Mars has a number of interesting features that make it one of the most studied planets in the solar system. One of the most often noted features of Mars is its reddish color, which earned it the nickname the Red Planet. The reddish hue results from iron oxide, or rust, in the soil.
Mars is about half the size of Earth. Mars has the tallest volcano in the solar system, Olympus Mons, which is 27 kilometers high. Astronomers have detected lava in Mons and believe it is an active volcano. Mars also has the largest canyon in the solar system, the Valles Marineris. The valley is 4,000 kilometers long and could stretch across the entire United States.
Scientists once thought Mars had water on its surface, but further investigation revealed that the surface actually consists of ice caps that expand and contract with changing climate conditions. The atmosphere of Mars includes a thin layer of clouds, but the atmosphere is gradually disintegrating due to solar winds. The atmosphere and winds support major dust storms, which impact scientific exploration of the planet. Mars is known for its cold surface temperatures, but the fact that its atmosphere consists of 95 percent carbon dioxide is one of the greatest inhibitors to human life on the planet.