the earth 's atmosphere is made of 21 percent oxygen by volume
composition_of_earth is 28_percent_oxygen. oxygen is gas_at_1_atmosphere. earth has atmosphere world has oxygen_and_nitrogen_atmosphere earth is 35_percent_iron. one_fifth_of_earth's_atmosphere is oxygen. composition_of_earth is 0.4_percent_aluminum. composition_of_earth is 35_percent_iron. earth's_atmosphere has oxygen air has oxygen