"One needs only to look upon the once-green planet of Mars to understand the full scope of the devastation the Rüstov leave in their wake."
In Real Life, Mars is understood as the lifeless, dusty red planet next door to the lush, green planet we call home, Earth. The implication that barren Mars once was as bountiful and full of life as Earth and has become a wasteland entirely through the activities of today's threat gives a chilling demonstration of what kind of potential damage could happen to our world. Often this sort of damage starts with Mars first and goes from the outside of the solar system to the interior.
Stories where Mars had a thriving civilization are getting to be a Discredited Trope
these days due to real-life Martian probing finding very little archeological evidence. The theorized reasons why Mars isn't thriving like Earth now has a lot to do with its significantly lower gravity being unable to hold in an atmosphere with enough air pressure to keep liquid water from evaporating away, or any ozone layer to protect it from deadly solar radiation; a slow environmental death of natural consequences. However, in the past before space probes, astronomers only had their telescopes and their imaginations pointed at Mars, giving plenty of room to think up entire alien civilizations living on it.
If Earth is going to be next, then Mars is the Sacrificial Planet
. Compare Pluto Is Expendable
- In the movie John Carter of Mars, it's said that Mars is dying out due to the actions of the Therns, and after the Therns are done with Mars they'll just move on to Earth. This doesn't happen in the book; in the book Mars is dying on its own and the natives have multiple methods in place to slow down the planet-dying process.
- Near the end of Mission to Mars the astronauts discover an ancient Martian orrery that explains that Mars was once very Earthlike and had spacefaring intelligent life on it. The planet suffered a cataclysm and the Martians abandoned their homeworld and seeded Earth with life on their way out of the Solar System.
- Total Recall showed that Mars was once inhabited by ancients, who had a massive machine that maintained a breathable atmosphere and biosphere on the planet—which was being uncovered by the mining operations going on in the movie's present.
- A throwaway line in the first Jack Blank book shows that the planet of Mars once was as green as Earth, and that the reason it's as barren as it we know it is because the planet-consuming Rüstov already finished with it, and they are presently attempting to invade the Earth.
- In C. S. Lewis's Out of the Silent Planet, it turns out that Mars was once lushly habitable before being attacked and ravaged by the bent Oyarsa of Earth (i.e., Satan), and now life there is mostly limited to a few geothermal oases.
- One of Niven's Svetz stories, Rainbow Mars involves time travel to Mars' verdant past, and chronicles what happened to it.
- H. G. Wells War of the Worlds had the Martians invade the Earth because Mars was dying. They would go to consume their solar system inward if they hadn't made their lifestyles so sterile that they couldn't survive an encounter from Earth's abundant microorganisms.
- Ray Bradbury's The Martian Chronicles showed a civilization living on Mars who didn't think Earthlings existed until they started landing on the planet, which the Martians attempt to resist as much as possible. Eventually, the Martians die off from a mild Earth disease and humans are all that remain on Mars.
- Doctor Who:
- In the serial "Image of the Fendahl", the Doctor says the Fendahl were responsible for Mars becoming a dead planet.
- In Doom III, a civilization existed on Mars that was destroyed by the Legions of Hell. The exact same legions that are faced by the human space marine protagonist.
- In Ultima: Worlds of Adventure 2: Martian Dreams, the Avatar travels in time to the 19th century, and from there, to Mars, where a native civilization is discovered. Said civilization is in ruins, however, and the Avatar needs to help them with restoring Mars to a habitable state.
- In the Ben 10: Alien Force episode "Fool's Gold", mischievous but harmless aliens come to a village every 17 years where they eat massive quantities of popcorn and defecate solid gold. When the town's mayor gets greedy and kidnaps one, he gives the alien a steak, causing the alien to grow into massive size and defecate unstable uranium. The alien's friend tells Ben that Mars "used to be called The Popcorn Planet" before his kind came there.
- The first episode of the Justice League cartoon displays an invasion of aliens coming to Earth. These aliens previously had taken Mars, leaving the Martian Manhunter as the sole survivor, who comes to Earth to warn the planet and help form the Justice League to fight them off.
- In Real Life, our probes have uncovered a lot of evidence indicating Mars once had oceans and running water (and possible fossilized microbes have been found on meteorites in Antarctica traced back to the Martian crust). For its first billion years of existence perhaps, Mars might have had a magnetic field strong enough to sustain a decent atmosphere and protect a primitive biosphere—but being smaller and further from the Sun its core might have cooled fairly quickly, weakening that magnetic field. (There's also some evidence that a very massive object, possibly a dwarf planet like Ceres, impacted Mars in such a way as to throw the core itself off balance and likely disrupt its magnetism—the fact that the Southern Hemisphere crust is significantly thicker than the Northern is related to this.)