The solar system — the Sun and its collection of nine orbiting planets — formed some 5 billion years ago. We are now at the dawn of a new era in exploring those planets and answering some of the many questions about them. Already we have examined meteorites from other worlds for signs of life, landed men on the Moon, and launched spacecraft to look for evidence of volcanic eruptions on Mars and to explore the moons of Jupiter, as well as photographed all the planets in the solar system and launched probes to all except Pluto. Discover what the Voyager and Pioneer spacecrafts told us about the outer planets, and what the Viking, Pathfinder, Mariner and Magellan spacecraft have revealed about the inner planets. Perhaps what we accomplish in the next years will help pave the way for manned missions to Mars so that, eventually, people will walk on its surface as they have walked on the Moon.