This image of the Jovian moon Europa was taken by Voyager 2 on July 9, 1979, as the spacecraft passed within 225,000 kilometers (140,625 miles). The area shown is about 600 by 800 kilometers, and the smallest features visible are about 4 kilometers in size. This image was taken along the evening terminator which best shows the surface topography of complex narrow ridges, seen as curved bright streaks, 5 to 10 kilometers wide, and typically 100 kilometers in length. Also visible are dark bands, more diffuse in character, 20 to 40 kilometers wide and hundreds to thousands of kilometers in length. A few features are suggestive of impact craters but are rare, indicating that the surface, thought to be dominantly ice, is still active, perhaps warmed by tidal heating like Io. The larger icy satellites, Callisto and Ganymede, are evidently colder with much more rigid crusts and ancient impact craters. The complex intersecting of dark markings and bright ridges suggests that the surface has been fractured and material from beneath has welled up to fill the cracks.