If one was to be asked to design an UltraLight that would be able to
fly on Mars, what would have to change?

Would the wingspan have to change significantly?
The atmosphere is thin, but the gravity is less.

Would the propellor size have to change because of the thin atmosphere?
Would a propellor be efficient at all anyway?

Would it be better to use a balloon/blimp vehicle for controlled
exploration rather than an ultralight?

If you needed an emergency parachute for the ultralight, it would need
to be larger than one on earth?

Is there something else that is missing?
A methane powered engine?