Mars

Mars is the setting of the series. The planet carries a name of the Roman god of war and is often referred to as the 'Red Planet '.

In Real Life
Mars' reddish appearance refers to the effect of the iron oxide prevalent on its surface. It is a terrestrial planet with a thin atmosphere, having surface features reminiscent both of the impact craters of the Moon and the valleys, deserts, and polar ice caps of Earth. There are ongoing investigations assessing the past habitability potential of Mars, as well as the possibility of extant life. Liquid water cannot exist on the surface of Mars due to low atmospheric pressure, which is less than 1% of the Earth's, except at the lowest elevations for short periods. The two polar ice caps appear to be made largely of water. The volume of water ice in the south polar ice cap, if melted, would be sufficient to cover the entire planetary surface to a depth of 11 meters (36 ft). In November 2016, NASA reported finding a large amount of underground ice in the Utopia Planitia region of Mars.

Avenger
In Avenger, Mars has been terraformed to allow human beings to inhabit. Since the moon causes ravage storms at night, everyone has been forced to live indoors such as the domed cities. By the end of the series, the ice underneath the surface broke, allowing the water to burst through. It can be deduced that the lower elevations, the northern part of Mars, have become an ocean.