<P> The atmosphere of Uranus is composed primarily of gas and various ices . It is about 83% hydrogen, 15% helium, 2% methane and traces of acetylene . Like Jupiter and Saturn, Uranus has a banded cloud layer, although this is not readily visible without enhancement of visual images of the planet . Unlike the larger gas giants, the low temperatures in the upper Uranian cloud layer, down to 50 K, causes cloud formation from methane rather than ammonia . </P> <P> Less storm activity has been observed in the Uranian atmosphere than in those of Jupiter or Saturn, due to the overlying methane and acetylene hazes in its atmosphere making the planet look like a bland, light blue globe . Images taken in 1997 with the Hubble Space Telescope showed storm activity in that part of the atmosphere emerging from the 25 - year - long Uranian winter . The general lack of storm activity may be related to the lack of an internal energy generation mechanism for Uranus, a feature unique among the gas giants . </P> <P> The atmosphere of Neptune is similar to that of Uranus . It is about 80% hydrogen, 19% helium, and 1.5% methane . However the weather activity on Neptune is much more active, and its atmosphere is much bluer than that of Uranus . The upper levels of the atmosphere reach temperatures of about 55 K, giving rise to methane clouds in its troposphere, which gives the planet its ultramarine color . Temperatures rise steadily deeper inside the atmosphere . </P> <P> Neptune has extremely dynamic weather systems, including the highest wind speeds in the Solar System, thought to be powered by the flow of internal heat . Typical winds in the banded equatorial region can possess speeds of around 350 m / s, while storm systems can have winds reaching up to around 900 m / s, nearly the speed of sound in Neptune's atmosphere . Several large storm systems have been identified, including the Great Dark Spot, a cyclonic storm system the size of Eurasia, the Scooter, a white cloud group further south than the Great Dark Spot, and the Wizard's eye / Dark Spot 2, a southern cyclonic storm . </P>

Which planets have an atmosphere that consists mostly of carbon dioxide