The planet known as the "Red Planet" is Mars. It earned this nickname due to its reddish appearance, which is a result of iron oxide (rust) on its surface. Mars is the fourth planet from the Sun and is known for its thin atmosphere, polar ice caps, and the largest volcano and canyon in the solar system. Its geological features and potential for past or present life have been a major focus of exploration by NASA and other space agencies. Robotic rovers, such as Perseverance and Curiosity, have been sent to Mars to study its composition and search for signs of life.