Most meteorites that fall to Earth belong to one of two broad groups – there are rocky ones, and there are metallic ones that were once molten iron. But one puzzling group of meteorites appears to belong to both camps at once, and now scientists have determined that the parent body had a rocky shell and a liquid metal core, which likely generated a strong magnetic field.

The most common type of meteorite found is the stony variety, which remain “unmelted” through their life cycle. Iron meteorites, on the other hand, bear the hallmarks of having been melted at some point, cooling and condensing into lumps of solid metal long before they hurtled to Earth.

And then there are the IIE meteorites. These weird middle-ground objects appear to be both types at once, made up of once-melted metal with rocky inclusions. More than 20 of these have been discovered since the 1960s, and they’ve been found to have come from a parent body that had a liquid metal core wrapped in a rocky outer layer.

Simulations suggest that an object with such a complex structure would have taken millions of years to form in the early days of the solar system. And it would have taken many collisions with other objects to dislodge the minerals in the liquid core. First they would have ended up in the rocky outer shell, where they cooled and recorded the imprint of the magnetic field. Then, further collisions would have shaken them loose, where they would float around and eventually fall to Earth.

https://newatlas.com/space/meteorites-asteroid-liquid-metal-core/

PermeateFree said:

Most meteorites that fall to Earth belong to one of two broad groups – there are rocky ones, and there are metallic ones that were once molten iron. But one puzzling group of meteorites appears to belong to both camps at once, and now scientists have determined that the parent body had a rocky shell and a liquid metal core, which likely generated a strong magnetic field.

The most common type of meteorite found is the stony variety, which remain “unmelted” through their life cycle. Iron meteorites, on the other hand, bear the hallmarks of having been melted at some point, cooling and condensing into lumps of solid metal long before they hurtled to Earth.

And then there are the IIE meteorites. These weird middle-ground objects appear to be both types at once, made up of once-melted metal with rocky inclusions. More than 20 of these have been discovered since the 1960s, and they’ve been found to have come from a parent body that had a liquid metal core wrapped in a rocky outer layer.

Simulations suggest that an object with such a complex structure would have taken millions of years to form in the early days of the solar system. And it would have taken many collisions with other objects to dislodge the minerals in the liquid core. First they would have ended up in the rocky outer shell, where they cooled and recorded the imprint of the magnetic field. Then, further collisions would have shaken them loose, where they would float around and eventually fall to Earth.

https://newatlas.com/space/meteorites-asteroid-liquid-metal-core/

This is interesting because naturally we expect something as small as an asteroid to cool within a few hundred million years of formation unless it is really, seriously, radioactive.

dv said:

This is interesting because naturally we expect something as small as an asteroid to cool within a few hundred million years of formation unless it is really, seriously, radioactive.

Faster than that. The dominant heating is from radioactive isotope 26Al which has a half life of 720 thousand years. It’s only this isotope that has allowed enough heat to be generated to melt the cores of small bodies such as asteroids.

As for melting in general, some meteorites have been melted very many times. The chondrules themselves in the most ancient types of meteorites were solidified from molten droplets. Then there’s extra surface layers on those that build up one at a time from molten material. Then after the chondrules are cemented together with matrix there is modification by heat – partial melting with recrystallisation – to form most normal chondrite meteorites. Then on top of that, further melting generates layers with surface rock depleted in iron – the stony meteorites. As well as iron-nickel meteorites from the core. And stony irons from the outside of the core.

Then there are subtleties on top of that.

mollwollfumble said:

dv said:

This is interesting because naturally we expect something as small as an asteroid to cool within a few hundred million years of formation unless it is really, seriously, radioactive.

Faster than that. The dominant heating is from radioactive isotope 26Al which has a half life of 720 thousand years. It’s only this isotope that has allowed enough heat to be generated to melt the cores of small bodies such as asteroids.

As for melting in general, some meteorites have been melted very many times. The chondrules themselves in the most ancient types of meteorites were solidified from molten droplets. Then there’s extra surface layers on those that build up one at a time from molten material. Then after the chondrules are cemented together with matrix there is modification by heat – partial melting with recrystallisation – to form most normal chondrite meteorites. Then on top of that, further melting generates layers with surface rock depleted in iron – the stony meteorites. As well as iron-nickel meteorites from the core. And stony irons from the outside of the core.

Then there are subtleties on top of that.

>>Most meteorites that fall to Earth belong to one of two broad groups – there are rocky ones, and there are metallic ones that were once molten iron. But one puzzling group of meteorites appears to belong to both camps at once, and now scientists have determined that the parent body had a rocky shell and a liquid metal core, which likely generated a strong magnetic field.<<