Color Variations on Eros from NEAR Multispectral Imaging

Murchie, S. L.; Robinson, M. S.; Clark, B. E.; Li, Han; Thomas, P. C.; Joseph, J.; Bussey, B.; Domingue, D. L.; Veverka, J.; Izenberg, N. R.; Chapman, C. R.

doi:10.1006/icar.2001.6756

Cited by 79 publications

(81 citation statements)

References 52 publications

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“…Additionally, it is found that some lower reflectance deposits exhibit unique color ratio values (see discussion FIG. 14. High-albedo smooth deposits are commonly found on walls of craters that exceed slopes of about 20-25 0 (Thomas et al, 2002a;Murchie et al, 2002b). Due to Eros' grossly non-spherical shape large slope differences commonly exist from one side of a crater interior to the other, resulting in the semicircular shapes of many of the higher albedo wall deposits (see Figs.…”

Section: Downslope Movementmentioning

confidence: 99%

“…Finally, on Eros high-albedo and relatively blue ejecta patterns are not found around small craters, while such features are found on the Main Belt S asteroids (Gaspra and Ida), Phobos and Deimos, and the lunar maria (Wilhelms, 1987;Carr et al, 1994;Sullivanetat., 1996;Pieters et al, 2001). Additionally, it was noted by Murchie et al (2002b) that on Eros there is a measurable dependence of the 950 to 750 nm ratio with incidence angle-materials appear "redder" at higher incidence angles, a common characteristic of silicate powders measured in the laboratory (Gradie et al, 1980;Gradie and Veverka, 1986).…”

Section: Introductionmentioning

confidence: 99%

“…Preliminary analyses of the color properties of Eros measured by the MSI are presented in Robinson et al, (2001) and Murchie et al (2002b). Murchie et al (2002b) raised four major questions.…”

Section: Introductionmentioning

confidence: 99%

“…Murchie et al (2002b) raised four major questions. (1) Are there large-scale color heterogeneities and what are their magnitude and spatial distribution?…”

Section: Introductionmentioning

confidence: 99%

“…The ponds also exhibit a somewhat elevated reflectance at 750 nm relative to their surroundings «5%). To date all analysis of NEAR Shoemaker remote sensing measurements (gamma-ray spectroscopy (GRS), magnetometer (MAG), MSI, near-infrared spectroscopy (NIS), x-ray spectroscopy (XRS)) ofthe asteroid imply a compositionally homogeneous body (Acuna et al, 2002;Bell et al, 2002;Murchie et al, 2002b;Evans et al, 2001;McCoy et al, 2001McCoy et al, , 2002Nittler et al, 2001;Trombka et al, 2001;Domingue et al, 2002;Lucey et al, 2002) discounting the possibility that the pond color properties indicate exposures of a different rock type. Alternative explanations for these color differences include secondary alteration (space weathering), mineral sorting, or differences in grain size (see discussion below).…”

Section: Introductionmentioning

confidence: 99%

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The geology of 433 Eros

Robinson

Thomas

Veverka

et al. 2002

Meteorit & Planetary Scien

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Abstract-The global high-resolution imaging of asteroid 433 Eros by the Near-Earth Asteroid Rendezvous (NEAR) Shoemaker spacecraft has made it possible to develop the first comprehensive picture of the geology of a small S-type asteroid. Eros displays a variety of surface features, and evidence of a substantial regolith. Large scale facets, grooves, and ridges indicate the presence of at least one global planar structure. Directional and superposition relations of smaller structural features suggest that fracturing has occurred throughout the object. As with other small objects, impact craters dominate the overall shape as well as the small-scale topography of Eros. Depth/diameter ratios of craters on Eros average -0.13, but the freshest craters approach lunar values of -0.2. Ejecta block production from craters is highly variable; the majority oflarge blocks appear to have originated from one 7.6 km crater (Shoemaker). The interior morphology of craters does not reveal the influence of discrete mechanical boundaries at depth in the manner of craters formed on lunar mare regolith and on some parts of Phobos. This lack of mechanical boundaries, and the abundant evidence of regolith in nearly every high-resolution image, suggests a gradation in the porosity and fracturing with depth. The density of small craters is deficient at sizes below -200 m relative to predicted slopes of empirical saturation. This characteristic, which is also found on parts ofPhobos and lunar highland areas, probably results from the efficient obliteration of small craters on a body with significant topographic slopes and a thick regolith. Eros displays a variety ofregolith features, such as debris aprons, fine-grained "ponded" deposits, talus cones, and bright and dark streamers on steep slopes indicative ofefficient downslope movement ofregolith. These processes serve to mix materials in the upper loose fragmental portion ofthe asteroid (regolith). In the instance of "ponded" materials and crater wall deposits, there is evidence of processes that segregate finer materials into discrete deposits. The NEAR observations have shown us that surface processes on small asteroids can be very complex and result in a wide variety of morphologic features and landforms that today seem exotic. Future missions to comets and asteroids will surely reveal still as yet unseen processes as well as give context to those discovered by the NEAR Shoemaker spacecraft.

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Section: Downslope Movementmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

“…Murchie et al (2002b) raised four major questions. (1) Are there large-scale color heterogeneities and what are their magnitude and spatial distribution?…”

Section: Introductionmentioning

confidence: 99%