The moon Tethys is pictured drifting across Saturn’s disc. Tethys is one of 3 medium sized moons (including Rhea and Dione) which are largely composed of ice with small amounts of rock and whose features consist mostly of craters. Tethys does have two outstanding features which are a huge 400km impact crater whose diameter is about 2/5 that of Tethys itself, as well as a giant 2000km valley that stretches across 3/4 of Tethys diameter.
IMAGE NOTE: This image was not altered other than extending Saturn’s rings to fill the page on the upper right side. The original image was in square format so the subtle ring outlines were more cropped than seen here.