Mars is the 4th planet from the Sun and the 2nd smallest in the solar system; only Mercury is smaller. Mars’ red color comes from iron (III) oxide, aka rust, on the surface. It’s one of the most Earth-like objects in the solar system, which has prompted missions studying past or extant life on the planet, and there are even plans of terraforming the planet for the future human population. Mars is located around 139 million miles from Earth on average, although the distance, and thus Mars’ apparent size, can vary greatly.