Why is Carbon considered volatile?

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Discussion Overview

The discussion revolves around the classification of carbon as a volatile substance in planetary science, despite its high sublimation point. Participants explore the definitions and implications of volatility, particularly in relation to carbon's behavior in various contexts, including planetary formation and chemical reactions.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants note that carbon is considered volatile in planetary science, despite its high sublimation point of 3900K, leading to confusion about its classification.
  • One participant suggests that the term "volatile" may refer specifically to hydrocarbons, but others argue that carbon is treated as a volatile element in its own right, not limited to its compounds.
  • Another viewpoint indicates that carbon in planetary sciences is regarded as volatile because it readily forms compounds that can outgas from magma or crust.
  • Participants mention that carbon can exist in various forms, such as carbonaceous chondrites, and that its behavior may depend on chemical conditions, including its interaction with magma.
  • One participant describes chemical reactions involving graphite, suggesting that it can produce gases like carbon monoxide and carbon dioxide when mixed with magma or subjected to solar wind bombardment.

Areas of Agreement / Disagreement

Participants express differing views on the definition and implications of carbon's volatility, with no consensus reached on the specific criteria that classify carbon as volatile in planetary science.

Contextual Notes

Participants highlight the lack of specific references in the discussion, which may contribute to the uncertainty regarding the classification of carbon as volatile. The discussion also touches on the complexity of carbon's behavior in different chemical contexts.

Qshadow
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TL;DR
Why Carbon is considered volatile in spite of its very high sublimation point?
Carbon is considered volatile by planetary science, eg Moon lacks volatiles and thus lacks carbon. However volatiles are defined as "elements or substances with low boiling point", but Carbon boiling point is very high! Its sublimation point is 3900K, so it should be refractory and not volatile.
I am confused why it is volatile with such high sublimation point.
Regards, Alex
 
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Lacking a specific reference one can only surmise that "planetary science" is talking about hydrocarbons.
 
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hutchphd said:
Lacking a specific reference one can only surmise that "planetary science" is talking about hydrocarbons.
I do not think they refer only to hydrocarbons, here are some links:
https://www.sciencedirect.com/science/article/abs/pii/0079194677900064
https://ui.adsabs.harvard.edu/abs/2017AGUFM.V22A..01M/abstract
https://agupubs.onlinelibrary.wiley.com/doi/pdf/10.1029/96GL03931

all these papers talk about Carbon as element and not it's particular compounds (be it hydrocarbons, or CO, CO2).
It is like Carbon behaves al volatile always even in elemental form.
 
I believe much is in the form of carbonaceous Chondrites. After you read the article you will know as much as I do...carbon is very gregarious!
 
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I've only done some cursory reading. From what I see, it would appear that carbon in planetary sciences is treated as a volatile because it readily forms compounds that then outgas from magma (or crust in general).
Similar to how 'carbon' in climate science refers to all carbon-containing greenhouse gasses, even though none of them is elemental carbon.
The third source linked above (the only one not behind a paywall) talks about the uncertainty of what form does the carbon took (in 'the early surface volatiles' section).
The one below appears to be discussing speciation of magmatic volatiles, i.e. what forms does e.g. carbon take under different chemical conditions:
https://www.sciencedirect.com/science/article/abs/pii/S0016703720302763
This paper (section V) talks about carbon as a volatile that is 'stored' in magma as e.g. diamond and then outgassed as CO2.
http://www.geo.mtu.edu/EHaz/ConvergentPlatesClass/wallace/Wallace & Anderson (1999).pdf
 
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If you mix graphite with magma you will get carbon monoxide and carbon dioxide gas. Steel is made by taking iron oxide ore and mixing it with coke. Graphite will also react with water to form hydrogen and carbon monoxide, carbon dioxide, hydrocarbons and/or carbohydrates depending on temperature and pressure.

A chunk of graphite sitting on the moon's surface will be bombarded by solar wind particles. The graphite is not subliming. It would be adsorbing and reacting with hydrogen or oxygen and then gassing off.
 
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