Atmosphere
Earth's atmosphere is a layered mixture of gases, mainly nitrogen (78%) and oxygen (21%). Argon, water vapour, carbon dioxide and methane are among the other gases present in small amounts. The atmosphere helps to protect our planet from asteroid impacts and solar radiation.
The innermost layer, the troposphere, contains most of the planet's weather and extends out to 10–15km above the surface.
The next layer out, the stratosphere, is drier and less dense and extends out to about 50km. The Sun's UV light breaks down oxygen in the stratosphere to form the Earth's protective ozone layer.
The mesosphere, thermosphere, and ionosphere make up the remaining outer layers that extend out to about 100km.
Image: The rising Sun highlights Earth's atmosphere in this photo taken from the International Space Station (credit: NASA/SPL)
Introduction
Atmosphere
TV clips (6)
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The edge of space
Joe Kittinger parachuted through 99% of the Earth's atmosphere.
Having reached a height of 15km in a fighter jet, Dr Iain Stewart marvels at military pilot Joe Kittinger's 1960 balloon ascent to 31km above the Earth. Kittinger parachuted from high in the stratosphere and plummeted through 99% of the gases that make up our atmosphere. Stewart also discusses the layers beyond the stratosphere that are even higher than Kittinger's jumping off point.
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The fluid troposphere
Iain Stewart explains how the troposphere behaves like a fluid.
Dr Iain Stewart explains how the troposphere, the innermost layer of the Earth's atmosphere, behaves like a fluid.
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Jet tour of the atmosphere
Iain Stewart flies through some of the atmosphere's layers.
Dr Iain Stewart takes a ride through some of the atmosphere's layers in an English Electric Lightning jet. He flies through the troposphere and stratosphere to an altitude of 15km.
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Wind feeds life
Wind transports large amounts of nutrient-rich dust around the planet.
Dr Iain Stewart explains how wind transports large amounts of nutrient-rich dust around the globe. This dust fertilizes the oceans and plants on land.
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Oxygen enters the atmosphere
Stromatolites pump oxygen into the early atmosphere.
Dr Iain Stewart explains how stromatolites, one of the earliest forms of life, first released oxygen over three billion years ago when they turned sunlight into energy. Oxygen was initially soaked up by iron in the seas but eventually entered the atmosphere.
Atmosphere
The atmosphere of Earth is a layer of gases surrounding the planet Earth that is retained by Earth's gravity. The atmosphere protects life on Earth by absorbing ultraviolet solar radiation, warming the surface through heat retention (greenhouse effect), and reducing temperature extremes between day and night (the diurnal temperature variation).
The common name given to the atmospheric gases used in breathing and photosynthesis is air. Dry air contains roughly (by volume) 78.09% nitrogen, 20.95% oxygen, 0.93% argon, 0.039% carbon dioxide, and small amounts of other gases. Air also contains a variable amount of water vapor, on average around 1%. While air content and atmospheric pressure vary at different layers, air suitable for the survival of terrestrial plants and terrestrial animals currently is only known to be found in Earth's troposphere and artificial atmospheres.
The atmosphere has a mass of about 5×1018 kg, three quarters of which is within about 11 km (6.8 mi; 36,000 ft) of the surface. The atmosphere becomes thinner and thinner with increasing altitude, with no definite boundary between the atmosphere and outer space. The Kármán line, at 100 km (62 mi), or 1.57% of the Earth's radius, is often used as the border between the atmosphere and outer space. Atmospheric effects become noticeable during atmospheric reentry of spacecraft at an altitude of around 120 km (75 mi). Several layers can be distinguished in the atmosphere, based on characteristics such as temperature and composition.
The study of Earth's atmosphere and its processes is called atmospheric science or aerology. Early pioneers in the field include Léon Teisserenc de Bort and Richard Assmann.
This entry is from Wikipedia, the user-contributed encyclopedia. If you find the content in the 'About' section factually incorrect, defamatory or highly offensive you can edit this article at Wikipedia.
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