The opposite of an iron planet

An iron planet is essentially a planetary core without the rocky mantle. Now formation mechanisms have been proposed which make coreless terrestrial planets. Such worlds may form further from the star or require lower planetary masses. Such worlds would be unsuitable for Earth-type habitability because they would lack magnetic fields.

Coreless Terrestrial Exoplanets

Are we sure that coreless terrestrial planets would lack magnetic fields? Can magnetic fields be produced by things other than the core?

The ice giants, Uranus and Neptune, seem to have magnetic fields that might be generated by something above the core.

Based on my memory, I recall reading something about Europa or Ocean worlds using the high level of salt as grabbing or manipulating magnetic fields around another planetary body.

So, you have a giant planet with a strong magnetic field and the salty-ocean moon orbiting it. The metallic salt extends the giant planet's magnetic field to encompass it. Though weaker, but still there.

Need confirmation on this, though.

I'm not sure it would totally negate Earth-like terrrestrial surface life.

Stuff down deep might not be affected at all. Things around smoker vents might be just fine. As long as the geochemical processes and the ability to have water is not affected by the lack of a magnetic field.

I think it would really depend on the radiation environment around the star. If there was a big solar radiation flux, that might eventually strip the atmosphere of any surface water. But if the solar flux were low, or there was some type of capping layer above the water-laden atmosphere (or perhaps if the gravity were high), the planet might hold onto it's water just fine. The key is to prevent the atmospheric chemistry that would cause dissociation into H2 and O2 and allow the H2 to escape.

-Mike

Well, I do not have a source at the moment.

But I read, Titan actually holds on to a magnetic field after if leaves Saturn's magnetic field. Thus, able to hold on to its atmosphere.

I'll try to find a source...

News release about Titan's "magnetic memory"

Quote :

"We basically recorded the 'magnetic memory' of Titan's ionized atmosphere," said Bertucci. Cassini observations show that this magnetic memory affects Titan's atmosphere from 20 minutes to 3 hours.

So don't rely on this kind of thing supporting a magnetic field over geological timescales perhaps?

Hi Guys

You do know that magnetic fields are generated by the ionosphere of planets without global magnetic fields? Venus has that kind of magnetic field, which deflects some of the solar wind. But at this present point in time the erosion rate of atmosphere by the solar wind is very low - it would take many billions of years to strip Earth's atmosphere, or even Mars's. When the Sun was much, much younger the Wind was stronger, enough to strip away ~ 90% of Mars's atmosphere, but barely touched Earth or Venus. When the Sun turns red-giant and is losing 25% of its mass, then the Wind will be highly erosive BUT that's the least of the planets' worries then.

Magnetism isn't quite my best subject. So I'll go ahead and ask--How would an ionosphere create a magnetic field?

Quote :

Stuff down deep might not be affected at all. Things around smoker
vents might be just fine. As long as the geochemical processes and the
ability to have water is not affected by the lack of a magnetic field.

However if it were coreless would it even have smoker vents?