The people problems are enough to sink the idea. The technical problems are staggering.
In a recent posting, I wrote a short story about what would happen if we had a colony on Mars and they had a child from hell. It is not an absurd proposition - we have crazy people and plenty of them, here on Earth. All it would take is one malcontent on Mars to destroy the entire colony. On Mars, you could not have 9/11 truthers, incels, proud boys, flat-earthers, anti-vaxxers and other delusional people. No crazy billionaires - or even capitalism! Even 2nd Amendment nuts and "Free Speech Absolutists" would not qualify, as the environment would be so harsh as to require that everyone follow orders and work like dogs in a military-style dictatorship. And you have to hope the dictatorship doesn't go off the rails, either - as they tend to do.
No, we are not cut out for Mars. Maybe that is why robots do so well there. Maybe our robotic AI descendants will settle there - it is a perfect environment for them, I think.
But this is not to discount the technical problems involved. And to begin with, we have to define what a "colony" is. It is some outpost that is constantly resupplied by rockets from Earth, or a self-sufficient closed-loop system that can survive on its own? Many posit that colonizing Mars is essential to the survival of the human race, as we have screwed up things here on Earth so badly that it is only a matter of time before Putin, Kim Jung-Il, and/or the Iranians start WW3 by throwing a few nukes.
And statistically speaking, they are right. The probability of a nuclear war starting in any given year is a finite number. The more nations that acquire nuclear weapons technology, the higher this probability becomes. But for any finite probability, integrated from 0 to infinity, the probability turns into a one - a certain outcome. It is a matter not of "if" but "when" someone gets desperate and decides that maybe "a little nuke" won't be so bad. Perhaps soon - if Putin feels backed into a corner. Potential successors are just flying out the windows - he realizes his days are numbered anyway. Why not go out with a bang?
I digress yet again. But the "people problem" here on Earth is the same "people problem" on Mars. Could we have a Martian colony with people believing in end times theology? Or even religion of any sort? Because when rational people base their decisions on irrational beliefs, all hell breaks loose. The people problem won't go away by colonizing Mars - even if it was technically feasible. And it isn't technically feasible.
NASA is making noises that the Chinese are going to colonize the Moon and lay claim to it. No doubt this is an angle to get additional funding - staring a new "space race" to land on and eventually establish an outpost there. Note I said an outpost and not a colony. It would be at least a little more practical to establish an outpost on the Moon, as opposed to Mars, as the cost (and time needed) to hoist supplies out of our gravity well and to the Moon would be far less than the cost of a sling-shotting mass to Mars.
But couldn't such a outpost become a colony and become self-sufficient? Maybe, after hundreds of years and trillions of dollars - trillions of trillions in fact (we need a new big number for this stuff). I was discussing this with a reader, and tried to illustrate the difficulty of making even one simple thing on Mars (or the Moon for that matter). I have a background in manufacturing and Engineering, so I understand firsthand all that is needed just to make one simple little thing that would be needed for an extra-planetary colony. And given the harsh condition on both the Moon and Mars, there would be a huge need for an awful lot of technology - from lighting for hydroponics, to power plants, to plumbing, to recycling, and so on and so forth. We would be 100% dependent on our technology at all times. It is not like Earth, where you can just camp out under the stars on occasion, and the air and water are free - and you can just shit in the woods.
To be a truly self-sufficient "colony" they would have to make everything locally as the cost of shipping would be outrageous and the colony would have nothing to export to Earth to offset the costs (unlike the American colonies or any other Earthbound colony in history).
Think of something simple - electrical wire. You'd need it to run the hydroponics, LED lighting, pumps, fans, and other equipment needed to insure survival.
Simple copper wire. You have to find copper ore first - does that exist on Mars? Our liquid core and huge moon mean we have tectonic plates and volcanic action - which tends to concentrate certain materials in a density enough to make them worth mining. Mars? I am not so sure.
But assuming you find copper ore - you have to dig it out, smash it up and then refine it, which requires a lot of water. Then you have to smelt it, which requires a lot of heat and precious oxygen. Oh, and all the machinery to do this - imported from Earth? Or do you make steel first and then build machines to mine and refined copper?
Once you have copper ingots, you have to use a wire-drawing machine to make the wire - and then a braiding machine if you want braided wire. Then there is insulation - usually rubber (which I guess you could get from a rubber plant) or plastic (using soybeans, which they do on Earth today, which is why mice eat the wiring harness on your car). Lots more hydroponics to grow those plants! Hundreds of acres, just to support a few people. All underground. Start digging!
That's just wire. Now add in all the other things you'd need. Those LED lights - semiconductors? Better get some silica, melt it down and "draw" a crystal, slice it into thin sheets, etch and sputter it into a workable chip and then cut it up. Where do you get the machinery and electricity to do all of this? You could also make solar panels this way, too, I suppose. Storing power - I wonder if there is lithium on Mars? I hope so - otherwise your solar energy is of little use. And importing heavy lithium-ion batteries from Earth would be prohibitive.
