HR: 0800h
AN: P11A-0099    [Abstracts]
TI: Global Study of Small-Scale Color Variations on Eros
AU: * Riner, M A
EM: mariner@earth.northwestern.edu
AF: Center for Planetary Sciences, Northwestern University, 1850 Campus Dr., Evanston, IL 60208 United States
AU: Eckart, J M
EM: j-eckart@northwestern.edu
AF: Center for Planetary Sciences, Northwestern University, 1850 Campus Dr., Evanston, IL 60208 United States
AU: Digilio, J G
EM: jdigilio@earth.northwestern.edu
AF: Center for Planetary Sciences, Northwestern University, 1850 Campus Dr., Evanston, IL 60208 United States
AU: Robinson, M S
EM: robinson@earth.northwestern.edu
AF: Center for Planetary Sciences, Northwestern University, 1850 Campus Dr., Evanston, IL 60208 United States
AB: Small-scale color variations on Eros provide information about composition and regolith processes. We mosaicked all multispectral image sequences of Eros acquired with the NEAR Shoemaker MultiSpectral Imager (MSI) [1] to produce an exhaustive catalog of all color features. Consistent with previous findings we identify four types of spectral/albedo units: 1) high albedo streaks found on the steep slopes, 2) low albedo soils found in topographic lows and in association with high albedo streaks, 3) ponds which are smooth, flat deposits that infill topographic lows normal to local gravity, 4) and average Eros. From our global survey we have cataloged and characterized 137 white streaks, 66 dark soils, 123 areas of typical regolith, and 66 ponded deposits, roughly an order of magnitude more data points than reported in previous studies. We confirm the findings of [2]; white streaks, dark soils, and typical Eros fall on a two end-member mixing line with white streaks and dark soils as end members. White streaks are bluer (550nm/760nm) and have a deeper 1-micron absorption band (950nm/760nm), while dark soils are redder (550nm/760nm) and have a shallower 1-micron band (950nm/760nm). These trends are consistent with varying degrees of space weathering, from relatively immature white streaks to mature typical regolith. The dark soils may be a concentration of mature components (i.e. agglutinates, submicroscopic metallic iron) [2,3]. We also found a significant spatial association between dark soils and white streaks; all observed dark soils occur adjacent to white streaks however not all white streaks have associated dark soils. These observations support the hypothesis that white streaks are fresh material exposed on slopes by mass wasting and that dark soils are accumulations of mature components at the bottoms of slopes [2,3]. We find that ponded deposits are bluer (550nm/760nm) than and have similar 1-micron absorption band depths (950nm/760nm) as white streaks. However there is significant residual scattered light that may influence these reflectance ratios (950nm/760nm and 550nm/760nm). We are working to quantify the scattered light residual at each wavelength. [1] Bussey B.D.J. et al. (2002) Icarus, 155, 38-50. [2] Robinson M.S. et al. (2002) Meteor. & Planet. Sci., 37, 1651-1684. [3] Clark B.E. et al. (2001) Meteor. & Planet. Sci., 36, 1617-1637; Murchie S. (2002) Icarus, 155, 145-168.
DE: 5470 Surface materials and properties
DE: 6055 Surfaces
DE: 6200 PLANETARY SCIENCES: SOLAR SYSTEM OBJECTS
DE: 6205 Asteroids
SC: Planetary Sciences [P]
MN: Fall Meeting 2005