From this image, it is easy to see why Mars, fourth planet from the Sun and named for the Roman god of war, is called the Red Planet. The reddish-orange color comes from a rust-colored sand, consisting of iron oxide and silica, that is found throughout the planet. The sand on Mars is actually a kind of dust—so fine that when Martian winds stir it up, the storms can last for months, the sand remaining aloft and obscuring the entire planet.
    Astronomers have long been intrigued by Mars’s surface, and the recent Viking planetary missions have provided amazing close-ups of its complex geography. From Earth, the most prominent Martian features are the so-called canals—dark,