Anyone with a reasonably good telescope can take a picture of Pluto, but seeing anything more than a blurry dot is all but impossible. Even with the Hubble telescope, Pluto is only five picture elements wide. But this past year a team led by Alan Stern, an astronomer at the Southwest Research Institute in Boulder, Colorado, teased some surface details out of that low-resolution view. Stern and his colleagues used the Hubble to take images of Pluto at various times during its 6.4-day rotation; by superimposing the overlapping images and plotting them on a globe, they could distinguish light and dark patches on Pluto’s icy surface. They found between seven and nine such patches, each of them hundreds of miles across, including a polar ice cap bisected by a dark strip.
Although some of the regions may be permanent physical features like basins or craters, Stern and his colleagues believe ...
