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If I push a couple of magnetic asteroids into mars gravitational field, could they form an interlocking series of magnetic fields able to protect mars from solar winds?

Size limits for asteroids is any that can become satellites or moons without majorly altering mars regular orbit, or so small that they would cause mars to have Kessler syndrome.

Bonus: If impossible for asteroids could I do it with electromagnets sent from a planet's surface or built into asteroids?

Clay Deitas
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Maybe.

You would use 1 magnetic shield, at the L1 Lagrange point. Lagrange points are places where an item can be placed and stably stay as relative to a planet and its star. There are 5. L1 is between the planet and star.

lagrange points https://www.space.com/30302-lagrange-points.html

I was wondering if you could put a magnetic asteroid (or better: a solar powered electromagnet) at L1 and shield Mars that way. NASA has beat me to the idea which is good, as it is pretty wild and I am sure would get thrashed thoroughly here if proposed first here by me. But NASA!

In answer to this challenge, Dr. Jim Green – the Director of NASA's Planetary Science Division – and a panel of researchers presented an ambitious idea. In essence, they suggested that by positioning a magnetic dipole shield at the Mars L1 Lagrange Point, an artificial magnetosphere could be formed that would encompass the entire planet, thus shielding it from solar wind and radiation. https://phys.org/news/2017-03-nasa-magnetic-shield-mars-atmosphere.html

So there you go. I suspect that a sprawling solar electromagnetic umbrella might be stronger and bigger than an ferromagnetic asteroid. But maybe a magnetic asteroid would suffice if that is what you had handy.

Magnetic field at Mars L1

Willk
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No

The issue isn't strength, it's size. Earth's magnetic field is remarkably weak. On the surface, Earth's magnetic field is only 0.25-0.65 gauss. Your average household 'fridge magnet is 100 gauss, up to 400X the strength of Earth's magnetosphere.

But Earth's magnetosphere is MASSIVE.

And that's your problem. Mars is a tenth the mass of Earth, but doesn't have a strong enough (per the needs of your question) magnetic field. An asteroid could be very strong, but without all that lovely mass (in the form of a liquid metal core), its field will be very, very small.

Long story short, by the time you have enough magnetic asteroids to produce a sufficient addition to Mars' magnetosphere, they'd be several times (perhaps many times) the mass of the planet. It would all collapse into a new planet.

The same problem applies to manufactured magnets. Strong, but small. Large fields require massive field-generators. You know, planet-sized.

So, no.

JBH
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  • Oh, thats a shame. – Clay Deitas Sep 01 '18 at 00:19
  • Yeah. Celestial mechanics be a harsh mistress, yessireebob. – JBH Sep 01 '18 at 00:22
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    According to this abstract, you can place a generator at the Martian L1 point to deflect the solar wind more efficiently. I don't know if it works, though. (Note that the L1 point isn't stable, so your generator will have to station-keep to a certain extent.) – Cadence Sep 01 '18 at 00:26
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    @Cadence - and if you're deflecting the solar wind, even if L1 were stable, station-keeping would be necessary. Deflecting particles takes energy. – jdunlop Sep 01 '18 at 00:28
  • @Cadence, you'll notice the article didn't go into detail as to how that field would be generated and only vaguely suggests plausibility based on current research to protect spacecraft... a bit smaller than a planet. Nice link, though. Excellent catch. – JBH Sep 01 '18 at 00:33
  • However, Clay, @Cadence's article is useful to you. Should you prefer to use Clarkean Magic, then you can simply describe a future where an anti-matter-powered space station at the L1 point generated a secondary magnetic shield for Mars, which could then bear its own atmosphere (still a bit thin, but at least breatheable). it also opens up all kinds of shenanigans that could happen on, to, or around the space station. Would that help your story? – JBH Sep 01 '18 at 00:39
  • I read that article before I asked my question. The only reason I ended up asking mine is because I couldn't figure out how to calculate the magnetic field size of asteroids, or basically any magnet for that reason. Magnetic fields seem to be an unpopular subject, or too complicated to look up on google at least. – Clay Deitas Sep 01 '18 at 00:49
  • Magnetic field calculation requires a substantial amount of Calculus. Check out this page. If you don't recognize the mathematical symbols they're using, then you have either one really intense year of study ahead of you, or several years with a social life. Field equations are cool juju, but they're not for the faint of heart. – JBH Sep 01 '18 at 00:54
  • You need to get a book, I suggest a physics for shorebirds and engineers, it's comprehensive and Peru easy to understand. I think you can hey offset versions for free – Pliny Sep 01 '18 at 00:56
  • Well crappadappadoo. I should have refreshed before all that posting because here @Cadence stole my thunder in the comments 49 minutes ago. But I am going to leave it up because it is slick and goes into detail and has nice images. – Willk Sep 01 '18 at 01:18
  • @Willk, this has happened to all of us at least once.... :-) – JBH Sep 01 '18 at 01:19
  • @Willk There's absolutely nothing wrong with posting an answer with content that should be in an answer, even if someone else mentioned it in a comment. If their comment inspired the answer, some credit is appropriate of course, but in this case, you thought of it independently anyway. – jpmc26 Sep 01 '18 at 06:03
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In my answer to this question:

How can I keep an atmosphere on Mars?1

I suggest another possible way to protect the natural or terraformed Martian atmosphere.

It is a rather bold idea, but no more so than terraforming Mars.

M. A. Golding
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