Relation of meteorite types and source material ? [astronomy]

[Externet]

Hello.

There is stony and metallic meteorites with all their sub-types and in-between compositions.  Could these differences correspond to the crust, mantle, core and in-between portions of exploded/collided celestial bodies ?

In other words, do stony meteorites come from geological crusts, iron ones from core fragments ?

[swansont]

I don't think asteroids are differentiated to the point that they have crusts and cores, so I think differences from collisions of them forming meteoroids wouldn't be caused by this. The ones that form from collisions with planets would likely be made of the crust of the planet

https://www.space.com/51-asteroids-formation-discovery-and-exploration.html

https://education.nationalgeographic.org/resource/meteoroid 

[mistermack]

I don't think you can generalise, you have to do some pretty intensive detective work on each sample. Sometimes it's simple enough. If the meteorite minerals match the composition of known Mars samples, then you know the source.

But the cloud that eventually formed the solar system will have had a long history. If it has metals etc, then it will have been involved in a supernova or neutron star collision, or a long history of both. Maybe the star that went supernova had their own planets, that were blown to bits in the explosion. That would leave a mixture of meteorites floating around, some from a core, others from a crust. 

I remember seeing a photo of a meteorite that had been cleanly cut in two, with the surfaces polished. It looked like pure iron, and was tested to be a very pure sample of iron. I can't see any other natural process that could form that, apart from a planet sized object that was smashed in some way. 

 

[Ken Fabian]

6 hours ago, Externet said:

Hello.

There is stony and metallic meteorites with all their sub-types and in-between compositions.  Could these differences correspond to the crust, mantle, core and in-between portions of exploded/collided celestial bodies ?

In other words, do stony meteorites come from geological crusts, iron ones from core fragments ?

In a sense, yes; not pre-existing planetary bodies but ones that coalesced in the early formation of the solar system and underwent differentiation from their own gravity and subsequently got broken up by later collisions. Metallic cores that formed when these proto-planets were hot and molten are where the nickel-iron we find now came from.

 

4 hours ago, mistermack said:

I remember seeing a photo of a meteorite that had been cleanly cut in two, with the surfaces polished. It looked like pure iron, and was tested to be a very pure sample of iron.

Surely that was Nickel-Iron, but it has been common to refer to metal meteorites as "Iron". So far as I know meteorite metal is always Ni-Fe and the only pure iron found in meteorites are small crystals and tiny nodules within a nickel-iron matrix (and not independent of it).

I have previously done some searches to learn whether pure iron or other relatively pure metals (like nuggets and seams of precious metals) are going to be found in asteroids myself - pure iron being more widely useful than alloys with nickel, although the nickel content is a lot more valuable in metal price terms, probably exceeding any precious metal value. I could not find any references to any metallic meteorite sample that was not nickel-iron, with other metals (eg cobalt, Platinum Group Metals) well mixed (in solution) within them.

It appears to be a case of processes that mix them occurring but with an ongoing absence of conceivable processes that can separate them again. (I asked this at https://space.stackexchange.com/questions/27329/can-we-expect-to-find-pure-iron-or-only-nickel-iron-alloys-in-asteroids - and someone answered with a claim to have found a very high, near pure iron content meteorite but he couldn't find any experts who agreed that it was a meteorite and not something with human/terrestrial origins.) 

 

 

Edited July 19, 2022 by Ken Fabian

[mistermack]

10 hours ago, Ken Fabian said:

Surely that was Nickel-Iron,

You're right. I was going from memory, from a long time ago. The "iron" meteorites are always nickel iron. What I remembered was either a complete freak, or a wrong memory on my part. 
Just to complicate it though, there is some pure iron IN iron meteorites, according to some sources. 

https://www.researchgate.net/publication/276236319_Pure_iron_and_other_magnetic_minerals_in_meteorites  

https://link.springer.com/article/10.1134/S0038094614060070 

so maybe there is a freak one out there that I read of years ago, but probably not. 

One thing I was surprised to learn, is that the suggested method of melting and separating of the original nickel/iron was in asteroids, via nuclear decay. Or by the heat of a collision. It's just at the hypothesis stage at the moment, but that's the general idea. 

It sounded unlikely to me, when I first read it, because of the rapid heat loss and lower gravity of an asteroid, compared to a planet or moon. But obviously, it makes sense, or they wouldn't be putting it forward as the mode of formation.