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)
play
The importance of phytoplankton
Tiny organisms in the oceans produce about half the planet's oxygen.
Dr Iain Stewart explains how phytoplankton produce about half of the Earth's oxygen.
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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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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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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.
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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.
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).
Atmospheric stratification describes the structure of the atmosphere, dividing it into distinct layers, each with specific characteristics such as temperature or composition. 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. An altitude of 120 km (75 mi) is where atmospheric effects become noticeable during atmospheric reentry of spacecraft. The Kármán line, at 100 km (62 mi), also is often regarded as the boundary between atmosphere and outer space.
Air is the name given to atmosphere used in breathing and photosynthesis. 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
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