Radiation, temperature and the lack of oxygen and gravity, for example?

Tell me how many underwater and arctic settlements we have today. They should be unclaimed territories just teeming with possibility, in our own backyard.

Yet they’re... not? You’d think that after space flight we’d have 8 metro lines in the Arctic by now, if it was all just a matter of waiting around.

And you want to fly how far for something that supposedly is full of some untapped potential?

"Cold, hard limitations of physics" is distinct from not yet having done all the engineering.

Mars colonies are way down the list of things I think worth trying to do, but it's absurd to call them physically impossible, even on a 60-year deadline.

Radiation: interpose some matter.

Temperature: heater.

Oxygen: Mars has plenty in situ.

Gravity: current humans might actually find this a problem for long-term health, I'm not sure, but it's a bounded one, not likely to compare to long-term zero-g life. There's no barrier in physics to spinning up big centrifuges, even though it's ridiculous. Biomedical approaches are more likely for a biomedical problem.

Unless there are significant breakthroughs you'd exhaust or pollute much of Earth's resources to build a poor substitute on a planet that cannot naturally sustain human life.

It'd be inefficient anyway to use Earth resources except for some early bootstrapping. Extraterrestrial resources (asteroids, the moon, solar power, local resources on Mars) are more accessible. And it's underappreciated that for what you do need from Earth, launch can get much cheaper/cleaner after enough development in space, just as an elevator system gets more efficient with a counterweight.

There are quite a few permanent arctic settlements. Alert comes to mind, as does Resolute Bay. There have also been innumerable sea ice settlements, but obviously none were permanent. Are you thinking of the Antarctic instead?

There are no self-sustaining Arctic settlements - i.e. Ones that grow their own food locally without hunting and without getting regular air drops, generate their own electricity, de-salinate or thaw their own water etc, create their own fabrics and building materials, and have some options to create their own microprocessors if needed. Oh, and that can launch its own rockets to space.

Musk is purportedly dreaming of a colony on Mars that would survive if the Earth were destroyed. That means that not only do they need to grow food, get water and generate electricity from Mars, but they will also have to have the manufacturing capacity to make everything from tunnel boring machines to microprocessors. An actually self-sustaining colony on Mars would likely have to be closer in size to a large city on Earth than to a permanent base in Antarctica.

Even a large city today doesn't do most of those things. How many microprocessors are fabbed in London, rockets launched in NYC, or lumber harvested in SF? This seems like an unreasonable standard to measure by.

Well, can you imagine a colony that could survive indefinitely if the Earth were destroyed (Musk's stated goal) without having all these things? If they couldn't build another water processor chip, how long would the colony last?

So I would look at it the other way: even a large city on Earth isn't entirely self sustainable. How could we hope to build a self-sustaining colony on Mars in 60 years?

Yes but regardless, I'm not going to pursue the fools errand of defending an elon musk schedule. That wasn't the bit my comment responded to. I simply pointed out there are already many permanent arctic settlements, and you came back with new goalposts that no city on earth meets.

"self sustaining settlements" was the goalpost

Yes, and again we're talking about the high arctic Inuit, one of the most historically self-sufficient groups out there. Like most other people on the planet, they don't produce a lot of microchips, but they've spent the past millennia or so producing everything else they needed out of what was available in the local environment.

The Inuit are self-sustaining by the standards of humans living on Earth, but they are in fact dependent on a huge, globe-spanning ecosystem for all of their food. Even disregarding the problems of high-tech required on Mars, they are not self-sustaining in the sense we were discussing here - they wouldn't be able to survive if the rest of the earth were barren.

But of a shot in the dark here but anyone know of good sci fi books from the perspective of someone colonizing another planet after their original plant died and humanity not having sufficient resources to maintain earth’s development rate?

Or, that sort of area.

This isn't exactly that, but there's https://www.amazon.com/gp/product/0451116534 for struggling colonies in space.

Large cities are not sustainable by themselves. They need the rest of a country to keep them alive. Really, this whole thing is a pipe dream.

SpaceX has done wonders for getting the cost of moving a kilo of matter into orbit. From a tech point of view it is a very large but still incremental step from where we were before.

A self sustaining Mars colony is science fiction.

Idk about others but Elon’s stated goal for settling Mars is to keep a second seed for humanity if Earth is somehow destroyed. Elon isn’t going to Mars for its appeal as a habitat directly, but because it can serve as a backup for humanity. It also makes other exploration of the solar system more likely as the ships needed to support Mars can also bring humans to the Jovian system etc.

So you’re telling me a) there’s going to be a self-sustaining colony on Mars, b) they’re happy to be there, and c) they’ll also be happy to leave their cozy colony behind to come rebuild Earth that was somehow wrecked so badly that human civilization has been wiped out?

