Gases:

* Hydrogen (H2): Around 96% of the atmosphere.

* Helium (He): About 3% of the atmosphere.

* Methane (CH4): Traces, but responsible for the planet's pale yellow color.

* Ammonia (NH3): Traces, contributing to the formation of clouds.

* Water (H2O): Traces, believed to be present in deeper layers.

* Other Trace Gases: Small amounts of hydrocarbons like ethane, acetylene, and phosphine.

Structure:

Saturn's atmosphere is divided into several layers:

* Upper Atmosphere: This region is dominated by hydrogen and helium, with traces of other gases. It's very cold and thin.

* Cloud Layers: Saturn has several distinct cloud layers, with different compositions:

* Uppermost Cloud Layer: Composed of ammonia ice crystals, giving the planet its pale yellow hue.

* Middle Cloud Layer: Composed of ammonium hydrosulfide (NH4SH) ice crystals.

* Lower Cloud Layer: Composed of water ice crystals.

* Interior: The exact composition of the deeper layers is unknown, but it is thought to be a mixture of gases and a rocky core.

Unique Features:

* Wind Speeds: Saturn has very strong winds, with speeds reaching up to 1,800 km/h (1,100 mph) in its upper atmosphere.

* Giant Storms: The planet experiences powerful storms, including the Great White Spot, a massive storm that occurs periodically.

* Auroras: Saturn's magnetic field interacts with the solar wind, creating stunning auroras near its poles.

Overall, Saturn's atmosphere is a complex and dynamic environment. While primarily composed of hydrogen and helium, the presence of trace gases like methane, ammonia, and water creates the planet's unique characteristics.