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At least 667 records · Page 37
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Infrared spectra and crystal chemistry of scapolites - Implications for Martian mineralogy

Near-IR and mid-IR spectra of 27 scapolites with a wide range of compositions were compared to the features of the 2.35-micron band absorption system that was recently discovered in reflectance spectra of Mars. Results suggest that the 2.36-micron features are due to the presence of small amounts (about 0.5 wt pct each) of HCO3(-) and HSO4(-) in the anion sites of a scapolite. Five of the scapolites (including two meionite and three mizzonite samples) showed absorption features unique to HCO3(-) and HSO4(-). It was determined that the features of the 2.36-micron-centered system are produced by a disordered anion site occupancy and that the band intensity also depends on the HCO3(-)/HSO4(-) ratio. It was found (Clark et al., 1990) that HCO3(-) and HSO4(-) bearing minerals other than scapolites do not exhibit spectral features of the scapolite.

Swayze, Gregg A.↗
NASA NTRS1989

Mineralogical and chemical properties of the lunar regolith

The composition of lunar regolith and its attendant properties are discussed. Tables are provided listing lunar minerals, the abundance of plagioclase feldspar, pyroxene, olivine, and ilmenite in lunar materials, typical compositions of common lunar minerals, and cumulative grain-size distribution for a large number of lunar soils. Also provided are charts on the chemistry of breccias, the chemistry of lunar glass, and the comparative chemistry of surface soils for the Apollo sites. Lunar agglutinates, constructional particles made of lithic, mineral, and glass fragments welded together by a glassy matrix containing extremely fine-grained metallic iron and formed by micrometeoric impacts at the lunar surface, are discussed. Crystalline, igneous rock fragments, breccias, and lunar glass are examined. Volatiles implanted in lunar materials and regolith maturity are also addressed.

Mckay, David S.↗
NASA NTRS1990

Towards a circumstellar silicate mineralogy

This paper reviews the formation, composition, and spectroscopy of circumstellar silicate grains. It is argued that 'clean' silicates (and oxides) are formed close to the stellar photosphere, but because of their low NIR absorptivity, these grains float with the gas in the pulsating photosphere until, at large distances from the stellar surface, enough Fe(2+) is incorporated (i.e., 'dirty' silicates) for radiation pressure to drive a dusty outflow. The silicate chemical condensation sequence is reviewed with emphasis on kinetics rather than thermodynamics, and likely condensates are identified. IRAS LRS spectra of tenuous dust shells show considerable variations in the shape of the 10-micron feature and at least 5 independent spectral components are indicated. These are compared with laboratory spectra and (preliminary) identifications are proposed.

Tielens, A. G. G. M.↗
NASA NTRS1991

Clays on Mars: Review of chemical and mineralogical evidence

Mafic igneous bedrock is inferred for Mars, based on spectrophotometric evidence for pyroxene (principally in optically dark areas of the globe) and the pyroxenite-peridotite petrology of shergottite nakhlite chassignite (SNC) meteorites. Visible and infrared spectra of reddish-brown surface fines (which dominate Martian bright areas) indicate ferric iron and compare favorably (though not uniquely) with spectra of palagonitic soils. Laboratory studies of SNC's and Viking Lander results support a model for Martian soil based on chemical weathering of mafic rocks to produce layer structured silicates (clay minerals), salts, and iron oxides.

Banin, Amos↗
NASA NTRS1991

Mineralogy of the Martian surface from Mariner 6/7 infrared spectrometer data

The Mariner 6/7 Infrared Spectrometer (IRS) experiment data from the 1969 Mars flyby encounters represent a valuable source of information about the IR reflection/emission spectrum of Mars in the 1.9 and 14.4 micron region. During 1990, the wavelength calibration of the IRS data was completely redone, using information from inflight spectra of Mars taken through a polystyrene film and from the locations of Martian CO2 bands. The response functions of the two instruments were then rederived using laboratory black body spectra. Also, a particular approach was taken to study the IRS data in which the effects of uncertain wavelength and intensity calibration can be minimized. This involves doing ratios of spectra. These are of particular value when applied to study contrasts between various albedo domains on the Mars surface and between spectra with differing emission angle. The latter provide a means of assessing the contribution of the atmosphere and airborne dust to the spectra. Given here are graphs showing two near infrared radiance spectra for very different albedo regions and a ratio of two spectra obtained at very different total solar pathlength (airmass).

