Detection of life on other planets requires identification of biosignatures, i.e., observable planetary properties that robustly indicate the presence of a biosphere. One of the most widely accepted biosignatures for an Earth-like planet is an atmosphere where oxygen is a major constituent. Here we show that lifeless habitable zone terrestrial planets around any star type may develop oxygen-dominated atmospheres as a result of water photolysis, because the cold trap mechanism that protects H2O on Earth is ineffective when the atmospheric inventory of non-condensing gases (e.g., N2, Ar) is low. Hence the spectral features of O2 and O3 alone cannot be regarded as robust signs of extraterrestrial life.
@article{arxiv.1403.2713,
title = {Abiotic oxygen-dominated atmospheres on terrestrial habitable zone planets},
author = {Robin Wordsworth and Raymond Pierrehumbert},
journal= {arXiv preprint arXiv:1403.2713},
year = {2015}
}
Comments
5 pages, 3 figures, accepted for publication in ApJ Letters. Minor changes from previous version