Mars, that's where aliens come from, a mainstay of Hollywood science fiction, the mysterious Red Planet. But what is Mars really? Mars is the fourth planet from the Sun, orbiting at 227,940,000 km. Its diameter of 6,794 km and its mass of 6.4219e23 kg make it the seventh largest planet in our solar system. Mars, which is the Greek name for the god of war, probably got this name because of its red color and is often called the red planet. What makes Mars red? Mars' atmosphere is primarily composed of carbon dioxide, which oxidizes iron on the planet's surface to create rust. Because there is very little water vapor on Mars, dry winds pick up and blow dust around the planet, coloring it red. What would you see if you went for a nature walk on Mars? Surface features include giant volcanoes and vast canyons. The largest volcano in the entire solar system is on Mars, Olympus Mons. It is classified as a shield volcano, similar to the volcanoes of Hawaii. Olympus Mons, three times higher than Mount Everest, is twenty-five kilometers high, surrounded by a 550 kilometer moat filled with lava. The VallesMarineris Canyon is 4,500 kilometers long and reaches seven kilometers in depth and 600 kilometers in diameter. There are also many meteorite impact craters. Why couldn't you take a nature walk on Mars? The atmosphere is not only very thin, but is almost entirely composed of CO2 and known for violent dust storms. You would do...