Titan is the largest
moon of Saturn, the only
natural satellite known to have a dense atmosphere, and the only object other than Earth for which clear evidence of stable bodies of surface liquid has been found. Discovered on 25 March 1655 by the Dutch astronomer
Christiaan Huygens, Titan is the sixth
ellipsoidal moon from Saturn. Frequently described as a planet-like moon, it is the
second-largest natural satellite in the Solar System, after Jupiter's moon
Ganymede, and it is larger by volume than the smallest planet, Mercury. Titan itself is primarily composed of water ice and rocky material. Its dense, opaque atmosphere meant that little was known of the surface features or conditions until the
Cassini–Huygens mission in 2004. Although mountains and several possible
cryovolcanoes have been discovered, its surface is relatively smooth and few
impact craters have been found. Owing to the existence of stable bodies of surface liquids and its thick nitrogen-based atmosphere, Titan has been cited as a possible host for microbial
extraterrestrial life or, at least, as a prebiotic environment rich in complex organic chemistry. This mosaic of nine processed images was acquired during
Cassini's first close flyby of Titan in 2004.
Photograph credit: NASA / JPL / Space Science Institute
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