Earth’s atmospheric composition as an example of comparative biosignatures and habsignatures. Earth, situated within the HZ (green annulus sector), emerges as an outlier. Compared to the abiotic baseline established by Venus and Mars, Earth exhibits significantly lower CO_2 levels (P. van Thienen et al. 2007) and considerably higher O_2 levels (indicated below each planet). All of these gases have plausible abiotic origins, but the abiotic baseline informs our expectation and identifies Earth as anomalous.
Published in #MNRAS: "Comparative biosignatures with systemic retrievals", Constantinou et al. This is Fig. 1: please visit academic.oup.com/mnras/articl... to read the paper. @royalastrosoc.bsky.social @academic.oup.com
