ASTR 151 Lecture Notes - Lecture 24: Calm Air, Sulfur Dioxide, Photodissociation
Document Summary
The composition of our atmosphere is not like our expectation of a secondary atmosphere dominated by co2. Earth"s early secondary atmosphere is expected to be mostly co2. Main constituents: nitrogen (78%, oxygen (21%, argon (0. 9%) Earth"s gravity is too low to keep the primary atmosphere of hydrogen and helium inherited from the solar nebula. Volcanic outgassing released gases trapped in earth"s interior create a secondary atmosphere: water vapor, methane, co2, sulfur dioxide, and nitrogen compounds. Inert n2 forms and builds up: loss of hydrogen atoms to outer space. Water condensed into oceans and dissolves much of co2 and sulfur dioxide. Remaining co2, sulfur dioxide, etc. reacts with surface rocks and becomes incorporated into the rocks. Stratosphere (17-50km: contains ozone layer, calm air where planes fly. Troposphere (0-17km: convection occurs, place where weather occurs, 80% of the mass. Boundaries between layers occur at temperature inversions: how temperature changes with altitude switches.
