Mars is the fourth planet from the Sun in our solar system. It is often called the "Red Planet" because of its reddish appearance, which comes from iron oxide, or rust, on its surface. Mars has a thin atmosphere, mostly made up of carbon dioxide, and features the largest volcano, Olympus Mons, and the deepest canyon, Valles Marineris, in the solar system. Mars has two small moons named Phobos and Deimos. The planet experiences seasons similar to Earth due to its axial tilt. Scientists are interested in Mars because it may have once had conditions suitable for life and is a target for future exploration and potential human colonization.