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 also been observed in the atmosphere of HD 189733 b, another hot gas giant planet. In October 2013, the detection of clouds in the atmosphere of Kepler-7b was announced, and, in December 2013, also in the atmospheres of Gliese 436 b and Gliese 1214 b. In April 2017, an atmosphere was confirmed around Gliese 1132 b. It is the most Earth-like exoplanet to date that is known to have an atmosphere. In May 2017, glints of light from Earth, seen as twinkling from an orbiting satellite a million miles away, were found to be reflected light from ice crystals in