Broadening the Habitability Frontier: From Habitable Zones to Subsurface Oceans and Biosignatures

To the point

Life beyond Earth may exist on many exoplanets, some in the habitable zone that could be rocky with oceans, but habitability there isn’t guaranteed because eccentric orbits, tidal locking, atmospheres, and stellar radiation can make conditions hostile, while moons such as Europa could hide subsurface oceans and life might exist in non-Earth–like environments, and biosignatures can be ambiguous or abiotic, with next‑generation instruments like ESO’s Extremely Large Telescope expected to shed more light.