<p>It's very stable.   Once created, it takes a lot of work to convert it into something else.   Most other organic compounds have greater potential energy and are unstable on geologic timescales.</p>
<p>The components are abundant.   Not to the extent of hydrogen, but you're more likely to have enough of it for an atmosphere than xenon.</p>
<p>It's fairly heavy as far as atmospheric gases go.  Any atomic hydrogen on Venus or Mars would be lost to space given the combination of atmospheric temperature and surface gravity.</p>
<p>See also:
<a href="https://astronomy.stackexchange.com/questions/14030/how-do-solar-winds-affect-the-atmospheric-composition-and-density-of-planets">How do solar winds affect the atmospheric composition and density of planets?</a></p>
<p><a href="https://astronomy.stackexchange.com/questions/10256/gravitational-pull-needed-to-keep-a-gas-in-atmosphere">Gravitational pull needed to keep a gas in atmosphere</a></p>
<p><a href="https://physics.stackexchange.com/questions/615311/what-is-this-atmospheric-escape-chart-actually-showing">https://physics.stackexchange.com/questions/615311/what-is-this-atmospheric-escape-chart-actually-showing</a></p>
<p>Besides the above, a planet (especially Venus above) may have geological processes that directly impact the atmosphere.</p>

CC BY-SA 4.0
2024-06-05T20:43:28.960Z
Why is it abundant? because carbon and oxygen are created during stellar nucleosynthesis?
Goose
CC BY-SA 4.0
2024-06-05T20:49:10.917Z
https://astronomy.stackexchange.com/questions/14649/why-are-certain-elements-so-common
BowlOfRed
CC BY-SA 4.0
2024-06-05T21:11:06.017Z
Basically, yeah.  Anything lighter than iron is generated in large amounts by stars and distributed when they explode, and the lighter the atoms, the more you get.
Darth Pseudonym
CC BY-SA 4.0
2024-06-05T20:12:02.887Z
2024-06-05T20:12:02.887Z
BowlOfRed
<p>I guess it's a basic question, but why do Venus and Mars have so much carbon dioxide in their atmospheres? The vast majority of the universe is hydrogen (and a small percentage is helium). Why did the specific compound CO2 become so dominant in those planets atmospheres rather than other compounds (a different organic compound, or an inorganic compound such as ammonia?), what is special about it, or what created it during the formation of the solar system?</p>

<solar-system><planetary-atmosphere>
Carbon dioxide on terrestrial planets
Goose
# Carbon dioxide on terrestrial planets

(Asked by: username_0 on 2024-06-05)

I guess it's a basic question, but why do Venus and Mars have so much carbon dioxide in their atmospheres? The vast majority of the universe is hydrogen (and a small percentage is helium). Why did the specific compound CO2 become so dominant in those planets atmospheres rather than other compounds (a different organic compound, or an inorganic compound such as ammonia?), what is special about it, or what created it during the formation of the solar system?

**Tags:** solar-system, planetary-atmosphere

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## 1 answers

### Answer by username_1 on 2024-06-05. Score: 4 | Accepted answer

It's very stable. Once created, it takes a lot of work to convert it into something else. Most other organic compounds have greater potential energy and are unstable on geologic timescales.

The components are abundant. Not to the extent of hydrogen, but you're more likely to have enough of it for an atmosphere than xenon.

It's fairly heavy as far as atmospheric gases go. Any atomic hydrogen on Venus or Mars would be lost to space given the combination of atmospheric temperature and surface gravity.

See also:
[How do 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)

[Gravitational pull needed to keep a gas in atmosphere](https://astronomy.stackexchange.com/questions/10256/gravitational-pull-needed-to-keep-a-gas-in-atmosphere)

<https://physics.stackexchange.com/questions/615311/what-is-this-atmospheric-escape-chart-actually-showing>

Besides the above, a planet (especially Venus above) may have geological processes that directly impact the atmosphere.

> **Comments:**
> **username_0**: Why is it abundant? because carbon and oxygen are created during stellar nucleosynthesis?  
> **username_1**: https://astronomy.stackexchange.com/questions/14649/why-are-certain-elements-so-common  
> **username_2**: Basically, yeah.  Anything lighter than iron is generated in large amounts by stars and distributed when they explode, and the lighter the atoms, the more you get.  

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