A Terminology and Quantitative Framework for Assessing the Habitability of Solar System and Extraterrestrial Worlds
The search for extraterrestrial life in the solar system and beyond is a key science driver in astrobiology, planetary science, and astrophysics. A critical step is the identification and characterization of potential habitats, both to guide the search and to interpret its results. However, a well-a...
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| Main Authors: | , , , , , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | The Planetary Science Journal |
| Subjects: | |
| Online Access: | https://doi.org/10.3847/PSJ/addda8 |
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| Summary: | The search for extraterrestrial life in the solar system and beyond is a key science driver in astrobiology, planetary science, and astrophysics. A critical step is the identification and characterization of potential habitats, both to guide the search and to interpret its results. However, a well-accepted, self-consistent, flexible, and quantitative terminology and method of assessment of habitability are lacking. Our paper fills this gap based on a 3 yr long study by the NExSS Quantitative Habitability Science Working Group. We review past studies of habitability but find that the lack of a universally valid definition of life prohibits a universally applicable definition of habitability. A more nuanced approach is needed. We introduce a quantitative habitability assessment framework that enables self-consistent, probabilistic assessment of the compatibility of two models: first, a habitat model, which describes the probability distributions of key conditions in the habitat, and second, a viability model, which describes the probability that a metabolism is viable given a set of environmental conditions. We provide an open-source implementation of this framework and four examples as a proof of concept: (a) comparison of two exoplanets for observational target prioritization, (b) interpretation of atmospheric O _2 detection in two exoplanets, (c) subsurface habitability of Mars, and (d) ocean habitability in Europa. These examples demonstrate that our framework can self-consistently inform astrobiology research over a broad range of questions. The proposed framework is modular so that future work can expand the range and complexity of models available, both for habitats and for metabolisms. |
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| ISSN: | 2632-3338 |