This has been covered before but saying that Mars would be a “humanity guarantee” is actually extremely illogical, not the most logical. Short of the Earth getting blasted to tiny pieces in some way there is no scenario where Mars is more habitable than Earth. This is the sort of sci-fi Utopianism that this sober article is standing in opposition to. Mars may be the second most habitable place in the solar system and it’s infinitely less habitable than a nuked-out fallout-ridden earth or an overheated green house earth. There is no magic scenario where Mars suddenly ends up with a magnetosphere and an atmosphere.

The whole "let's by insurance for humankind" story is totally valid in my opinion.

This article is however very useful to bring pragmatism to the discussion.

Maybe the best insurance for humankind is to start shipping a continuous stream of robots to Mars to prepare human landing in many (many) years.

We could buy insurance for humankind underground here on Earth much sooner and much cheaper. Plus that could kick start post human Eloi so win win.

Mars not having a magnetosphere isn't as short term a need. The atmosphere stripping away is on geologic timescales, not human ones. Even then, we could put a superconducting ring between Sol and Mars and get the same effect as far as solar wind stripping the atmosphere. It would be a big project, but not impossible. It's also a project that won't possibly start until people live there permanently.

Worrying about the atmosphere stripping away is akin to worrying about the smaller of Mars two moons being on a path that will impact in 100,000+ years with the surface of mars.

In many problem domains mars is an easier target for long term habitation than the moon, the biggest challenge is getting there. The retorts from people here about farming miss that we don't need 'soil' to farm, there are techniques that mostly just need water and vitamins that can dissolve into it. At Epcot they have a system to breed fish and use the fish waste for feeding plants to grow. Throw in mycelium for handling human waste and you have an efficient system for augmenting food production.

A serious effort for mars will have as many or more spinoff technologies as Apollo gave us. The computers we are using today are further along in development from the massive influx of effort to make computers that could fit in space capsules. With the acidification we are causing in the ocean, a reliable way of converting C02 to oxygen at scale might be needed here on earth to prevent an oxygen collapse within decades. Climate change is a bitch, and it could give an excuse to start charging people for breathable air here on earth so the cynics may be right about that eventually happening. That possible disaster just isn't on even most climate scientist radars yet.

There will be other spinoff technologies we just don't see yet. The large rocketry needed to get there also opens up resource extraction from near earth objects. There's massive material wealth just barely outside our present grasp. It would be nice for materials like platinum and gold to follow in the footsteps of aluminum in becoming common enough to be usable for trivial items. Aluminum was a precious metal just a few hundred years ago in its refined form. Gold nanoparticles look like a candidate that could make current GLP-1 drugs obsolete, it works in animal studies but not tested in humans yet. Manufacturing in space is also on the verge of practicality. Metal foams, ultra low attenuation glass and optically transparent aerogels can be made in microgravity that are superior to the versions that can be made here on earth. Metal foams would be ideal for making ships, cars and planes that are much lower weight than we can make now without loss of strength, less weight means fewer watts per mile and less material needed.

The people whining about the idea always seem to miss the secondary effects of making the effort and always see to paint the optimistic take as naive, really they are just demonstrating short sighted thinking.

This logic does not necessitate Mars ever being more habitable than Earth. Imagine one of the countless doomsday scenarios - a large asteroid impact. What kills you is not necessarily the asteroid, but it flinging debris into the sky that blots out the sun, not only creating a massive cold, but also rapidly killing all plants which starts a rapid series of extinction events on up the food chain.

If that happened Earth itself would still, even during the extinction event, be a dramatically more pleasant place than Mars. But nonetheless that event would kill off the overwhelming majority of people on Earth, and very possibly 100%, because it's such a significant change from the status quo we expect to continue on Earth. But having a parallel society or societies would ensure that even in the 100% scenario, life could get back up and organized relatively quickly. And even in the "only" 99% of people killed scenario, the outside help could help to reestablish order and kickstart society.

You could build a better 'colony' on earth to survive that event for way less money/effort/risk than a colony on mars. You aren't going to have a colony on Mars contributing back to the home planet in any meaningful way, and 1% of people left on Earth is still 80,000,000, many more than will be in a Mars colony.

> You could build a better 'colony' on earth to survive that event for way less money/effort/risk than a colony on mars.

How though? Not in terms of engineering, but in terms of politics and economics. The biggest charter city in the world just got ruled illegal and Honduras is about to take their stuff. Building colonies in Antarctica is forbidden by treaty. And much like Thoreau's cabin in the woods, if you try to make a self-sufficient colony somewhere that's not actually isolated, you might think you've succeeded but actually have been cheating all along.

Yes, objectively there are better options, just as e.g. ITER could have been built a lot more efficiently if most of the countries had agreed to pay one country to make it, instead of making precision parts in a bunch of different countries and having to assemble them together. But engineering and politics are the art of the possible.

Building colonies in-planet that could survive all possible scenarios would probably be impossible. But even if it were you'd face a pretty simple problem - who would ever want to live for there? You'd likely end up living in conditions that would make life on Mars look pleasant, without any of the upsides that might take people to Mars - adventure, ideology, commercial aspirations, perhaps even religious (you know the Mormons will want a planet or two), and of course 0.3g!

And who knows what the future holds in terms of population sizes? I also strongly disagree on the colonies not being able to engage in exchange. For a silly but very practical example sports in 0.3g are going to be insane. Jordan could jump something like 11ft and stay airborn for several seconds on Mars. That's going to be just be stupidly awesome to watch and play. MMA will look like a something out of a Chinese martial arts movie. For more mundane things, as the price of shipping cargo decreases the number of things available for trade increases. For example wine made in 0.3g will taste very different. Whether that's better or worse is yet to be discovered, but obviously such ideas will have no difficulty finding a market.

For better or for worse Mars (or the Moon) will also probably make amazing retirement places, especially if we can work on the scenery a bit. Taking that load of old bones might not only provide comfort but even increase longevity enabling a weaker heart to keep pumping a bit longer. And so on endlessly.