[clarification: Ed and I are actually in complete agreement that mars has no export of mass that would be profitable. I simply don't limit industry to exports only.]
[Update: CJ provides the answer Ed was looking for.]
You can’t identify a single industry that you expect to establish on Mars?Amazing! Ed is a really smart guy so how could he make such a statement? Because there isn't any possible industry that couldn't be established on mars. Before getting to that, let's consider the false assumptions that might have lead to this amazing statement.
Is he defining industry as anything they can't currently do on mars? Is anything not involving earth/mars import/export not industry?
Ok, now let's show how industrial development on mars may occur...
A dozen permanent colonists arrive in mars orbit. They do some prep of there landing site with rover/tractors. Then four of the dozen land for more site prep followed soon after by the remaining colonists.
These dozen have everything they need for basic ISRU life support. They can do some exploring (both directly and remotely in a limited range, satellites provider farther views) but it is a very modest life with many desires unfulfilled. They have habitats and farms but little food diversity. They have energy to survive, but little for industry. Water and oxygen are abundant. Fuel for vehicles will be abundant as well. Machines will require maintenance and repair eventually beyond the replacement materials they brought with them. Recycling and 3D printing having its limitations. They will need to develop local resources but that will always be a progressive operation.
Living on mars will tell them by experience what priorities are, which they will communicate to the next missions leaving earth.
What is industry? It doesn't start out full blown. It grows to fill the needs of its customers. What do they need more of? Energy. Any industry is going to need energy so that will be the first priority. Electricity is one convenient form. Methane and oxygen would be another. They will extract iron from the dust for mechanisms. People will specialize and trade. Eventually they can make more solar panels but steam is easier at first. So they concentrate solar energy for steam. The steam powers a generator (car alternator sized at first, getting bigger over time.) They'll need more batteries, using whatever chemical elements they find to use. They will have a lot of options, but it will depend on what they find. Battery making is an industry that some will specialize in. They will trade those batteries, not give them away.
Do I really need to identify every modern item of trade? It all works the same. New arrivals will bring things they haven't yet developed on mars. This is a source of wealth for all new arrivals.
How will existing colonists pay for this new stuff? With things they produce on mars so new arrivals don't have to waste mass bringing it with them. This is the basis of all economics.
There is no industry that could not eventually evolve. The pace is faster as more millionaires arrive (everyone that arrives with personal property chosen well will be a millionaire on landing.)
Why? Because trade for earth products will compete. Do I buy from the new arrivals or pay $60k per kg to get it delivered from earth? Can I build it myself or will the new colonist accept something less than $60k. Will my neighbor buy it for more leaving me out? Hey, I got that 50 inch tv for only 4 grand!
Can I call my lawyer and accuse them of price gouging... wait, no lawyers. Can I steal it? Oh no, everybody knows everything in a small town.
Trade works, unless you have a very blinded concept of economics.
Tell me again what industry they could not develop on mars?