Mars is the fourth planet from the sun. The volume of mars is 0.15 times the volume of earth. Its density is 3.95 times the density of water. Its mass is 0.11 times the mass of earth. Mars is called the red planet. This cold and dusty planet is covered in red dust. Sometimes the wind whips this up into huge, red sandstorms. In many ways, this is the most similar planet to the earth. It has a thin atmosphere and a day lasts almost the same time as on earth. The sky is pink with a few wispy clouds. The wind blows across orange dunes, craters, huge dead volcanoes, and mountains. One of these, the Olympus Mons, is the highest mountain in the solar system. Mars has two moons called Phobos and Deimos. They both orbit mars. Phobos and Deimos are much smaller than the earth’s moon. Mars orbits the sun roughly 228 million kilometers away. Mars is about 6794 kilometers in diameter. The average temperature on Mars is minus -23 degrees Celsius. Mars takes 24.5 earth hours to rotate one time. It takes 687 earth days for the red planet to go around the sun one time. Mars has two moons.