P34C-05
NOx in the Atmosphere of Early Earth as Electron Acceptors for Life
Wednesday, 16 December 2015: 17:00
2009 (Moscone West)
Michael L Wong1, Benjamin Charnay2, Peter Gao3, Yuk L Yung3 and Michael J Russell4, (1)Caltech, Pasadena, CA, United States, (2)Virtual Planetary Laboratory, University Of Washington, Seattle, United States, (3)California Institute of Technology, Pasadena, CA, United States, (4)Jet Propulsion Laboratory, Pasadena, CA, United States
Abstract:
We quantify the amount of NOx produced in the Hadean atmosphere and available in the Hadean ocean for the emergence of life. Atmospherically generated nitrate (NO3–) and nitrite (NO2–) are the most attractive high-potential electron acceptors for driving the highly endergonic reactions at the entry points to autotrophic metabolic pathways at submarine alkaline hydrothermal vents (Ducluzeau, 2008; Russell, 2014). The Hadean atmosphere, dominated by CO2 and N2, will produce nitric oxide (NO) when shocked by lightning and impacts (Ducluzeau, 2008; Nna Mvondo, 2001). Photochemical reactions involving NO and H2O vapor will then produce acids such as HNO3 and HNO2 that rain into the ocean and dissociate into NO3– and NO2–. Previous work suggests that 1018 g of NOx can be produced in a million years or so, satisfying the need for micromolar concentrations of NO3– and NO2– in the ocean (Ducluzeau, 2008). But because this number is controversial, we present new calculations based on a novel combination of early-Earth GCM and photochemical modeling, calculating the sources and sinks for fixed nitrogen. Finally, it is notable that lightning has been detected on Venus and Mars along with evidence of atmospheric NO; in the distant past, could NOx have been created and available for the emergence of life on numerous wet, rocky worlds?
