NOx in the atmospheres of aquaplanets as electron acceptors for life

Abstract:

A high potential electron acceptor is required to drive the highly endergonic reactions at the entry points to the autotrophic metabolic pathways that would lead to life on any wet rocky world. Nitrate and nitrite in the earliest oceans are the most attractive candidates (Ducluzeau et al., 2009, 2014). It has been estimated that, given a CO₂ and N₂ atmosphere, lightning (a proportion of it volcanic), meteorite impacts and volcanic gases would have produced enough NOx in a million years or so (>10¹⁸ g) to generate micromolar amounts of NO₃^- and NO₂^- in the ocean (Yung and McElroy, 1979; Kasting, 1990; Navarro-González et al., 1998; Martin et al., 2007). It is notable that lightning has been detected on Venus and Mars along with evidence of atmospheric NO.

Because a figure 10¹⁸ g of nitrate/nitrite is controversial, we will present new calculations based on 10 atmospheres of CO₂, two atmospheres of N₂ and stepped concentrations of water vapor dependent on surface temperatures.