<p>All the material that eventually formed our solar system is essentially recycled star dust.   All iron on Earth was produced by large stars that existed before our Sun formed: the iron was created during nuclear fusion and later released when the parent star(s) exploded, presumably supernova.  After our solar nebula had formed and material had been gravitationally compacted, dense elements like iron did not get far from the center of the nebula before "precipitating" out into planets and meteors.  Thus the inner solar system has a high abundance of iron. This is in contrast to low-density elements/molecules that were in general able to escape the center of the nebula and make it pretty far before being pulled into a large mass.  So we have high iron planets and meteors close to the sun (relatively speaking), and very little iron in the "gas giants" part of the solar system.  I would consider this to be material that is "already there" but certainly some iron has been added by meteors.</p>

CC BY-SA 3.0
2014-08-06T04:23:55.233Z
2014-08-06T05:34:05.160Z
2014-08-06T05:34:05.160Z
f.thorpe
<p>I believe the <em>element</em> iron (Fe) is formed by <a href="http://en.wikipedia.org/wiki/Stellar_nucleosynthesis" rel="nofollow noreferrer">stellar nucleosynthesis</a>.</p>

<h1>stellar nucleosynthesis:</h1>

<p>it's a process of continuous fusion of the star element to reach heavier and heavier elements. starting from hydrogen (H) till iron (Fe) (the heaviest element the process could reach). </p>

<p>Each 2 atoms of light elements fuse together to form heavier element atom. </p>

<p>For example 2 hydrogen atoms (H --> 1 proton) fuse to form helium (He --> 2 protons). </p>

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2014-08-12T23:45:55.503Z
Could you explain a little more what stellar nucleosynthesis is in your answer? Thanks!
hichris123
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2014-08-06T00:18:29.367Z
2016-11-26T02:11:01.793Z
2016-11-26T02:11:01.793Z
Mark Rovetta
<p><strong><em>Somewhat more from volcanic activity than meteor impacts, but both are important.</em></strong></p>

<p>The Earth has an <a href="http://en.wikipedia.org/wiki/Structure_of_the_Earth#Core" rel="nofollow">iron-nickel ($\ce{Fe}$-$\ce{Ni}$) core</a> that originates from Earth's formation out of the collision of <a href="http://en.wikipedia.org/wiki/Planetesimal" rel="nofollow">planetesimals</a> which themselves contained iron, rock and ice. The Earth was very hot at that time, and the iron along with some <a href="http://en.wikipedia.org/wiki/Goldschmidt_classification#Siderophile_elements" rel="nofollow">siderophilic elements</a> sunk to the center to form the core. Relatively little of that iron is in the crust. It is mostly <a href="http://www.researchgate.net/profile/B_Wood4/publication/7004632_Accretion_of_the_Earth_and_segregation_of_its_core/links/54e48d180cf2dbf60696e081.pdf" rel="nofollow">sequestered in the core (pages 326, 327)</a>.</p>

<p>The iron that is mined on Earth is mostly from <a href="http://en.wikipedia.org/wiki/Banded_iron_formation" rel="nofollow">banded iron formation from geochemical leeching of basalts and subsequent sedimentary depositing of the iron oxides in anoxic ocean beds</a>. But <a href="http://en.wikipedia.org/wiki/Sudbury_Basin#Modern_uses" rel="nofollow">some of the best iron ore and native metal alloy deposits come from iron meteorite impacts</a>.</p>

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2016-11-26T16:32:19.717Z
The *first* iron used by humans was meteoric.
Spencer
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2015-11-22T23:53:43.323Z
2015-12-05T06:28:32.337Z
2015-12-05T06:28:32.337Z
Eubie Drew
<p>So (naturally occurring) elements on earth can only come to be here in three ways.</p>

<p>Either they are formed here via radioactive decay.<br>
They came via meteor.<br>
They were already here.</p>

<p>As mistermarko stated above iron isn't normally formed via radioactive decay, so we're left with the last two choices.</p>

<p>However if we go back far enough, earth itself was a bunch of meteors and dust that clumped together to form the earth. All matter on earth came from dust, a meteor or a comet. Some of that matter has changed from one element to another, but not iron.</p>

<p>Thus all iron came via meteor. </p>

<p>It isn't a matter of tracing this theory through history, because we know which elements decay into other elements and none of the ones found on earth end in iron.</p>

CC BY-SA 3.0
2014-08-06T00:55:52.400Z
I don't think this rules out "they were already here", but I suppose there's a semantic argument around what "already here" means. Can we say, exactly, when the Earth was "formed", and which meteors are part and parcel of the original item, and which came later?
andy holaday
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2014-08-06T00:06:33.797Z
2014-08-06T00:06:33.797Z
user2296858
<p>Where is the current body of science learning towards, that iron came from meteor or it was somehow formed on earth?</p>

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2015-12-14T10:28:37.320Z
Iron came 'down' from above: http://bit.ly/1I3vjDs
strangetimes
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2015-01-23T19:28:32.837Z
Do you mean the element itself (in which case the answers below are sufficient), or deposits of ore or even metallic iron that people could use?
jamesqf
CC BY-SA 3.0
2015-02-04T06:08:02.667Z
Or the Earth's core? (I assume not, but...)
naught101
<geology><geochemistry><core><meteorite><iron>
Which theory is stronger, that iron came from outside or was formed within earth?
public static
# Which theory is stronger, that iron came from outside or was formed within earth?

