Planetary science or, more rarely, planetology , is the scientific study of planets (including Earth ), moons , and planetary systems (in particular those of the Solar System ) and the processes that form them. It studies objects ranging in size from micrometeoroids to gas giants , aiming to determine their composition, dynamics, formation, interrelations and history. It is a strongly interdisciplinary field, originally growing from astronomy and earth science , but which now incorporates many disciplines, including planetary geology (together with geochemistry and geophysics ), cosmochemistry , atmospheric science , oceanography , hydrology , theoretical planetary science , glaciology , and exoplanetology . Allied disciplines include space physics , when concerned with the effects of the Sun on the bodies of the Solar System, and astrobiology .