From Anoxic to Oxic Earth: Detectability of Atmospheric Biosignatures across Stellar Hosts with ELT/ANDES

Dwaipayan Dubey; Spandan Dash; Liton Majumdar

paper

From Anoxic to Oxic Earth: Detectability of Atmospheric Biosignatures across Stellar Hosts with ELT/ANDES

arXiv:2610.41621

Abstract

Earth's atmosphere evolved from an anoxic, methane-bearing Archean state through Proterozoic oxygenation to the O $_{2}$ -rich modern atmosphere. However, most biosignature detectability studies focus on modern Earth, leaving earlier atmospheric states comparatively unexplored. We investigate how atmospheric evolution and stellar environments influence the detectability of O $_{2}$ , CH $_{4}$ , H $_{2}$ O, and CO $_{2}$ , and their potential to distinguish anoxic from oxygenated atmospheres. We construct two complementary photochemical grids: representative Archean, Proterozoic, and modern-Earth scenarios around the Sun, and four geological epochs (3.9, 2.0, 0.8 Ga, and modern Earth) across FGKM hosts. Combining one-dimensional photochemical modeling, high-resolution transmission spectral simulations, and instrument-noise modeling, we assess molecular detectability with ELT/ANDES under optimistic photon-noise-limited conditions. For solar-host Archean and Proterozoic models, CH $_{4}$ requires approximately 33 and 42 transits, respectively, to reach the adopted 5 $σ$ criterion, whereas O $_{2}$ remains below 3 $σ$ within the observing limits. Modern-Earth O $_{2}$ reaches 3 $σ$ after approximately 38 transits. Across the FGKM grid, O $_{2}$ does not reach 5 $σ$ for the 3.9 Ga models. However, For the M3V, K2V, and M8V proxies, modern-Earth O $_{2}$ reaches 5 $σ$ in 9, 15, and 20 transits, respectively, whereas CH $_{4}$ requires 11, 12, and 28 transits at 3.9 Ga and only 2--4 transits across the oxygenated epochs. These results reveal a strong O $_{2}$ detectability contrast around M and K-dwarfs, but not Sun-like hosts in the YJH bands. Robust biosignature interpretation requires complementary molecular constraints, including informative non-detections, within the context of atmospheric evolution and stellar environment.

arXiv commentSubmitted to AAS (31 pages, 20 figures). Comments are most welcome