(Asked by: username_0 on 2014-08-05)

Where is the current body of science learning towards, that iron came from meteor or it was somehow formed on earth?

**Tags:** geology, geochemistry, core, meteorite, iron

> **Comments:**
> **username_2**: Do you mean the element itself (in which case the answers below are sufficient), or deposits of ore or even metallic iron that people could use?  
> **username_3**: Or the Earth's core? (I assume not, but...)  
> **username_1**: Iron came 'down' from above: http://bit.ly/1I3vjDs  

---

## 4 answers

### Answer by username_4 on 2014-08-06. Score: 11

All the material that eventually formed our solar system is essentially recycled star dust. All iron on Earth was produced by large stars that existed before our Sun formed: the iron was created during nuclear fusion and later released when the parent star(s) exploded, presumably supernova. After our solar nebula had formed and material had been gravitationally compacted, dense elements like iron did not get far from the center of the nebula before "precipitating" out into planets and meteors. Thus the inner solar system has a high abundance of iron. This is in contrast to low-density elements/molecules that were in general able to escape the center of the nebula and make it pretty far before being pulled into a large mass. So we have high iron planets and meteors close to the sun (relatively speaking), and very little iron in the "gas giants" part of the solar system. I would consider this to be material that is "already there" but certainly some iron has been added by meteors.


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### Answer by username_5 on 2014-08-06. Score: 6

I believe the *element* iron (Fe) is formed by [stellar nucleosynthesis](http://en.wikipedia.org/wiki/Stellar_nucleosynthesis).

# stellar nucleosynthesis:

it's a process of continuous fusion of the star element to reach heavier and heavier elements. starting from hydrogen (H) till iron (Fe) (the heaviest element the process could reach).

Each 2 atoms of light elements fuse together to form heavier element atom.

For example 2 hydrogen atoms (H --> 1 proton) fuse to form helium (He --> 2 protons).

> **Comments:**
> **username_6**: Could you explain a little more what stellar nucleosynthesis is in your answer? Thanks!  

---

### Answer by username_7 on 2015-11-22. Score: 6

***Somewhat more from volcanic activity than meteor impacts, but both are important.***

The Earth has an [iron-nickel ($\ce{Fe}$-$\ce{Ni}$) core](http://en.wikipedia.org/wiki/Structure_of_the_Earth#Core) that originates from Earth's formation out of the collision of [planetesimals](http://en.wikipedia.org/wiki/Planetesimal) which themselves contained iron, rock and ice. The Earth was very hot at that time, and the iron along with some [siderophilic elements](http://en.wikipedia.org/wiki/Goldschmidt_classification#Siderophile_elements) sunk to the center to form the core. Relatively little of that iron is in the crust. It is mostly [sequestered in the core (pages 326, 327)](http://www.researchgate.net/profile/B_Wood4/publication/7004632_Accretion_of_the_Earth_and_segregation_of_its_core/links/54e48d180cf2dbf60696e081.pdf).

The iron that is mined on Earth is mostly from [banded iron formation from geochemical leeching of basalts and subsequent sedimentary depositing of the iron oxides in anoxic ocean beds](http://en.wikipedia.org/wiki/Banded_iron_formation). But [some of the best iron ore and native metal alloy deposits come from iron meteorite impacts](http://en.wikipedia.org/wiki/Sudbury_Basin#Modern_uses).

> **Comments:**
> **username_8**: The *first* iron used by humans was meteoric.  

---

### Answer by username_9 on 2014-08-06. Score: 5

So (naturally occurring) elements on earth can only come to be here in three ways.

Either they are formed here via radioactive decay.  
They came via meteor.  
They were already here.

As mistermarko stated above iron isn't normally formed via radioactive decay, so we're left with the last two choices.

However if we go back far enough, earth itself was a bunch of meteors and dust that clumped together to form the earth. All matter on earth came from dust, a meteor or a comet. Some of that matter has changed from one element to another, but not iron.

Thus all iron came via meteor.

It isn't a matter of tracing this theory through history, because we know which elements decay into other elements and none of the ones found on earth end in iron.

> **Comments:**
> **username_10**: I don't think this rules out "they were already here", but I suppose there's a semantic argument around what "already here" means. Can we say, exactly, when the Earth was "formed", and which meteors are part and parcel of the original item, and which came later?  

---

