A patchwork of images from the Cassini spacecraft shows the surface of Titan, the largest moon of Saturn. An orange hydrocarbon smog tops the moon's cold, dense atmosphere, blocking the surface from view of optical telescopes and cameras. But Cassini's infrared and ultraviolet cameras, as well as a radar system, peer through the smog. They have revealed lakes and seas near the north pole, deep riverbeds, mountains up to two miles high, huge dune fields (the dark regions in this infrared image), and other features. At Titan's frigid surface temperatures, the lakes and seas are filled with liquid ethane and methane, which also carved the riverbeds. [NASA/JPL/Univ. Arizona/Univ. Idaho]