IIRC, wipers were evaluated and decided against for Mars rover solar panels because of the risk of scratches to the glass. I'd imagine the same applies here.
Blowers then? Drones, especially flying ones, seem to be a colossal waste of energy here. That is, on Earth; on Mars it'll be hard to make such drone, because the air is much, much less dense. AFAIR NASA only figured out how to fly a long-distance recon plane there.
