What is the composition of Saturn's outer layer?

The outer layer of Saturn is primarily composed of hydrogen and helium, which aligns with the characteristics of gas giants. Saturn is known for its thick atmosphere, where hydrogen is the most abundant element, making up about 96% of its atmosphere, followed by helium, which accounts for about 3%. This composition is a defining feature of gas giants in our solar system, contrasting sharply with terrestrial planets like Earth that have solid surfaces made of rock and ice. The presence of trace amounts of other gases and compounds can also be found in Saturn's atmosphere, but hydrogen and helium dominate. This explains why the choice that identifies the outer layer's composition as hydrogen and helium is correct.