canyon - a deep valley with steep sides.

cliff - a very steep, high wall of rock.

crater - a big, round hole in the surface of a planet or a moon.

dwarf planet - a body that orbits a star, but does not have enough gravity to clear its orbit of similarly sized objects.

moon - a body which orbits a planet.

mountain - land that rises to a great height.

orbit - the path a planet takes when it moves around the Sun. The path a moon takes when it moves around a planet.

planet - a body that orbits a star. The eight planets in our solar system in order from the Sun are Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, and Neptune.

rings - smalls pieces of ice and rock grouped together that orbit a planet.

solar system - a group of planets around a star. Our solar system has eight planets orbiting the Sun.

spacecraft - a vehicle made to travel in the solar system.

star - a ball of hot, glowing gases.

Sun - the star closest to Earth. The center of our solar system. A ball of hot, glowing gases which gives Earth heat and light.

telescope - an instrument used for observing bodies in the solar system.

valley - a low-lying area between mountains and hills.

volcano - an opening in the surface of a planet or moon through which melted rock and steam flow.