The Saturn satellite Tethys was viewed by Voyager 2 on Aug. 25 from a distance of 1 million kilometers (620,000 mi.). Evident on the surface of this icy moon is an enormous impact crater almost 400 km. (250 mi.) in diameter and about 15 km. (10 mi.) deep. Tethys itself is only 1,050 km. (650 mi.) in diameter. The crater contains a central peak about as high as the crater is deep; it is the result of rebound after the impact. Tethys resembles its sister satellite Mimas, seen closeup by Voyager 1 last fall. That body has a crater 130 km. (80 mi.) in diameter. The Tethys crater, which is so large that Mimas would fit inside, is on the opposite side of the great rift valley observed by Voyager 1. Many other, smaller craters pock-mark the surface here. The Voyager project is managed for NASA by the Jet Propulsion Laboratory, Pasadena, Calif.