The Planets
For centuries, people believed the bright objects that seemed to wander among the stars were everything from gods to good-luck charms. It takes more than imagination, however, to see distant, moving points of light as planets.
Telescopes let us see them as other worlds, and spacecraft exploration revealed their landscapes. The four planets closest to the Sun are small, hard, and rocky. The four giant outer planets are mostly gas and ice. Beyond them lie icy worlds that were frozen into shape when the solar system was born.
Mercury
Mercury is the closest planet to the Sun. This rocky world gets hotter than an oven and colder than a freezer. Its desolate surface is heavily cratered and split by cracks.
Venus
Volcanic Venus is a place of crushing atmospheric pressure and broiling heat, one we cannot visit in person. Its desolate surface is hidden from our view by a blanket of clouds.
Our Earth
Our home world is warm, wet, and teeming with life. It is the place we understand best. We use what we know to explore other planets and learn about the solar system.
Mars
Mars has places that look like Earth, yet it is very different from our world. The surface of this dry and dusty desert planet freezes beneath a thin carbon dioxide atmosphere.
Jupiter
Jupiter is a gas giant and the largest world in the solar system. High-speed winds shape its cloud layers and send huge whirling windstorms racing across the planet.
Saturn
Particles of ice form a complex set of rings that circle gas giant Saturn. The planet belches clouds of ammonia ice crystals from deep within its atmosphere.
Uranus
Uranus is a planet tipped on its side, and its thick atmosphere is unevenly heated by the Sun. The result is a world with extreme weather and seasons.
Neptune
Neptune’s windy atmosphere is speckled with huge dark spots that appear and disappear. One large moon and a swarm of smaller ones orbit the planet.
Pluto and Beyond
Frigid Pluto lies in the solar system’s outer reaches. It orbits far from the Sun along with its companion Charon. The surfaces of these two worlds are frozen ice deserts.