title: Atmospheric production of glycolaldehyde under hazy prebiotic conditions.
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 1 × 10(7) mol yr(-1). Somewhat greater amounts of GA production, up to 2 × 10(8) mol yr(-1), 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 μM, much smaller than the 1-2 M concentrations required for prebiotic synthesis routes like those proposed by Powner et al. (Nature 459:239-242, 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.
authors.affiliation: Department of Geosciences, Penn State University, University Park, PA 16802, USA. ceharmanjr@psu.edu
authors.forename: Chester E
authors.initials: CE
authors.lastname: Harman
authors.forename: James F
authors.initials: JF
authors.lastname: Kasting
authors.forename: Eric T
authors.initials: ET
authors.lastname: Wolf
mesh_terms: D000079:Acetaldehyde / Q000031:analogs & derivatives* / Q000737:chemistry; D001272:Atmosphere / Q000737:chemistry*; D002245:Carbon Dioxide / Q000737:chemistry; D018534:Earth, Planet; D008697:Methane / Q000737:chemistry; D008956:Models, Chemical
chemical_list: D002245:Carbon Dioxide; D000079:Acetaldehyde; D008697:Methane; C010972:glycolaldehyde