Martian sunrise, artwork. Mars is a rocky desert world with no surface water. The orange colour of the rocks is due to a high content of iron oxides. The Martian atmosphere, less dense than Earth's, is mostly carbon dioxide. Surface temperatures are usually well below freezing, ranging from -20 degrees Celsius in the day to -80 degrees Celsius during the night. The Martian day is 37 minutes longer than an Earth day. The gravity is about one third of that on Earth.