Atmosphere of Earth the top of the thermosphere at an altitude of about 700 km above sea level, to about 10,000 km (6,200 mi; 33,000,000 ft) where it merges into the solar wind. This layer is mainly composed of extremely low densities of hydrogen, helium and several heavier molecules including nitrogen, oxygen and carbon dioxide closer to the exobase. The atoms and molecules are so far apart that they can travel hundreds of kilometers without colliding with one another. Thus, the exosphere no longer behaves like a gas, and the particles constantly escape into space. These free-moving particles follow ballistic trajectories and may
Extraterrestrial atmosphere strong absorber of visible and ultraviolet radiation, and can only exist as a gas in a hot atmosphere. WASP-33b is the hottest exoplanet known, with a temperature of and is approximately four and a half times the mass of Jupiter. In February 2016, it was announced that NASA Hubble Space Telescope had detected hydrogen and helium (and suggestions of hydrogen cyanide), but no water vapor, in the atmosphere of 55 Cancri e, the first time the atmosphere of a super-earth exoplanet was analyzed successfully. The atmospheric circulation of planets that rotate more slowly or have a thicker atmosphere allows more