Actually I don't think oxygen has been detected in any exoplanet atmosphere. And typically the atmospheres in which water has been detected are large Jovian exo

Actually I don't think oxygen has been detected in any exoplanet atmosphere. And typically the atmospheres in which water has been detected are large Jovian exoplanets. My sense is that we don't yet have the telescopes/instrumentation to detect things like oxygen in the atmosphere of an Earth-sized planet in the habitable zone.