Named after the Roman god of war, Mars has fascinated people for thousands of years. Did you know that . . .

* A year on Mars is 687 Earth days, almost twice as long as a year on Earth

* Long ago, people believed that there were Martians living on Mars

* Mars's biggest valley, Valles Marineris, is four times as deep as the Grand Canyon

* Scientists think that Mars, now rocky and barren, once had an ocean, rivers, and a thicker atmosphere

Explore the wonders of Mars, the red planet, with award-winning science writer Seymour Simon in this new, updated edition filled with dramatic full-color photographs and spacecraft images. Plus there's an author's note, glossary, and index.