Our solar system consists mainly of nine planets which revolve in elliptical orbits around the sun. The four inner planets; mercury, venus, earth, and mars, are terrestrial planets made up of an metal core and a silicate crust. Beyond the orbit of mars is a belt of asteroids, known as the Kuiper Belt. The remaining outer planets, jupiter, saturn, uranus, and neptune, are gas giants, much larger than the terrestrial planets and consisting mainly of a thick atmosphere of very light gases. Pluto, the most distant planet, is terrestrial and follows a very odd orbit, very elliptical and highly inclined. Choose a planet from the menu at the left to find more on the properties of the planets.