This to me seems like an immense number of mental hoops, when you can’t even make people wear a piece of cloth over their face literally for the sake of humanity.

Yes I think that if SpaceX succeeds with Starship and starts building the colony as they hope, that 50-200 years from now the settlement would be at least partially self sustainable (can self sustain in an emergency).

There are many reasons an independent settlement makes sense. Earth could get stalled in political deadlock, have a nuclear war, or fall under the control of autocratic regimes.

But there are direct benefits to humanity even without these worst case scenarios. Independent thought and political control at a time when the countries on earth become ever more intertwined (China’s Belt and Road) will probably serve some benefit in our future.

And then regular rockets between Earth and Mars would pave the way for asteroid mining, which would allow construction of massive solar energy harvesters.

That’s 200-500 years out but if we’re capable of starting now I’m not opposed to folks trying!

What do you think could possibly happen to the Earth that would make it as un-inhabitable as Mars?

Even an asteroid strike in the middle of a nuclear war wouldn't come anywhere close.

I’m not sure, but I don’t just mean physically destroyed but perhaps engaged in a new world war or ruled by autocrats. Either place could become that but if it happens to Earth it could set back human progress hundreds of years. It would be nice to have some more distant human thought, I think, with a broader view on existence than those of us here.

I think there are benefits to an independent settlement beyond physical destruction. In any case I’m saying Musk isn’t going there because it’s full of resources as was suggested up thread. He’s going there for the long term benefits to humanity he believes it will achieve. If you want to get rich in space mine asteroids. Which will probably become more viable if Mars colony ships ever routinely travel between Earth and Mars.

And even then Earth would be much more habitable than Mars will ever be.

Elon Musk may end up going to Mars, I don't think after the last decade anybody will bet against that. He could very well be this generations Neil Armstrong in being the first person to set foot on another planet. Which would be a stupendous achievement in and of itself, even if he dies in the attempt to land there itself.

But after that he'll either die there anyway when his resources run out or he'll run right back to mamma earth assuming they can manage to resupply their fuel and make it back here somehow.

Even then - if the Earth were completely taken over by autocrats, it would still be easier to construct and defend an impenetrable fort on Earth than it would be to construct one on Mars - else the autocrats controlling the Earth would easily conquer (or destroy) Mars as well.

Now, if we were to think of a colony ship or a colony on a distant planet light years away, that would make some sense, but that is probably a project for the year 5000, not 2000.

60 year relative to the first flight to the moon a settlement is entirely off the deep end.

Is that what was meant? I didn't think of that -- normally the word means 60 years from now.

Yes, I'll be surprised if they manage a crewed mission at all by 2029.

Ok, we'll make it 2081. Still bullshit. There is absolutely no way that there will be a Mars based self sustaining colony in that time period. Real life and Hollywood are both able to surprise us but only one of those two dabbles in self sustaining Mars settlements for the foreseeable future.

When the moonlandings first happened the papers and popular science writers (and SF writers) were all over what would happen next. What happened next is nothing. Sure, we have the ISS, it's been a neat little testbed and good PR for space development.

But colonizing another planet is a lot harder than it may seem. I'll challenge anybody that believes that this can be done to 10 30 ton semis full of gear, food and oxygen, then to set up shop right off the coast somewhere and prove that within a decade they can be self sustaining. That's many orders of magnitude easier than doing the same thing on Mars and it is still very much this side of impossible.

The 'self sustaining' bit is the nasty part here, as long as you can ship in food, oxygen, water, toilet paper and whatever else you think you might need on your faraway planet you'll be fine within your little environmental cocoon. But another planet without a breathable atmosphere is so incredibly hostile to life that your first mistake will be your last.

If "absolutely no way" is everyday hyperbole for "I think it's unlikely" then sure, I think that's reasonable. It would need a break in current trends.

60 years is the interval between Zuse's first Turing-complete relay computer and the popping of the dotcom bubble. Or between the Wright flyer and Project Gemini. Outer space has ridiculously more resources available than Earth surface, making it economically irresistible. Powerful economics plus 60 years of development can equal... a lot, as I said to start this subthread. Mars itself is not very attractive, but if space happens bigtime then even a sideshow can also happen.

100% self-sustaining would be unlikely (there's no real point in the last increment towards that), but colonies on Earth always had trade too.

They had trade because they could. A Mars colony has to be self sustaining otherwise it will simply vanish at some point. For trade to work the cost to trade has to be acceptable.

Think of a world with many orders of magnitude more space travel, at an energy cost on the same order as the net energy difference between source and destination (which can be negative depending on net flow). Is that a world of autarkies? No, except where people prize autarky for its own sake.