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Gaffey, M. J.

Publications and source records attributed to Gaffey, M. J..

44 records · Page 3
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Asteroid surface materials - Mineralogical characterizations from reflectance spectra

The use of general and specific diagnostic spectral features and parameters to interpret most of the published high-quality reflectance spectra of asteroids is discussed. Such diagnostics are shown to provide the most complete and sophisticated mineralogically and petrologically based interpretation of the asteroid surface materials. Previous investigations of asteroid surface materials are exhaustively reviewed, emphasizing the general approaches employed, sources of information, previous characterizations of asteroid surface materials, and asteroid spectral groups. The interpretive methodology is then applied to spectral reflectance data for many individual members of the various spectral groups. A range of mineral assemblages similar to certain meteorite classes is identified, and evidence is presented for a selective high-temperature event that melted certain asteroid parent bodies and permitted their differentiation as some function of distance from the sun or the protosun and of the size of the protoasteroid. Possible candidates are proposed for the source bodies of different meteorite groups.

Gaffey, M. J.↗
NASA NTRS1977

Asteroid surface materials: Mineralogical characterizations from reflectance spectra

Mineral assemblages analogous to most meteorite types, with the exception of ordinary chondritic assemblages, have been found as surface materials of Main Belt asteroids. C1- and C2-like assemblages (unleached, oxidized meteoritic clay minerals plus opaques such as carbon) dominate the population throughout the Belt, especially in the outer Belt. A smaller population of asteroids exhibit surface materials similar to C3 (CO, CV) meteoritic assemblages (olivine plus opaque, probably carbon) and are also distributed throughout the Belt. The majority of remaining studied asteroids (20) of 65 asteroids exhibit spectral reflectance curves dominated by the presence of metallic nickel-iron in their surface materials. The C2-like materials which dominate the main asteroid belt population appear to be relatively rare on earth-approaching asteroids.

Gaffey, M. J.↗
NASA NTRS1977

Asteroid surface materials - Mineralogical characterizations and cosmological implications

The theoretical basis for the interpretation of diagnostic spectral features is examined and previous characterizations of asteroid surface materials are considered. A summary is provided of results reported by Gaffey and McCord (1977) who have utilized the most sophisticated interpretive techniques available to interpret the spectral reflectance data of about 65 asteroids for mineralogic and petrologic information. Cosmological implications related to the study of asteroid surface materials are also considered, taking into account source bodies for the meteorites, postaccretionary thermal history, significant factors of asteroid thermal history, and the Apollo and Amor asteroids. It is found that the asteroids exhibit surface materials made up of assemblages of meteoritic minerals. The relative abundance of meteorite types reaching the earth's surface is very different from the population of mineralogic types on asteroid surfaces. The earth-crossing or -approaching asteroids apparently derive from a restricted source region or population which is very strongly depleted in the C2-like assemblages that dominate the belt as a whole.

Gaffey, M. J.↗
NASA NTRS1976

Spectrophotometry /0.33 to 1.07 microns/ of 433 Eros and compositional implications

The spectral reflectance (0.33-1.07 micrometers) for the asteroid 433 Eros was determined as a function of rotational phase during January 28-30, and February 15, 1975. Interpretation of absorption features suggests Eros is composed of an undifferentiated assemblage of moderate to high temperature minerals (iron, pyroxene, and olivine, but no carbon). H-type ordinary chondrites are such assemblages, but it would be premature to conclude that Eros is like an H chondrite meteorite in composition until a better understanding is reached of possible physical differences between laboratory powders and asteroid regoliths for metal-bearing assemblages. There are no large-scale major compositional variations on the different sides of Eros.

Pieters, C.↗
NASA NTRS1976

Spectral reflectance characteristics of the meteorite classes

The results are presented of spectral reflectance measurements on more than 150 individual meteorite specimens representing essentially all types and subtypes of meteorites. A brief review is provided of the nature of the compositional information contained in a reflection spectrum of a natural material. Attention is given to the spectral reflectance characteristics of mineral assemblages, and to meteorite class spectral characteristics.

Gaffey, M. J.↗
NASA NTRS1976

Age-color relationships in the lunar highlands

The depth of the absorption feature near 1 micron in the reflectance spectra of immature lunar soils is determined primarily by the amount of pyroxene present in the soil. As a soil matures, the agglutinitic glass content increases and the Fe(2+) glass band dominates the absorption feature. An empirical relationship between the 1 micron band depth and the percentage of magnetic agglutinates, and hence maturity, is demonstrated for mature highland soils of a given composition. A similar variation of 1 micron band depth is observed in the telescopic spectra of lunar highland craters and is positively correlated with the surface maturity as determined by the small-impact erosion model of Soderblom (1970). Knowledge of both maturity and the 1 micron band depth of a lunar surface feature allows compositional information to be derived.

Charette, M. P.↗
NASA NTRS1974

Asteroids - Surface composition from reflection spectroscopy

Minerals partly composing the surfaces of 14 asteroids are determined by using asteroid reflectance spectra and optical properties of meteorites and other materials. Individual electronic absorption features are identified in the asteroids' spectra. The energies, relative strengths, and shapes of these features are interpreted by using laboratory and theoretical studies. Analysis of the initial 14 asteroid reflectance spectra indicates the presence of the following types of surface materials: six carbonaceous chondrite-like; two stony-iron-like (metal/silicate ratio approximately equal to 1); one iron meteorite-like; one basaltic achondrite-like; and four silicate-metal assemblages (metal/silicate ratio approximately equal to 0.25). These results support the conclusion that the asteroid belt is a source of at least some meteoritic material, and they show a relation between certain asteroids and certain classes of meteorites.

Mccord, T. B.↗