Saturn

Saturn is the sixth planet from the Sun and, after Jupiter, the Solar System's second largest. It is a gas giant composed mostly of hydrogen and helium and has no solid surface on which a spacecraft could land. Saturn rotates rapidly, completing a rotation in about 10.7 hours, while one orbit around the Sun takes about 29.4 Earth years. Its axial tilt gives it seasons.

Saturn's broad, bright ring system consists of countless particles, mostly water ice mixed with rock and dust, ranging from small grains to much larger bodies. The main rings extend far from the planet but are extraordinarily thin in comparison. The rings are divided into named components and gaps, including the prominent Cassini Division between the A and B rings. Their origin and age remain scientific questions: analyses of material measured by Cassini have supported relatively recent formation scenarios, but the history of the rings is still debated.

Saturn's moons range from small, irregular bodies to worlds with complex environments. Titan has a dense atmosphere and lakes and seas of liquid hydrocarbons, while Enceladus has a global subsurface ocean beneath an icy shell and ejects water-rich plumes. NASA reported 274 confirmed Saturnian moons as of March 2025; counts can change as new objects are confirmed and officially named. Studying the planet's moons helps scientists investigate how planetary systems form and where environments potentially suitable for life may occur. No life has been detected in the Saturn system.

Pioneer 11 made the first close spacecraft encounter with Saturn in 1979, followed by Voyager 1 and Voyager 2 flybys in 1980 and 1981. The Cassini spacecraft entered orbit around Saturn in 2004 and studied the planet, rings and moons for more than 13 years; it carried ESA's Huygens probe, which landed on Titan in 2005. In its 2017 Grand Finale, Cassini made a series of close passes between Saturn and its rings before NASA deliberately sent it into Saturn's atmosphere on September 15. The mission's data continue to inform research on the Saturn system.