In this picture you can see two of the moons, Io and Europa.
Jupiter is a gas giant, compared to the rocky planets like Earth or Mars. This means it is mostly made of Hydrogen and Helium (a little like the Sun), it is the biggest planet in the solar system and weights more than 300 times that of the Earth. Jupiter may have a small rocky core at it's centre but we don't really know yet whether this still exists (it was almost certainly there when the planet began).
Jupiter has many bands of different colours and you can see the Great Retd spot in this picture.
These different bands of colour that we see on Jupiter can move at different speeds (there is a wee video of it here). The Great Red spot is actually a storm on Jupiter that was first observed in 1665, nobody knows how long it has been raging for, but recently scientists think it may be a permanent feature (and I think Scottish weather is bad..). Jupiter has such a massive influence on the solar system, with it's gravity being the strongest apart from the Sun's. We think it helps protect the inner solar system as it attracts many of the comets and meteors that may have hit us!
Saturn's Rings systems are the famous, but Jupiter also has a ring around it (as shown it above), but we'll talk about these tomorrow!
What do you thing of the King of the Planets?