Comment by ianai

They’re unsure whether it’s from the planet or the star. Can’t they just check whether it’s from an ion of water or the stable molecule? (Which IIRC is a question of the spectra observed.) I remember from undergrad the chemistry in stars would often have pretty extreme ionizations like OH^-12. If it’s a high ionization and still on the planet that seems unlikely to be habitable as we know it (or something fleeting from a lightning strike).