Mars

"The Chances of anything comming from Mars is a million to one he said..."

Mars is the fourth planet from the Sun and the seventh largest planet in earth's solar system.

Mars in Science Fiction

In the classic science fiction series The War of the Worlds, Victorian England is invaded by brainlike creatures from Mars
In Warhammer 40,000, Mars is the capital of the Adeptus Mechanicus and sleeping place of the C'tan known as the Void Dragon.
In Star Trek, Mars was colonised in the late 21st century and partially terraformed through the deflection of asteroids into the polar caps. By the 24th century, Mars housed the Utopia Planitia shipyards in geo-synchronous orbit over the plains of the same name; a memorial station dedicated to Carl Sagan; and served as a perimeter in the defence of the solar system.
In Babylon 5, Mars is an Earth Alliance colony with a history of uprisings. Many Mars colonists resent what they consider to be unresponsive and even tyrannical government from Earth.
In X-COM, the Cydonia region of Mars has a Sectoid base.

Mars at NinePlanets.org.