Mars is known as the "Red Planet" because of its distinctive reddish color, which comes from iron oxide, or rust, present in the dust and rocks on its surface. This iron oxide formed when iron in Martian rocks reacted with small amounts of water or oxygen in the atmosphere, causing the surface to appear red. The dust containing this iron oxide is spread across the planet by winds, giving Mars its iconic rusty hue visible from afar. This red coloration has been recognized since ancient times and even influenced the name Mars, which was given by the Romans after their god of war, associating the color with blood. Recent scientific studies have identified a particular water-rich iron mineral, ferrihydrite, as likely responsible for the red color, evolving the previous understanding that hematite (a dry iron oxide) was the cause. Thus, Mars's red appearance is primarily due to the oxidized iron minerals covering its surface, which both ancient cultures and modern science have connected to its distinct color and nickname.