In June 2004, the Cassini spacecraft reached its ultimate destination: the Saturn system.

1. In June 2004, the Cassini spacecraft reached its ultimate destination: the Saturn system.

2. Although Cassini’s primary sponsors are NASA, the European Space Agency (ESA), and the Italian Space Agency (ASI), the mission’s team includes partners in 18 other nations.

3. The mission was named for two 17th-century scientists, Jean Dominique Cassini of Italy and Christiaan Huygens of Holland. Both men made important discoveries about Saturn. Cassini discovered 4 of Saturns’ moons and the gap between the rings, called the Cassini Gap in his honor. Huygens discovered the moon Titan in 1655, so the Titan landing probe is named for him.

4. The Cassini spacecraft traveled for over six years to reach Saturn. It was launched on October 15, 1997 aboard a Titan IV-Centaur rocket.

5. On its way to Saturn, Cassini captured this breathtaking image of Jupiter and its moon Io, moving across the cloud tops.

6. Cassini compiled this early image of Saturn in November 2003, from a distance of 111.4 million km (69.2 million miles).

7. At that time, Cassini was not yet close enough to capture the clarity of this ultraviolet image taken by the Hubble space telescope, which orbits Earth. Cassini photo. Hubble ultraviolet image.

8. As Cassini approached Saturn, however, it sent back increasingly detailed images. Astronomers watched two storms merge in Saturn’s southern hemisphere from February to March, 2004.

9. Intricate details of the rings and small nearby moons became visible as the spacecraft sped toward its destination. Cassini image of rings and moons, May 2004.

10. On June 11, 2004, Cassini entered the Saturn system with a flyby of Phoebe, an outer moon. Artist’s conception of an ice crevasse on Phoebe. Artist’s conception

11. April 2 June 3 September 16 Then, in July 2004, Cassini fired its thrusters and was captured into Saturn’s orbit, passing through the ring plane on its first swing around the planet.

12. When the craft entered Saturn’s orbit, it took the closest-range images ever taken of the rings. This will be Cassini’s closest approach to Saturn’s rings during the mission.

13. But Cassini is much more than a close-up camera. Cassini can "see" in wavelengths the human eye cannot, and "feel" magnetic fields and tiny dust particles no human hand could detect.

14. Ultraviolet ring images: red is dust, blue is water ice. The orbiter is providing information on Saturn’s planetary structure and rings, as well as temperature, winds, clouds, magnetic fields and lightning.

15. Scientists will use this information to understand the nature and environment of Saturn during its formation and early evolution.

16. Cassini is also studying Saturn’s numerous moons and "icy satellites.” Its orbits will bring it close to many of the moons.

17. Compare the Voyager 2 photo of Phoebe on the left, taken in 1981 from 2.2 million kilometers (1.36 million miles) away, to the 2004 Cassini image on the right, taken from a distance of only 32,500 kilometers (20,200 miles).

18. False-color image of Titan. Radar image of Titan’s surface. Geology of Titan’s South Pole region. The giant moon Titan is a primary science target. Cassini will fly past Titan many times and study its methane-rich nitrogen atmosphere and icy, hydrocarbon-rich surface.

19. The Cassini mission has another component: a moon landing. In December 2004, the Huygens probe, built by the ESA, separated from Cassini and began a 22-day journey to Titan.

20. After arriving on January 14, 2005, the probe descended through Titan’s murky atmosphere and landed on its surface.

21. These Cassini images show the landing site of the Huygens probe: on the left, the location of the site on Titan, and on the right, a close-up of that area.

22. Titan’s surface, with a temperature of -255°F, may contain tar-like compounds and water/ammonia ice. Titan may also have liquid methane seas and lakes. Artist’s conception of Huygens floating on a methane/ethane lake.

23. The probe carried instruments to sample Titan’s atmosphere and obtain images of the surface as it descended. Huygens survived for several hours after landing.

24. The first images released to the world of Titan from the Huygens probe: above, during the descent, and at right, from the surface. Photos courtesy ESA/NASA/ University of Arizona

25. Though the Huygens mission lasted only a few hours, Cassini’s four-year exploration will entail over 70 orbits around the ringed planet and its moons. For the latest on the Cassini mission and the Huygens landing, click here.