upper atmosphere

The atmosphere of Earth is a band of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects activity on Earth by arresting ultraviolet solar radiation, abating the apparent through calefaction assimilation (greenhouse effect), and abbreviation temperature extremes amid day and night. Dry air contains almost (by volume) 78% nitrogen, 21% oxygen, 0.93% argon, 0.038% carbon dioxide, and baby amounts of added gases. Air additionally contains a capricious bulk of baptize vapor, on boilerplate about 1%.

The atmosphere has a accumulation of about bristles quintillion (5 × 1018 or 5,000,000,000,000,000,000) kg, three abode of which is aural about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner and thinner with accretion altitude, with no audible abuttals amid the atmosphere and alien space. An distance of 120 km (75 mi) is area atmospheric furnishings become apparent during atmospheric reentry of spacecraft. The Kármán line, at 100 km (62 mi), additionally is generally admired as the abuttals amid atmosphere and alien space.

Air is mainly composed of nitrogen, oxygen, and argon, which calm aggregate the above gases of the atmosphere. The actual gases are generally referred to as trace gases,[1] amid which are the greenhouse gases such as baptize vapor, carbon dioxide, methane, nitrous oxide, and ozone. Filtered air includes trace amounts of abounding added actinic compounds. Abounding accustomed substances may be present in tiny amounts in an unfiltered air sample, including dust, pollen and spores, sea spray, agitable ash, and meteoroids. Various automated pollutants additionally may be present, such as chlorine (elementary or in compounds), fluorine compounds, basal mercury, and sulfur compounds such as sulfur dioxide [SO2].