Mars

Mars, named after the Roman god of war, is the fourth planet in Earth's solar system, and has been depicted as either the home planet or staging ground for many different monsters in both literature and popular culture throughout recent history.

Description
In reality a dry and dusty world, Mars nevertheless holds large quantities of frozen water in both of its polar ice caps and also in aquifers which exist beneath its surface. This has led many to theorise that life has existed or does exist on the planet. It is also home to the largest volcano in the solar system, Olympus Mons, although the formation has been extinct for many millions of years.

Whilst there is no known life on Mars, its proximity to Earth and visibility to the naked eye at certain times of the year has led to the planet being a popular choice for authors and movie-makers who wish to portray creatures from another world. These aliens are often depicted as living beneath the Martian soil in caverns or subterranean cities tunnelled through the bedrock, where they are protected from Mars' inhospitable surface conditions. In particular, the natural formations dubbed canals are frequently touted as creations of an extraterrestrial intelligence.

Inhabitants

 * D.C. Comics: The intelligent and peaceful Green Martians, who have spawned several superheroes, originate on Mars.
 * H.G. Wells: The Martians which launched their failed conquest of Earth evolved there.
 * Cthulhu Mythos: Several of the beings featured in the Mythos either call Mars home or have visited it on their travels, including the Yorhi and Aihai races, along with the powerful alien creature Vulthoom.
 * Captain Scarlet: The antagonists of Gerry Anderson's series were the incorporeal alien Mysterons who wished to conquer the Earth.