Prebiotic Organic Synthesis in Neutral Planetary Atmospheres

摘要

It is now widely held that the early Earth's atmosphere was likely neutral, dominated by N_2 and CO_2. The synthesis of organic compounds by the action of electric discharges on neutral gas mixtures has been shown to be much less efficient than with reducing gas mixtures. We show here that contrary to previous findings, significant amounts of amino acids are produced under these conditions. The low yields found previously were likely the result of oxidation of the organic compounds during hydrolytic workup by nitrite and nitrate produced in the reactions. Addition of oxidation inhibitors prior to hydrolysis results in the recovery of several hundred times more amino acids than reported previously. Organic synthesis from neutral atmospheres may thus have depended as much on oceanic conditions as on the characteristics of the primitive atmosphere itself. These findings imply the need for a critical re-evaluation of the importance of such syntheses on the primitive Earth and other planetary bodies that, like Mars, may have been endowed with CO_2 and N_2-rich atmospheres throughout most of their history.