Disabled Javascript!  

Science Library.info

 You are reading this message because you have attempted to access a page on www.umwelt.science which requires Javascript to be enabled.

Javascript is an essential tool for much functionality on the internet, and is perfectly safe to use, since modern browsers prevent abusive use. If you have it disabled, you will not be able to run any interactive software.

You can enable it from the menubar of your browser, following these instructions: Instructions for enabling Javascript on different Browsers

Dictionary

Planetary Science

  • Atmospheric levels
    • Earth's atmosphere consists of 5 main levels, each with distinct characteristics.

      Troposphere

      Ground to 12 km. The atmosphere has a total mass of about 5.15×1018 kg, half of which is found in the first 5.6 km of the troposphere. This part of the atmosphere is dense and turbulent, and is where nearly all clouds and meteorological phenomena occur.

      Stratosphere

      12 to 50 km. The tropopause separates the troposphere from the stratosphere. Air pressure at the top of the stratosphere is about 1000 pascals, or one-thousandth the air pressure at sea level. It is where the vital ozone layer is located, a protective shield of O3, preventing dangerous solar UV light reaching the Earth's surface. The temperature at the tropopause may be as low as -60°C, but rises to around 0°C at the top of the stratosphere.

      Mesosphere

      50 to 80 km. Temperature decreases with increasing altitude in the mesosphere. The mesosphere is too high to be accessed by aircraft or balloon, and too low for satellites.

      Thermosphere

      80 to 700 km. The exact height of the thermosphere varies with solar activity. The ionosphere (the part of the atmosphere ionised by solar radiation) is located in the lower part of the thermosphere. The atmosphere is very low density, and the molecules are very energetic. Temperature increases with altitude in the thermosphere. There is no water vapour, so there are no clouds. The ISS (International Space Station) orbits in the thermosphere, at 320 - 380 km.

      Exosphere

      700 to 10,000 km. The exosphere has practically no atmosphere, and is the zone where most satellites are located.

  • Composition of the atmosphere
    • Earth's atmosphere consists of a mixture of different gases, mainly nitrogen and oxygen.

        Earth atmospheric gases by percentage of volume:
      • N2 = 78.084 %
      • O2 = 20.946 %
      • Ar = 0.9340 %
      • CO2 = 0.043 %
      • Ne = 0.00182 %
      • He = 0.000524 %
      • CH4 = 0.00018 %
      • Kr = 0.000114 %
      • H2 = 0.000055 %

      There is also a variable amount of water vapour (0.001 - 5%), or an average of about 0.25%.

      All of the gases in the atmosphere have a total mass of 5.1480×1018 kg (5 million billion tonnes).