The Sun A Chinese legend held that there were 10 suns. Over the course of history, the Sun has been deified by many cultures. Today, we know that the five-billion-year-old Sun is a ball of gas that produces titanic explosions and supports life on Earth. More on the Sun.
		Mercury Named for the winged messenger of Roman mythology, Mercury is the planet closest to the Sun. Its surface alternately bakes and freezes, due to its slow rotation. More on Mercury.
		Venus Shrouded by insulating clouds, Venus has high temperatures at its surface. It was the first planet to be explored by visitor from Earth, the unmanned Mariner 2 in 1962. Due to its similar size and mass, it has been thought of as Earth's sister planet.More on Venus.
		Earth Home to an astonishing variety of life, Earth is a complex array of interdependent ecosystems. As humanity continues to expand, the planet experiences more environmental pressure. Today, Earth is being studied from space at an unprecedented rate. More on Earth.
		The Moon As Earth's nearest companion in the solar system, the Moon is thought to have been born from a cosmic impact about 4.5 billion years ago. The Moon was last visited by astronauts in 1972, and more recently has been studied by unmanned missions. More on the Moon.
		Mars Named by the Romans after their god of war, Mars is the outermost of the four terrestrial planets. Its distinctive red color comes from iron oxide contained in the Martian soil. Two recent missions to the planet have failed, suspending future U.S. missions to Mars and prompting NASA to re-examine its guidelines. More on Mars.
		Asteroids Asteroids, comets and meteors are cosmic debris left from the formation of the solar system. NASA and other organizations hope that planned missions to some of these bodies will uravel mysteries about the early planets. More on Asteroids.
		Jupiter The first of the gas giants, Jupiter is the largest planet in the solar system. Its striated atmosphere reflects processes that take place on Earth, but on a much greater scale. Four of Jupiter's moons have caught the attention of astronomers because of the presence of volcanic activity and magnetic fields on some of the moons. One of them, Europa, is believed to have the largest ocean in the solar system. More on Jupiter.
		Saturn The dominating feature of this planet is its ring system. Saturn's rings are actually trillions of particles held in the planet's orbit. With 18 moons, Saturn is the second of the gas giants. More on Saturn.
		Uranus Mysterious Uranus has barely visible rings and is the only planet that rotates on its side, with its south pole pointing at the Sun. It has 21 moons, the most of any planet in the solar system. More on Uranus.
		Neptune Neptune, located through mathematical predictions based on the expected orbit of Uranus, was discovered in 1846, along with Triton, its largest moon. The fourth and smallest gas giant, Neptune has eight moons. A visit by Voyager in 1989 provided new data on the planet. More on Neptune.
		Pluto During the last two decades of the 20th century, Pluto was actually closer to the Sun than Neptune, due to Pluto's highly elliptical orbit. Some scientists theorize that Pluto -- smaller than Earth's moon -- isn't a true planet and believe it could be a comet or large chunk of space debris. More on Pluto.

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