| Constituent | Chemical symbol | Mole percent |
|---|---|---|
| Nitrogen | N2 | 78.084 |
| Oxygen | O2 | 20.947 |
| Argon | Ar | 0.934 |
| Carbon dioxide | CO2 | 0.0350 |
| Neon | Ne | 0.001818 |
| Helium | He | 0.000524 |
| Methane | CH4 | 0.00017 |
| Krypton | Kr | 0.000114 |
| Hydrogen | H2 | 0.000053 |
| Nitrous oxide | N2O | 0.000031 |
| Xenon | Xe | 0.0000087 |
| Ozone* | O3 | trace to 0.0008 |
| Carbon monoxide | CO | trace to 0.000025 |
| Sulfur dioxide | SO2 | trace to 0.00001 |
| Nitrogen dioxide | NO2 | trace to 0.000002 |
| Ammonia | NH3 | trace to 0.0000003 |
* Low concentrations in troposphere; ozone maximum in the
30- to 40-km regime of the equatorial region.
Mackenzie, F.T. and J.A. Mackenzie (1995) Our changing
planet. Prentice-Hall, Upper Saddle River, NJ, p 288-307.
(After Warneck, 1988; Anderson, 1989; Wayne, 1991.)