#atmosphere.gas  the envelope of gases surrounding any celestial body
  supertype:  gas  a fluid in the gaseous state having neither independent shape nor volume and being able to expand indefinitely
  part:  exosphere  the outermost atmospheric layer
  part:  mesosphere  the atmospheric layer between the stratosphere and the thermosphere
  part:  stratosphere  the atmospheric layer between the troposphere and the mesosphere
     part:  ozone_layer__ozonelayer__ozonosphere  a layer in the stratosphere (at approximately 20 miles) that contains a concentration of ozone sufficient to block most ultraviolet radiation from the sun
        part:  ozone_hole__ozonehole  an area of the ozone layer (near the poles) that is seasonally depleted of ozone
  part:  thermosphere  the atmospheric layer between the mesosphere and the exosphere
  part:  troposphere  the lowest atmospheric layer; from 4 to 11 miles high (depending on latitude)
     part:  tropopause  the region of discontinuity between the troposphere and the stratosphere

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