60,000550.40.16315080* Phoebe moves around Saturn in a retrograde direction.Rhea, Dione, Tethys, and Mimas have icy, cratered surfaces. One huge crater on Mimas has more than one-third the diameter of the satellite itself, so that, if the crater were formed by impact, it seems that Mimas would have been in danger of breaking up. Enceladus was not well shown from Voyager 1, but it may be comparatively smooth.Titan, by far the largest of Saturn’s satellites, is in a class of its own because of its dense atmosphere. Data obtained from Voyager 1 indicate that the atmospheric pressure at Titan’s surface is 1.5 to two times that of the Earth at sea level. The actual surface of the satellite has an orange-colored layer of what may be called “photochemical smog.” Titan’s atmosphere is made up almost entirely of nitrogen with little amounts of methane and cyanide. It is possible that the intensely cold surface is covered, at least in part, by oceans of liquid nitrogen....
