JTW's Evolutionary Origins Page

Primordial Atmospheric Conditions

"The atmosphere assumed by Miller and Urey in their spark-discharge experiment (Miller 1953) was a mixture of CH₄, NH₃, H₂, and H₂O. Current hypotheses regarding the atmospheric composition of the post heavy-bombardments era exclude CH₄ and NH₃, indicating a 'weakly reduced' atmosphere; this is dominated by CO₂, N₂, and H₂O, with small amounts of H₂, CO, SO₂, and H₂S (see Kasting, 1993a)."

Noam Lahav [2000, pp. 138]

Weakly Reducing Vs. Reducing Atmosphere

• Reducing Atmosphere:
  CH₄, NH₃, N₂, H₂O, H₂
• Reducing Atmosphere:
  CO₂, N₂, H₂O, H₂
• Reducing Atmosphere:
  CO₂, N₂, H₂O
• Neutral Atmosphere:
  CO₂, N₂, H₂O
• Oxidizing Atmosphere:
  CO₂, N₂, H₂O, O₂

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