Hubble reveals surface of Pluto

17 Jun 2002

For the first time since Pluto's discovery 66 years ago, astronomers have at last directly seen details on the surface of the solar system's farthest known planet. Pictures sent back by the European Space Agency's Faint Object Camera aboard NASA's Hubble Space Telescope canvass nearly the entire surface of Pluto. Taken as the planet rotated through a 6.4-day period, the snapshots show that Pluto is a complex object, with more large-scale contrast than any planet, except Earth.

The images reveal almost a dozen distinctive albedo features, or provinces. Features include a "ragged" northern polar cap bisected by a dark strip, a bright spot seen rotating with the planet, a cluster of dark spots, and a bright linear marking that is intriguing the scientific team analyzing the images. The images confirm the presence of icy-bright polar cap features, which had been inferred from indirect evidence for surface markings in the 1980s.

Some of the sharp variations across Pluto's surface detected in the Hubble images may potentially be caused by such topographic features as basins, and fresh impact craters, such as those found on Earth's Moon. Most of the surface features unveiled by Hubble, however, are likely produced by the complex distribution of frosts that migrate across Pluto's surface with its orbital and seasonal cycles, according to researchers. So distant is Pluto that nitrogen, carbon monoxide, and methane gases partially freeze onto its surface during that century-long period in its highly-elliptical orbit when it is furthest from the Sun.