Mercury's Caloris Basin

Mercury

. A Mariner 10 mosaic image of the sunlit portion of the Caloris Basin. This multi-ring feature spans 1.34 million meters, and its rim is marked by rough mountainous blocks that rise up to 1,000 meters above the surrounding terrain. The collision resulted in a flat basin floor (left); it has been subsequently marked by smaller craters. (Courtesy of JPL and NASA.)

Copyright 2010, Professor Kenneth R. Lang, Tufts University