A bright highlight on Pluto indicates that it might have a smoothly reflecting surface layer. A detailed analysis of the HST image also suggests that there is a bright area parallel to the equator of Pluto. However, subsequent observations are needed to confirm that this feature is real. These images, which were made in blue light, show that Pluto is an unusually complex object, with more large-scale contrast than any planet, except Earth. The two smaller inset pictures at the top are actual images from Hubble.
North is up.
Opposite hemispheres of Pluto are seen in these two views. 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 Hubble, 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 byproducts deposited out of Pluto's nitrogen-methane atmosphere. Discovered in 1930, Pluto has always appeared as nothing more than a dot of light in even the largest earth-based telescopes because Pluto's disk is much smaller than can be resolved from beneath the Earth's turbulent atmosphere. Hubble imaged nearly the entire surface of Pluto, as it rotated through its 6.4-day period, in late June and early July 1994.