Layers
| Layer | Altitude | Temp range | Pressure | Notes |
|---|---|---|---|---|
| Troposphere | 0 – 12 km | 15 → −56 °C | 101 → 19 kPa | Weather, 75% of atmosphere mass |
| Tropopause | ~12 km | −56 °C | 19 kPa | Boundary — jet streams |
| Stratosphere | 12 – 50 km | −56 → 0 °C | 19 → 0.08 kPa | Ozone layer; commercial jets at ~10–13 km |
| Stratopause | ~50 km | 0 °C | 0.08 kPa | |
| Mesosphere | 50 – 85 km | 0 → −90 °C | 0.08 → 0.001 kPa | Meteors burn here |
| Mesopause | ~85 km | −90 °C | 0.001 kPa | Coldest region |
| Thermosphere | 85 – 600 km | −90 → 1 500+ °C | <0.001 kPa | ISS orbits ~408 km; auroras here |
| Exosphere | 600 – 10 000 km | — | near vacuum | Molecules rarely collide — gradually transitions to space |
Composition (by volume, dry air)
| Nitrogen (N₂) | 78.08% |
|---|---|
| Oxygen (O₂) | 20.95% |
| Argon (Ar) | 0.93% |
| Carbon dioxide (CO₂) | ~0.04% (rising) |
| Trace (Ne, He, CH₄, Kr, H₂, N₂O, Xe) | <0.003% combined |
Notes
- Commercial aviation cruises at the top of the troposphere or bottom of the stratosphere (FL350–410, 10.7–12.5 km).
- The Kármán line (100 km) is the conventional boundary of "space".
- Scale height H ≈ 8.5 km — pressure drops by factor e every H of altitude.
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