Abstract EANA2025-44

By shifting the focus from a narrow, Earth-centric habitable zone to the full diversity of atmospheric settings, we introduce the multiparametric life score, a unified, continuous metric for assessing atmospheric habitability. We exploit two distinct databases: one detailing exoplanetary conditions (pressure, temperature, radiation profiles) and the other cataloging the environmental tolerances of terrestrial extremophiles. By comparing each world’s atmospheric characteristics with the survival limits of hardy microbes, we assign a graded habitability score that reflects the degree of compatibility on a multidimensional scale, rather than a simple binary condition.

Drawing on extremophile physiology, we define for each planet an atmospheric “life-compatible shell,” the contiguous region whose environmental parameters fall within the known tolerance bounds of extremophiles. We compute the shell’s volume relative to Earth’s, then integrate compatibility scores for pressure, temperature, and radiation into the multiparametric life score. This composite index ranks worlds by both the size and quality of their potential biospheres, revealing candidates overlooked by classical binary habitability criterium.

To demonstrate the framework, we present preliminary results for the eight Solar System bodies with appreciable atmospheres—Venus, Earth, Mars, Titan, Jupiter, Saturn, Uranus, and Neptune. This case study illustrates how the multiparametric life score pinpoints potential ecological niches across drastically different atmospheric regimes. Rather than aiming to detect specific extremophile signatures, we posit that the universal principle of adaptability —rooted in the interplay between atmospheric structure and a planet’s surface and interior— may itself serve as a biosignature; our current study offers a preliminary, atmosphere-focused proof of concept to be extended in future work to coupled surface and subsurface processes.