Martin, T. Z.↗
NASA NTRS1991

Iddingsite in the Nakhla meteorite: TEM study of mineralogy and texture of pre-terrestrial (Martian?) alterations

Rusty-colored veinlets and patches in the Nakhla meteorite, identified as iddingsite, are pre-terrestrial. The rusty material is iddingsite (smectites + hematite + ferrihydrite); like terrestrial iddingsites, it probably formed during low-temperature interaction of olivine and water. Fragments of rusty material with host olivine were removed from thin sections of Nakhla with a tungsten needle. Fragments were embedded in epoxy, microtomed to 100 nanometers thickness, and mounted on Cu grids. Phase identifications were by Analytical Electron Microscopy/Energy Dispersive X-ray Analysis (EM/EDX) standardless chemical analyses (for silicates), electron diffraction (hematite and ferrihydrite), and lattice fringe imaging. This iddingsite in Nakhla is nearly identical to some formed on Earth, suggesting similar conditions of formation on the Shergottites-Nakhlites-Chassigny (SNC) meteorite parent planet. A more detailed account of the results is presented.

Treiman, Allan H.↗
NASA NTRS1992

Charge-coupled device imaging spectroscopy of Mars. II - Results and implications for Martian ferric mineralogy

Materials similar to nanophase ferric oxides are presently seen to dominate the spectral behavior of the Martian surface in the visible-to-near-IR, in view of imaging spectroscopic observations of Mars. Attention is accordingly given to models for the formation of hematite and other ferric minerals in both current terrestrial environments and in the current and past, possibly wetter Martian climate. It is noted that imaging spectroscopy is an ideal tool for high spatial resolution spacecraft and telescopic studies of the Martian surface.

Bell, James F., III↗
NASA NTRS1993

Lunar ferroan anorthosites - Mineralogy, compositional variations, and petrogenesis

Results of a study of 16 samples from the anorthositic ferroan subgroup, or 'typical' ferroan anorthosites, are reported. The presence of heterogeneous, bimodal, and/or trimodal pyroxene compositions suggests that some of the anorthosites are polymict rocks; however, they are composed entirely of ferroan-anorthosite-suite lithologies. It is suggested that complex processes operated during the formation of the ferroan anorthosites. It is argued that original igneous compositional characteristics were altered during and/or after crystallization. Processes operative during anorthosite formation may have included some mixing of different melts, trapping of variable amounts of intercumulus liquid, postcrystallization redistribution of elements, or perturbations both during adcumulus growth and subsequent to crystallization by impact events.

Mcgee, J. J.↗
NASA NTRS1991

An evaluation of short-wave-infrared (SWIR) data from the AVIRIS and GEOSCAN instruments for mineralogical mapping at Cuprite, Nevada

An evaluation was performed on SWIR (2000-2400 nm) data from two airborne remote sensing systems for discriminating and identifying alteration minerals at Cuprite, Nevada. The data were acquired by the NASA Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS) and the GEOSCAN Mk II multispectral scanner. The evaluation involved comparison of processed imagery and image-derived spectra with existing alteration maps and laboratory spectra of rock samples from Cuprite. Results indicate that both the AVIRIS and GEOSCAN data permit the discrimination of areas of alunite, buddingtonite, kaolinite, and silicification using color composite images formed from three SWIR bands processed with either the decorrelation stretch or a log residual algorithm. The laboratory spectral features alunite, kaolinite and buddingtonite could be seen clearly only in the log residual processed AVIRIS data. However, this does not preclude their identification with the GEOSCAN data.

Hook, Simon J.↗
NASA NTRS1990

Lunar meteorite Yamato-86032 - Mineralogical, petrological, and geochemical studies

Yamato-86032 is a shock-lithified anorthositic fragmental breccia. It consists mainly of highly feldspathic meta-breccias and meta-meltrocks and possibly contains a small contribution from mare lithologies, but there is no indication of a KREEP component. In many respects Y-86032 is similar to the previously described lunar meteorites Y-82192/3, but there are some notable differences. We have analyzed about 40 major and trace elements in bulk matrix, impact melt, and clast samples from two chips of Y-86032. The abundances of most lithophile and incompatible elements are lower in Y-86032 than in Y-82192 (which contains very low abundances compared to normal lunar highland rocks). The REE abundances are comparable to those of Y-82192. The elements Sc, Cr, Mn, Fe and Co have significantly lower abundances than in Y-82192, and the siderophile element pattern is also different. Since cosmic ray exposure data indicate pairing of Y-86032 with Y-82192/3, the source region for these meteorites on the moon must have been fairly heterogeneous.

