Rust staining in the soil, imparted by iron oxide, is the simple reason why Mars' surface is so distinctly red. But its color is just one of the planet's unique surface features. In recent years, the Martian surface has been revealed as rich and varied landscape, shaped by great natural forces such as meteorite impacts, floods, volcanoes, earthquakes and glaciers. Mars' surface is continuing to evolve, due to the seasonal freezing and thawing and powerful winds that transport vast clouds of dust accross its face.

We know a great deal about the Martian surface, thanks to 19th century astronomers, who identified and named many of its features, and more recently to uncrewed Mars probes that have provided us with stunning close-ups of the entire planet.

Most of the surface of mars is a barren stony desert that looks and behaves much like deserts on Earth. But mars has a range of distinctive features. Most of them, such as mountains, canyons extinct volcanoes and craters, were created early in the planet's life. Mars' rivers, and probably its seas, have since shaped and modified many of these landmarks. Some of Mars' most unusual features - like the "Main Pyramid,""City Square" and "The Face" - have led to the claims that they are ruins left by an ancient civilization, although most scientists believe they are natural features.

But the planet's reddish soil can be found everywhere on Mars - the result of billions of years of rock erosion by wind and water and pulverized meteorites. This soil, blown around by the wind, covers virtually the entire planet and can be a few inches or many feet deep. It collects to form drifts, which can be seen from high above the planet's surface as distinctive tapered streaks of soil, often deposited on the leeward sides of craters.

What is known about the composition of Martian soil comes from experiments performed by the Viking Landers. The detected iron-rich clays, calcium carbonite, iron oxides, and magnesium sulfate, as well as the silicon dioxide that makes up 50% of Mars soil.

The Martian surface can be split into two regions. The highlands, in the southern hemisphere, contain Mars' oldest surface rocks. Many craters and basins (craters more than about 50 miles wide) are found here. The lowlands, in the northern hemisphere, are less cratered. This is the flattest, smoothest region known in the solar system. Some scientists believe it was shaped by ancient ocean water, as it resembles the heavily sedimented floors on Earth's oceans. Mars' largest volcanoes also exist here in an area called the Tharsis Ridge.

Next to the Tharsis ridge, in the equatorial region, lies the Valles Marineris, the canyon stretching almost the distance from New York to California. But unlike Earth's Grand Canyon, which was cut by the Colorado River, it is thought to be an ancient tectonic feature, caused by movement in Mars' surface mantle. Other features found her are channels, probably cut by frequent flooding more than a billion years ago, and large sand dunes.

More impressive sand dunes surround the poles. A big dune field entirely circles the northern pole, showing just how important the Martian wind is in the carving and the shaping of this unique landscape.

mars was first seen in a telescope by Galileo in 1610, but it was not until 1867 that astronomer Richard Proctor systematically named Mars' features after scientists who had studied the planet. Ten years later, Italian astronomer Giovanni Schiaparelli refashioned Mars as a romantic place, creating evocative names such as Mare Sirenium (Sea of Sirens) and Elysium Planatia (Delightful Plains), based on classic literature.