Martians

In H.G. Wells' War of the Worlds (1897), aliens on Mars began plotting an invasion of Earth because their own resources are dwindling. It is one of the first works to theorize the existence of a race intelligent enough to invade Earth.

Charles Darwin's theory of natural selection inspired the emergence of other-planetary life at a suitable geological age in a planet's development. There had been three centuries of observation of Mars through telescopes, including features misconstrued as artificial "canals" which fueled the belief in intelligent extraterrestrial life on the planet.

The Martians travel to the Earth in cylinders, fired from a huge space gun on Mars. This concept was also used by Jules Verne in From the Earth to the Moon. Although not scientifically plausible, Robert H. Goddard was inspired by the story and spent much of his life building rockets, culminating in the Apollo program's manned landing on the Moon, and the landing of robotic probes on Mars.

The Martians' principal weapons are the Heat-Ray (which would inspire laser weapons) and poisonous Black Smoke, similar to chemical weapons. These weapons are used by their "Tripods" which are fast-moving, three-legged walkers, reported to be 100 feet tall, with multiple whip-like tentacles used for grasping. This inspired George Lucas' design of his walker. There are also flying machines and others, which are later described as cybernetic.

When it was dramatized in a 1938 radio program directed by Orson Welles, it caused public panic among some listeners who did not know the Martian invasion was fictional.