Chemistry and Composition of Planetary Atmospheres

摘要

This chapter summarizes atmospheric chemistry and composition for the seven planets in our solar system that have significant atmospheres. The terrestrial planets (Venus, Earth, and Mars) have secondary atmospheres that originated by the outgassing of volatile-rich material during and/or after planetary accretion. The gas giant planets (Jupiter, Saturn, Uranus, and Neptune) have primary atmospheres that were captured from the solar nebula. Some of the important chemical cycles that presently operate in planetary atmospheres are illustrated. Thermochemistry controls the atmospheric composition on Venus and in the deep atmospheres of the gas giant planets. In contrast, photochemistry dominates atmospheric chemistry on Mars and in the upper atmospheres of the gas giants. Biochemistry is the key process on Earth, with photochemistry also playing an important role. Some speculations about atmospheric chemistry and composition on extrasolar Earth-like planets are also presented.