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As someone interested in terraforming, the main obstacle to colonizing Mars is the lack of a magnetosphere and Atmosphere. To create a magnetosphere of sufficient magnitude the Martian core must be reignited. There are several ways to do this, some of which involve using electric current to restart the core, but the most feasible way it seems would be to take an asteroid of sufficient size and slingshot it into Mars. Doing so would reignite the core resulting in increased volcanic activity, the formation of a thick and stable atmosphere, etc.

It seems to be the perfect solution despite the fact that doing so would be a long term investment. I was wondering - based on what we know of the Earth's development - how long would it take Mars to cool after an asteroid impact of sufficient size? are we talking millions or billions of years?

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closed as off-topic by Jan Doggen, Gimelist, Fred, Pont, arkaia Jan 13 '16 at 10:03

This question appears to be off-topic. The users who voted to close gave this specific reason:

  • "This question does not appear to be about earth science, within the scope defined in the help center." – Gimelist, Fred, Pont
If this question can be reworded to fit the rules in the help center, please edit the question.

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    $\begingroup$ meta.earthscience.stackexchange.com/questions/1517/… Voting to close. $\endgroup$ – Jan Doggen Jan 13 '16 at 7:51
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    $\begingroup$ "the most feasible way" - sure. We do it every day! $\endgroup$ – Gimelist Jan 13 '16 at 7:55
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    $\begingroup$ I fail to see how is this off-topic. $\endgroup$ – milancurcic Jan 13 '16 at 16:59
  • $\begingroup$ There's no good reason why an asteroid impact should generate a magnetic field. I like the way you think, but it's not that simple. Curiously a large moon (Ceres?) in a tight orbit around Mars just might. The tidal flexing just might do it. I don't want to say for sure, only that it's possible. Moving Ceres into that orbit, however - no easy feat. $\endgroup$ – userLTK Feb 25 '18 at 7:16
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It would be interesting to read peer reviewed scientific papers that discuss the feasibility of "restarting Mars' core" via an asteroid impact. Some links would be appreciated.

I am very sceptical that it could be achieved in such a manner. Small asteroid impacts would change the topography of the surface by creating new craters and spraying crater ejecta over the surface.

Impacts from extremely large asteroids would only create larger craters or possibly blast out large chunks of Mars and even destroy the planet: such as a collision with Ceres.

One of the flaws I see in trying to "restart the core" is how to keep a solid inner core within a molten outer core, while at the same time creating relative movement between the two.

The Earth's magnetic field exist because its solid inner iron-nickel core and the metallic molten outer core move relative to one another creating a geodynamo. Without a solid core and relative movement between the two the only thing that will be achieved will be a molten core without a magnetic field.

If it were possible to remelt the core of Mars, a magnetic field would not be created by simply remelting the core.

The other flaw I see is that if it were possible to remelt the core, the core will expand due to thermal expansion. This will then increase ground stresses within the overlying rock which will result in cracking of the overlying rock and the generation of Mars-quakes.

Another flaw I see is concerns the energy required to remelt the core. A significant volume of core would need to be remelted. That would require a lot of energy over a prolonged period of time. The effect of an asteroid impact would dissipate quickly.

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