In a recent paper written by myself and my two graduate advisers, we argue that small quantities of O₂ could have reached the surface of early Earth through transport by atmospheric dynamics. This transport would primarily occur in the Wintertime hemisphere, where a “polar Winter vortex” develops near the polar region, because the lack of sunlight in Winter would allow for greatest amount of O₂ to accumulate. Our calculations show that enough dissolved O₂ could have accumulated in polar Winter waters to allow early forms of marine life (i.e. microbial life) to develop and use respiration–without needing to wait for photosynthesis to oxygenate the atmosphere. Although our model calculations cannot prove that respiration did in fact evolve first, they least demonstrate a proof-of-concept that the “early-respiration” hypothesis is in fact viable.

Our paper is titled “Availability of O₂ and H₂O₂ on pre-photosynthetic Earth” and appears in the May issue of the journal Astrobiology.

We argue that the warm, ice-free climate of the early Earth (2.8 billion years ago) was maintained by a water vapor/carbon dioxide/methane/ethane atmospheric greenhouse effect that offset the ~20% reduction in solar luminosity from the faint young sun. Furthermore, a stabilizing feedback between life and the climate system may have resulted in a thin stratospheric organic haze that maintained above-freezing temperatures and shielded ultraviolet radiation. An excellent write-up of our work is available at The Planetologist.

I’ve given this talk several times over the past couple years, most recently on the Forum for Astrobiology Research (which should eventually be available as a podcast), and it feels good to finally see the paper come out.