Saturn

The planet with the Big Ring around it.  Saturn is fairly far from Jupiter, it's neighbor planet.  It 's also the second largest planet in our solar system, just a bit smaller than Jupiter.  Like Jupiter it is mostly made up of hydrogen and helium and has no solid surface.  Although all four of the giant planets have rings, Saturn is the only one that you can see through a telescope.  These rings are made up of small particles that orbit the planet like a moon does.  Saturn has many moons, most are the size of a small asteroid or comet.  The most interesting moon is Titan, which is larger than Mercury.  

Titan is the only moon known to have a dense atmosphere and surface liquid evidence.  The surface temperature is -180 degrees Celsius.  Because the temperature is so low the water would be solid ice,  but there is strong evidence for liquid hydrocarbons having flowed on Titan.  The atmosphere is %90 Nitrogen and there is no appreciable oxygen to breathe.  Even if there is no biology on this moon, the study of it could still tell us a lot.