The planet Mars is a fascinating subject, don't you think? Named after the Roman god of war, its red coloration and distinctive appearance has long made it a foreboding and noteworthy place. Suspicions that life might be free to thrive here go back a long ways, fueled by everything from outright hoaxes to detailed scientific calculations. Nonetheless, observable organisms remain elusive for the moment, despite a host of missions to locate or disprove such a thing. A far more grim, but arguably more likely, possibility lies in the idea that simple life existed once but has since gone extinct, likely due to solar winds liberating all of the planet's water and most of its atmosphere in the distant past.
One thing these missions will probably not find is termites. This is tragic for a number of reasons, but the main one is that red-earth alien termite mounds would be rad as hell. Termite mounds can grow absolutely massive relative to their builders, far outstripping the largest skyscrapers in comparative scale. A cluster of termite mounds could therefore be compared to Times Square, with all that entails. Despite this impressive feat, most models suggest the actual mound part has no function save for generating air flow, with the actual city-like nest parts all located well underneath it. Waste of prime real estate, if you ask me.
Another fun-but-unlikely discovery would be ravening monsters. Horrible things are a common discovery in Mars-related fiction, often starting with tantalizing clues and ending with terrified screaming. A fun example of this would be the movie Doom: Annihilation, which is about as high quality but enjoyable as you'd expect. A team of marines is sent to figure out what happened to a research facility located not on Mars proper, but on its moon Phobos- which they call "The Doomed Moon." Now is that metal or what? Anyway demons eat all of their faces, except whoever makes it through the hellportal which will eventually enable demons to invade Earth. Call it a draw, then?