Dust
- Dust is bad for planes.
from https://www.nasa.gov/feature/goddard/the-fact-and-fiction-of-martian-dust-storms
Mars has beaucoup dust. The movie The Martian starts with a sweet dust storm. It is bad to fly your aircraft through a dust storm. Dust chews up machines. The parallel situation on Earth which was recently in the news is clouds of volcanic ash - comparably tiny, sharp and high flying mineral bits.
from https://www.theguardian.com/science/2010/apr/15/volcanic-ash-bad-for-planes
Aircraft avoid any airspace that has volcanic ash in it for a simple
reason: the ash can wreck the function of propeller or jet aircraft,
because it is so fine that it will invade the spaces between rotating
machinery and jam it – the silica melts at about 1,100C and fuses on
to the turbine blades and nozzle guide vanes (another part of the
turbine assembly), which in modern aircraft operate at 1,400C.
That, in turn, can be catastrophic – as the crew of two aircraft,
including a British Airways Boeing 747, discovered in 1982 when they
flew through an ash cloud from the Galunggung volcano in Indonesia. On
both planes, all four engines stopped; they dived from 36,000ft (11km)
to 12,000ft before they could restart them and make emergency
landings.
That's not the only problem. Ash can pit the windscreens of the
pilot's cabin, damage the fuselage and light covers, and even coat the
plane so much that it becomes tail-heavy. At runways, ash creates an
extra problem because takeoffs and landings will throw it into the air
again – where the engines can suck it in and it will create horrific
damage to moving parts that suddenly find themselves in contact.
- Dry dust is sticky and electrically active.
Lunar explorers were not trying to fly planes, but ran into adhesion and static electricity problems from moon dust.
from https://www.space.com/3080-lunar-explorers-face-moon-dust-dilemma.html
Halekas recounted a technical debrief by Apollo 17's Gene Cernan after
his 1972 Moon voyage.
Cernan said that "one of the most aggravating, restricting facets of
lunar surface exploration is the dust and its adherence to everything
no matter what kind ... and its restrictive friction-like action to
everything it gets on." The astronaut added: "You have to live with it
but you're continually fighting the dust problem both outside and
inside the spacecraft."
Electrically active
Although the lunar environment is often considered to be essentially
static, Halekas and his fellow researchers reported at the workshop
that, in fact, it is very electrically active.
The surface of the Moon charges in response to currents incident on
its surface, and is exposed to a variety of different charging
environments during its orbit around the Earth. Those charging
currents span several orders of magnitude, he said.
Dust adhesion is likely increased by the angular barbed shapes of
lunar dust, found to quickly and effectively coat all surfaces it
comes into contact with. Additionally, that clinging is possibly due
to electrostatic charging, Halekas explained.
You could have the static electricity generated by dust inactivate any electronics. Also there would be constant discharges of static electricity within the dust cloud - lightning.
- Terraforming will make Martian dust storms 100 times worse.
Consider wind. It can exert force because air has mass and velocity. The force exerted by the wind is what lifts dust and blows it along. The force exerted by a mass (m) of air at velocity v is 1/2 mv^2.
The Martian atmosphere is 0.6% as dense as that of Earth at sea level. At 20,000 feet elevation in Earth you could get away with no mask, maybe; at that elevation atmospheric pressure is half of that at sea level so Mars is 1.2% of that. You need to increase the air density or mass of the Martian atmosphere by 2 orders of magnitude to get to where your pioneers can wear a mask outside. The force exerted by the Martian atmosphere on the dust will also increase by 2 orders of magnitude. The wind will be able to lift 100 times as much dust as it does now.
- Monsters. I will stick to the known stuff here, and leave to your imagination the tenacious airborne filaments of protein-hungry Martian dust fungus.
These are daunting impediments. But not totally insurmountable. In my mind there are comparably great impediments to fishing the North Atlantic in an open boat, and people have done it for millennia. The rare Martian planes that there are would have to be robust in special ways, and their pilots insane in special ways. That makes for fun narrative!
ADDENDUM
from comments - /Do you have ideas for how to work around the static thing?/
I am glad you asked!
from http://www.iontis.de/unsere-produkte/entladung/passive-ionisatoren/f801/
Sharp points made of conductive materials will bleed off charge into the atmosphere. It is one way lightning rods work. You will see these points on planes. You can see the effect on a child who gets charged by sliding down a plastic slide - her hair will stand on end. In small items prone to accumulating charge, you can put copper foil strips or this copper fuzz. The tiny threads of copper serve as miniature lightning rods to dispel accumulated charge.
I will restrain myself from writing prose but I can envision your Mars pioneers, covered with fuzzy copper threads and strips as they move along. A cloud of dust moves near and suddenly all the threads and strips stand straight out. They curse.