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



A lot.

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


The atmosphere tapers off a lot faster than the gravity. Gravity is
about 1/3 Earth's gravity, but the atmosphere is about 1% of Earth's.
The losses do not offset well as you lose lifting capacity far more than
weight to be lifted.

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


Hmm. Depends on size. There would be a breakpoint that would be very
dependant upon vehicle mass for that equation.

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



Definately. hydrogen is a viable lifting gas on Mars and the Martian
atmosphere is actually a lot better in terms of bouyancy. (hydrogen is
about 2g/mole. Earth's atmosphere is about 29g/mole, given a ratio of
about 14.4 to 1 between the gases. Mars has an atmosphere that is about
44g/mole. For a 22 to 1 ratio.).


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

Yes.

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

methane. carbon monoxide. Electric. Any number of possibilities.