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Earth has an iron-nickel core which gives us a magnetosphere. Based on this question that replaces our iron core with a mercury core, would we be likely get a magnetosphere?

Mercury is highly conductive and forms mercury(Hg ii) crystals at high pressures. At low temperatures and high pressures it becomes superconductive. Given the conductivity, mercury might form a magnetosphere but I'm just not sure.

What happens to the crust or how life might form on such a planet is outside the question scope but if you'd like to speculate on these topics or on how the planet was formed, you are welcome to do so.

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  • $\begingroup$ I am guessing you don't want us to consider how in the world (puntastic) a mercury core was created in the first place right? $\endgroup$
    – James
    Commented Oct 9, 2015 at 14:43
  • $\begingroup$ @James far be it for me to prevent your speculation about how such a planet might form. :) I'll make it extra credit though I think it's from a very old portion of the universe, perhaps a Population IV star. $\endgroup$
    – Green
    Commented Oct 9, 2015 at 14:45
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    $\begingroup$ You might want to ask this over at the physics SE - I expect you'd get more reliable answers. $\endgroup$
    – Rob Watts
    Commented Oct 9, 2015 at 16:14

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Considering this is world building site instead of physics/astronomy (as pointed by Rob Watts), I would try to give an explanation that is best to my knowledge (but might not be very precise or accurate, as I am not a professional astronomer).

The magnetic field of an astronomical body is linked to the presence of electrically conductive fluid, so Hg would do the trick assuming it supports suitable convection cells.

Now there's one thing that needs to be pointed out immediately. We do not know what form mercury would take under extreme pressure. To understand what I mean, you might want to read about ice phases of common hydrogen oxide (water). Under extreme pressures, ice starts to take the form of crystals (very unexpected thing for ice!). Similarly, we don't know what form mercury would take in the core of a planet.

Depending on the size of core, the planet might get distorted out of shape if it is spinning above a threshold angular velocity as the crust would give in and crack due to the enormous pressure of circulating mercury core (atomic mass 200 versus iron that has atomic mass 56). I think it would be a horrible scene to behold, even looking at it from million miles away!

As for life, well, I don't know why would life forms be any different from what they are on Earth except that the magnetosphere plays an important role in the formation of organic molecules.

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  • $\begingroup$ Edit my answer with the accuracy of your knowledge, O you wise and brave one. For I find myself meek and inaccurate and clumsy on such a daunting task as that! $\endgroup$
    – Youstay Igo
    Commented Oct 11, 2015 at 23:25
  • $\begingroup$ OK, I edited the second paragraph based on the citation from my comment. $\endgroup$
    – JDługosz
    Commented Oct 12, 2015 at 11:23
  • $\begingroup$ No objections about that. $\endgroup$
    – Youstay Igo
    Commented Oct 12, 2015 at 13:00
  • $\begingroup$ Another thing to think about is, if like our nickel-iron core, how would mercury behave at the temperature of the core (~6,000°C), considering mercury boils at 356.7°C. Would the pressure be enough to contain the boiling? What would happen when an eruption occurred and the mercury escaped from the core? Would life be able to sustain itself with an atmosphere completely saturated with mercury vapor? Iron itself boils at 2,862°C and nickel at 2,913°C. It's easily conceived how our core does not boil with the amount of pressure which is on it. $\endgroup$
    – Pᴀᴜʟsᴛᴇʀ2
    Commented Oct 31, 2015 at 23:00
  • $\begingroup$ The question title is aimed at the prospect of a magnetic field around a mercury based core planet, not how life would evolve on it. The core dynamics would be far too complex to be simply decided by temperature alone, but I agree, it would certainly be a big factor in the game. Volcanic activity would probably be a magnitude of dozens more violent and frequent than what we have on Earth. $\endgroup$
    – Youstay Igo
    Commented Nov 1, 2015 at 11:36

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