The fourth planet orbiting the Sun. A red planet that is easily found in the night sky. It is considered to be composed of a single planetoid that did not grow due to further collisions with other planetoids due to disruptions by Jupiter. Most likely planet outside of the Earth to have once had liquid water and life and the most likely next destination for mankind. Had active volcanic and hydrological past. Has significant but thin atmosphere. Has two tiny moons which were probably captured. Has highest mountains and deepest valleys in Solar System due to its low gravity. Visited by more space probes, orbiters, landers, and rovers than any other planet. Currently being orbited by Mars Reconnaissance Orbiter and Mars Express and explored by Opportunity rover.