Mars wouldn't instantly become uninhabitable once the shield collapses. Atmosphere loss is something that occurs over the timespan of millions of years, it would be entirely reasonable for a civilization with sufficient spacelift capacity to terraform Mars without a shield, with the understanding that the atmosphere would require active management over millennia.

Also "throwing space rocks will be trivial for a terrorist cell" makes a lot of presumptions about how social organization will work in orbit. IMHO there will never be the spacer society presupposed by so much sci-fi, because any spaceship with an interesting propulsion system is also always a weapon of mass destruction (and not just against orbital infrastructure). The solution to this is that weapons of mass destruction are only owned and operated by large, powerful states with things to lose. It's worked for nukes for 80 years soonish.

Fusion bomb is technologically hard problem even today. Fission is simple but required a of the material which can only be produced by technologically hard devices. This gates it for now. But even today we can see that countries wishing to destabilize neighbors can simply gift complete assembly to their allies. Like russia did with North Korea, and is now probably doing with Iran. So ownership of the tech by large political entities doesn't matter if one of such entities decides to defect and abandon common rules.

So, yes, there won't be some independent spacer terror cell. But what if one of the space faring countries will decide to simply sponsor some Hamas 2.0 to attack their opponents? Considering that this will be a new age of conquest possibly, where nothing in the Solar System is yet owned by anyone and there will be a lot of takers. Like a simplest question - who's are Luna and Mars? :)

Next issue is that chemical rockets are much simpler and cheaper, also they are not gated by any tech or material. Sure, there are important secrets around nozzles and stuff, but I suppose a simple crude rocket will work just fine. So assuming we are at the level when humans can travel to the asteroids to mine them (also a big if, due to it being economically unfeasible) they can setup such a kamikaze rocket. Attack will be from outside of the ecliptic plane, so likely undetected. Attack can be scaled to more than one rock, so that every single point of failure, every dome etc must have dozens of anti-spacecraft level defense rockets (nukes most likely). It is not feasible.

Of course all of this is about far far future, we can't predict what will happen.

> Attack will be from outside of the ecliptic plane, so likely undetected.

It won't be. There is no stealth in space, and telescopes are really good. Once there will be a lot of man-made objects in space, it will be trivial for a state actor to continuously track the exact position (and complete history) of every single man-made object large enough to have an engine in the solar system, and I would assume that everyone with major space interests would do that.

There is no stealth in space, but space is also very large.

If throwing space rocks is trivial (which I'm not sure I buy), surely knocking them off course will also be trivial.

an object in motion stays in motion

and inertia is a bitch

you have to choose to hit something, because the energy to completely eject that mass from being dangerous would be a lot

Seems like redundancy could solve this. Instead of a single huge magnet you create a constellation of smaller magnets with aligned fields that orbit the LaGrange point.

We're decent at tracking large space rocks, and small space rocks will likely have to be dealt with anyway since some occur randomly.

It's somewhat interesting that terrorism already isn't such a problem for huge skyscrapers. Skyscrapers can be destroyed with just a small fraction of the explosive energy required to launch an orbital rocket yet it rarely happens.

Your last paragraph is an excellent point that highlights the likely risk factor by using existing infrastructure as an example.

Skyscraper are not a good or a primary target. Why bother with a tower if the same number of people can be hit easier on a surface - a demonstration, Sunday market, transportation hub etc. Also I suspect that a lot of conventional explosives is needed to topple one, and it also requires to have a specific faults. You need at least half a ton of explosives to maybe do something (basing on the amounts russia uses in their ballistic missiles against cities), and that is not guaranteed.

"Technology exists" and "technology will be trivially deployable by any terrorist" are two different things.

ICBMs have existed for a long time, as have nuclear weapons. Terrorists cannot "trivially" deploy them.

These kind of extremely powerful magnets will not be trivial, and doing anything in space even less so.

While they are not ICBM, the mid range, nuke capable, ballistic missiles are used daily against Ukraine and Israel cities. Imagine that these two countries had domed cities on Mars. Even a single rocket would kill whole population immediately.

The small dingy rockets fired by Hamas are utterly incomparable to ICBMs. It's not the same thing at all. Theoretically almost everything is "nuke capable" and that means nothing in this context.

You were talking about the "total destruction" of the ecosystem on Earth, because "throwing space rocks" will be "trivial for any terrorist cell". Talk about hypothetical rockets fired on hypothetical domes on a hypothetical Mars colony bears absolutely zero relation to that.

Do you have any evidence to back this up? It seems like it was the SV's dream in the nineties, yet so far it failed. Economical and intellectual connections doesn't seem to prevent us from being divided and ultimately waging war...

What does this even mean? What is your definition of truly connected?