano and Colony were investigated. Their bulk compositions in terms of Al2O3 vs. CaO were plotted.

Bischoff, A.↗

NASA NTRS1984

Hydrothermal alteration of CM carbonaceous chondrites: Implications of the identification of tochilinite as one type of meteoritic PCP

Poorly characterized phases (PCP's) constitute up to 30 volume percent of some CM carbonaceous chondrites, and are therefore an important key to an understanding of the physico-chemical conditions attending matrix evolution. An iron rich form of the terrestrial phase tochilinite was recently identified as a common type of PCP. Tochilinite has the general formula 6Fe(0.9)S.5(Mg,Fe)(OH)2 and consists of alternating machinawite (FeS) and brucite ((Mg,Fe)(OH)2) sheets, with iron vacancies in the sulfide sheets. In iron rich tochilinite, ferrous hydroxide, called amakinite, replaces brucite. If CM carbonaceous kchondrites have underdone hydrothermal alteration, iron rich tochilinite, at least, probably grew from aqueous solutions characterized by low FO2, high FS2, pH 10 to 12, and at a temperature at or below 170 C.

Zolensky, M. E.↗

NASA NTRS1985

Carbon isotopes in bulk carbonaceous chondrites

The chemical and physical processes involved in the formation of the solar system are examined. Primitive matter has been found on a microscopic scale in a variety of meteorites: fragments of small solar system bodies that were never part of a large planet. This primitive matter has, in most cases, been identified by the presence of anomalous abundances of some isotopes of the chemical elements. Of particular interest for carbon isotope studies are the primitive meteorites known as carbonaceous chondrites. Using a selective oxidation technique to sort out the carbon contained in different chemical forms (graphite, carbonates, and organic matter), four carbonaceous chondrites are analyzed. The presence of the (13) C-rich component was confirmed and additional carbon components with different, but characteristic, isotopic signatures were resolved.

Halbout, J.↗

NASA NTRS1983

Ferromagnesian chondrules in carbonaceous chondrites

Carbonaceous chondrites (groups CO and CV) contain three types of ferromagnesian chondrules that can be distinguished on the basis of mineralogy and texture. Statistical analysis of the bulk chemical compositions of these chondrule types suggest that two of the three types are genetically related. The chondrules in carbonaceous chondrites can thus be separated into two populations. These populations are also apparently distinct in terms of redox state and oxygen isotopic composition. The more abundant population (I) is clearly different from chondrules in unequilibrated ordinary chondrites, but the minor population (II) is similar to them in many respects. These chondrule populations may have formed by melting of solid, locally homogeneous precursor materials in different regions of the nebula, and were mixed after solidification was complete.

Mcsween, H. Y., Jr.↗

NASA NTRS1984

Interstellar dust, comets, comet dust and carbonaceous meteorites

Evidence is adduced to show that comets, and carbonaceous meteorites have a common origin via aggregation of interstellar dust. The dust to gas ratio for comets and the trend in its variation with solar distance is derived from the sequential evaporation of the various comet dust constituents. The 'missing carbon' in comets is explained as residing predominantly in the approximately 20 percent fraction of the comets consisting of the complex organic component of interstellar dust. The C-12/C-13 isotopic ratios in interstellar dust, comets and carbonaceous meteorites are linked by dividing the carbon into its 'pure' and molecular parts. The silicate signature in circumstellar, interstellar, comet and interplanetary dust is compared.

Greenberg, J. M.↗

NASA NTRS1985

Hydrated interplanetary dust particle linked with carbonaceous chondrites?

The results of transmission electron microscope observations of a hydrated interplanetary dust particle (IDP) containing Fe-, Mg-rich smectite or mica as a major phase are reported. The sheet silicate appears to have formed by alteration of anhydrous silicates. Fassaite, a Ca, Al clinopyroxene, also occurs in this particle, and one of the crystals exhibits solar-flare tracks, clearly indicating that it is extraterrestrial. Fassaite is a major constituent of the Ca-, Al-rich refractory inclusions found in the carbonaceous chondrites, so its presence in this particle suggests that there may be a link between hydrated IDPs and carbonaceous chondrites in the early history of the solar system.

