Mars is the fourth planet from the Sun and is the second smallest planet in the solar system. Named after the Roman god of war, Mars is also often described as the “Red Planet ” due to its reddish appearance. Mars is a terrestrial planet with a thin atmosphere composed primarily of carbon dioxide. Mars is the fourth planet from the Sun, and the seventh largest. It’s the only planet we know of inhabited entirely by robots. Mars is the fourth planet from the Sun and the second-smallest planet in the Solar System, nicknamed The Red Planet . Mars is a terrestrial planet with caps of water and carbon dioxide. [5][6] It has the largest volcano in the Solar System, and some very large impact craters. Mars Nearing Earth In 2003, the Hubble Space Telescope snapped this photo of the red planet 11 hours before its closest approach to Earth in 60,000 years. How close? It was a mere 34,648,840 miles ...