Within our solar system are four giant planets. We have named them the outer planets because they are farthest from the sun. But what do we know about these huge spheres of gas and liquid? The Outer Planets explores the gas giants of our solar system and uncovers the space science that has helped us learn about them. Science-filled explanatory text reveals what and how we have learned about the outer planets, the history of this space science, and what the future holds. Detailed sidebars set out fascinating facts about our solar system's giant balls of gas.