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Thread: Widmanstätten in meteorites

  1. #1 Widmanstätten in meteorites 
    Forum Bachelors Degree PetTastic's Avatar
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    Widmanstätten pattern - Wikipedia, the free encyclopedia

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    The standard theory is that these patterns formed when the nickel iron slowly cooled over millions of years at the core of a large asteroid. Then this solid iron core was shattered into meteoroids by an impact.

    I am thinking it is more likely these patterns are the result of radiation-induced recrystallization of the cold metal over billions of years.
    Google: "radiation recrystallization metals"

    To me the meteoroids being formed by high speed impact shattering the solid iron core of an asteroid is unlikely. The impact would leave little orbiting in the asteroid belt.

    However, a slow impact with an asteroid that has a still molten core, could squirt white-hot liquid iron out into the asteroid belt, to cool rapidly then for the patters later.
    Anther alternative is the formation by cold welding cause by radiation-induced recrystallization.

    This is nothing to do with my Scifi projects. I am just interested in opinions on the idea.


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    ▼▼ dn ʎɐʍ sıɥʇ ▼▼ RedPanda's Avatar
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    Quote Originally Posted by PetTastic View Post
    However, a slow impact with an asteroid that has a still molten core, could squirt white-hot liquid iron out into the asteroid belt, to cool rapidly then for the patters later.
    I had previously thought that asteroids were cold but, after some checking, I found out that is not always the case.
    So...erm...thanks!


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    Quote Originally Posted by RedPanda View Post
    Quote Originally Posted by PetTastic View Post
    However, a slow impact with an asteroid that has a still molten core, could squirt white-hot liquid iron out into the asteroid belt, to cool rapidly then for the patters later.
    I had previously thought that asteroids were cold but, after some checking, I found out that is not always the case.
    So...erm...thanks!
    This is a process that happens in cold materials, including most metals, many crystalline minerals and ice.

    After doing some more reading, this process is much faster than I originally thought.
    I first assumed it would take millions of years for the Widmanstätten pattern to develop in cold nickel iron, but from reading up on lab experiments with metal foil, visible changes can be seen only after hours of exposures to low-level radiation.

    A cold iron asteroid in the space environment potentially containing some uranium could form the patter in only thousands of years.
    Furthermore, ice (snow) recrystallise very fast just exposed to visible light. Ice in comets could recrystallise in days if disturbed.

    I think this effects how we calculate the age of these objects from radioisotopes.
    Every time crystals get deformed by only microns in an impact or thermal change the material could recrystallise.
    Each time it recrystallise the growing crystals push out impurities ahead of them, and changing the distribution of material we would use for dating.

    This makes cold asteroids geologically active with a radiation driven processes.
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