137x Filetype PPTX File size 0.68 MB Source: projects.iq.harvard.edu
HISTORY OF EARTH’S ATMOSPHERE N 2 CO2 O 2 O reaches HO 2 2 current levels; oceans CO form 2 life invades dissolves continents Outgassing Life forms Onset of in oceans photosynthesis 4.5 Gy 4 Gy 3.5 Gy 0.4 Gy present B.P B.P. B.P. B.P. Evolution of oxygen and ozone over Earth’s history Life appears on land RUNAWAY GREENHOUSE EFFECT ON VENUS due to accumulation of water vapor from volcanic outgassing early in its history …did not happen on Earth because farther from Sun; as water accumulated it reached saturation and precipitated, forming the oceans EARTH VENUS Comparing the atmospheres of Earth and Venus Venus Earth Radius (km) 6100 6400 Surface pressure (atm) 91 1 -4 CO (mol/mol) 0.96 3x10 2 -2 N (mol/mol) 3.4x10 0.78 2 -5 O (mol/mol) 6.9x10 0.21 2 -3 -2 HO (mol/mol) 3x10 1x10 2 BIOGEOCHEMICAL CYCLING OF ELEMENTS: examples of major processes Physical exchange, redox chemistry, biochemistry are involved Surface reservoirs
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