page_title: Planet
section_title: Atmosphere
hierarchical_section_title: Planet / Attributes / Physical characteristics / Atmosphere
caption_attribution_description: English: View of the crescent moon through the top of the earth's atmosphere. Photographed above 21.5°N, 113.3°E. by International Space Station crew Expedition 13 over the South China Sea, just south of Macau (NASA image ID: ISS013-E-54329). Français&#160;: Photo des couches hautes de l'atmosphère terrestre. Polski: Zdjęcie górnych warstw atmosfery ziemskiej z widocznym przejściem w przestrzeń kosmiczną. Ελληνικά: Η Γήινη ατμόσφαιρα, η φωτογραφία ελήφθη από το διάστημα κι ύψος 335 χιλιόμετρα
context_page_description: A planet is an astronomical body orbiting a star or stellar remnant that is massive enough to be rounded by its own gravity, is not massive enough to cause thermonuclear fusion, and has cleared its neighbouring region of planetesimals.
  The term planet is ancient, with ties to history, astrology, science, mythology, and religion. Apart from Earth itself, five planets in the Solar System are often visible to the naked eye. These were regarded by many early cultures as divine, or as emissaries of deities. As scientific knowledge advanced, human perception of the planets changed, incorporating a number of disparate objects. In 2006, the International Astronomical Union officially adopted a resolution defining planets within the Solar System. This definition is controversial because it excludes many objects of planetary mass based on where or what they orbit. Although eight of the planetary bodies discovered before 1950 remain "planets" under the current definition, some celestial bodies, such as Ceres, Pallas, Juno and Vesta, and Pluto, that were once considered planets by the scientific community, are no longer viewed as planets under the current definition of planet.
context_section_description: All of the Solar System planets except Mercury have substantial atmospheres because their gravity is strong enough to keep gases close to the surface. The larger giant planets are massive enough to keep large amounts of the light gases hydrogen and helium, whereas the smaller planets lose these gases into space. The composition of Earth's atmosphere is different from the other planets because the various life processes that have transpired on the planet have introduced free molecular oxygen.
  Planetary atmospheres are affected by the varying insolation or internal energy, leading to the formation of dynamic weather systems such as hurricanes, (on Earth), planet-wide dust storms (on Mars), a greater-than-Earth-sized anticyclone on Jupiter (called the Great Red Spot), and holes in the atmosphere (on Neptune). At least one extrasolar planet, HD 189733 b, has been claimed to have such a weather system, similar to the Great Red Spot but twice as large.
  Hot Jupiters, due to their extreme proximities to their host stars, have been shown to be losing their atmospheres into space due to stellar radiation, much like the tails of comets. These planets may have vast differences in temperature between their day and night sides that produce supersonic winds, although the day and night sides of HD 189733 b appear to have very similar temperatures, indicating that that planet's atmosphere effectively redistributes the star's energy around the planet.
caption: Earth's atmosphere
exif: {}