<p>Yes! It just depends on this main factors that affects whether a reaction will take place or not:</p>
<ul>
<li><a href="https://en.wikipedia.org/wiki/Gibbs_free_energy" rel="nofollow noreferrer">Gibbs free energy</a></li>
</ul>
<p>Gibbs free energy <span class="math-container">$G$</span>, is a determiner of whether a reaction takes place spontaneously or not. So if on a planet the <span class="math-container">$G$</span> is negative, then the reaction is spontaneous, if it is positive, then it is not spontaneous.</p>
<p>Now, some reactions like you mentioned, combustion for example specifically requires oxygen to react with the compound, so some planets without certain elements or compounds in their atmosphere won't be able to have reactions that require external elements/compounds to take place.</p>
<p>However, majority of reactions <strong>can</strong> take place, <em>provided that the proper compounds/elements are available of course</em>, through exothermic (reaction releases heat) or endothermic reactions (reaction absorbs heat). It all comes down to the amount on so-called &quot;energy&quot; (mainly thermal energy) in the atmosphere that the reaction can take in if the reaction has a positive <span class="math-container">$G$</span>.</p>
<p>You can also read <a href="https://astronomy.stackexchange.com/questions/14030/how-do-solar-winds-affect-the-atmospheric-composition-and-density-of-planets">this question on how solar winds affect the atmospheric composition and density of planets</a>, per the OP's comments below.</p>

CC BY-SA 4.0
2022-10-31T11:06:59.457Z
This is a good start, but if my layman's understanding of Gibbs energy is correct, it only imposes a limit on the temperature of the environment, and only a lower limit. Could there be more requirements besides minimum temperature (and the presence of reactants which you also mention)? Are all reactions possible on, say, Mercury, or maybe any molecule heavier than water will be shred into atoms by the solar wind and blown away?
Alex Serenko
CC BY-SA 4.0
2022-10-31T11:29:49.867Z
@AlexSerenko hmm good question! I'll look into it soon
DialFrost
CC BY-SA 4.0
2022-10-28T10:22:54.733Z
2022-11-02T00:51:55.887Z
2022-11-02T00:51:55.887Z
DialFrost
<p>Chemical reactions we are used to here on Earth are hardly possible in most of interstellar space due to extremely low temperature and density (though <a href="https://en.wikipedia.org/wiki/List_of_interstellar_and_circumstellar_molecules" rel="nofollow noreferrer">some pretty complex molecules</a> are found there, that Wikipedia article listing</p>
<blockquote>
<p>gas-phase ion chemistry (often driven by cosmic rays) and surface
chemistry on cosmic dust</p>
</blockquote>
<p>among possible formation mechanisms). On the other extreme, close to a star or other energy source, chemical reactions also make little sense because they would be overtaken by other processes with energy much higher than that of chemical bonds. This is why astronomers call all elements except hydrogen and helium metals.</p>
<p>Somewhere in between lies our home, where schoolchildren study all the diversity:</p>
<blockquote>
<p>combination, decomposition, single-replacement, double-replacement,
and combustion.</p>
</blockquote>
<p>Obviously, all of these types of chemical reactions are possible on any other Earth-like planet. However, what about <a href="https://en.wikipedia.org/wiki/List_of_planet_types" rel="nofollow noreferrer">other types of planets</a>?</p>

CC BY-SA 4.0
2022-10-26T10:34:41.850Z
You might be interested in the [Kinetic Database for Astrochemistry](https://kida.astrochem-tools.org/), which provides chemical networks for a range of astrophysical environments.
lucas
<planet><astrochemistry>
How diverse are chemical reactions outside Earth?
Alex Serenko
# How diverse are chemical reactions outside Earth?

(Asked by: username_0 on 2022-10-25)

Chemical reactions we are used to here on Earth are hardly possible in most of interstellar space due to extremely low temperature and density (though [some pretty complex molecules](https://en.wikipedia.org/wiki/List_of_interstellar_and_circumstellar_molecules) are found there, that Wikipedia article listing

> gas-phase ion chemistry (often driven by cosmic rays) and surface
> chemistry on cosmic dust

among possible formation mechanisms). On the other extreme, close to a star or other energy source, chemical reactions also make little sense because they would be overtaken by other processes with energy much higher than that of chemical bonds. This is why astronomers call all elements except hydrogen and helium metals.

Somewhere in between lies our home, where schoolchildren study all the diversity:

> combination, decomposition, single-replacement, double-replacement,
> and combustion.

Obviously, all of these types of chemical reactions are possible on any other Earth-like planet. However, what about [other types of planets](https://en.wikipedia.org/wiki/List_of_planet_types)?

**Tags:** planet, astrochemistry

> **Comments:**
> **username_1**: You might be interested in the [Kinetic Database for Astrochemistry](https://kida.astrochem-tools.org/), which provides chemical networks for a range of astrophysical environments.  

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## 1 answers

### Answer by username_2 on 2022-10-28. Score: 4

Yes! It just depends on this main factors that affects whether a reaction will take place or not:

* [Gibbs free energy](https://en.wikipedia.org/wiki/Gibbs_free_energy)

Gibbs free energy $G$, is a determiner of whether a reaction takes place spontaneously or not. So if on a planet the $G$ is negative, then the reaction is spontaneous, if it is positive, then it is not spontaneous.

Now, some reactions like you mentioned, combustion for example specifically requires oxygen to react with the compound, so some planets without certain elements or compounds in their atmosphere won't be able to have reactions that require external elements/compounds to take place.

However, majority of reactions **can** take place, *provided that the proper compounds/elements are available of course*, through exothermic (reaction releases heat) or endothermic reactions (reaction absorbs heat). It all comes down to the amount on so-called "energy" (mainly thermal energy) in the atmosphere that the reaction can take in if the reaction has a positive $G$.

You can also read [this question on how solar winds affect the atmospheric composition and density of planets](https://astronomy.stackexchange.com/questions/14030/how-do-solar-winds-affect-the-atmospheric-composition-and-density-of-planets), per the OP's comments below.

> **Comments:**
> **username_0**: This is a good start, but if my layman's understanding of Gibbs energy is correct, it only imposes a limit on the temperature of the environment, and only a lower limit. Could there be more requirements besides minimum temperature (and the presence of reactants which you also mention)? Are all reactions possible on, say, Mercury, or maybe any molecule heavier than water will be shred into atoms by the solar wind and blown away?  
> **username_2**: @AlexSerenko hmm good question! I'll look into it soon  

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