Just stock AP2v3, I periodically see these imprints on the front wheels...
So were they touched by something/someone?

(I know, I need a car wash)

1 & 2


3


1 close-up

 

Condensation droplets from your rotors.
At night the steel of the rotor/wheel hub gets cold.
When exposed to warm moist air, moisture condenses on the rotor/wheel hub, and falls or is spun off as water droplets on your wheel.
Or it could be alien pee, or gremlin spit.

 

I came in here to say that it's obviously alien pee or gremlin spit but I see it's already been covered.