Mimas . ... The surface is icy and heavily cratered. ... Because Mimas has such a low temperature of about -200њ C (-328њF), the impact features may date back to the time of the moon's creation. One of the craters, named Herschel, is surprisingly large in comparison to the size of the moon. The crater is 130 kilometers (80 miles) wide, one-third the diameter of Mimas. Herschel is 10 kilometers (6 miles) deep, with a central mountain almost as high as Mount Everest on Earth. ...