We've been conjecturing about life on Mars for centuries. In popular culture, the concept of intelligent life on Mars was championed by astronomer Percival Lowell in the late 1800s and his theories on the Martian canals. Science fiction writers -- always game for some reckless conjecture -- took up the banner from there.
Perhaps the most famous Martians in the history of sci-fi and popular culture, the invaders in H.G. Wells' 1898 novel "War of the Worlds," have since spawned dozens of films, TV shows, comic books and one very famous radio drama.
Telescopic observations of Mars in the late 19th and early 20th centuries appeared to show long surface lines that some believed were man-made (well, Martian-made) irrigation canals. Italian astronomer Giovanni Schiaparelli made this map of Mars from his notes on the telescope images.
Science fiction writers often depicted Martians as an advanced humanoid race intent on conquering Earth. In "Flash Gordon's Trip To Mars" (1938), Azura Queen of Mars subjugates her own Martian people. Ray Bradbury would later conceive of a kinder, gentler race in "The Martian Chronicles."
Space explorer stories were a regular staple in the pulp fiction magazines of the early 1900s, and Edgar Rice Burroughs was another author to speculate at length on Mars' inhabitants. His Martians included the six-limbed, green-skinned Tharks and humanoid Red Martians.
The so-called Grey Alien is a kind of archetype image of an extraterrestrial -- not necessarily from Mars -- that has arisen from fictional depictions, alleged alien abduction stories and conjecture on what an advanced race of beings would look like.
On July 25, 1976, NASA's Viking 1 orbiter captured the above image on the surface of Mars' Cydonia region. The infamous "Face on Mars" prompted decades of speculation, although scientists have long dismissed the image as an example of pareidolia; e.g. seeing shapes in the clouds, or Jesus in your toast.
Legendary Looney Tunes animator Chuck Jones created the character of Marvin the Martian in 1948 as a foil for Bugs Bunny. As devotees of Saturday morning cartoons know, Marvin is forever plotting to destroy the Earth by way of his Illudium Q-36 Explosive Space Modulator. Apparently, we obstruct his view of Venus.
Director Tim Burton played around with B-movie tropes and pop art notions of Martians in his 1996 film "Mars Attacks!" Brian De Palma followed up a few years later with "Mission to Mars," a huge critical and commercial bomb. (Although the French critics liked it -- really.)
As is its eternal wont, pop culture is constantly recycling its own ideas -- Martians included. In 1999, Christopher Lloyd starred as the titular alien in director Donald Petrie's reboot of the 1960s TV show "My Favorite Martian," which was itself inspired by earlier pulp sci-fi stories.
Of course, these are only some of the ways we've envisioned Martians over the years. But how do we look to the Martians? Um, pretty small. This first-ever image of the Earth taken from Mars was snapped by the Mars Exploration Rover Spirit in 2004.