On Earth, oxygen came to comprise a substantial part of our atmosphere as a direct result of photosynthetic life, thus begging the question: Is oxygen a diagnostic signature for life for terrestrial planets around sun-like stars? Only sometimes, according to Krissansen-Totton et al.  who model long-term evolution of planets, including a magma ocean phase, volcanism, weathering, and atmospheric escape. While they show that the most Earth-like worlds may generate significant oxygen only by biology, “waterworlds” and “desert worlds” can have significant oxygen buildup even without life because other geologic processes that destroy oxygen are suppressed while atmospheric escape generates oxygen over long time. The work has implications for telescope design and the types of observations that would need to be made to distinguish biotic versus abiotic oxygen on habitable exoplanets around sun-like stars.
Citation: Krissansen‐Totton, J., Fortney, J. J., Nimmo, F., & Wogan, N. . Oxygen false positives on habitable zone planets around sun‐like stars. AGU Advances, 2, e2020AV000294. https://doi.org/10.1029/2020AV000294
—Bethany Ehlmann, Editor, AGU Advances