Io's Limb (RAW b/w NASA-Galileo Spacecraft Original Frame)

Caption NASA:"This picture of Io was taken on the morning of March 5 at a range of 75.445 Km. The area shown is at approx. 15° South Latitude and 244° East Longitude. Many depressions and elevations are shown. The light is coming from the left, so a depression has a bright right wall and shadow on the left wall. The depressions are complex in shape and do not resemble impact craters. Two of the depressions are joined by a shallow trough. The elevations are irregular and comical. They are cut by linear and irregular troughs. The surface is smooth and plain-like, that is, the surface is not pockmarked by abundant impact craters so are probably geologically young.