[bloopernova]

I guess that depends on what end effect of the magnetic field we are trying to replicate.

If it's protection from radiation, then we have multiple avenues of research and action. We can use particular materials in our domed cities, we can build underground, and we could bioengineer plants and ourselves to better cope with radiation damage. We could even create a huge solar array or nuclear reactor in space and create enough of a magnetic field to deflect solar and extrasolar radiation. It's a difficult problem, for sure, but not an impossible one.

If it's depletion of the Martian atmosphere, then once we've added a whole bunch of material to it, the depletion happens over millions of years. So there's not a huge effect even in the 1000s of years timescale.

[dannypgh]

The idea of terraforming Mars seems increasingly quaint given how hard it's been for us to keep the Earth comfortable for humans.

I think it makes far more sense to work on geo-engineering solutions to climate change first - it's also more likely to have a viable business model, on the assumption that the people will eventually demand action rather than applaud their leaders for pulling out of the Paris Accord.

I think pretty much all of the tech applicable to terraforming Mars could also be useful for reducing Earth's CO2 levels, no? Maybe let the problems on Earth guide development and drive funding, and pivot to Mars once it's clear success is being had on Earth.