Photochemistry of planetary atmospheres

Photochemistry plays a major role in the composition of planetary atmospheres. Different photochemistry processes are reviewed for both reducing and oxidised atmospheres, paying special attention to the most important chemical cycles. In this way, we present different chemical cycles able to produce hydrocarbons and nitriles in reducing atmospheres as well as those able to maintain the mixing ratios of molecules bearing oxygen, such as CO2, O-2 and H2O. Other important processes such as condensation, sputtering processes and sublimation have to be also considered when atmospheres are simulated.