The Atmospheric Production of Glycolaldehyde Under Hazy, Prebiotic Conditions

Open Access
Author:
Harman, Chester Ervin
Graduate Program:
Geosciences
Degree:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 18, 2013
Committee Members:
  • James Kasting, Thesis Advisor
Keywords:
  • glycolaldehyde
  • prebiotic
  • chemistry
  • atmosphere
  • RNA precursor
  • hydrocarbon haze
Abstract:
The early Earth's atmosphere, with extremely low levels of molecular oxygen and an appreciable abiotic flux of methane, could have been a source of organic compounds necessary for prebiotic chemistry. Here, we investigate the formation of a key RNA precursor, glycolaldehyde (2-hydroxyacetaldehyde, or GA) using a 1-dimensional photochemical model. Maximum atmospheric production of GA occurs when the CH4:CO2 ratio is close to 0.02. The total atmospheric production rate of GA remains small, only 1x10^7 mol/yr. Somewhat greater amounts of GA production, up to 2x10^8 mol/yr, could have been provided by the formose reaction or by direct delivery from space. Even with these additional production mechanisms, open ocean GA concentrations would have remained at or below ~1 micromolar, much smaller than the 1-2 M concentrations required for prebiotic synthesis routes like those proposed by Powner et al., 2009. Additional production or concentration mechanisms for GA, or alternative formation mechanisms for RNA, are needed, if this was indeed how life originated on the early Earth.