A "Voyager" type spacecraft with a Golden Record but with contents depicting a civilization of Cats in Mars, and the Space Craft + Golden Record are made from materials from Mars. Put this in orbit around Mars, and have it emit a signal on loop with an Arecibo Message depicting the Cat Civilization.
The scientific community would just collapse and we'd be worshipping cats as a world wide religion.
Maybe even an older model.
Bonus points if it was a popular model in a science fiction show.
My take of that would be the station from the little martian from Looney Tunes in the full 3D cartoon style.
Sort of like a cell shaded structure in a realistic lighted environment.
Life. Soemthing like massive jellyfish living in the middle of space. Nothing around them, no atmosphere, no oxygen, no water, no light. Just massive jellyfish-like creatures "swimming" through the vacuum of space.