1) Year discovered: 1610
2) Discovered by: Galileo Galilei (though he couldn't identify them as rings)
3) Year idenfitied as rings: 1655
4) Identified as rings by: Christiaan Huygens
5) First extensively photographed by: Pioneer 11 (1979) took the first low-resolution photos, but the planet was much more extensively photographed by Voyager 1 (1980) and Voyager 2 (1981).
6) Distance of rings from Saturn's center: 66,000 to 480,000 km (that's 41,010 to 298,258 miles)
7) Thickness: No more than 1000 km or 621 feet
8) Size of particles in rings: anywhere from 1 cm to several meters, with some larger objects and "moonlets"
9) Composition of particles in rings: Make up of mainly water ice with trace amounts of silicate materials.
10) Estimated total mass of rings: Possibly more than three times that of Saturn's moon Mimas (which is 3.75 x 10^19 kg or 8.27 x 10^19 lbs)
11) Types of rings: The main rings (A, B and C), the dusty rings (D, E and G), F Ring
12) How rings were named: In the order of discovery (i.e., "A" was discovered first)
13) Innermost ring: D Ring (67,000 to 74,500 km, or 41,632 to 46,292 miles, from Saturn's center)
14) Outermost ring: E Ring (180,000 to 480,000 km, or 111,847 to 298,258 miles, from Saturn's center)
15) Leading theory for ring formation: Breakup of a moon (either through tidal forces or meteor impact), leftover remnants from the early solar system
16) Likely source of material in E Ring: Microscopic, cryovolcanic material from the moon Enceladus
17) Age of rings: Uncertain (theories range from 100 million years to 4 billion years old, though recent data from Cassini-Huygens indicate the older age is more likely)
18) Other ring features: "Braided" rings, ringlets, spokes (radial features)
19) Likely cause of spokes: Saturn's magnetic field
20) Largest gap in rings: Cassini Division (4,700 km, or 2,920 miles, wide)
21) Likely causes of gaps in rings: Gravitational pull of "shepherd" moons, resonance effects between ring particles and moons
Above left: A natural-color mosaic image of Saturn's rings, taken by Cassini. (Image credit: NASA/JPL/Space Science Institute, http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=5723)
Right: A closeup of Saturn's A Ring. (Image credit: NASA/JPL/Space Science Institute, http://solarsystem.nasa.gov/multimedia/display.cfm?IM_ID=2724)