Because building infrastructure on Earth takes forever and I don't think that it goes faster on Mars. Supply chains for even trivial things are terribly long. It's a lot of work to build replacements off-world. I mean, just having the life support to sustain a sufficient population to run and maintain the machines for simple steel production is a huge task in itself. And then you also need chemical manufacturing (without the benefit of having oil), semiconductors, electronics... modern civilization is hard.

Indeed. I look at the effort required to get a teeny tiny solar powered helicopter to Mars, and while the achievement itself is noteworthy the difficulty in doing so is illuminating. Dreams of human colonization of Mars are largely coping mechanisms to help with the fears that arise when considering the very real apocalypse humanity faces.

> building infrastructure on Earth takes forever

China has built cities basically from scratch in few years, and big infrastructure very quickly, as a counterpoint.

Yes, but only after they spent decades on building out their construction industry with lots of imported equipment from elsewhere. Mars will not be able to construct big roads and buildings until they bootstrap a concrete industry and they can't do that without a steel industry, and they can't do that without mining sites, which need vehicles and mining equipment, etc etc etc. All these things will need either large amounts of people (and thus food) or large amounts of automation (and thus microchips etc) and Mars will not be able to bootstrap either without billions and billions of investment from Earth.

What's the minimum amount of mass/volume of equipment needed to bootstrap, and what is the doubling rate of this infrastructure?

Yes yes, we all know that exponential growth is pretty cool. But take into account that you can't explode outwards in the Martian environment like some algae growing in a food rich environment, every new person and every piece of infrastructure will need (a lot of) maintenance and that slows down doubling rate by a lot. You also can't use a lot of Earth-based shortcuts either, since there is no oxygen for fossil fuels and you won't be able to grow food in open atmosphere.

Big industrial equipment is really heavy btw, so you could fit at most 1 or 2 pieces of big equipment in the 100 ton payload of a Starship rocket. It could easily be a few hundred launches just to get a proper scale foundry going on mars, if you take into account all the required auxiliary equipment like ore scrubbers, cranes and forklifts. Don't forget all the solar panels and/or nuclear plants for power generation too. It would probably be at least tens of billions of support from Earth.

All in all, I would think that 5-10% growth rate is already pretty ambitious, leading to a doubling rate of 7 to 14 years. If you start your colony with about 50 people, it would rise to a thousand people in a little over 50 years.

Mars is colder than Antarctica, drier than the Sahara desert, and has lower air pressure than the top of Mt Everest, and the air is notably lacking in both oxygen (for us) and nitrogen (for plants). Making an independent colony on Mars in one generation basically needs us to invent von Neumann machines — not impossible, but a larger economic change than the entire industrial revolution, and even then we might need to use that economic power to crash-land some comets on the red planet to give it useful quantities of nitrogen and water (that said, TIL Curiosity found 1100 ppm nitrates in the soil: https://www.nasa.gov/content/goddard/mars-nitrogen/).

> the air is notably lacking in both oxygen (for us) and nitrogen (for plants)

Minor nitpick: There are only very few plants that are able to extract nitrogen from the air. That's because N2 is a very stable molecule and it takes a lot of energy to use it chemically. Almost all plants are dependent on other nitrogen compounds they extract using their roots.

[That's the reason why the invention of the Haber-Bosch process, which fixes the N2 from the air into NH3 (ammonia), was such a big deal. It is estimated that 50% of the nitrogen atoms in your body once passed through the Haber-Bosch process.]

There's probably plenty of nitrogen in various minerals on Mars. Just not in the atmosphere.

Good point. I was thinking about nitrogen-fixing bacteria etc., but even with that, your point is sufficient.

One thing that I only learned recently is that a lot of terraforming is very destructive.

So you would NOT want to colonize a planet first and then terraform it. Instead you would terraform it first. Terraforming Mars for example could involve sending a large number of comets to crash to the planet. If there were existing colonies on the planet, they might be destroyed by the impacts or be inundated by the torrential rains.

Isaac Arthur has some thought provoking videos about this.

Just this week I discovered Isaac A. on youtube. I can not recommend him enough if space is thing of interest. (to anybody else reading this)

Imagine what it will take to go from space rock to underground chip factories. If we started today, it will take a thousand years or more to have a fully independent Mars colony (one that could survive indefinitely if the Earth were hit by a gamma-ray burst, let's say).

The sheer population needed to run a complete supply chain for high-technology (on which Mars would be entirely dependent for basic life-support) is staggering. Having the entire thing built and operated underground would be an engineering and social feat of unprecedented scale in humanity's history.

Iamgining doing it in a generation is simply impossible. Its more likely to happen by quantum fluctuation in a second than by humanity's efforts in a generation with current technology.

A gamma-ray burst killing Earth could also kill Mars. I don't know but perhaps the death ray could be as wide as several sun systems.

Sure, my point was only the idea of a Mars colony surviving with 0 resources from Earth.

Of course I understand that, only the example with the gamma ray burst is not really useful here.

Well, one point I didn't make here but that made me pick that example is that, with the exception of a gamma ray burst, there is no tragedy that could realistically affect the Earth in such a way as to make it even CLOSE to how uninhabitable Mars is.

Global warming, nuclear winter, asteroid hit, massive solar flare, supervolcano, plate tectonics - anything we care to imagine will leave the Earth much closer to being habitable than Mars.

A near supernova would also be extremely disastrous and also kill Mars. Perhaps global warming on Venus scale?

Just playing along...

> If we started today, it will take a thousand years or more to have a fully independent Mars colony

But how do you know this? Are there any papers or reports that say that a thousand years is the lower bound on a self sustaining colony on another planet?

It seems to me that this idea is a common wisdom that people often say because in their mind colonization is an out of reach idea so they just pick a random big sounding number like "a thousand years" as a placeholder for 'it is impossible" when there isn't any actual research that says it will take a thousand years.

Sure, it's a made up number. But it's meant to give a sense of scale.

Think about how economically unviable and hard it is to just create 1 new chip fab on Earth. And think about the fact that on Mars you would need to re-create the entire supply chain that already exists on Earth. Remember that the minerals that you need are probably about as spread-out on Mars as they are on Earth, so you will need a global network of mining stations and processing plants to get the various necessary metals - all this without any access to fossil fuels of any kind, and with all of humanity spending little time outside for fear of radiation.

Perhaps establishing a colony that gets the vast majority of its supplies from Earth is doable in a generation or two (though of questionable value). But creating a self-sustaining colony is entirely out of reach for the forseeable future. You don't need actual research to tell you this any more than you need actual research to tell you that humans can't flap their wings to fly - a little bit of back-of-the-napkin calculations will quickly elucidate it.

Singularity, robots...

Not certain to happen but a fair bit more than your quantum fluctuation.

First ask yourself how quickly you could build a self-sustaining society deep in the Sahara, or at the south pole. Then realize that both of those places are waaay more habitable than the surface of Mars, since they both have a breathable atmosphere and a notable lack of perchlorates in the soil.

Most likely reason is that there is no clear return on investment for throwing resources at building a colony on Mars - so what politician is going to choose to spend money to make life possible on Mars when it could be spent (or the taxes not raised) down here?

NB I don't think private capital would ever be enough to get a self sufficient colony started.