Extraterrestrial atmosphere other trace elements, including compounds based on hydrogen, nitrogen, sulfur, carbon, and oxygen. The atmosphere of Venus is much hotter and denser than that of Earth, though shallower. As greenhouse gases warm a lower atmosphere, they cool the upper atmosphere, leading to compact thermospheres. By some definitions, Venus has no stratosphere. The troposphere begins at the surface and extends up to an altitude of 65 kilometres (an altitude at which the mesosphere has already been reached on Earth). At the top of the troposphere, temperature and pressure reach Earth-like levels. Winds at the surface are a few metres per second,
Extraterrestrial atmosphere 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. 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