Abiotic O2 Levels on Planets around F, G, K, and M Stars: Effects of Lightning-produced Catalysts in Eliminating Oxygen False Positives

C. E. Harman, R. Felton, R. Hu, S. D. Domagal-Goldman, A. Segura, F. Tian, J. F. Kasting

Research output: Contribution to journalArticlepeer-review

21 Scopus citations

Abstract

Over the last few years, a number of authors have suggested that, under certain circumstances, molecular oxygen (O2) or ozone (O3) generated by abiotic processes may accumulate to detectable concentrations in a habitable terrestrial planet's atmosphere, producing so-called "false positives" for life. But the models have occasionally disagreed with each other, with some predicting false positives, and some not, for the same apparent set of circumstances. We show here that photochemical false positives derive either from inconsistencies in the treatment of atmospheric and global redox balance or from the treatment (or lack thereof) of lightning. For habitable terrestrial planets with even trace amounts of atmospheric N2, NO produced by lightning catalyzes the recombination of CO and O derived from CO2 photolysis and should be sufficient to eliminate all reported false positives. Molecular oxygen thus remains a useful biosignature gas for Earth-like extrasolar planets, provided that the planet resides within the conventional liquid water habitable zone and has not experienced distinctly non-Earth-like, irrecoverable water loss.

Original languageEnglish (US)
Article number56
JournalAstrophysical Journal
Volume866
Issue number1
DOIs
StatePublished - Oct 10 2018

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science

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