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We are standing on the cusp of a major discovery in planetary sciences. For the first time in human history, upcoming surveys and telescopes will be able to remotely detect potential biosignatures in exo-Earth atmospheres and discover signs of life beyond our Solar System. In order to make the most of the limited observational resources available, target selection has focused on ’habitable worlds’ defined as rocky bodies (with enough surface gravity to sustain an atmosphere) orbiting their host stars at a distance where stellar radiation is suitable for the presence of surface liquid water. With the ever-increasing number of exoplanets being detected, we might end up with hundreds of planets that suit these criteria and are accordingly all equally likely to host life. Therefore, we must rethink our classification of what makes a planet habitable. Continuing to expand to a multi-parameter approach to habitability (M-PAtH) by including factors such as magnetic field, plate tectonics, albedo, stellar type, orbit characteristics, tidal locking, impact events, salts, and brines, will enable us to prioritise planets most likely to maintain liquid water. By analysing, modelling, and constraining how these factors interact on any given planetary body, we can generate a flexible framework for prioritisation involving multiple observable characteristics that influence continuous planetary habitability. Spoiler alert: No aliens. |
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