Earht's early atmosphere - controlling factors
G.Arrhenius

Scripps Institution of Oceanography, University of California San Diego, La Jolla, California 92093-0236, USA

ABSTRACT

The oldest record giving clues to the properties of Earth's atmosphere- ocean system is provided by the laminated banded iron formations from Isukasia and Akilia in southern West Greenland with ages exceeding 3.8·109 years. If considered in equilibrium with the atmosphere they would point to a low mixing ratio of oxygen in the atmosphere.

The nature of the atmosphere in the preceding 700 million years is a matter of speculation with widely ranging estimates of physical and chemical atmospheric conditions. These would be mainly depending on the rate of accretion, the possible segregation of iron in the solar nebula (heterogeneous vs. homogeneous core-mantle accretion), catastrophic events such as possible impact formation or capture of Moon, and impacts postulated to parallel the late bombardment on the Moon.

Atmospheric production of organic compounds is of particular interest as a prebiotic process and would in an anoxic atmosphere be kinetically controlled by plasma reactions in the lower ionosphere and upper atmosphere, particularly in and below the auroral current and in extended atmospheric discharges such as sprites and elves where low kinetic temperatures coupled with high electron and ion temperatures favor the formation of complex molecules, Experimental data confirm the formation under these conditions of glycolaldehyde, a fundamental component of sugar phosphates that form the backbone in RNA.

©Copyright 2002 Arrhenius Laboratory - All Rights Reserved