On 1 July, 2004, the Cassini spacecraft arrived at Saturn, marking the end of the spacecraft’s nearly seven-year journey through the solar system and the beginning of its tour of Saturn and the planet’s rings and moons.
This picture was taken in ultraviolet on 30 June, 2004 during Cassini’s orbital insertion maneuver. It shows, from left to right, the outer portion of the C ring and inner portion of the B ring which begins a little more than halfway across the image. The “dirty” particles are indicated by red, and “cleaner: ice particles shown in turquoise.
Saturn’s ring system is labeled from the inside out with the D, C, B and A rings followed by the F, G and E rings.
As the Cassini spacecraft was running out of maneuvering fuel, it was directed to a series of orbits around Saturn that took in between the planets and its rings, and then progressively lower until it entered the atmosphere and burned up.
Saturn’s rings are mostly water ice in chunks that range in size from smaller than a grain of sand to mountains. The ring system extends 282,000 km from the planet, but it’s only about 10 m thick in most places. Looking from some angles, it’s possible to see through the rings—as in this that looks from south to north. The Cassini spacecraft took the images stitched together in this natural-color mosaic in April, 2007, when it was about 725,000 kim from Saturn.
The shadow Saturn casts on its rings is getting shorter. Later this month, the planet’s solstice will occur. At that point in time, the shadow will extend only as far as the innermost A ring, leaving the middle and outer A ring completely free of the planet’s shadow.