The Outer Solar System refers to the region beyond the orbit of the planet Mars, primarily consisting of the gas giants: Jupiter, Saturn, Uranus, and Neptune. This area is characterized by large planets with thick atmospheres, many moons, and complex ring systems. In addition to the gas giants, the Outer Solar System includes the Kuiper Belt, a region filled with icy bodies and dwarf planets like Pluto. Beyond the Kuiper Belt lies the Oort Cloud, a theoretical shell of icy objects that may be the source of long-period comets.