Nitrous oxide (N2O) is a powerful greenhouse gas, and is thought to have been an important atmospheric constituent during the Proterozoic (roughly 2.5 to 0.5 billion years ago (Ga)). Earth’s ocean during this time was rich in iron oxides, and a recent study examines the affect of these oceans on the atmospheric content of N2O. Researchers tested whether or not chemodenitrification, which refers to the reduction of nitric oxide by ferrous iron, could have enhanced the flux of N2O from the seas to the atmosphere.

If this pathway led to an increase in the greenhouse gas N2O, it might help explain what is known as the Proterozoic “greenhouse gap.” This ‘gap’ refers to geological evidence that the surface of Earth was ice-free during the Mesoproterozoic (roughly 1.6 to 1 billion years ago), even though the Sun was less luminous at that time. The researchers also suggest that N2O could have played an important role in the evolution of life during this period, when the surface biosphere transitioned from anaerobic to aerobic metabolisms.

The study, “Nitrous oxide from chemodenitrification: A possible missing link in the Proterozoic greenhouse and the evolution of aerobic respiration,” was published in the journal Geobiology. The work was supported by NASA Astrobiology through the Exobiology Program.