Planetary Aeronomy is a modern and concise introduction to the underlying physical and chemical processes that govern the formation and evolution of the upper atmospheres of planets. The general approach employed permits consideration of the growing number of extrasolar planets, the detailed observation of which will become possible over the next decades. The book explains the physics behind many atmospheric processes, which are relevant for the evolution of planetary atmospheres and their water inventories, and also contains useful scaling laws and analytical expressions that can be applied to any planet. Readers thus gain insight into the evolution of terrestrial planets and their long-time habitability, atmospheric stability, etc. This volume can be used both as graduate textbook for students wishing to specialize in the field as well as succinct compendium for researchers in the field.