Tomeoka, K.↗

NASA NTRS1985

Carbon, hydrogen and nitrogen in carbonaceous chondrites Abundances and isotopic compositions in bulk samples

Whole-rock samples of 25 carbonaceous chondrites were analyzed for contents of C, H and N and delta C-13, delta D and delta N-15. Inhomogeneous distribution of these isotopes within individual meteorites is pronounced in several cases. Few systematic intermeteorite trends were observed; N data are suggestive of isotopic inhomogeneity in the early solar system. Several chondrites revealed unusual compositions which would repay further, more detailed study. The data are also useful for classification of carbonaceous chondrites; N abundance and isotopic compositions can differentiate existing taxonomic groups with close to 100 percent reliability; Al Rais and Renazzo clearly constitute a discrete 'grouplet', and there are hints that both CI and CM groups may each be divisible into two subgroups.

Kerridge, J. F.↗

NASA NTRS1985

Survival of interstellar matter in meteorities - Evidence from carbonaceous material

An interstellar origin has been attributed to certain organic and apparently elemental forms of C which occurs in carbonaceous meteorites. Evidence for such an origin comes from anomalous isotopic composition either of the C itself or of elements, such as N, H, or the noble gasses, which are combined with or trapped within the carbonaceous material. Suggested sources for these anomalous compositions include atmospheres of red giant stars, novae and super-novae, and interstellar molecular clouds.

Kerridge, J. F.↗

NASA NTRS1987

Plagioclase-rich inclusions in carbonaceous chondrite meteorites - Liquid condensates?

The characteristics and formation of coarse-grained, plagioclase-rich inclusions are investigated. The textures, mineralogical compositions, and initial Al-26/Al-27 ratios for the plagioclase-rich inclusions are described. It is observed that plagioclase-rich inclusions in carbonaceous chondrites are either Ca-Al-rich inclusions (CAIs) composed of 30-60 vol pct anorthite, and less than 35 vol pct Ti-Al-pyroxene and melilite, or CA chondrites composed of plagioclase, pyroxene, olivine, spinel, and melilite. It is observed that CA chondrules are chemically and mineralogically the most similar components shared by carbonaceous and ordinary chondrites. The textural changes observed in the inclusions are examined. The data reveal that the CAIs have three textural groups: coarse anorthite laths, equigranular anorthite and Ti-Al-pyroxene, and lacy Ti-Al-pyroxene and fine-grained anorthite.

Wark, D. A.↗

NASA NTRS1987

Analytical electron microscopy of extraterrestrial materials - Results from microtome sections of carbonaceous chondrites and interplanetary dust particles

The paper describes a method for embedding, sectioning, and observing two types of extraterrestrial materials, including hydrated interplanetary dust particles (IDPs) and carbonaceous chondrite meteorites. The technique, which produces large thin areas suitable for both high-resolution imaging and thin-film microanalysis, was applied to study the petrology of the IDP Ames-DE C86-11, the Murchison carbonaceous chondrite matrix, and the Allende dark inclusion. The technique makes it possible to maintain delicate interfaces, boundaries, and phase relationships between grains. Because phases are held in place, layer lattice silicates and other minerals with strong preferred orientations can be viewed in any orientation, including the orientation normal to their basal planes.

Blake, D. F.↗

NASA NTRS1989

Evolution of carbonaceous chondrite parent bodies: Insights into cometary nuclei

It is thought that cometary samples will comprise the most primitive materials that are able to be sampled. Although parent body alteration of such samples would not necessarily detract from scientists' interest in them, the possibility exists that modification processes may have affected cometary nuclei. Inferences about the kinds of modifications that might be encountered can be drawn from data on the evolution of carbonaceous chondrite parent bodies. Observations suggest that, of all the classes of chondrites, these meteorites are most applicable to the study of comets. If the proportion of possible internal heat sources such as Al-26 in cometary materials are similar to those in chondrites, and if the time scale of comet accretion was fast enough to permit incorporation of live radionuclides, comets might have had early thermal histories somewhat like those of carbonaceous chondrite parent bodies.

Mcsween, Harry Y., Jr.↗

NASA NTRS1989

Theoretical predictions of volatile bearing phases and volatile resources in some carbonaceous chondrites

Results are presented from theoretical calculations to predict the modal abundances and compositions of the major mineral phases and the vapor phase that could develop in the bulk compositions of carbonaceous chondrites. The abundances and compositions are obtained as functions of temperature and pressure. The calculations are used to evaluate the volatile and mineralogical resource potential of C1 and C2 carbonaceous chondrites.

