<P> Earth 's biosphere has significantly altered its atmosphere . Oxygenic photosynthesis evolved 7000270000000000000 ♠ 2.7 Gya , forming the primarily nitrogen -- oxygen atmosphere of today . This change enabled the proliferation of aerobic organisms and , indirectly , the formation of the ozone layer due to the subsequent conversion of atmospheric O into O . The ozone layer blocks ultraviolet solar radiation , permitting life on land . Other atmospheric functions important to life include transporting water vapor , providing useful gases , causing small meteors to burn up before they strike the surface , and moderating temperature . This last phenomenon is known as the greenhouse effect : trace molecules within the atmosphere serve to capture thermal energy emitted from the ground , thereby raising the average temperature . Water vapor , carbon dioxide , methane , nitrous oxide , and ozone are the primary greenhouse gases in the atmosphere . Without this heat - retention effect , the average surface temperature would be − 18 ° C , in contrast to the current + 15 ° C , and life on Earth probably would not exist in its current form . In May 2017 , glints of light , seen as twinkling from an orbiting satellite a million miles away , were found to be reflected light from ice crystals in the atmosphere . </P>
<P> Earth 's biosphere has significantly altered its atmosphere . Oxygenic photosynthesis evolved 7000270000000000000 ♠ 2.7 Gya , forming the primarily nitrogen -- oxygen atmosphere of today . This change enabled the proliferation of aerobic organisms and , indirectly , the formation of the ozone layer due to the subsequent conversion of atmospheric O into O . The ozone layer blocks ultraviolet solar radiation , permitting life on land . Other atmospheric functions important to life include transporting water vapor , providing useful gases , causing small meteors to burn up before they strike the surface , and moderating temperature . This last phenomenon is known as the greenhouse effect : trace molecules within the atmosphere serve to capture thermal energy emitted from the ground , thereby raising the average temperature . Water vapor , carbon dioxide , methane , nitrous oxide , and ozone are the primary greenhouse gases in the atmosphere . Without this heat - retention effect , the average surface temperature would be − 18 ° C , in contrast to the current + 15 ° C , and life on Earth probably would not exist in its current form . In May 2017 , glints of light , seen as twinkling from an orbiting satellite a million miles away , were found to be reflected light from ice crystals in the atmosphere . </P>
principle constituent of the atmosphere of the earth
principle constituent of the atmosphere of the earth
nitrous oxide
nitrous oxide