What about simple things like lime? Need that to make cement, and we get it from limestone which is fossilized seashells. No life on Mars, no seashells, no limestone, no lime. Maybe no cement?
And no oil. So no plastics, unless you could grow a LOT of soybeans. Even then, we'd need a vast manufacturing plant to make various rubbers and plastics. Polycarbonates for space suit helmets? Good luck with that. Cotton for clothing? It could be done - but it becomes clear that the colony would need thousands of acres of agriculture, all underground, to avoid the searing radiation. Keep digging!
Some argue that robots could be sent to Mars to start building infrastructure for a colony. Some people have made nice videos about this - and about as real as "rotating skyscrapers
" or "the air powered car". They claim that martian soil could be "3-D printed" by robots to build underground lairs. I am not sure how that would work, but even assuming they could do that, creating all the manufactured goods needed to survive would be challenging. In order to 3-D print something, you need raw materials to print with. Well, that, and a 3-D printer.
Don't get me started on forging steel, hardening furnaces, making ball bearings - or any process that produces noxious fumes, such as plastics, fiberglass, adhesives, paints. That would all have to be done in an isolated manufacturing area, because once you have solvents in the air, they would be damn hard to get rid of - sort of like when someone farts on the ISS (can you imagine the smell there - or on any spaceship?).
And then there are the biggies, such as a power plant. With enough energy you can do almost anything, and a "Mars Colony" would require staggering amounts of power. In what form? An array of solar panels is appealing - but you'd also need battery storage. Importing these from Earth would be staggeringly expensive. You'd have to set up production on Mars and hope the raw materials are available and can be refined. Nuclear power is the only other option, but requires a lot of cooling water (I suppose a liquid sodium reactor could work) but again, a heavy and bulky thing to transport to another planet. There are no easy answers.
So how did we do this on Earth? Well, our technology took millennia to develop. We had a stone age, a bronze age, and and iron age. In each instance, small industries sprung up that lead to larger and larger industries. The big projects we have today could not have started from scratch with one guy, some iron ore, and a hot fire. It certainly helped that on Earth, oxygen and water were freely available, and as I noted, highly concentrated ores were relatively easy to find.
To set his up on Mars could be done but at a staggering expense. And we've already seen, in the past, how people get fed up with space exploration when the bills come due. "If they can put a man on the Moon," they used to say, "Why can't they feed the homeless?" - or whatever other need here on Earth is perceived as more important. Now take the moon program and multiply the costs by a trillion, factoring in inflation as well, and you've got an idea of the cost of "colonizing" Mars to be self-sufficient. Taxpayers would revolt.
The people problem - again! People on Earth would see little benefit to them directly from a Mars colony. They might not see the benefit to overall mankind. In fact, there may not be a benefit to mankind, in the long run, if such a colony doesn't "take hold" and become self-sufficient. Even then, the only benefit is to the colonists, other than some abstract benefit of "survival of the species" which posits that we will destroy the only planet really suitable for colonization - Earth. What's to say the same won't eventually happen to Mars?
It isn't as simple as just getting there. You can build a rocket to Mars tomorrow, but a colony could take hundreds of years, thousands of rockets and a lot of effort to become self-sufficient. It would be easier to colonize the Moon, or at least establish an outpost there.
Really, even visiting Mars has little real practical or scientific value. To do so, would mean supplying a team for at least two years (the cycle between conjunction and opposition) and require a heroic amount of materials and supplies, not only for the months-long journey, but the two-year stay. And what could "boots on the ground" accomplish better than another unmanned rover or probe - in terms of scientific exploration?
People say "Oh, Mars has water!" - as if that solves the problem. A pitiful amount of water, sadly. Our huge oceans are another thing that made life possible on Earth (until we kill off all the algae and plankton, that is). And no, "terraforming" is not a thing, Without that magnetosphere, any attempt to create an atmosphere (how?) on Mars would be futile. Where do you think Mars' original atmosphere went? It didn't help that they have a much lower gravity there as well.
I think, like the moon, at best we might send some people there, but they will come back. It will be a stunt. Colonizing the Moon may be more immediate, and even then, not a self-sufficient colony, but one supplied daily from Earth at great expense. And the only reason we will do it, is to make sure the Chinese don't do it first..... which they might do!
Hmmmm..... Maybe we should let the Chinese bankrupt themselves colonizing the moon. Or maybe the whole paranoia NASA is creating of "Chinese Hordes" taking over the Moon is just as much bullshit as the prospect of a Chinese aircraft carrier fleet (they have two, one a used Russian carrier that they finished, and a copy of that they made themselves. Both diesel powered. We have 11 - nuclear powered). Maybe we are over-estimating China's capabilities? I mean, it is a large country, but they have a lot of catching up to do.
I would love to be proven wrong about this, but right now, a Mars colony is wishful thinking and nothing else. And I doubt the guy who is running Twitter into the ground is going to get us there.