The Red Planet is a term used to refer to MARS, the fourth planet from the Sun. MARS is known for its red hue, which is caused by iron oxide on its surface. It is the second smallest planet in the Solar System and has two moons, Phobos and Deimos. MARS is also home to the largest volcano in the Solar System, Olympus Mons. It is believed that MARS may have once had liquid water on its surface, making it a potential habitat for life.