Final answer:
Jupiter and Saturn have more 'cosmic' compositions with active and visible cloud layers, while Uranus and Neptune are depleted in hydrogen and helium with more stable atmospheric appearances—Uranus lacks visible cloud layers, and Neptune shows thin methane cloud layers.
Step-by-step explanation:
The composition and differentiation of planetary atmospheres within our solar system are influenced by various factors, including mass, presence of internal heat sources, and their ability to retain hydrogen and helium.
Jupiter and Saturn, being more massive, have extensive mantles of liquid hydrogen and exhibit a composition closest to the so-called 'cosmic' composition, which is rich in hydrogen and helium. They have deep atmospheres and opaque clouds with active cloud patterns and storms, and their appearance includes visible cloud layers composed of ammonia crystals. Both have significant internal heat sources contributing to their atmospheric dynamics.
In contrast, Uranus and Neptune are depleted in hydrogen and helium relative to Jupiter and Saturn. They have high-density atmospheres resulting from their core compositions of ice and rock. Uranus, with a very stable atmosphere due to the absence of an internal heat source, has no obvious cloud layers and appears featureless. Neptune, while similar in basic atmospheric temperature to Uranus, has visible clouds composed of methane and a pale blue color due to the scattering of sunlight.