Half-Way Point

The Cassini spacecraft celebrated the half-way mark of its four-year mission to Saturn on Sunday by staging its 16th close encounter with Titan, the planet's largest moon. As shown in this earlier Cassini image, Titan (with the smaller moon Enceladus passing in front of it) is surrounded by a thick atmosphere that is topped by a layer of orange 'smog.' Cassini and the Huygens probe, which landed on Titan last year, have found giant sand dunes, a possible lake of liquid methane, and a possible ice volcano on the big moon. They also discovered what look like dry riverbeds, gullies that may have been carved by rainstorms, and other Earth-like features on the cold moon. [Credit: NASA/JPL/SSI]