Watch Europa report the movie ... It's in netflix

There is definitely concept art of these areas. But I think this will be DLC / Future releases. I believe what Bungie has talked about is Mars, Venus, Earth and the Moon. Edit: It should also be mentioned that these four locations are the only areas that any gameplay footage / screenshots have been shown from.

Saturn being the planet of my astronomical sign... I'd love to visit. [quote]Saturn was the Roman name for Cronus, the lord of the Titans in Greek mythology. Saturn is the root of the English word "Saturday."[/quote] (Case Rested) [spoiler]Shadow Agent out[/spoiler]

We have seen concept art of Europa, and a video of a ship flying to Saturn, although it is important to remember that it is believed that we will be able to go to the rings Of Saturn, not the planet.