Plate 2

The European Space Agency's Faint Object Camera on the Hubble Space Telescope (HST) imaged most of the surface of Pluto, as it rotated through its 6.4-day period, in late June and early July 1994. The maps shown here are from a global map constructed through computer image processing performed on the Hubble data and rendered onto three-dimensional globes at 90° increments in longitude. The rendered color was derived from the rotationally averaged ground-based observations of Pluto. With a resolution corresponding to more than 600 km, HST discerns roughly 12 major “regions” where the surface is either bright or dark. These images show that Pluto is an unusually complex object, with more large-scale contrast than any planet except Earth. Some of the variations across Pluto's surface may be caused by topographic features such as basins or fresh impact craters. However, most of the surface features unveiled by HST, including the prominent northern polar cap, are likely produced by the complex distribution of frosts that migrate across Pluto's surface with its orbital and seasonal cycles and chemical by-products deposited out of Pluto's nitrogen-methane atmosphere. Image courtesy of Alan Stern, Southwest Research Institute; Marc Buie, Lowell Observatory; NASA; and ESA.