Daniel Britt | The University of Texas at Austin (original) (raw)
Papers by Daniel Britt
The dark fine grained matrix of gas-rich ordinary chondrites replicates many of the physical, mor... more The dark fine grained matrix of gas-rich ordinary chondrites replicates many of the physical, morphological, and spectral characteristics of the highly shocked and optically altered black chondrites. Spectral mixture modeling shows that the darkening and spectral attenuation seen in the dark matrix can be simulated with realistic mass fractions of light host material and black chondritic material. All these factors point to the conclusion that the dark matrix of gas-rich ordinary chondrites is dark due to the same processes that darkens black chondrites, shock distributed small particle size FeNi metal and troilite. Because the darkening is not seen in any of the non-gas-rich light portions and is only seen in the gas rich grains of the meteorite, the shock darkening would have to occur as part of the matrix's exposure to regolith processes. Since all gas-rich grains are darkened, it follows that darkening is not only common, but pervasive in asteroidal regoliths. These results imply that the upper, optically active layer of an ordinary chondrite parent body should have the spectral characteristics of a black chondrite, which are a dark, relatively featureless spectrum with modest red slope in the infrared. These are the characteristics of special type C asteroids.
Journal of Geophysical Research, 1999
The Imager for Mars Pathfinder (IMP) acquired four spectra of parts of the sub-Mars hemispheres o... more The Imager for Mars Pathfinder (IMP) acquired four spectra of parts of the sub-Mars hemispheres of Phobos and Deimos. The measured region of Phobos is expected to be a mixture of the two spectral units identified on that satellite from Phobos 2 data, and the IMP spectra of Phobos are intermediate to the two units as expected. The derived geometric albedo is consistent with the value for that part of Phobos determined from Viking imagery. The IMP spectrum of Deimos is generally consistent with previous measurements acquired from the ground and from the Hubble Space Telescope (HST), but the signal-to-noise ratio is lower than that of the Phobos data. The spectral contrast between the two moons is similar to that seen in HST and Phobos 2 data. Mars Pathfinder measurements therefore substantiate recent results which indicate that Phobos and Deimos are not, as previously believed, analogous to C-type asteroids. They also provide some indications for an absorption near 700 nm, perhaps like that seen in other lowalbedo asteroids. Both Martian moons are redder than most asteroids, and most closely resemble two analog materials believed to have undergone very dissimilar histories: primitive D-like asteroids, and highly space-weathered, mafic-rich assemblages, such as are present in lunar mare soils.
Icarus, 1992
The spectra of 103 meteorites and 411 asteroids have been statistically compared via principal co... more The spectra of 103 meteorites and 411 asteroids have been statistically compared via principal component analysis, in order to arrive at an overview of spectral similarities between and among asteroids and meteorites; the result is a map of statistically defined relative spectral similarities measured by distance. There is much more spectral variance in the meteorites than in the asteroids. The analysis indicates no direct meteorite analogs from the outer-belt B, D, F, P, and T type asteroids, indicating that only a limited portion of the inner asteroid belt is sampled by meteorites.
The Phobos 2 mission provided multispectral observations of Phobos over a large wavelength range ... more The Phobos 2 mission provided multispectral observations of Phobos over a large wavelength range and with relatively high spectral resolution. Here, researchers integrate results from three multispectral detectors by determining the ultraviolet-visible near infrared spectral properties of color and brightness features recognized in VSK TV images. Researchers present evidence that there are two fundamental spectral units within the region of overlapping coverage by the detectors. They describe the units' spectral and reflectance properties and discuss the implications of these results for the composition of Phobos.
The relationship between ordinary chondrites and S-type asteroids is an unresolved issue in meteo... more The relationship between ordinary chondrites and S-type asteroids is an unresolved issue in meteorite science. S-type asteroids exhibit a positively red-sloped spectrum that is interpreted to indicate the presence of elemental iron on the surfaces. The characteristic red-sloped spectrum of iron-rich meteorites is produced by only the specular component of the reflectance. Complex metallic surfaces can be modeled as linear mixtures of specular and nonspecular components. It is the geometry of the metal on a surface and its interaction with surrounding material, rather than the absolute amount of metal, that determine the redness of resulting spectra. In order to distinguish between ordinary chondrite and differentiated parent bodies it is important to understand how regolith processes affect the nature and form of metal on asteroid surfaces.