Koeberl, Christian↗
NASA NTRS1993

Mineralogy of chondritic interplanetary dust particle impact residues from LDEF

A detailed structural and compositional analysis of several impactor residues was performed utilizing transmission electron microscopy, energy dispersive spectroscopy, and electron diffraction. Residues from the interior of several craters in gold surfaces were removed with a tungsten needle, mounted in EMBED-812 epoxy, and ultramicrotomed. The presence in these residues of equilibrated ferromagnesian minerals, recrystallization textures, glass, and melted metal and sulfide bodies decorating grain boundaries is indicative of varying degrees of shock metamorphism in all impact residues we have characterized.

Barrett, R. A.↗
NASA NTRS1993

Venus mountain-top mineralogy: Misconceptions about pyrite as the high radar-reflecting phase

Altitude-dependent, high radar-reflectivity surfaces on Venus are observed on most mountainous volcanic terranes above a planetary radius of about 6054 km. However, high radar-reflectivity areas also occur at lower altitudes in some impact craters and plain terranes. Pyrite (FeS2) is commonly believed to be responsible for the high radar reflectivities at high elevations on Venus, on account of large dielectric constants measured for sulfide-bearing rocks that were erroneously attributed to pyrite instead of pyrrhotite. Pentlandite-pyrrhotite assemblages may be responsible for high reflectivities associated with impact craters on the Venusian surface, by analogy with Fe-Ni sulfide deposits occurring in terrestrial astroblemes. Mixed-valence Fe(2+)-Fe(3+) silicates, including oxyhornblende, oxybiotite, and ilvaite, may contribute to high radar reflecting surfaces on mountain-tops of Venus.

Burns, Roger G.↗
NASA NTRS1993

Cronstedtite and iron sulfide mineralogy of CM-type carbonaceous chondrites from cryogenic Moessbauer spectra

Determinations of oxidation states and the crystal chemistry of iron-bearing minerals in CM meteorites by Moessbauer spectroscopy are complicated by thermally-induced electron hopping in cronstedtite and by ill-defined contributions from the hydrous iron sulphide phase believed to be tochilinite. Moessbauer spectral measurements at 30 K of several cronstedtite and tochilinite specimens have enabled modal proportions of these minerals, as well as Fe(3+)/Fe(2+) ratios, to be determined quantitatively for a suite of CM-type carbonaceous chondrites that included Murchison, Murray, Cold Bokkeveld, ALH 83100, and LEW 90500.

Fisher, Duncan S.↗
NASA NTRS1993

Petrography, mineralogy, and Mg isotope composition of VICTA: A vigarano CaAl4O7-bearing type A inclusion

Thermodynamic calculations predict that Ca-dialuminate (CaAl4O7) condenses from a cooling gas of solar composition after hibonite and before melilite. Although Ca-dialuminate has now been recorded from Ca Al-rich inclusions (CAI's) in at least 9 meteorites, compared to hibonite it is a relatively rare phase. As pointed out by Michel-Levy et al., the absence of Ca-dialuminate from most hibonite-bearing inclusions poses a serious problem for the condensation model of CAI formation. Here we describe an inclusion which contains abundant CA-dialuminate partially altered to a hercynite-rich (FeAl2O4) assemblage. The evidence from VICTA indicates that compared to all other phases in type A inclusions, Ca-dialuminate is the most susceptible to secondary alteration; a feature which may explain its restricted occurrence. Unaltered Ca-dialuminate and melilite in VICTA display excess Mg-26 indicative of in situ decay of Al-26.

Greenwood, R. C.↗
NASA NTRS1993

Deucalionis Regio, Mars: Evidence for a unique mineralogic endmember and a crusted surface

