Color Variations on the Surface of Gaspra.

Abstract

3-filter color images of Gaspra (0.41, 0.56 and 0.99mm) reveal that the asteroid's surface is spectrally heterogeneous, with violet/ green and IR/green ratios varying by up to 10% and 20-30% respectiv- ly. Two types of spectral variations are recognized and correlate spatially with resolvable morphologic features. (I) Approximately the small patches have anomalously high violet/green ratios and low IR/green ratios. Indicating a bluer spectral slope and enhanced matic absorption. Most of these patches correlate with small impact craters, suggesting that relativly fresh substrate is exposed. (II) Central portions of the asteroid's "facets" have high violet/ green and high IR/green ratios, indicating subdued spectral contrast and mafic absorptions. Bluer, mafic patches associated with small craters are noticeably absent from these latter regions. The spatial and spectral properties of these spectrally subdued areas are suggesttive of accumulation of optically altered. Laterally transported material on gravitationally low portions of the asteroid.We are investigating mechanisms that could produce this distinct type of spectral heterogeneity.