I wonder if the contamination of mars with mushrooms from spores from the rubber tires of the rover was not an accident but a secret effort to begin terraforming mars, first with bacteria and fungi, and later everything else?
Discussion
Fungi would definitely be my choice to start with.
Photosynthetic cyanobacteria are meant to the first thing to oxidise the world you would probably want to send that with the bacteria that was around before that before sending the fungi 🙂. I guess being fairly simple they might be on the tyres.