Named for the Roman god of war for it’s reddish appearance, Mars is the 4th planet from the sun and is the last of the terrestrial planets, however is only about half the diameter and 11% of the mass of Earth.

Mars is believed to have lost most of it’s atmosphere millenia ago as it’s gravity is not sufficient to have retained it, therefore the atmospheric pressure is only 0.6% that of Earth, meaning that liquid water is not retained at surface. With a reduced atmosphere and no running water, the Martian surface retains features over a much longer period than Earth therefore contains conspicuous cratering in addition to the solar systems largest volcano (Olympus Mons). The reddish hue of the planet is due to significant levels of iron oxide in the Martian rocks and soils.