Using what little I gleaned from my professor's lectures (rehashed from when they were students no doubt) I determined that an aircraft on mars would have to have a 100 meter wingspan and cruise at a speed of about 300 m/s to stay aloft. It's high speed meant certain destruction upon landing, and getting it into the air in the first place depended on a parachute drop from orbit. Fixed wing aircraft just don't have enough lift to be useful on Mars.

Insect wings develop 5-times more lift than conventional wings, despite the fact that my aerodynamics training says they shouldn't fly at all. It is conceivable therefore that an entomopter may be the only way to go for low-altitude mars reconnaissance. One design for an entomopter appears to have been granted a patent for a device that demonstrates the fundamentals.

Phase I Entomopter Study
Phase II Entomopter Study

US Patent No.6082671

So far only Helios, a flying wing, has achieved sustained flight near 100,000 feet. Perhaps an entomopter could go further?