They're like major planets, but not quite. They circle around the sun. They're round. But they haven't cleared everything out of their path. Explore these unusual objects in this book about the dwarf planets.

Describes the planet Mercury as the fastest planet in the solar system and demonstrates that its orbital path is shaped like an egg. Explains that Mercury is closest to the sun, has no atmosphere, and moves from a very high temperature to one that is very low. Notes that only one spacecraft has flown by Mercury, in 1974 and 1975, and another trip has been planned for 2011.

Presents the planet Saturn to young readers, focusing on its orbit, its rings, its relationships to other planets, and an ongoing scientific investigation of its attributes, like density, heat, and gravity.

Named for the god of war because of its blood-red color, Mars is the second-smallest planet in our solar system. Explore its cold canyons, ice caps, and more in this book about Mars.