Atmosphere Atmosphere An atmosphere (from Modern Greek ἀτμός "(atmos)", meaning 'vapour', and σφαῖρα "(sphaira)", meaning 'sphere') is a layer or a set of layers of gases surrounding a planet or other material body, that is held in place by the gravity of that body. An atmosphere is more likely to be retained if the gravity it is subject to is high and the temperature of the atmosphere is low. The atmosphere of Earth is composed of nitrogen (about 78%), oxygen (about 21%), argon (about 0.9%) , carbon dioxide (0.03%) and other gases in trace amounts. Oxygen is used by most organisms
Carbon dioxide in Earth's atmosphere time in 55 years of measurement—and probably more than 3 million years of Earth history." The current concentration may be the highest in the last 20 million years. Carbon dioxide concentrations have varied widely over the Earth's 4.54 billion year history. It is believed to have been present in Earth's first atmosphere, shortly after Earth's formation. The second atmosphere, consisting largely of nitrogen and co2 was produced by outgassing from volcanism, supplemented by gases produced during the late heavy bombardment of Earth by huge asteroids. A major part of carbon dioxide emissions were soon dissolved in water and incorporated in