The relationship between ordinary chondrites and S-type asteroids is an unresolved issue in meteo... more The relationship between ordinary chondrites and S-type asteroids is an unresolved issue in meteorite science. S-type asteroids exhibit a positively red-sloped spectrum that is interpreted to indicate the presence of elemental iron on the surfaces. The characteristic red-sloped spectrum of iron-rich meteorites is produced by only the specular component of the reflectance. Complex metallic surfaces can be modeled as linear
The dark fine grained matrix of gas-rich ordinary chondrites replicates many of the physical, mor... more The dark fine grained matrix of gas-rich ordinary chondrites replicates many of the physical, morphological, and spectral characteristics of the highly shocked and optically altered black chondrites. Spectral mixture modeling shows that the darkening and spectral attenuation seen in the dark matrix can be simulated with realistic mass fractions of light host material and black chondritic material. All these factors point to the conclusion that the dark matrix of gas-rich ordinary chondrites is dark due to the same processes that darkens black chondrites, shock distributed small particle size FeNi metal and troilite. Because the darkening is not seen in any of the non-gas-rich light portions and is only seen in the gas rich grains of the meteorite, the shock darkening would have to occur as part of the matrix's exposure to regolith processes. Since all gas-rich grains are darkened, it follows that darkening is not only common, but pervasive in asteroidal regoliths. These results imply that the upper, optically active layer of an ordinary chondrite parent body should have the spectral characteristics of a black chondrite, which are a dark, relatively featureless spectrum with modest red slope in the infrared. These are the characteristics of special type C asteroids.
Journal of Geophysical Research, 1999
The Imager for Mars Pathfinder (IMP) acquired four spectra of parts of the sub-Mars hemispheres o... more The Imager for Mars Pathfinder (IMP) acquired four spectra of parts of the sub-Mars hemispheres of Phobos and Deimos. The measured region of Phobos is expected to be a mixture of the two spectral units identified on that satellite from Phobos 2 data, and the IMP spectra of Phobos are intermediate to the two units as expected. The derived geometric albedo is consistent with the value for that part of Phobos determined from Viking imagery. The IMP spectrum of Deimos is generally consistent with previous measurements acquired from the ground and from the Hubble Space Telescope (HST), but the signal-to-noise ratio is lower than that of the Phobos data. The spectral contrast between the two moons is similar to that seen in HST and Phobos 2 data. Mars Pathfinder measurements therefore substantiate recent results which indicate that Phobos and Deimos are not, as previously believed, analogous to C-type asteroids. They also provide some indications for an absorption near 700 nm, perhaps like that seen in other lowalbedo asteroids. Both Martian moons are redder than most asteroids, and most closely resemble two analog materials believed to have undergone very dissimilar histories: primitive D-like asteroids, and highly space-weathered, mafic-rich assemblages, such as are present in lunar mare soils.
Icarus, 1992
The spectra of 103 meteorites and 411 asteroids have been statistically compared via principal co... more The spectra of 103 meteorites and 411 asteroids have been statistically compared via principal component analysis, in order to arrive at an overview of spectral similarities between and among asteroids and meteorites; the result is a map of statistically defined relative spectral similarities measured by distance. There is much more spectral variance in the meteorites than in the asteroids. The analysis indicates no direct meteorite analogs from the outer-belt B, D, F, P, and T type asteroids, indicating that only a limited portion of the inner asteroid belt is sampled by meteorites.
The Phobos 2 mission provided multispectral observations of Phobos over a large wavelength range ... more The Phobos 2 mission provided multispectral observations of Phobos over a large wavelength range and with relatively high spectral resolution. Here, researchers integrate results from three multispectral detectors by determining the ultraviolet-visible near infrared spectral properties of color and brightness features recognized in VSK TV images. Researchers present evidence that there are two fundamental spectral units within the region of overlapping coverage by the detectors. They describe the units' spectral and reflectance properties and discuss the implications of these results for the composition of Phobos.
The relationship between ordinary chondrites and S-type asteroids is an unresolved issue in meteo... more The relationship between ordinary chondrites and S-type asteroids is an unresolved issue in meteorite science. S-type asteroids exhibit a positively red-sloped spectrum that is interpreted to indicate the presence of elemental iron on the surfaces. The characteristic red-sloped spectrum of iron-rich meteorites is produced by only the specular component of the reflectance. Complex metallic surfaces can be modeled as linear mixtures of specular and nonspecular components. It is the geometry of the metal on a surface and its interaction with surrounding material, rather than the absolute amount of metal, that determine the redness of resulting spectra. In order to distinguish between ordinary chondrite and differentiated parent bodies it is important to understand how regolith processes affect the nature and form of metal on asteroid surfaces.
The relationship between ordinary chondrites and S-type asteroids is an unresolved issue in meteo... more The relationship between ordinary chondrites and S-type asteroids is an unresolved issue in meteorite science. S-type asteroids exhibit a positively red-sloped spectrum that is interpreted to indicate the presence of elemental iron on the surfaces. The characteristic red-sloped spectrum of iron-rich meteorites is produced by only the specular component of the reflectance. Complex metallic surfaces can be modeled as linear