A small equatorial region south of Sinus Meridiani, Deucalionis Regio, has been found spectrally distinct from other regions as seen in a high spectral resolution telescopic image of the meridian hemisphere of Mars. Analysis of Viking IRTM and other related data suggest that Deucalionis Regio has a crusted surface. The crust-bonding minerals may contribute to the spectral uniqueness of this region. Two independent analyses of spectral images, linear spectral mixing and supervised classification based on the spectral shapes, showed that in addition to the well-known spectral endmember regions in this image (western Arabia, south Acidalia, and Sinus Meridiani), Deucalionis Regio has spectral properties that are unique enough to make it a principle endmember unit. In those earlier works, Deucalionis Regio was referred to as 'Meridiani Border.' Analysis of thermal inertia, rock abundance, and albedo information derived from Viking images and Infrared Thermal Mapper (IRTM) data obtained 1977-80 also indicate that Deucalionis Regio has a surface of distinctly different physical properties when compared to Arabia, Sinus Meridiani, and Acidalia. Deucalionis Regio has a thermal inertia equivalent to the Martian average, a low rock abundance (less than 5 percent), and an intermediate albedo and color. Considerable effort by previous investigators has revealed a consistent model for the surface (upper few cm) properties of the endmember reigons Arabia, Sinus Meridiani, and Acidalia. Compared with these regions, we consider that Deucalionis Regio is not a region of either (1) unconsolidated, fine bright dust like Arabia, (2) considerable windblown unconsolidated sand like Sinus Meridiani, or (3) a rocky-and-sandy surface like Acidalia. Thus, we are forced to consider that either the surface of Deucalionis Regio is made of unconsolidated fine to medium sand (about 250 microns) of an unusual and previously unreported color and albedo, or that the surface is crusted, fine-grained weathered soil, and the thermal inertia is an indicator of the degree to which the surface sediments have become indurated. We favor the latter.

Merenyi, E.↗
NASA NTRS1993

Mineralogy of dark clasts in primitive versus differentiated meteorites

The presence of dark lithic clasts within meteorites can provide information concerning asteroidal regolith processes, the extent of interactions between asteroids, and the relationship between meteorite types, micrometeorites, and interplanetary dust particles. Accordingly, we have been seeking and characterizing dark clasts found within carbonaceous chondrites, unequilibrated ordinary chondrites, howardites, and eucrites. We find that unequilibrated chondrites in this study contain fine-grained, anhydrous unequilibrated inclusions, while the howardites often contain inclusions from geochemically processed, hydrous asteroids (type 1 and 2 carbonaceous chondrites). Eucrites and howardities contain unusual clasts, not easily classified.

Zolensky, M. E.↗
NASA NTRS1992

Determination of Martian soil mineralogy and water content using the Thermal Analyzer for Planetary Soils (TAPS)

Physical and chemical interactions between the surface and atmosphere of Mars can be expected to embody a strong cause-and-effect relationship with the minerals comprising the martian regolith. Many of the minerals in soils and sediments are probably products of chemical weathering (involving surface/atmosphere or surface/hydrosphere reactions) that could be expected to subsequently influence the sorption of atmospheric gases and water vapor. Therefore, identification of the minerals in martian surface soils and sediments is essential for understanding both past and present interactions between the Mars surface and atmosphere. Clearly, the most definitive mineral analyses would be achieved with well-preserved samples returned to Earth-based laboratories. In advance of a Mars sample return mission, however, significant progress could be made with in situ experiments that fill current voids in knowledge about the presence or abundance of key soil minerals such as clays (layered-structured silicates), zeolites, and various salts, including carbonates. TAPS is intended to answer that challenge by providing first-order identification of soil and sediment minerals.

Gooding, James L.↗
NASA NTRS1994

The Lunar Scout Program: An international program to survey the Moon from orbit for geochemistry, mineralogy, imagery, geodesy, and gravity

The Lunar Scout Program was one of a series of attempts by NASA to develop and fly an orbiting mission to the moon to collect geochemical, geological, and gravity data. Predecessors included the Lunar Observer, the Lunar Geochemical Orbiter, and the Lunar Polar Orbiter - missions studied under the auspices of the Office of Space Science. The Lunar Scout Program, however, was an initiative of the Office of Exploration. It was begun in late 1991 and was transferred to the Office of Space Science after the Office of Exploration was disbanded in 1993. Most of the work was done by a small group of civil servants at the Johnson Space Center; other groups also responsible for mission planning included personnel from the Charles Stark Draper Laboratories, the Lawrence Livermore National Laboratory, Boeing, and Martin Marietta. The Lunar Scout Program failed to achieve new start funding in FY 93 and FY 94 as a result of budget downturns, the de-emphasis of the Space Exploration Initiative, and the fact that lunar science did not rate as high a priority as other planned planetary missions, and was cancelled. The work done on the Lunar Scout Program and other lunar orbiter studies, however, represents assets that will be useful in developing new approaches to lunar orbit science.

Morrison, Donald A.↗