Major atmospheric components
| Body | Surface P | Main gases (approx %) |
|---|---|---|
| Mercury | ~10⁻¹⁵ atm (exosphere) | O₂ 42, Na 29, H₂ 22, He 6 |
| Venus | 92 atm | CO₂ 96.5, N₂ 3.5 |
| Earth | 1.0 atm | N₂ 78, O₂ 21, Ar 0.9, CO₂ 0.04 |
| Mars | 0.006 atm | CO₂ 95, N₂ 2.8, Ar 2 |
| Jupiter | — | H₂ 90, He 10 |
| Saturn | — | H₂ 96, He 3 |
| Uranus | — | H₂ 83, He 15, CH₄ 2 |
| Neptune | — | H₂ 80, He 19, CH₄ 1.5 |
| Titan | 1.45 atm | N₂ 95, CH₄ 5 |
| Pluto | ~10⁻⁵ atm | N₂ 99, CH₄ + CO |
| Moon | ~10⁻¹⁴ atm | Ar, He, Ne (very thin exosphere) |
| Io | ~10⁻⁹ atm | SO₂ |
| Triton | 14 µbar | N₂ |
Notes
- Gas giants don't have a "surface" — pressure rises continuously. Quoted compositions are upper atmosphere.
- Venus runaway greenhouse: 96.5% CO₂ keeps surface at ~465 °C despite being farther from Sun than Mercury.
- Titan is the only moon with a substantial atmosphere — thicker than Earth's.
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