The largest satellite in the solar system is a strange quilt of dark and bright terrains. The dark regions, like Galileo Regio (below, top left), are heavily cratered; the large crater in the foreground is 19 kilometers in diameter. Deep furrows may contain dust left behind after water ice sublimated away. The bright regions, like Uruk Sulcus (top right), have fewer craters and more tectonic features such as grooves. This image depicts an area roughly 400 kilometers square. Some regions, like Tiamat Sulcus (bottom left), shown here just after sunrise, contain both types of terrain. The bottom right illustration is an artist's impression of the surface.