The Cassini mission, a joint venture of NASA and the European and Italian space agencies has been orbiting Saturn for five Earth years as of Tuesday.

NASA officials said that is about one sixth of a Saturnian year -- enough time for the spacecraft to have observed seasonal changes on the planet, its moons and sunlight's angle on the dramatic rings.

"Cassini passed through a gap in the rings as it entered orbit on June 30, 2004," NASA said. "It finished its prime mission in 2008 and continues to use its 12 instruments in an extended mission that includes extensive further studies of the moons Titan and Enceladus."

The Cassini-Huygens mission was launched Oct. 15, 1997, and entered orbit around Saturn July 1, 2004, according to Wikipedia. The spacecraft consisted of two main elements, NASA's Cassini orbiter and the ESA's Huygens probe. The probe separated from the orbiter and reached Saturn's moon Titan on Jan. 14, 2005, where it descended to the surface and relayed scientific information.

NASA's Jet Propulsion Laboratory in Pasadena, Calif., manages the mission.