Ganguly, Jibamitra↗

NASA NTRS1990

Aqueous alteration in the Kaba CV3 carbonaceous chondrite

Results from TEM and SEM examinations of the Kaba CV3 carbonaceous chondrite are presented, showing that the chondrules and the matrix of Kaba have undergone pervasive low-temperature aqueous alteration, resulting in the formation of Fe-bearing saponite from glass and enstatite in chondrules, and from anhydrous silicates in matrix. The alteration products in Kaba were found to resemble those in other aqueously altered carbonaceous chondrites such as the Mokoia CV3 and in Orgueil CI chondrites and Y-82162 chondrites. However, Kaba lacks the abundant high-Al phyllosilicates, reported for CAIs from Mokoia, and the serpentine and ferrihydrite, found in Orgueil.

Keller, Lindsay P.↗

NASA NTRS1989

Raman properties of various carbonaceous materials and their astrophysical implications

It is well known that a large number of celestial objects exhibit, in the range 3 to 12 micron, a family of emission features called unidentified infrared bands (UIR). They usually appear together and are associated with UV sources. Recently various authors have suggested that these features could be attributed to solid carbonaceous materials. Following this interest, a systematic analysis was performed of various types of amorphous carbon grains and polycyclic aromatic hydrocarbons (PAH), produced in lab. Updating results of Raman measurements performed on several carbonaceous materials, chosen according to their astrophysical interest, are presented. The measurements were made by means of a Jobin-Yvon monochromator HG2S and standard DC electronic. The line at 5145 A of an Ar+ laser was used as excitation source.

Blanco, A.↗

NASA NTRS1989

Abundances of volatile-bearing phases in carbonaceous chondrites and cooling rates of meteorites based on cation ordering of orthopyroxenes

Results of preliminary calculations of volatile abundances in carbonaceous chondrites are discussed. The method (Ganguly 1982) was refined for the calculation of cooling rate on the basis of cation ordering in orthopyroxenes, and it was applied to the derivation of cooling rates of some stony meteorites. Evaluation of cooling rate is important to the analysis of condensation, accretion, and post-accretionary metamorphic histories of meteorites. The method of orthopyroxene speedometry is widely applicable to meteorites and would be very useful in the understanding of the evolutionary histories of carbonaceous chondrites, especially since the conventional metallographic and fission track methods yield widely different results in many cases. Abstracts are given which summarize the major conclusions of the volatile abundance and cooling rate calculations.

Ganguly, Jibamitra↗

NASA NTRS1990

Volatile-bearing phases in carbonaceous chondrites: Compositions, modal abundance, and reaction kinetics

The spectral and density characteristics of Phobos and Deimos (the two small natural satellites of Mars) strongly suggest that a significant fraction of the near-earth asteroids are made of carbonaceous chondrites, which are rich in volatile components and, thus, could serve as potential resources for propellants and life supporting systems in future planetary missions. However, in order to develop energy efficient engineering designs for the extraction of volatiles, knowledge of the nature and modal abundance of the minerals in which the volatiles are structurally bound and appropriate kinetic data on the rates of the devolatilization reactions is required. Theoretical calculations to predict the modal abundances and compositions of the major volatile-bearing and other mineral phases that could develop in the bulk compositions of C1 and C2 classes (the most volatile rich classes among the carbonaceous chondrites) were performed as functions of pressure and temperature. The rates of dehydration of talc at 585, 600, 637, and 670 C at P(total) = 1 bar were determine for the reaction: Talc = 3 enstatite + quartz + water. A scanning electron microscopic study was conducted to see if the relative abundance of phases can be determined on the basis of the spectral identification and x ray mapping. The results of this study and the other studies within the project are discussed.

Ganguly, Jibamitra↗

NASA NTRS1992

Maralinga, a metamorphosed carbonaceous chondrite found in Australia

The Maralinga meteorite was found near the village of Maralinga, South Australia in 1974, but was not recognized as a meteorite until 1989. One weathered individual was recovered with a total mass of 3.38 kg. The bulk composition and petrography of Maralinga indicate that it is a metamorphosed (petrographic type 4) carbonaceous chondrite with major similarities to the Vigarano-subtype. However, recent trace element data from the literature suggest that Maralinga should be included with the CK (Karoonda-type) carbonaceous chondrites. Maralinga is classified as an anomalous CK4 chondrite because of its abundant chondrules and refractory inclusions relative to other known members of the CK group. Maralinga contains homogeneous silicates, including Ni-bearing olivines (Fa34), high-Ca clinopyroxene, and rare orthopyroxene. Plagioclase is chemically heterogeneous and falls into two distinct compositional groups one of about An20 and an about An80 group. Highly oxidizing conditions during metamorphism of Maralinga are indicated by the abundance of magnetite and the paucity of Fe-Ni metal.

Keller, Lindsay P.↗