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I found out about Ferrovolcanism on asteroids and its a pretty neat idea for a space sci fi setting. Moreover, I have come up with a hypothetical way that an asteroid could be heated by induction heating. enter image description here

Above is a crude illustration of this hypothetical setup.

There are two asteroids, A and B. A is much large made of materials the could generate a magnetic field. And B is much smaller, orbiting around A, its orbital path is illustrated in blue. A has a magnetic field which is illustrated in red with its poles, but A also rotates, and its rotational axis which is in green is perpendicular to the magnetic field and spinning faster and in the opposite direction B is orbiting. This should make B experience an alternating magnetic field causing Eddy currents to heat up the deep metal core of B slowly, and if B is poor at radiating heat it will eventually build enough heat to cause an eruption after many centuries or eons.

Besides the rare chance of this setup existing, could this realistically heat up an asteroid and cause an eruption.

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  • $\begingroup$ Link up your reading on ferrovolcanism? $\endgroup$
    – Willk
    Jun 11, 2022 at 17:14
  • $\begingroup$ Interesting idea. Naturally occurring situations are problematic. But I see no reason this couldnt be engineered ie manmade. $\endgroup$
    – Gillgamesh
    Jun 11, 2022 at 23:32

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I doubt such a setup would last long enough to store enough energy and cause an eruption: if you ever used a dynamo on a bicycle you know they drag a lot from the wheel, stopping it quicker than just air and bearing drag does.

The same would happen here: as soon as the currents start flowing, they will do it at the expenses of the body's momentum, meaning it would alter the orbit and not be there for long.

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  • $\begingroup$ "There is no such thing as a free lunch'. Lenz's Law. The heat energy comes at the expense of the rotational speed diminishing. There would have to be some factor that supplies input energy to keep the asteroids spinning, rotating, and orbiting. $\endgroup$
    – Justin Thyme the Second
    Jun 11, 2022 at 21:53
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It might not need to get that hot to erupt.

Your setup clearly can heat the bodies involved. We are used to thinking of volcanoes spewing forth really hot stuff like lava and hot ash and winged kaiju. But colder places can have volcanoes that spew colder stuff.

NASA Discovers "Lonely Mountain" on Ceres Likely a Salty-Mud Cryovolcano

ceres

Although the volcano is not active now, the team was surprised that it appears geologically recent. Young volcanism on an isolated dwarf planet is a surprise, as usually only planets, or satellites orbiting around them, have volcanism. Also, volcanic eruptions require bodies to be rocky, like Earth or Mars, or icy, like Saturn's moon Enceladus. Ceres is made of salts, muddy rocks and water ice: exotic and unexpected ingredients for volcanism. Ahuna Mons on Ceres indicates such physical and chemical limitations to volcanism are only apparent. As a consequence, volcanism might be more widespread than previously thought.

I like the idea of your asteroid's volcano spewing fizzing slushy mud. If you were nearby it would be like driving through freezing rain, except brown and yellow with metal sulfides and oxides. The liquid might be liquid ammonia which is even colder than water, or even substances we usually think of as gases like methane / ethanes. The erupting mud would probably stick to stuff and freeze again once it was out. It would take the paint off. It would be an unholy mess.

No reason I can think of that winged kaiju should not pop out too.

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  • $\begingroup$ Actually, your suggestion of Cryovolcanoes has made me come up with a novel idea. What if B was some sort of comet with a rocky outer layer, icy mid-layer, and iron core. The outer rocky layer prevents solar wind from heating the icy mid layer to become a comet coma and tail. but the heating caused by magnetic induction from A causes cryovolcanoes on B to form. These cryovolcanoes would strip the rocky outer layer exposing the icy layer, transforming B into a comet. $\endgroup$
    – spaceamoeba1010
    Jun 12, 2022 at 6:29
  • $\begingroup$ Probably the ice cryovolcanoes would burst thru the rocky outer layer. As regards induced current / ohmic heating - remember salt water can conduct electricity too! $\endgroup$
    – Willk
    Jun 12, 2022 at 16:06
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The Ferrovolcanism is pretty neat. I had always thought of asteroids as being cold, but in the early formation they would be molten and as they cooled they could have spewed molten iron. Going down that rabbit hole a while, apparently for the asteroid to have a magnetic field it needs to have a molten core. And that molten core lasts several million years. So it appears if your solar system was young, you could have molten cores and a magnetic field.

From an orbital mechanics point of view, I think it would be difficult for one asteroid to orbit another asteroid for a long time in a stable way. As L. Dutch points out if there was significant eddy current heating the orbit would also decay.

My guess is that the amount of eddy heating would be relatively small. There is a paper that seems indicate that Tidal heating for the moon Io orbiting Jupiter is much larger than the electromagnetic heating. Another paper seems to think in our solar system it is small but there are some other papers that claim magnetized stars can heat up planets.

But maybe for the proposes of your story you don't have to have the complicated orbit, just the molten core of the asteroid and as it is cooling down it erupts.

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