Generating a magnetic field for planets with iron-cores that is revertable?

Question

I'm looking for a solution to generate a strong enough magnetic field for planets with iron-cores - in my case, Mars - to keep the atmosphere from getting blow away by the solar winds (and ignoring the low gravity). The solution has to be something that could have been quickly deployed - so no hurling asteroids to Mars - and something that can be destroyed to revert the effects.

I've come up with two solutions myself, first: giant pieces of metal orbiting the planet at high speeds that generate the magnetic field. I don't know how big they would have to be or what kind metal. These could be destroyed with a missile or simply pushing them out of the orbit.

Second: giant electromagnets at the "corners" of the planet, making a grid of some sort. The con with this is that they'd need fuel but they'd be easier to reach for destroying purposes.

Would either of these work or what else I could use if keeping in mind that the field had to be generated relatively quickly, some hundred years instead of thousands it would take with asteroids and something that can be destroyed/reverted? Also I'm building this Mars world for a game, how they would look visually, how often the orbiters would be visible (if at all?) or what kind sound the electromagnets would make?

Answer 1

An Iron core is just a third of the puzzle pieces required to form a magnetic field. It is quite likely the Moon has an iron core to some extent, but it is still a very weak magnetic field. Rotation is also required (faster the better) and a fluid core is required. If the interior of Mars has cooled to the point where it is no longer liquid (like the Moon likely has), then no magnetic field would form in normal circumstances.

You can induce magnetic fields...a flow of electricity will cause magnetic fields...however I cannot see masses circling the planet generating a magnetic core, especially if one of the 3 conditions above are not met.

I am also unsure if magnet 'stations' at the 'corners' of any planet would generate the desired result...you would either need some fancy mono-pole magnetic generators (positive on one end of the planet and negative on the other) or they would just generate their own magnetic fields (you'd have a series of magnetic fields existing on the surface). Once again unsure if this would induce a permanent magnetic field on the planet, definitely not if the core has solidified.

To artificially generate a planetary sized magnetic field...Stick a long solid metal rod through the entire planet. Encircle it with wire and let massive amounts of electricity flow through it (ya, it's basically a planet sized electromagnet at this time). Once again, I'm unsure if this field would generate a longer lasting magnetic core or if it would simply generate a magnetic field until the flow of electricity to this giant electromagnet was halted...

Answer 2

The current consensus is that the rotation in one direction of the Earth's outer core (liquid) at >9000K is what generates the field.

If you could find a way to inject a few MT of sodium near Mars's core it might generate a short lived field but the technology to do this is beyond us for now. On the other hand, a few very large thermonuclear detonations would also work, the scale would be huge however. To even start to affect something that big even assuming that the outer core isn't completely solid and merely too cold to spin (unlikely, Mars has been tectonically dead for at least 1BY) would take about 80 200MT blasts exactly spaced to both liquefy and spin the metal.

Answer 3

Current thinking is that it's the liquid outer core not the solid inner one that generates most of the Earth's magnetic field, and mostly because it's mobile. So based on that thinking what you'd need would be a torus of magnetic liquid, Iron, Nickel or Cobalt or some combination thereof in orbit around the magnetic equator of your choice. I'm not even going to try to look at the math but to create a decent field strength externally you're probably looking at a similar mass of metal to the planet itself and it's going to have to be and stay white hot so it doesn't freeze and stop working, once you no longer need the field cool the torus cut it up and ship it out. Incidentally if you spin the artificial magnetic field against the existing rotation of the planet you should also heat the core and jump-start a natural magnetic field and even possibly if there's enough heat generated restart planetary tectonics.