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E. F. Young (SwRI), R. P. Binzel (M.I.T.), K. Crane (Boulder High School)
The six year series of transits and occultations between Pluto and Charon (collectively called ``mutual events'') continue to produce new and useful results even though the last event was recorded in 1990. We present here a two-color map of Pluto's sub-Charon hemisphere based on lightcurves taken during four transits of Pluto by Charon in alternating B and V Johnson filters. These lightcurves are sufficient to derive B-V colors for the central part of Pluto's sub-Charon hemisphere but not the bright south polar region.
We find that the dark albedo feature which forms a band below Pluto's equator is not comprised of a single color unit. We detect ratios of V-filter/B-filter normal reflectances ranging from ~1.15 to ~1.39 on Pluto's sub-Charon hemisphere, making it the most variegated region among those resolved by this map. The bluest parts of this dark band are significantly bluer than the disk average (although still redder than a gray surface), which suggests that some coloring mechanism other than lag deposits of methane photolysis by-products must be in effect.
EFY and KC have been supported in this work by a grant from NASA's Planetary Astronomy program.